Method for producing polybutylene carbonate, method for producing paste composition for sintering, and method for producing binder composition

Abstract

Provided is a method for producing polybutylene carbonate, having a step 1 for generating a reaction liquid containing polybutylene carbonate, by polymerizing butylene oxide (C) and carbon dioxide in the presence of a catalyst (B) containing zinc glutarate in a solvent (A) containing methylbenzene.

Description

Process for producing polybutylene carbonate, process for producing paste composition for sintering, and process for producing binder composition

[0001] The present invention relates to a process for producing polybutylene carbonate, a process for producing a paste composition for sintering, and a process for producing a binder composition.

[0002] As a method for joining members to each other, there is known a method in which a joining material containing metal particles and a binder resin is interposed between members to be joined (hereinafter also referred to as "members to be joined"), heated while being pressed, and fired to join the members to be joined to each other. According to this method, the binder resin is decomposed by firing the joining material, and the metal particles are melted and bonded to each other, thereby forming a metal sintered layer that joins the members to be joined to each other.

[0003] Since the metal sintered layer formed from metal particles has excellent heat dissipation, the above joining method is used, for example, for joining power semiconductor elements (power devices). A joining material containing metal particles and a binder resin is excellent in shape retention and flexibility due to the binder resin, and therefore has a high degree of freedom in shape design and usage, for example, by being molded into a film for use.

[0004] It is known to use an aliphatic polycarbonate as the binder resin. For example, Patent Document 1 describes an aliphatic polycarbonate having a predetermined molecular weight distribution as a molding binder used together with an inorganic material such as metal particles. Patent Document 1 describes that various products are produced through a molding step and a firing step using a slurry containing the aliphatic polybutylene carbonate and an inorganic material. Among aliphatic polycarbonates, polybutylene carbonate is particularly preferred because of its excellent low-temperature sinterability and dispersion stability.

[0005] When using a bonding material containing metal particles and binder resin as a sintering paste composition, it is required that the amount of residual carbon after firing be kept to a minimum. Furthermore, in the production of polybutylene carbonate, in order to efficiently produce high-quality polybutylene carbonate, it is required to quickly remove the catalyst used during polymerization from the reaction solution generated by polymerization.

[0006] Japanese Patent Publication No. 2022-153292

[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, and there was room for improvement. In addition, conventional methods for producing polybutylene carbonate have the problem that it takes time to remove the catalyst used during polymerization from the reaction solution.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for producing polybutylene carbonate, a method for producing a sintering paste composition, and a method for producing a binder composition that produce polybutylene carbonate with excellent catalyst removal properties, a low content ratio of structural units consisting of an ether skeleton, and low carbon residue during heating.

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

[0010] In other words, the present invention relates to the following [1] to

[10] . [1] A method for producing polybutylene carbonate, comprising step 1, in which butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce a reaction solution containing polybutylene carbonate. [2] The method for producing polybutylene carbonate according to [1], wherein in step 1, the mass of solvent (A) is 50 to 2,000 parts by mass per 100 parts by mass of butylene oxide (C). [3] The method for producing polybutylene carbonate according to [1] or [2], wherein in step 1, the mass of catalyst (B) is 0.001 to 50 parts by mass per 100 parts by mass of butylene oxide (C). [4] The method for producing polybutylene carbonate according to any one of [1] to [3], wherein butylene oxide (C) is 1,2-butylene oxide. [5] A method for producing polybutylene carbonate according to any one of [1] to [4] above, wherein in step 1, butylene oxide (C) and carbon dioxide are polymerized in solvent (A) in the presence of catalyst (B) and chain transfer agent (D) to produce the polybutylene carbonate. [6] A method for producing polybutylene carbonate according to [5] above, wherein the chain transfer agent (D) is 1-butanol. [7] A method for producing polybutylene carbonate according to any one of [1] to [6] above, wherein the ratio of structural units consisting of an ether skeleton in the polybutylene carbonate obtained in step 1 is 15 mol% or less. [8] A method for producing polybutylene carbonate according to any one of [1] to [7] above, further comprising step 2 of removing catalyst (B) from the reaction solution. [9] A method for producing a sintering paste composition, comprising step P of adding metal particles (E) and a solvent (F) to polybutylene carbonate obtained by the method for producing polybutylene carbonate described in [7] or [8] above.

