Method for producing polybutylene carbonate composition and method for producing paste composition for printing

Abstract

Provided is a method for producing a polybutylene carbonate composition, having a step 1 for obtaining a reaction liquid having a polybutylene carbonate concentration of 10 mass % or more, by polymerizing butylene oxide (C) and carbon dioxide in the presence of a catalyst (B) in a solvent (A) having a boiling point of 130°C or higher, in order to generate polybutylene carbonate.

Description

Method for producing polybutylene carbonate composition and method for producing printing paste composition

[0001] The present invention relates to a method for producing a polybutylene carbonate composition and a method for producing a printing paste composition.

[0002] It is known to use aliphatic polycarbonate as a binder resin. For example, Patent Document 1 describes an aliphatic polycarbonate exhibiting a predetermined molecular weight distribution as a molding binder used together with inorganic materials such as metal particles. When a bonding material containing metal particles and a binder resin is used as a sintering paste composition, it is required that residual carbon after firing is as small as possible.

[0003] As paste compositions containing a binder resin, printing paste compositions used in various printing methods are known. It is also known to form patterns of electronic elements such as wiring boards and displays by printing methods. Printing paste compositions used for such applications contain inorganic materials such as metal particles, for example, to exhibit conductivity after printing. In order not to cause a decrease in conductivity, it is required that less residue derived from the binder resin is generated during firing after printing.

[0004] Aliphatic carbonates generally have high thermal decomposability, and thus are considered suitable for the above-mentioned sintering paste compositions and printing paste compositions. Among aliphatic polycarbonates, polybutylene carbonate is particularly preferable because it is excellent in low-temperature sinterability and dispersion stability.

[0005] On the other hand, printing paste compositions are required to have high stability because a large change in viscosity over time during printing tends to cause printing defects. In addition, it is required that the composition is difficult to dry at printing temperatures and dries quickly when exposed to a high-temperature environment. For this reason, it has been proposed to use a high-boiling solvent in printing paste compositions (for example, Patent Document 2).

[0006] Japanese Patent Application Laid-Open No.2022-153292Japanese National Publication of International Patent Application No.2009-534498

[0007] However, the polybutylene carbonate obtained by conventionally proposed methods for producing polybutylene carbonate tends to have a high content of structural units consisting of the ether skeleton, resulting in a large amount of residual carbon generated during calcination, indicating room for improvement. Furthermore, conventionally proposed methods for producing polybutylene carbonate required a step to remove the solvent used during polymerization and replace it with a more stable solvent. As a result, the removed solvent had to be discarded, indicating room for improvement in terms of process simplification and environmental impact.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a polybutylene carbonate composition and a printing paste composition that produce a polybutylene carbonate composition with a low content ratio of the ether skeleton of the polybutylene carbonate contained in the polybutylene carbonate composition and excellent stability in fewer steps, while also having a low environmental impact.

[0009] As a result of diligent research, the inventors discovered that the above problem can be solved by generating a predetermined reaction solution by polymerizing butylene oxide and carbon dioxide in a specific solvent, and thus completed the present invention described below.

[0010] In other words, the present invention relates to the following [1] to [9]. [1] A method for producing a polybutylene carbonate composition, comprising step 1, of polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) having a boiling point of 130°C or higher in the presence of a catalyst (B) to produce polybutylene carbonate, thereby obtaining a reaction solution in which the concentration of the polybutylene carbonate is 10% by mass or more. [2] The method for producing a polybutylene carbonate composition according to [1], wherein in step 1, butylene oxide (C) and carbon dioxide are polymerized in the solvent (A) in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate. [3] The method for producing a polybutylene carbonate composition according to [1] or [2], wherein in step 1, the mass of solvent (A) per 100 parts by mass of butylene oxide (C) is 50 to 2,000 parts by mass. [4] A method for producing a polybutylene carbonate composition according to any one of [1] to [3] above, wherein the butylene oxide (C) is 1,2-butylene oxide. [5] A method for producing a polybutylene carbonate composition according to any one of [1] to [4] above, wherein in step 1, the butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) in the presence of a catalyst (B) and a chain transfer agent (D) to produce the polybutylene carbonate. [6] A method for producing a polybutylene carbonate composition according to [5] above, wherein the chain transfer agent (D) is 1-butanol. [7] A method for producing a polybutylene carbonate composition according to any one of [1] to [6] above, wherein the solvent (A) is at least one selected from the group consisting of propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, propylene glycol diacetate, and butyl carbitol acetate. [8] A method for producing a polybutylene carbonate composition according to any one of [1] to [7] above, further comprising step 2 of removing catalyst (B) from the reaction solution obtained by step 1. [9] A method for producing a printing paste composition, comprising step P of adding inorganic particles (E) to the polybutylene carbonate composition obtained by the method for producing a polybutylene carbonate composition according to [8] above.

[0011] According to the present invention, it is possible to provide a method for producing a polybutylene carbonate composition and a printing paste composition that have a low content ratio of the ether skeleton of the polybutylene carbonate contained in the polybutylene carbonate composition and excellent stability, in fewer steps, and with a low environmental impact.

[0012] In this specification, the lower and upper limits described in steps for a preferred numerical range can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60."

[0013] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

[0014] It should be noted that the mechanism of action described herein is speculative and does not limit the mechanism by which the effects of the present invention are achieved. Hereinafter, a method for producing a polybutylene carbonate composition according to one or more embodiments of the present invention may be referred to as "the method for producing a polybutylene carbonate composition of this embodiment."

