JP7512658B2 - Compound manufacturing method, compound masterbatch, compound, molded body, and cured product of compound - Google Patents

Description

The present invention relates to a method for producing a compound, a masterbatch for the compound, the compound, a molded body, and a cured product of the compound.

Compounds containing metal powder and resin compositions are used as raw materials for a variety of industrial products, depending on the physical properties of the metal powder. For example, compounds are used as raw materials for inductors, sealing materials, electromagnetic shields (EMI shields), bonded magnets, etc. (see Patent Document 1 below).

JP 2014-13803 A

When manufacturing industrial products from a compound, the compound is supplied and filled into a mold, and parts such as coils are embedded in the compound inside the mold. These processes require the compound to have good fluidity. However, the fluidity of the compound is easily reduced when the compound is stored for a long time. Therefore, when manufacturing industrial products using a compound that has been stored for a long time, there is a problem that it becomes difficult to supply and fill the compound into a mold. To prevent such problems from occurring, the compound is required to have a property that makes it difficult for the fluidity to deteriorate during storage (storage stability). Furthermore, when a molded body made from the compound is used as an industrial product, the molded body is required to have high mechanical strength after the compound hardens.

The present invention aims to provide a compound manufacturing method capable of producing a molded body having excellent mechanical strength and a compound having excellent storage stability. The present invention also aims to provide a compound masterbatch that can be used to produce a molded body having excellent mechanical strength and a compound having excellent storage stability, a compound, a molded body, and a cured product of the compound that uses the masterbatch.

A method for producing a compound according to one aspect of the present invention includes a step of preparing a master batch by mixing a urea-based curing accelerator and a curing agent, and a step of mixing the master batch, a metal element-containing powder, and a thermosetting resin.

In the method for producing the compound according to one aspect of the present invention, the thermosetting resin may contain an epoxy resin. The thermosetting resin may further contain a phenolic resin. Furthermore, the epoxy resin may contain at least one selected from the group consisting of biphenylene aralkyl type epoxy resins and orthocresol novolac type epoxy resins.

In the method for producing the compound according to one aspect of the present invention, the curing agent may contain a phenolic resin.

In the method for producing the compound according to one aspect of the present invention, the mass ratio of the curing agent to the urea-based curing accelerator in the master batch may be 3.4 to 5.0.

In the method for producing the compound according to one aspect of the present invention, the content of the metal element-containing powder in the compound may be 90% by mass or more and less than 100% by mass based on the total amount of the compound.

In the method for producing the compound according to one aspect of the present invention, the thermosetting resin may include an epoxy resin, and the content of the urea-based curing accelerator in the compound may be 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the epoxy resin.

In one aspect of the method for producing the compound according to the present invention, in the step of preparing the master batch, the curing agent may be mixed while being heated to a temperature at which the curing agent melts.

The compound masterbatch according to one aspect of the present invention is a mixture of a urea-based curing accelerator and a curing agent.

In the compound masterbatch according to one aspect of the present invention, the curing agent may contain a phenolic resin.

In the compound master batch according to one aspect of the present invention, the mass ratio of the curing agent to the urea-based curing accelerator may be 3.4 to 5.0.

The compound according to one aspect of the present invention contains the compound master batch, a metal element-containing powder, and a thermosetting resin.

In the compound according to one aspect of the present invention, the thermosetting resin may contain an epoxy resin. The thermosetting resin may further contain a phenolic resin. Furthermore, the epoxy resin may contain at least one selected from the group consisting of biphenylene aralkyl type epoxy resins and orthocresol novolac type epoxy resins.

In the compound according to one aspect of the present invention, the content of the metal element-containing powder may be 90% by mass or more and less than 100% by mass.

In the compound according to one aspect of the present invention, the thermosetting resin may include an epoxy resin, and the content of the urea-based curing accelerator may be 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the epoxy resin.

A molded article according to one aspect of the present invention contains the above compound.

The cured product according to one aspect of the present invention is a cured product of the above compound.

According to the present invention, it is possible to provide a compound manufacturing method that can produce a molded body having excellent mechanical strength and can produce a compound with excellent storage stability. The present invention also provides a compound masterbatch that can produce a molded body having excellent mechanical strength and can be used to obtain a compound with excellent storage stability, a compound, a molded body, and a cured product of the compound that uses the masterbatch.

The following describes preferred embodiments of the present invention. However, the present invention is not limited to the following embodiments.

<Outline of compound manufacturing method>
The method for producing the compound according to this embodiment includes a process for preparing a master batch by mixing a urea-based curing accelerator and a curing agent (hereinafter also referred to as a "master batch preparation process"), and a process for mixing the master batch, a metal element-containing powder, and a thermosetting resin (hereinafter also referred to as a "compound preparation process").