[10] A method for producing a binder composition, comprising step 1 of polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate.

[0011] The present invention provides a method for producing polybutylene carbonate, a method for producing a sintering paste composition, and a method for producing a binder composition, which produce polybutylene carbonate that has excellent catalyst removal properties, a low content ratio of structural units consisting of an ether skeleton, and low carbon residue during heating.

[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, the method for producing polybutylene carbonate according to one or more embodiments of the present invention may be referred to as "the method for producing polybutylene carbonate of this embodiment."

[0015] [Method for Producing Polybutylene Carbonate] The method for producing polybutylene carbonate according to this embodiment includes step 1, which involves polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce a reaction solution containing polybutylene carbonate. Hereinafter, the solvent (A) containing methylbenzene may be simply referred to as "solvent (A)," and the catalyst (B) containing zinc glutarate may be simply referred to as "catalyst (B)."

[0016] In step 1 described above, a reaction solution containing polybutylene carbonate with a low content of structural units consisting of an ether skeleton (hereinafter sometimes referred to as "ether units") is produced by polymerizing butylene oxide (C) and carbon dioxide in solvent (A). The polybutylene carbonate contained in the above reaction solution has a lower content of ether units compared to polybutylene carbonate produced by a bulk polymerization method that does not use a solvent. Therefore, when the above polybutylene carbonate is used in a sintering paste composition, etc., the amount of residual carbon during heating is reduced. Furthermore, in the above reaction solution, the catalyst (B) settles rapidly in the reaction solution, resulting in excellent removal of the catalyst (B).

[0017] The reason why the proportion of ether units in the polybutylene carbonate produced by the above-described method for producing polybutylene carbonate is small is not limited to this, but one possible reason is as follows. In other words, since the above polymerization is a copolymerization reaction between monomer and carbon dioxide, the concentration of carbon dioxide in the solution increases as carbon dioxide dissolves in the solvent, methylbenzene. Therefore, alternating polymerization of epoxide and carbon dioxide proceeds more easily, and the progress of the reaction by epoxide alone is suppressed, and as a result it is presumed that the proportion of ether units decreases. In addition, butylene oxide (C) has relatively high compatibility with methylbenzene, and the produced polybutylene carbonate is also easily soluble in methylbenzene, so it is presumed that in the above-described method for producing polybutylene carbonate, catalyst (B) settles rapidly, improving the removeability of catalyst (B). The details of each step in the method for producing polybutylene carbonate of this embodiment and the materials used in each step will be described below.

[0018] <Solvent (A) containing methylbenzene> The methylbenzene contained in solvent (A) used in step 1 above is a compound that is liquid at room temperature (23°C) and has a structure in which one or more hydrogen atoms of carbon constituting the benzene ring are replaced with methyl groups, and exhibits relatively high compatibility with butylene oxide (C) and the product polybutylene carbonate used in step 1 above. Examples of the methylbenzene include toluene and xylene. The xylene may be o-dimethylbenzene, m-dimethylbenzene, or p-dimethylbenzene. Among the methylbenzenes, toluene is preferred from the viewpoint of concentration efficiency in volatilizing the solvent after the production of polybutylene carbonate, and from the viewpoint of being able to easily remove the solvent before the thermal decomposition of polybutylene carbonate begins when sintering metal particles. Solvent (A) may contain one type of solvent or multiple types, but it is preferable that solvent (A) contains toluene alone.

[0019] The methylbenzene content in solvent (A) is preferably as high as possible from the viewpoint of making it easier to reduce the ether unit content of the resulting polybutylene carbonate and from the viewpoint of catalyst removal, for example, 90% by mass or more, or 95% by mass or more. There is no particular upper limit to the above content, and it may be 100% by mass. Impurities that are inevitably contained in the methylbenzene may remain, but from the viewpoint of making it easier to increase the purity of the product, from the viewpoint of catalyst removal, and from the viewpoint of reducing the content of structural units consisting of an ether skeleton, it is preferable that the content be as low as possible, for example, 1% by mass or less, or 0.1% by mass or less.