[0015] [Method for Producing Polybutylene Carbonate Composition] The method for producing the polybutylene carbonate composition according to this embodiment includes step 1, which involves polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) having a boiling point of 130°C or higher in the presence of a catalyst (B) to produce polybutylene carbonate, thereby obtaining a reaction solution in which the concentration of the polybutylene carbonate is 10% by mass or higher. Hereinafter, the solvent (A) having a boiling point of 130°C or higher may be simply referred to as "solvent (A)".

[0016] In step 1 described above, butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) having a boiling point of 130°C or higher to obtain a reaction solution in which the concentration of polybutylene carbonate is 10% by mass or higher. As a result, a polybutylene carbonate composition is produced in which the content ratio of structural units consisting of the ether skeleton of polybutylene carbonate (hereinafter sometimes referred to as "ether units") contained in the polybutylene carbonate composition is lower than that of the polybutylene carbonate production method by bulk polymerization without solvent. Structural units consisting of the ether skeleton are a cause of carbon residue when heated, such as during calcination, but because the polybutylene carbonate obtained by the production method of the polybutylene carbonate composition of this embodiment has a low content ratio of structural units consisting of the ether skeleton, even when used in sintering paste compositions or printing paste compositions, there is less carbon residue when heated.

[0017] Furthermore, the polybutylene carbonate produced in step 1 is included in the reaction solution (i.e., the polybutylene carbonate composition) together with solvent (A) having a boiling point of 130°C or higher, and dissolves in the polybutylene carbonate composition at a concentration of 10% by mass or more. As a result, the stability of the polybutylene carbonate composition is increased, and high workability is ensured when inorganic materials are added to the polybutylene carbonate composition to form a printing paste composition. In addition, when the solvent used during polymerization is a low-boiling point solvent different from the solvent to be included in the printing paste composition, solvent substitution is necessary. However, in the method for producing the polybutylene carbonate composition according to this embodiment, the solvent used for polymerization is the same as the solvent included in the polybutylene carbonate composition, so at least the step of removing the solvent from the reaction solution is unnecessary. As a result, the manufacturing process of the polybutylene carbonate composition is simplified. Furthermore, since there is no need to dispose of the solvent removed from the reaction solution, the environmental burden is reduced.

[0018] <Polybutylene Carbonate Composition> The polybutylene carbonate composition obtained by the above method for producing the polybutylene carbonate composition (more specifically, the reaction solution from which catalyst (B) has been removed) contains polybutylene carbonate and a solvent (A) having a boiling point of at least 130°C, and the concentration of the polybutylene carbonate is 10% by mass or more. The total content of polybutylene carbonate and the solvent (A) in the above polybutylene carbonate composition is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the polybutylene carbonate composition. There is no particular upper limit; for example, it may be 90% by mass or less, 95% by mass or less, or even 100% by mass. The content of polybutylene carbonate in the above polybutylene carbonate composition is preferably 10% by mass or more, more preferably 12% by mass or more, even more preferably 14% by mass or more, and also preferably 70% by mass or less. The content of solvent (A) in the above polybutylene carbonate composition is preferably 90% by mass or less, preferably 88% by mass or less, more preferably 86% by mass or less, and also preferably 30% by mass or more.

[0019] <Solvent (A) with a boiling point of 130°C or higher> Solvent (A) enhances the stability of the polybutylene carbonate composition by having a boiling point of 130°C or higher. From the viewpoint of further enhancing the stability of the printing paste composition, the boiling point of solvent (A) is preferably 140°C or higher, more preferably 145°C or higher, and even more preferably 150°C or higher. Also, from the viewpoint of facilitating drying, the upper limit of the boiling point of solvent (A) is preferably 300°C, more preferably 280°C, and even more preferably 260°C.

[0020] The solvent (A) is preferably compatible with the product, polybutylene carbonate. Compatibility of solvent (A) with polybutylene carbonate enhances the stability of the polybutylene carbonate composition. The solvent (A) is preferably capable of dissolving 10% by mass or more of the produced polybutylene carbonate in the reaction solution generated by polymerization, more preferably 12% by mass or more, and even more preferably 14% by mass or more. There is no particular upper limit, but from the viewpoint of keeping viscosity low and ensuring ease of handling, for example, it is 70% by mass. By using such a solvent (A), a reaction solution with a polybutylene carbonate concentration of 10% by mass or more can be obtained in step 1.

[0021] From the viewpoint of suppressing volatilization and solubility of polybutylene carbonate, solvent (A) is preferably at least one selected from the group consisting of propylene glycol monomethyl ether acetate (abbreviated as "PGMEA", boiling point 146°C), diethylene glycol dimethyl ether (abbreviated as "diglyme", boiling point 162°C), propylene glycol diacetate (abbreviated as "PGDA", boiling point 191°C), and butyl carbitol acetate (boiling point 246°C). These solvents may be a single solvent or a mixture of multiple solvents. When solvent (A) is a mixture of multiple solvents, the boiling point of all solvents must be 130°C, or the boiling point of the entire mixture must be within the above-mentioned numerical range. In the latter case, as long as the boiling point of the entire mixture is 130°C or higher, the multiple solvents may include solvents with a boiling point of less than 130°C. In this specification, the boiling point may be measured by a general procedure, for example, by an automatic boiling point measuring device. Alternatively, the boiling point may be the value listed in the catalog.