[0020] <Catalyst (B) containing zinc glutarate> The catalyst (B) used in step 1 above contains zinc glutarate. Zinc glutarate exhibits high polymerization activity in the polymerization reaction between butylene oxide (C) and carbon dioxide. Catalyst (B) may also contain metal catalysts other than zinc glutarate. Examples of metal catalysts other than zinc glutarate include metal salen complex catalysts, complex metal cyanide complex catalysts (DMC catalysts), and organometallic catalysts that do not contain zinc glutarate.

[0021] The zinc glutarate content in catalyst (B) is preferably as high as possible from the viewpoint of increasing the activity for polymerization reactions, for example, 90% by mass or more, or 95% by mass or more. There is no particular upper limit to the above content, and it may be 100% by mass. Impurities that are inevitably contained in the zinc glutarate may remain, but from the viewpoint of making it easier to increase the purity of the product and increasing the activity for polymerization reactions, it is preferable that the content be as small as possible, for example, 1% by mass or less, or 0.1% by mass or less.

[0022] 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).

[0023] <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).

[0024] <Chain Transfer Agent (D)> In step 1 above, an optional component that can be used is a chain transfer agent (D). 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. 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.

[0025] <Step 1> In Step 1 above, butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce a reaction solution containing polybutylene carbonate. Except for using specific components (A) to (C) (i.e., a solvent (A) containing methylbenzene, a catalyst (B) containing zinc glutarate, and butylene oxide (C)), the conditions for the polymerization reaction can be, for example, those described in International Publication No. 2011 / 142259.

[0026] 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 solvent (A), a catalyst (B), butylene oxide (C), and at least one of a co-catalyst and chain transfer agent (D) used as needed into an autoclave, mixing them, and then injecting carbon dioxide under pressure into the resulting mixture to carry out the reaction. In step 1 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 butylene oxide (C), from the viewpoint of reactivity.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In step 1, the mass of catalyst (B) per 100 parts by mass of butylene oxide (C) 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, from the viewpoint of reactivity. In step 1, the mass of zinc glutarate as catalyst (B) per 100 parts by mass of butylene oxide (C) is preferably 0.0009 to 50 parts by mass, more preferably 0.009 to 45 parts by mass, even more preferably 0.09 to 40 parts by mass, and even more preferably 0.9 to 35 parts by mass, from the same viewpoint.

[0032] In step 1, from the viewpoint of ease of adjusting the viscosity of the solution after polymerization and ease of adjusting the molecular weight after polymerization, 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.

[0033] <Step 2> The method for producing polybutylene carbonate according to this embodiment may further include step 2, which involves removing catalyst (B) from the reaction solution. By including step 2, the amount of binder component when producing paste can be increased. In step 2, methods for removing catalyst (B) from the reaction solution include, for example, allowing the reaction solution to stand for a predetermined time to allow catalyst (B) to settle and collecting the supernatant, or using centrifugation. In the reaction solution obtained by the method for producing polybutylene carbonate according to this embodiment, catalyst (B) settles more rapidly than when a solvent that does not contain methylbenzene is used as the solvent. In step 2, the time for allowing the reaction solution to stand to allow catalyst (B) to settle is, for example, 30 minutes to 3 hours, or it may be 30 minutes to 2 hours, or 30 minutes to 1.5 hours.

[0034] After the polymerization reaction is complete, polybutylene carbonate can be extracted by known methods after performing any known post-treatment procedures. The obtained polybutylene carbonate may also be purified if necessary.

[0035] <Polybutylene Carbonate> The polybutylene carbonate manufacturing method of this embodiment produces polybutylene carbonate having the following physical properties. The polybutylene carbonate functions as a binder resin in the binder composition and firing paste composition described later. When polybutylene carbonate is used in the firing paste composition, it plays a role in improving the shape retention, flexibility, and adhesion to the joined members of the firing paste composition and the firing material formed by processing the firing paste composition.