[0022] <Catalyst (B)> Examples of catalyst (B) include metal salen complex catalysts, complex metal cyanide complex catalysts (DMC catalysts), and organometallic catalysts. Among these, DMC catalysts and organozinc catalysts are preferred from the viewpoint of exhibiting high polymerization activity. Examples of DMC catalysts include Zn3(Co[CN] ６ ) ２This is preferable. As an organozinc catalyst, zinc aliphatic dicarboxylate is preferred. Among these, zinc catalysts are preferred from the viewpoint of exhibiting high polymerization activity, and zinc glutarate is more preferred.

[0023] The amount of catalyst (B) used is preferably 0.001 to 50 parts by mass, more preferably 0.01 to 45 parts by mass, even more preferably 0.1 to 40 parts by mass, and even more preferably 1 to 35 parts by mass, per 100 parts by mass of the raw material monomer, butylene oxide (C), from the viewpoint of reactivity. In the case of a DMC catalyst, the amount of catalyst (B) used is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 3 parts by mass, per 100 parts by mass of the raw material monomer, butylene oxide, from the viewpoint of reactivity. In the case of an organozinc catalyst, the amount of catalyst (B) is preferably 0.1 to 40 parts by mass, more preferably 1.0 to 25 parts by mass, per 100 parts by mass of the raw material monomer, butylene oxide, from the viewpoint of reactivity.

[0024] The polymerization reaction described above may also use a co-catalyst in addition to catalyst (B). Examples of co-catalysts include bis(triphenylphosphoranylidene)ammonium chloride, 4-dimethylaminopyridine, tetrabutylammonium chloride, tetrabutylammonium bromide, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, and 1,4-diazabicyclo[2.2.2]octane. The amount of co-catalyst used is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 14 parts by mass, per 100 parts by mass of the raw material monomer, butylene oxide (C).

[0025] <Butylene Oxide (C)> The butylene oxide (C) used as a raw material monomer in step 1 above can be 1,2-butylene oxide, isobutylene oxide, a derivative of 1,2-butylene oxide, a derivative of isobutylene oxide, a mixture of several different derivatives of 1,2-butylene oxide, a mixture of several different derivatives of isobutylene oxide, or a mixture of two or more of these. From the viewpoint of availability and reactivity, 1,2-butylene oxide is preferred for butylene oxide (C).

[0026] <Chain transfer agent (D)> In step 1 above, a chain transfer agent (D) is an optional component that can be used. By using a chain transfer agent in step 1 above, it becomes easier to obtain polybutylene carbonate having an appropriate molecular weight as a binder resin.

[0027] Examples of chain transfer agents (D) include α-methylstyrene; and alcohols such as methanol, ethanol, propanol, and butanol. Among these, 1-butanol is preferred from the viewpoint of being able to appropriately adjust the performance and volatility as a chain transfer agent.

[0028] <Step 1> In Step 1 above, butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) having a boiling point of 130°C or higher in the presence of a catalyst (B) to produce polybutylene carbonate, thereby obtaining a reaction solution in which the concentration of polybutylene carbonate is 10% by mass or higher. Except for using specific components (A) and (C) (i.e., a solvent (A) and butylene oxide (C) having a boiling point of 130°C or higher) and obtaining a reaction solution in which the concentration of polybutylene carbonate is 10% by mass or higher, the conditions for the polymerization reaction can be, for example, those described in International Publication No. 2011 / 142259.

[0029] The method for carrying out the polymerization reaction is not particularly limited as long as the target product is obtained, but for example, one method involves charging a butylene oxide (C), a catalyst (B), a solvent (A), and optionally at least one of a co-catalyst and a chain transfer agent (D) into an autoclave, mixing them, and then injecting carbon dioxide under pressure into the resulting mixture to carry out the reaction.

[0030] The pressure at which carbon dioxide is injected during the polymerization reaction is preferably 0.1 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.1 to 5 MPa. If the pressure at which carbon dioxide is injected is above the lower limit, the polymerization reaction proceeds more easily. Also, if the pressure at which carbon dioxide is injected is below the upper limit, excessive use of carbon dioxide is suppressed, improving economic efficiency.

[0031] The reaction temperature during the polymerization reaction is preferably 20 to 100°C, more preferably 25 to 80°C, from the viewpoint of reaction rate and suppression of side reactions. The reaction time for the polymerization reaction can be adjusted as appropriate according to the reaction temperature, but is preferably 2 to 40 hours.

[0032] During the polymerization reaction, it is preferable to keep the amount of water in the reaction system at 5 mol% or less relative to the amount (moles) of catalyst (B) used.

[0033] In step 1, from the viewpoint of reactivity, it is preferable to polymerize butylene oxide (C) and carbon dioxide in the solvent (A) in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate.

[0034] In step 1, the mass of solvent (A) per 100 parts by mass of butylene oxide (C) is preferably 50 to 2,000 parts by mass, more preferably 60 to 1,500 parts by mass, even more preferably 70 to 1,000 parts by mass, and even more preferably 80 to 500 parts by mass, from the viewpoint of reactivity.

[0035] In step 1, from the viewpoint of reactivity, it is preferable to polymerize butylene oxide (C) and carbon dioxide in solvent (A) in the presence of catalyst (B) and chain transfer agent (D) to produce the polybutylene carbonate.

[0036] In step 1 described above, the amount of chain transfer agent (D) used is preferably 0.1 to 20 mol%, more preferably 0.15 to 10 mol%, and even more preferably 0.2 to 5 mol%, relative to 1,2-butylene oxide, from the viewpoint of reactivity.

[0037] [Step 2] The method for producing the polybutylene carbonate composition of this embodiment may further include step 2, in which catalyst (B) is removed from the reaction solution. Including step 2 allows for an increase in the amount of binder component. In step 2, a method for removing catalyst (B) from the reaction solution may be, for example, filtration to remove catalyst (B).

[0038] After the polymerization reaction is complete, polybutylene carbonate can be extracted by known methods after performing any known post-treatment procedures as necessary. The obtained polybutylene carbonate may also be purified as needed.

[0039] <Polybutylene Carbonate> In step 1 of the method for producing the polybutylene carbonate composition of this embodiment, a polybutylene carbonate having the following physical properties is produced.

[0040] (Ratio of ether units in polybutylene carbonate) The ratio of ether units in the polybutylene carbonate obtained in step 1 is preferably 15 mol% or less, more preferably 12 mol% or less, and even more preferably 10 mol% or less, from the viewpoint of reducing residual carbon during heating. There is no particular lower limit, and it may be 0 mol% or more, but from the viewpoint of ease of manufacture, for example, it is 1 mol% or more. The ratio of structural units consisting of an ether skeleton in polybutylene carbonate is, １ It is measured by nuclear magnetic resonance spectroscopy using H-NMR, specifically by the method described in the examples.

[0041] (Mass average molecular weight (Mw) and number average molecular weight (Mn) of polybutylene carbonate) The mass average molecular weight (Mw) of polybutylene carbonate is preferably 5,000 to 1,000,000, more preferably 8,000 to 800,000, still more preferably 10,000 to 600,000, and even more preferably 30,000 to 500,000. The number average molecular weight (Mn) of polybutylene carbonate is preferably 2,000 to 300,000, more preferably 5,000 to 250,000, still more preferably 7,000 to 200,000, and even more preferably 8,000 to 150,000. When the mass average molecular weight (Mw) or number average molecular weight (Mn) of polybutylene carbonate falls within the above range, the balance between shape retention and flexibility of the fired material formed from the firing paste composition tends to be more favorable. The mass average molecular weight (Mw) and number average molecular weight (Mn) refer to values converted to standard polystyrene as measured by gel permeation chromatography (GPC), and can be measured by the method described in the Examples.

[0042] [Method for producing printing paste composition] The method for producing a printing paste composition according to the present embodiment comprises a step P of adding inorganic particles (E) to the polybutylene carbonate composition obtained by any one of the above methods for producing a polybutylene carbonate composition. As described above, the polybutylene carbonate composition obtained by the method for producing a polybutylene carbonate composition of the present embodiment (more specifically, the polybutylene carbonate composition obtained through the above steps 1 and 2) has compatibility between polybutylene carbonate and the solvent (A), and the solvent (A) has a high boiling point, so it has high stability. Therefore, the printing paste composition obtained by adding inorganic particles (E) to the above polybutylene carbonate composition does not dry immediately in the printing step, and exhibits high workability.

[0043] In the above step P, other optional components that are used as necessary may be further added. In the above step P, a polybutylene carbonate composition, inorganic particles (E), and other optional components used as necessary are mixed. The method for mixing the respective components is not particularly limited, and for example, a known mixing method using a mixing device such as a rotation-revolution stirrer, a kneader, a three-roll mill, a ball mill, a sand mill, a planetary mixer, a paint shaker, a homomixer, a homodisper, a homogenizer, or an ultrasonic disperser can be employed.

[0044] <Printing Paste Composition> The printing paste composition obtained by the method for producing a printing paste composition of the present embodiment contains polybutylene carbonate, a solvent (A), and inorganic particles (E). The printing paste composition is used in various printing methods such as an inkjet method, a screen printing method, a relief printing method, an offset printing method, a gravure printing method, a microcontact printing method, and a nanoimprint method, and is particularly preferably used in a screen printing method.

[0045] By containing polybutylene carbonate as a binder, the printing paste composition is excellent in low-temperature sinterability and dispersion stability, and has less residual carbon after calcination. Furthermore, since it contains the catalyst (A) having a boiling point of 130°C or higher and compatibility with polybutylene carbonate, it has high stability and is excellent in workability.

[0046] Hereinafter, each component contained in the printing paste composition obtained by the method for producing a printing paste composition of the present embodiment will be described. (Polybutylene Carbonate and Solvent (A)) Polybutylene carbonate and the solvent (A) are incorporated into the printing paste composition by using the polybutylene carbonate composition obtained by the above-described method for producing a polybutylene carbonate composition of the present embodiment. Among these, polybutylene carbonate serves, as the binder resin of the printing paste composition, the function of improving the shape retention of the printing paste composition during printing and the adhesion to a printing object.