[0036] (Content ratio of ether units in polybutylene carbonate) The ratio of structural units consisting of an ether skeleton 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 is１ It is measured by nuclear magnetic resonance spectroscopy using H-NMR, specifically by the method described in the examples.

[0037] (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, even 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, even 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 is within the above range, a better balance between shape retention and flexibility of the fired material formed from the firing paste composition is more likely to be achieved. The mass-average molecular weight (Mw) and number-average molecular weight (Mn) refer to values ​​on a standard polystyrene basis measured by gel permeation chromatography (GPC). Mw can be measured by the method described in the examples.

[0038] [Method for Producing Binder Composition] The method for producing the binder composition of this embodiment includes step 1, in which butylene oxide (C) and carbon dioxide are polymerized in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate. The above method for producing the binder composition includes step 1, which is the same as described above. As described above, step 1 produces polybutylene carbonate with a low ether unit content. In addition, by performing polymerization in step 1, the catalyst (B) becomes easier to remove.

[0039] The method for producing the binder composition of this embodiment preferably includes a step 2 for removing the catalyst. The details of steps 1 and 2 are the same as those described for the method for producing polybutylene carbonate.

[0040] The method for producing a binder composition of the present embodiment may further include a step 3 of removing the solvent (A) after removing the catalyst (B) from the reaction solution in step 2.

[0041] The method for producing a binder composition of the present embodiment may further include a step 4 of adding another solvent different from the solvent (A) to obtain the binder composition after the step 3. Further, if it is permissible when considering the application, usage environment and the like of the binder composition, the reaction solution after removing the catalyst (B) in the step 2 may be used as a binder composition containing the solvent (A) including methylbenzene and polybutylene carbonate. In the former case, it is easy to combine a solvent suitable for the application and usage environment with polybutylene carbonate. In the latter case, the production process is simplified. In any case, the binder composition can be stored in a container or distributed as an intermediate product used as a raw material for a final product (for example, a sintering paste composition described later).

[0042] [Method for Producing Sintering Paste Composition] The method for producing a sintering paste composition of the present embodiment includes a step P of adding metal particles (E) and a solvent (F) to the polybutylene carbonate obtained by any one of the above methods for producing polybutylene carbonate. As described above, the polybutylene carbonate obtained by the method for producing polybutylene carbonate of the present embodiment (more specifically, the polybutylene carbonate obtained through the above steps 1 to 3) has a small content ratio of ether units as described above. Therefore, when the sintering paste composition obtained by adding the metal particles (E) and the solvent (F) to the above polybutylene carbonate is sintered, the generation of residual carbon derived from ether units can be reduced.

[0043] In the step P described above, other optional components used as necessary may be further added. In the step P described above, polybutylene carbonate, metal particles (E), a solvent (F), and other optional components used as necessary are mixed. There are no particular limitations on the method for mixing each component, and for example, a known mixing method using a mixing apparatus such as a rotation-revolution stirrer, kneader, three-roll mill, ball mill, sand mill, planetary mixer, paint shaker, homomixer, homodisper, homogenizer, or ultrasonic disperser can be employed.

[0044] <Firing Paste Composition> The firing paste composition obtained by the method for producing a sintering paste composition of the present embodiment contains polybutylene carbonate, metal particles (E), and a solvent (F). The firing paste composition described above is used for joining members to be joined together. Specifically, it is used in a joining method for forming a metal sintered layer that joins members to be joined together, by interposing the firing paste composition or a fired material formed by processing the firing paste composition, for example in a film form, between the members to be joined, heating them while applying pressure, and firing the joining material.

[0045] Since the firing paste composition described above contains polybutylene carbonate as a binder, it is excellent in low-temperature sinterability and dispersion stability, and leaves little residual carbon after firing.

[0046] Hereinafter, each component contained in the firing paste composition obtained by the method for producing a sintering paste composition of the present embodiment will be described.

[0047] (Metal Particles (E)) When the firing paste composition described above is fired, the metal particles (E) form a metal sintered layer that joins members to be joined together.

[0048] Examples of metal particles (E) 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. Metal particles (E) may be used alone or in combination of two or more. 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.

[0049] From the viewpoint of low-temperature sinterability, the metal particles (E) 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.