[0047] (Solvents other than solvent (A)) The above printing paste composition may or may not contain solvents other than solvent (A). If a solvent other than solvent (A) is included, the solvent other than solvent (A) should be selected to the extent that the stability and ease of drying of the printing paste composition are not impaired. Examples of solvents other than solvent (A) include toluene (boiling point: 110°C) and ethyl acetate (boiling point: 77°C). By using a solvent other than solvent (A), in other words, a solvent with a boiling point of less than 130°C, it is possible to improve the dispersibility of each raw material and the separation of polybutylene carbonate from the reaction solution when producing polybutylene carbonate. Furthermore, when using a reaction solution in which the solvent used in the reaction remains as the polybutylene carbonate composition, it may contribute to improving the drying properties of the composition. When using solvents other than solvent (A) in combination, it is preferable to use solvents in a range where the boiling point of the entire solvent, including solvent (A), is 130°C or higher, in order to easily obtain a reaction solution in which the concentration of polybutylene carbonate is 10% by mass or more. From the viewpoint of stability, the content of solvents other than solvent (A) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the total mass of the solvent. In other words, when using solvents other than solvent (A) in combination with solvent (A), the content of solvent (A) in the total mass of the solvent (solvent (A) and solvents other than solvent (A)) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0048] (Inorganic particles (E)) The inorganic particles (E) contained in the above printing paste composition may exhibit any of the following functions: conductive function, insulating function, or semiconductor function. For example, inorganic particles made of one or more materials selected from the group consisting of glass frit, metal oxides, dielectric materials and other metallic materials, and ion conductor materials. The amount of inorganic particles (E) added may be within a range that does not impair the effects of the present invention, and is preferably 25 to 900% by mass, more preferably 40 to 900% by mass, even more preferably 40 to 800% by mass, and even more preferably 40 to 700% by mass, relative to the total mass (100% by mass) of polybutylene carbonate and the total solvent (solvent (A) and solvents other than solvent (A)).

[0049] (Other Additives) The above printing paste composition may contain other additives. Examples of other additives include organic or inorganic pigments, dispersants, defoamers, stabilizers, antioxidants, curing accelerators, sensitizers, fillers, UV absorbers, anti-flocculation agents, etc. The content of the above other additives is not particularly limited and may be used as needed, within a range that does not impair the effects of this embodiment.

[0050] [Firing Paste Composition] A firing paste composition can be obtained by adding at least metal particles (F) to the polybutylene carbonate composition obtained by the method for producing the polybutylene carbonate composition of this embodiment (i.e., a polybutylene carbonate composition containing polybutylene carbonate and solvent (A)). The firing paste composition is used to join members to be joined together. Specifically, it is used in a joining method in which the firing paste composition or a firing material formed by processing the firing paste composition, for example in the form of a film, is interposed between members to be joined, and these are heated under pressure to fire the joining material, thereby forming a metal sintered layer that joins the members to be joined together.

[0051] The above-mentioned firing paste composition contains polybutylene carbonate as a binder, resulting in excellent low-temperature sinterability and dispersion stability, as well as low charcoal residue after firing.

[0052] The following describes each component contained in the above-mentioned baking paste composition.

[0053] (Polybutylene carbonate and solvent (A)) The polybutylene carbonate and solvent (A) are incorporated into the baking paste composition by using the polybutylene carbonate composition obtained by the method for producing the polybutylene carbonate composition of this embodiment described above.

[0054] Of these, polybutylene carbonate serves as a binder resin in the above-mentioned firing paste composition, and plays a role in enhancing the shape retention, flexibility, and adhesion to the member to be joined of the firing paste composition and the firing material formed by processing the firing paste composition. The content of polybutylene carbonate in the above-mentioned firing paste composition is preferably 1 to 30% by mass of the total mass (100% by mass) of all components other than the solvent (A), from the viewpoint of maintaining the shape of the firing material formed by processing the firing paste composition and from the viewpoint of ensuring a sufficient content of metal particles (F).

[0055] (Solvents other than solvent (A)) The above-mentioned paste composition for firing may or may not contain solvents other than solvent (A). From the viewpoint of maintaining the purity of the polybutylene carbonate composition, it is preferable that the above-mentioned paste composition for firing does not contain solvents other than solvent (A). Examples of solvents other than solvent (A) include toluene (boiling point: 110°C) and ethyl acetate (boiling point: 77°C). From the viewpoint of maintaining the purity of the polybutylene carbonate composition, the content of solvents other than solvent (A) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the total mass of the solvent. In other words, when solvents other than solvent (A) are used in combination with solvent (A), the content of solvent (A) in the total mass of the solvent (solvent (A) and solvents other than solvent (A)) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0056] (Metal particles (F)) When the above-mentioned firing paste composition is fired, the metal particles (F) form a metal sintered layer that joins the members to be joined together.

[0057] Examples of metal particles (F) include one or more selected from the group consisting of silver particles, gold particles, copper particles, iron particles, nickel particles, aluminum particles, tungsten particles, silicon particles, palladium particles, platinum particles, titanium particles, barium titanate particles, and oxide particles of the metals constituting the particles or alloy particles of the metals constituting the particles. Among these, one or more selected from the group consisting of silver particles and copper particles are preferred from the viewpoint of electrical conductivity, thermal conductivity and bonding strength of the metal sintered layer, as well as low-temperature sinterability. One type of metal particle (F) may be used alone, or two or more types may be used in combination. In this specification, "metal particles" means particles containing metal, and may consist only of metal, or may contain metals and non-metallic elements, such as metal oxides.

[0058] From the viewpoint of low-temperature sinterability, the metal particles (F) preferably contain metal particles with a particle size of 1.0 μm or less. The metal particles with a particle size of 1.0 μm or less are preferably one or more selected from the group consisting of silver particles and copper particles among the metal particles listed above, and are more preferably silver particles.