[0050] From the viewpoint of low-temperature sinterability, the metal particles (E) 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 (E) may be 0.1 nm or more. In this specification, the particle diameter of the metal particles (E) refers to the equivalent circle diameter corresponding to the projected area of ​​the metal particles (E). The projected area of ​​the metal particles (E) 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 (E) refers to the particle diameter of the primary particles.

[0051] The shape of the metal particles (E) 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.

[0052] The metal particles (E) may be pre-dispersed in a solvent. A high-boiling point solvent such as isobornylcyclohexanol or decyl alcohol is preferred as the solvent for dispersing the metal particles (E). The boiling point of the high-boiling point solvent is, for example, 200 to 350°C.

[0053] The surface of the metal particles (E) may be coated with an organic substance. The surface of the metal particles (E) coated with an organic substance has improved affinity with the binder resin, thus suppressing aggregation of the metal particles (E) in the baking paste composition and allowing for more uniform dispersion. When the surface of the metal particles (E) is coated with an organic substance, the mass and particle size of the metal particles (E) include the value of the coating.

[0054] The content of metal particles (E) 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 (F), from the viewpoint of the fusion properties of the metal particles (E) during baking and from the viewpoint of making it easier to ensure the content of the binder resin.

[0055] The polybutylene carbonate content 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 (F), from the viewpoint of maintaining the shape of the firing material formed by processing the firing paste composition, and from the viewpoint of easily ensuring a sufficient content of metal particles (E).

[0056] In the above-mentioned paste composition for firing, the mass ratio of metal particles (E) to polybutylene carbonate [metal particles (E) / polybutylene carbonate] is preferably 1 / 5 to 50 / 1 from the viewpoint of bonding strength and shape retention of the fired material.

[0057] (Solvent (F)) The solvent (F) contained in the above-mentioned paste composition for firing serves to disperse the metal particles (E) and polybutylene carbonate. Solvent (F) may be used alone or in combination of two or more types.

[0058] The boiling point of solvent (F) is not particularly limited, but is preferably 65 to 350°C. If the boiling point of solvent (F) is above the lower limit, the volatilization of solvent (F) during the manufacture and storage of the firing paste composition is suppressed, resulting in excellent handling. If the boiling point of solvent (F) is below the upper limit, the solvent is easily volatilized after application, making it easier to obtain a firing material of the desired shape. Furthermore, it is easier to suppress the residue of solvent (F) after drying and firing of the firing paste composition. Note that the boiling point of solvent (F) is the boiling point at 1 atmosphere (101325 Pa).

[0059] Examples of solvents (F) include ketones such as methyl ethyl ketone (2-butanone), methyl isobutyl ketone, cyclohexanone, acetylacetone, and isophorone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; isopropanol, butanol, cyclohexanol, 1-decanol, and isoborn. Examples include alcohols such as rucyclohexanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers or glycol ether acetates such as butyl carbitol, propylene glycol monomethyl ether acetate, butyl carbitol acetate (diethylene glycol monobutyl ether acetate), and ethyl carbitol acetate (diethylene glycol monoethyl ether acetate); cellosolve acetates; sulfoxides such as dimethyl sulfoxide; and amides such as dimethylformamide and dimethylacetamide. Among these, one or more selected from the group consisting of isophorone (boiling point: 215°C), 1-decanol (boiling point: 233°C), isobornylcyclohexanol (boiling point: 318°C), butyl carbitol acetate (boiling point: 245°C), and ethyl carbitol acetate (boiling point: 217°C), which have a boiling point of 200°C or higher, are preferred.

[0060] The solvent (F) content in the above-mentioned baking paste composition is preferably 5 to 50% by mass relative to the total mass (100% by mass) of the baking paste composition. When the solvent (F) content is within this range, the dispersion stability and coating suitability of the baking paste composition tend to be better. In addition, it is easier to suppress the residue of solvent (F) after drying and baking of the baking paste composition.

[0061] (Other Optional Components) The above-mentioned baking paste composition may contain other optional components as needed. Examples of other optional components include resins other than polybutylene carbonate, dispersants, plasticizers, tackifiers, preservatives, defoamers, thermal decomposition accelerators, antioxidants, etc. 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.

[0062] The total content of polybutylene carbonate, metal particles (E), and solvent (F) in the above-mentioned paste composition for firing is preferably 90 to 100% by mass.

[0063] <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.

[0064] 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.

[0065] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The measurement and evaluation of each physical property in the examples and comparative examples described later were carried out in the following procedure.

[0066] [ 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. ３ Measurements were performed using a solution containing 0.03 volume% tetramethylsilane. From the measurement results, the conversion rate to polymer (mol%) was calculated based on the ratio of residual monomer to generated polymer. In addition, based on the measurement results, the ratio of polybutylene carbonate (PBC) in the product, the ratio of cyclic carbonate (CC) in the product, and the ratio of ether units (EU) in the generated polybutylene carbonate were calculated (all units are in mol%).

[0067] [Measurement of Mass-Average Molecular Weight (Mw)] The mass-average molecular weight (Mw) of the polybutylene carbonate obtained in each example and comparative example was measured using a gel permeation chromatograph (Tosoh Corporation, product name "HLC-8320") under the following conditions, and was measured in terms of standard polystyrene equivalent. <GPC Measurement Conditions> ・Column: "TSK guard column SuperH-H", "TSK gel SuperHM-H", "TSK gel SuperHM-H", "TSK gel SuperH2000" (all manufactured by Tosoh Corporation) linked in sequence ・Column temperature: 40℃ ・Developing solvent: Tetrahydrofuran (polymer concentration 1% by mass) ・Injection volume: 20 μl ・Flow rate: 0.6 mL / min ・Detector: Differential refractometer ・Standard sample: Polystyrene

[0068] [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 mixture was then dried in a vacuum dryer at 120°C for 5 hours to obtain an organozinc compound (zinc glutarate). This powder was used as a catalyst (B) in the production of polybutylene carbonate.

[0069] [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 4.02 g of toluene to obtain a mixture (monomer concentration: 42% by mass). Next, the system of a 50 mL autoclave equipped with a stirrer, gas inlet tube 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 4 MPa. After that, the temperature was raised to 60°C, and the polymerization reaction was carried out for 4 hours while replenishing the carbon dioxide consumed by the reaction. After the reaction was completed, the autoclave was cooled and depressurized, and toluene was added in an amount twice the weight of the reaction solution to dilute it. After the reaction solution was allowed to stand for 1 hour, the supernatant was collected to remove catalyst (B). The obtained solution was dried to obtain the product, polybutylene carbonate.

[0070] [Example 2] Polymerization was carried out in the same manner as in Example 1, except that the amount of toluene used was changed to 7.48 g, the polymerization temperature was changed to 70°C, and the reaction time was changed to 2 hours, to obtain polybutylene carbonate.

[0071] [Example 3] Polymerization was carried out in the same manner as in Example 2, except that the amount of toluene used was changed to 4.69 g, to obtain polybutylene carbonate.

[0072] [Example 4] Polymerization was carried out in the same manner as in Example 3, except that the amount of zinc glutarate used was changed to 0.291 g, to obtain polybutylene carbonate.

[0073] [Example 5] Polymerization was carried out in the same manner as in Example 2, except that the reactor was a 2 L autoclave, the amount of 1,2-butylene oxide used was changed to 415 g, the amount of toluene used to 1075 g, and the amount of zinc glutarate used to 83 g, and the reaction time was set to 4 hours, to obtain polybutylene carbonate.

[0074] [Example 6] Polymerization was carried out in the same manner as in Example 5, 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.

[0075] [Comparative Example 1] Polymerization was carried out in the same manner as in Example 2, except that ethyl acetate was used instead of toluene, to obtain polybutylene carbonate.

[0076] [Comparative Example 2] Polymerization was carried out in the same manner as in Example 2, except that methyl ethyl ketone was used instead of toluene, to obtain polybutylene carbonate.

[0077] [Comparative Example 3] Polymerization was carried out in the same procedure as in Example 2, except that no solvent was used and the reaction time was changed to 1 hour, to obtain polybutylene carbonate.