[0059] From the viewpoint of low-temperature sinterability, the metal particles (F) preferably contain metal particles with a particle diameter of 700 nm or less. The particle diameter of the metal particles contained in the metal particles (F) may be 0.1 nm or more. In this specification, the particle diameter of the metal particles (F) means the equivalent circle diameter corresponding to the projected area of ​​the metal particles (F). The projected area of ​​the metal particles (F) can be obtained, for example, by observing the film-like fired material formed by applying and drying the above-mentioned firing paste composition using an electron microscope or the like. Furthermore, the particle diameter of the metal particles (F) means the particle diameter of the primary particles.

[0060] The shape of the metal particles (F) is not particularly limited and includes, for example, spherical, polygonal, plate-like, flake-like, angular, needle-like, and rod-like shapes. Among these, spherical is preferred. In this specification, "spherical" means a perfect sphere or ellipsoid with an aspect ratio (major axis diameter / minor axis diameter) of 1.2 or less.

[0061] The metal particles (F) may be pre-dispersed in a solvent. Preferred solvents for dispersing the metal particles (F) include high-boiling point solvents such as isobornylcyclohexanol and decyl alcohol. The boiling point of the high-boiling point solvent is, for example, 200 to 350°C.

[0062] The surface of the metal particles (F) may be coated with an organic substance. The surface of the metal particles (F) coated with an organic substance has improved affinity with the binder resin, thus suppressing aggregation of the metal particles (F) in the baking paste composition and allowing for more uniform dispersion. When the surface of the metal particles (F) is coated with an organic substance, the mass and particle size of the metal particles (F) include the value of the coating.

[0063] The content of metal particles (F) in the above-mentioned baking paste composition is preferably 20 to 95% by mass of the total mass (100% by mass) of all components other than the solvent (A), from the viewpoint of ensuring the fusion properties of the metal particles (F) during baking and ensuring the content of the binder resin.

[0064] In the above-mentioned paste composition for firing, the mass ratio of metal particles (F) to polybutylene carbonate [metal particles (F) / polybutylene carbonate] is preferably 1 / 5 to 50 / 1 from the viewpoint of bonding strength and shape retention of the fired material.

[0065] (Other Optional Components) The above-mentioned baking paste composition may contain other optional components besides those listed above, as needed. Examples of other optional components include resins other than polybutylene carbonate, dispersants, plasticizers, tackifiers, preservatives, defoamers, thermal decomposition accelerators, and antioxidants. Each of these may be used individually or in combination of two or more. These additives can be appropriately selected from those commonly used in this field. The content of the above-mentioned optional components in the above-mentioned baking paste composition is not particularly limited and may be used as needed, within a range that does not impair the effects of this embodiment. Furthermore, the above-mentioned baking paste composition may not contain the above-mentioned optional components, depending on the desired performance.

[0066] The total content of polybutylene carbonate, metal particles (F), and solvent (A) in the above-mentioned paste composition for firing is preferably 90 to 100% by mass.

[0067] <Members to be joined and applications of the firing paste composition> The material of the members to be joined using the above firing paste composition is not particularly limited, and examples include: metallic materials such as copper, gold, and aluminum; semiconductor materials such as silicon (Si), germanium, gallium arsenide, gallium phosphide, cadmium sulfide, silicon nitride, graphite, yttrium oxide, magnesium oxide, silicon carbide (SiC), and gallium nitride; plastic materials such as polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate; and ceramic materials such as glass.

[0068] The above-mentioned baking paste composition is suitable for joining components for semiconductor devices. Examples of such components include semiconductor elements, LED elements, substrates, leads, frames, and heat sinks.

[0069] (Other Optional Components) The baking paste composition of this embodiment may contain other optional components in addition to the above components as needed. Examples of other optional components include resins other than polybutylene carbonate, dispersants, plasticizers, tackifiers, preservatives, defoamers, thermal decomposition accelerators, and antioxidants. Each of these may be used individually or in combination of two or more. These additives can be appropriately selected from those commonly used in this field. The content of the above optional components in the baking paste composition of this embodiment is not particularly limited and may be used as needed, within a range that does not hinder the effects of this embodiment. Furthermore, the baking paste composition of this embodiment may not contain the above optional components depending on the desired performance.

[0070] In the baking paste composition of this embodiment, the total content of polybutylene carbonate, metal particles (F), and the solvent (A) is preferably 90 to 100% by mass.

[0071] <Method for Manufacturing the Firing Paste Composition> The method for manufacturing the firing paste composition of this embodiment is not particularly limited and can be manufactured by mixing the polybutylene carbonate composition described above, metal particles (F), a solvent other than the solvent (A) used as needed, and other optional components used as needed. The method for mixing each component is not particularly limited and, for example, known mixing methods using mixing equipment such as a rotary-orbiting agitator, kneader, three-roll mixer, ball mill, sand mill, planetary mixer, paint shaker, homomixer, homodisper, homogenizer, ultrasonic disperser, etc., can be employed.

[0072] <Members to be joined and applications of the firing paste composition> The material of the members to be joined using the above firing paste composition is not particularly limited, and examples include: metallic materials such as copper, gold, and aluminum; semiconductor materials such as silicon (Si), germanium, gallium arsenide, gallium phosphide, cadmium sulfide, silicon nitride, graphite, yttrium oxide, magnesium oxide, silicon carbide (SiC), and gallium nitride; plastic materials such as polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate; and ceramic materials such as glass.

[0073] The above-mentioned baking paste composition is suitable for joining components for semiconductor devices. Examples of such components include semiconductor elements, LED elements, substrates, leads, frames, and heat sinks.

[0074] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0075] [ １ [H-NMR measurement] Nuclear magnetic resonance spectroscopy is used to analyze the reaction solution obtained by polymerization. １ ¹H-NMR (Biospin Avance 500, Bruker) was used as the solvent, with CDClone. ３Measurements were performed using a solution containing 0.03% by volume of tetramethylsilane. Based on the measurement results, the conversion rate to polybutylene carbonate, the ratio of PBC to cyclic carbonate (CC), and the carbonate / ether unit ratio in the polymer were calculated based on the ratio of residual monomer to generated polymer.

[0076] [Measurement of Mass-Average Molecular Weight (Mw) and Number-Average Molecular Weight (Mn)] The mass-average molecular weight (Mw) and number-average molecular weight (Mn) of the polybutylene carbonate obtained in each example and comparative example were measured using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8320") under the following conditions, and the measurements were converted to standard polystyrene equivalents. In addition, the molecular weight dispersion (PDI = Mw / Mn) was calculated from the obtained mass-average molecular weight (Mw) and number-average molecular weight (Mn). <GPC Measurement Conditions> ・Column: A series of "TSK guard column SuperH-H", "TSK gel SuperHM-H", "TSK gel SuperHM-H", and "TSK gel SuperH2000" (all manufactured by Tosoh Corporation) linked together. ・Column temperature: 40°C ・Developing solvent: Tetrahydrofuran (polymer concentration 1% by mass) ・Injection volume: 20 μl ・Flow rate: 0.6 mL / min ・Detector: Differential refractometer ・Standard sample: Polystyrene

[0077] [Production Example 1] (Production of Organozinc Compounds) 2.00 g of zinc oxide and 3.12 g of glutaric acid were placed in a 50 mL glass container. The reaction vessel was rotated at room temperature for 24 hours using a mix rotor (set rotation speed 100 rpm) to stir the raw materials. After stirring, a white powder was obtained. The organic zinc compound (zinc glutarate) was then dried in a vacuum dryer at 120°C for 5 hours. This powder was used as a catalyst (B) in the production of a polybutylene carbonate composition.

[0078] [Example 1] 2.91 g of 1,2-butylene oxide as the raw material monomer and 0.582 g of zinc glutarate as catalyst (B) obtained in Production Example 1 were dissolved in 7.41 g of propylene glycol monomethyl ether acetate (PGMEA) to obtain a mixture. The concentration of the raw material monomer was 28% by mass, with the total of the solvent and monomer being 100% by mass. Next, the system of a 4 L autoclave equipped with a stirrer, gas inlet pipe and thermometer was pre-filled with a nitrogen atmosphere, and the above mixture was charged in. Next, while stirring the mixture in the autoclave, carbon dioxide gas was added to the reaction system until the pressure reached 2.5 MPa. After that, the temperature was raised to 70°C. After that, carbon dioxide gas was added to the reaction system until the pressure reached 4 MPa, and the polymerization reaction was carried out for 4 hours. After the reaction was completed, the autoclave was cooled and depressurized, the contents were diluted with PGMEA, and catalyst (B) was removed by reprecipitation purification to obtain the polybutylene carbonate composition as the product. Then, by drying the resulting solution, polybutylene carbonate was obtained from the polybutylene carbonate composition.

[0079] [Example 2] Polymerization was carried out in the same manner as in Example 1, except that 1-butanol was added as a chain transfer agent (D) at a concentration of 1 mol% relative to 1,2-butylene oxide, to obtain polybutylene carbonate.

[0080] [Example 3] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with diethylene glycol dimethyl ether (diglyme).

[0081] [Example 4] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with propylene glycol diacetate (PGDA).

[0082] [Example 5] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with butyl carbitol acetate.

[0083] [Comparative Example 1] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with toluene.

[0084] [Comparative Example 2] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with ethyl acetate.

[0085] [Comparative Example 3] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with terpineol.

[0086] [Comparative Example 4] A polybutylene carbonate composition was prepared in the same manner as in Example 1, except that PGMEA was replaced with butyl carbitol.

[0087] [Comparative Example 5] Polymerization was carried out using the same procedure as in Example 1, except that no solvent was used and the reaction time was changed to 1 hour, to produce polybutylene carbonate.

[0088] [Evaluation Method] The polybutylene carbonate composition and polybutylene carbonate obtained above were evaluated by the following method. The results, along with the type of solvent, monomer concentration, and the measurement results, are shown in Table 1.

[0089] [Solubility of Polybutylene Carbonate] The reaction solutions (i.e., polybutylene carbonate compositions) obtained in Examples 1-5 and Comparative Examples 1-4, after removing catalyst (B), were dried in a dryer. The resulting dried material was then dissolved in the solvent used in each example to a concentration of 1% by mass. If the material dissolved, additional dried material was dissolved in increments of 1% by mass to increase the concentration further, and the concentration of any remaining undissolved material was checked. If the material dissolved completely when the concentration reached 10% by mass, it was considered to have a concentration of 10% by mass or higher (i.e., it was evaluated as having solubility).