[0078] Tables 1-1 and 1-2 show the materials used in each example and comparative example, their quantities, polymerization conditions, and the measurement results of the obtained polybutylene carbonate.

[0079] [Evaluation of Polybutylene Carbonate] The polybutylene carbonate obtained above was evaluated by the following method. The results are shown in Table 1-2.

[0080] [Catalyst Removal Performance] A test solution was prepared by dissolving the polybutylene carbonate obtained in the examples and comparative examples in toluene. At this time, the mass ratio of polybutylene carbonate to the mass of the test solution was set to 1% by mass. Then, 20% by mass of zinc glutarate relative to the mass of solids in the test solution was added, and the mixture was stirred for 60 minutes at a rotation speed of 100 rpm using a mix rotor. The light transmittance at a position 2 cm below the liquid surface was measured using Turviscan (MICROTRAC), and the settling velocity of zinc glutarate was confirmed by measuring the time required from the cessation of stirring until the light transmittance reached 80% or more. A shorter time indicates better catalyst removal performance.

[0081] [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

[0082]

[0083]

[0084] In Tables 1-1 and 1-2, the meaning of each symbol is as follows: MEK: Methyl ethyl ketone; ZnGA: Zinc glutarate; PBC: Polybutylene carbonate; CC: Cyclic carbonate; EU: Ether unit; Mw: Mass-average molecular weight. In Table 1-1, "-" indicates that the corresponding ingredient was not included. In Table 1-2, "-" indicates that the corresponding evaluation was not performed.

[0085] As shown in Tables 1-1 and 1-2, the manufacturing methods in Examples 1 to 6, in which 1,2-butylene oxide and carbon dioxide are polymerized in toluene in the presence of zinc glutarate, resulted in a low proportion of ether units in the polybutylene carbonate produced by polymerization and low carbon residue during heating. Furthermore, the catalyst removal efficiency was good.

[0086] On the other hand, in the production method of Comparative Example 1, in which 1,2-butylene oxide and carbon dioxide were polymerized in ethyl acetate, the catalyst removal efficiency was significantly reduced. Also, in the production method of Comparative Example 2, in which 1,2-butylene oxide and carbon dioxide were polymerized in methyl ethyl ketone, the conversion rate was reduced. Furthermore, although the evaluation of the ether ratio in the polybutylene carbonate produced by polymerization and the residual carbon during heating were equivalent to those of the Examples, the catalyst removal efficiency was inferior to that of the production methods of the Examples. Moreover, in the production method of Comparative Example 3, in which 1,2-butylene oxide and carbon dioxide were polymerized without a solvent, the ratio of ether units in the polybutylene carbonate produced by polymerization was significantly higher than that of Examples 1 to 6, and residual carbon was present during heating.

[0087] From the above results, it can be seen that the method for producing polybutylene carbonate according to this embodiment, which has step 1 of polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce a reaction solution containing polybutylene carbonate, has excellent catalyst removal properties, produces polybutylene carbonate with a low ether unit content, and produces less carbon residue during heating.

Claims

1. A method for producing polybutylene carbonate, comprising step 1 of polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce a reaction solution containing polybutylene carbonate.

2. The method for producing polybutylene carbonate according to claim 1, 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.

3. The method for producing polybutylene carbonate according to claim 1 or 2, wherein in step 1, the mass of catalyst (B) per 100 parts by mass of butylene oxide (C) is 0.001 to 50 parts by mass.

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

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

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

7. The method for producing polybutylene carbonate according to claim 1 or 2, wherein the ratio of structural units consisting of an ether skeleton in the polybutylene carbonate obtained in step 1 is 15 mol% or less.

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

9. A method for producing a sintering paste composition, comprising step P of adding metal particles (E) and a solvent (F) to polybutylene carbonate obtained by the method for producing polybutylene carbonate according to claim 7.

10. A method for producing a binder composition, comprising step 1 of polymerizing butylene oxide (C) and carbon dioxide in a solvent (A) containing methylbenzene in the presence of a catalyst (B) containing zinc glutarate to produce polybutylene carbonate.

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