[0090] [Carbon Residue During Heating] For each example and comparative example, the polybutylene carbonate was subjected to a thermal decomposition test using a thermogravimetric analyzer (TGA; Shimadzu Corporation, product name "DTG-60") under the following conditions. After heating to 500°C, the bottom of the sample pan was visually inspected. If metallic luster was observed, it was judged that there was sufficiently little carbon residue. If discoloration was present, it was judged that there was more carbon residue than acceptable. <TGA Measurement Conditions> Heating rate: 10°C / min Sample amount: 10-20 mg Upper limit of heating temperature: 500°C Measurement pressure: Atmospheric pressure Measurement atmosphere: Air or nitrogen atmosphere with oxygen partial pressure of 0.1 kPa or less

[0091] [Stability] A paste composition for firing was prepared by mixing 20 parts by mass of the polybutylene carbonate composition obtained in each example and comparative example with 80 parts by mass of alumina powder (manufactured by Sumika Alchem ​​Co., Ltd., product name "Advanced Alumina AA-2", median diameter 2.2 μm (measured by laser diffraction and scattering method)) at 2,000 rpm for 10 minutes using a rotation-revolution mixer (manufactured by Thinky Co., Ltd., product name "Awatori Rentaro"). The obtained paste composition for firing was left to stand for 30 minutes in an environment of 23°C and 50% humidity, and its stability was confirmed by touch with a finger. If no solvent adhered to the finger, it was evaluated as having good stability (A), and if solvent adhered to the finger, it was evaluated as having insufficient stability (F).

[0092]

[0093] The meaning of each symbol in Table 1 is as follows: ・PGMEA: Propylene glycol monomethyl ether acetate ・diglyme: Diethylene glycol dimethyl ether ・PGDA: Propylene glycol diacetate ・PBC: Polybutylene carbonate ・CC: Cyclic carbonate ・EU: Ether unit ・Mw: Mass average molecular weight ・PDI: Molecular weight dispersion ・PBC: Polybutylene carbonate In Examples 1 to 5 and Comparative Examples 1 to 4 in Table 1, "-" indicates that the corresponding component was not used, or that the reaction did not proceed and the corresponding physical properties could not be measured or evaluated. For Comparative Example 5 in Table 1, since no solvent was used, "-" is written in the "Boiling point," "Chain transfer agent concentration," and "PBC solubility" columns. Also, since stability was not evaluated, "-" is written in the "Stability" column.

[0094] As shown in Table 1, the polybutylene carbonate contained in the polybutylene carbonate compositions obtained by the manufacturing methods of Examples 1 and 2 had a low ether unit content and a sufficiently small amount of residual carbon during heating. For the polybutylene carbonate compositions obtained by the manufacturing methods of Examples 3 to 5, since the solvent used contains an ether skeleton, １ ¹H-NMR measurements could not accurately determine the ether unit content of the polybutylene carbonate. However, since the evaluation of the residual carbon during heating of these polybutylene carbonates was the same as in Example 1, it can be understood that the ether unit content in the polybutylene carbonate was small, similar to that in Example 1. The polybutylene carbonate compositions obtained by the manufacturing methods of Examples 1 to 5 showed good stability.

[0095] On the other hand, the manufacturing method of Comparative Example 1, which used toluene with a boiling point of 110°C, and the manufacturing method of Comparative Example 2, which used ethyl acetate with a boiling point of 77°C, showed inferior stability compared to the examples. Furthermore, the manufacturing methods of Comparative Examples 3 and 4, which used solvents with boiling points of 200°C or higher but low solubility of polybutylene carbonate, did not proceed.

[0096] From the above results, it can be seen that the method for producing a polybutylene carbonate composition according to this embodiment, which has step 1 of polymerizing butylene oxide (C) and carbon dioxide in the presence of catalyst (B) in a solvent (A) having a boiling point of 130°C or higher to produce polybutylene carbonate, thereby obtaining a reaction solution in which the concentration of the polybutylene carbonate is 10% by mass or more, has a low content ratio of the ether skeleton of the polybutylene carbonate contained in the polybutylene carbonate composition, and produces a polybutylene carbonate composition with excellent stability in fewer steps, while also having a low environmental impact.

Claims

1. A method for producing a polybutylene carbonate composition, comprising step 1, which involves polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) having a boiling point of 130°C or higher in the presence of a catalyst (B) to produce polybutylene carbonate, thereby obtaining a reaction solution in which the concentration of the polybutylene carbonate is 10% by mass or higher.

2. A method for producing a polybutylene carbonate composition according to claim 1, wherein in step 1, butylene oxide (C) and carbon dioxide are polymerized in the solvent (A) in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate.

3. A method for producing a polybutylene carbonate composition according to claim 1 or 2, wherein in step 1, the mass of solvent (A) per 100 parts by mass of butylene oxide (C) is 50 to 2,000 parts by mass.

4. A method for producing a polybutylene carbonate composition according to claim 1 or 2, wherein the butylene oxide (C) is 1,2-butylene oxide.

5. A method for producing a polybutylene carbonate composition according to claim 1 or 2, wherein in step 1, butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) in the presence of a catalyst (B) and a chain transfer agent (D) to produce the polybutylene carbonate.

6. A method for producing a polybutylene carbonate composition according to claim 5, wherein the chain transfer agent (D) is 1-butanol.

7. A method for producing a polybutylene carbonate composition according to claim 1 or 2, wherein the solvent (A) is at least one selected from the group consisting of propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, propylene glycol diacetate, and butyl carbitol acetate.

8. A method for producing a polybutylene carbonate composition according to claim 1 or 2, further comprising step 2 of removing catalyst (B) from the reaction solution obtained in step 1.

9. A method for producing a printing paste composition, comprising step P of adding inorganic particles (E) to the polybutylene carbonate composition obtained by the method for producing a polybutylene carbonate composition according to claim 8.

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