According to the above manufacturing method, a molded body having excellent mechanical strength can be produced, and a compound having excellent storage stability can be produced. The inventors speculate that the reason for this effect is as follows. The urea-based curing accelerator has the property that the accelerator itself cleaves when the temperature reaches a certain level or higher, and exhibits a curing acceleration ability. And, since the curing acceleration ability is latent before cleavage, even if the compound is stored for a long time, the curing reaction of the thermosetting resin is unlikely to proceed, and the fluidity is unlikely to deteriorate. Therefore, by using a urea-based curing accelerator, a compound having excellent storage stability can be produced. In addition, when an imidazole-based curing accelerator is used, the curing reaction easily proceeds at room temperature, so sufficient storage stability cannot be obtained. In addition, imidazole-based curing accelerators with latent ability are known, but when a urea-based curing accelerator is used in a compound, better storage stability can be obtained than when an imidazole-based latent curing accelerator is used. On the other hand, the present inventors have found that the use of a urea-based curing accelerator improves the storage stability of the compound, but the mechanical strength (bending strength, etc.) of the molded body tends to decrease. This is presumably because the compatibility between the thermosetting resin and the urea-based curing accelerator is not necessarily high, and the urea-based curing accelerator is insufficiently dispersed in the compound, resulting in uneven distribution and uneven progress of curing. In contrast, according to the above-mentioned manufacturing method, the urea-based curing accelerator and the curing agent are mixed in advance to prepare a master batch, which is then mixed with the metal element-containing powder and the thermosetting resin, thereby preventing uneven distribution of the urea-based curing accelerator and suppressing a decrease in the mechanical strength of the molded body. Therefore, the compound manufactured by the above-mentioned manufacturing method has excellent storage stability and can be used to produce a molded body having excellent mechanical strength.

Below, we will explain each step of the compound manufacturing method according to this embodiment.

<Masterbatch production process>
In the master batch preparation process, a urea-based curing accelerator and a curing agent are mixed to prepare a master batch. The urea-based curing accelerator and the curing agent may be mixed while being heated, or may be mixed while being heated to a temperature at which the curing agent melts. In the master batch preparation process, for example, the urea-based curing accelerator and the curing agent may be mixed with a stirrer while being heated. By the master batch preparation process, a master batch in which the urea-based curing accelerator is sufficiently dispersed in the curing agent can be obtained.

The heating temperature during mixing is adjusted appropriately depending on the type of curing agent and urea-based curing accelerator to be mixed, but from the viewpoint of further improving the dispersibility of the urea-based curing accelerator, it is preferably 140°C or higher, more preferably 150°C or higher, and even more preferably 160°C or higher.

The mixing time depends on the type of mixer, the volume of the mixer, and the amount of masterbatch produced, but is preferably, for example, 10 minutes or more, more preferably 20 minutes or more, and even more preferably 30 minutes or more. The mixing time is preferably 5 hours or less, more preferably 2 hours or less, and even more preferably 1 hour or less. A mixing time of 10 minutes or more improves the dispersibility of the urea-based curing accelerator in the masterbatch, suppresses variation in the degree of cure of the compound, and tends to further improve the mechanical strength of the molded body.

The masterbatch preparation process can be carried out, for example, by the following procedure. First, the curing agent is added to a mixing means such as an agitator, and the curing agent is melted by heating to a predetermined temperature. Next, a urea-based curing accelerator is added to the molten curing agent, and the mixture is thoroughly mixed by the mixing means while being heated. Next, the resulting mixture is removed from the mixing means and cooled. Next, if necessary, the cooled lumpy mixture is pulverized to a desired particle size to facilitate weighing and mixing when preparing the compound. In this way, the masterbatch can be obtained. However, the procedure of the masterbatch preparation process is not limited to this.

The mass ratio of the curing agent to the urea-based curing accelerator in the masterbatch (mass of curing agent/mass of urea-based curing accelerator) may be 3.4 to 5.0, 3.5 to 4.6, or 3.9 to 4.1. If the mass ratio is less than 3.4, the masterbatch tends to be insufficiently dispersed.

The urea-based curing accelerator used in the master batch preparation process may be the entire amount of the urea-based curing accelerator constituting the compound, or may be only a portion of the amount. From the viewpoint of suppressing uneven distribution of the urea-based curing accelerator in the compound, the amount of the urea-based curing accelerator used in the master batch preparation process is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 100% by mass, based on the total amount of the urea-based curing accelerator constituting the compound.

The curing agent used in the masterbatch preparation process may be the entire amount of the curing agent constituting the compound, or may be only a portion of it. Since the curing agent is less likely to be unevenly distributed in the compound compared to urea-based curing accelerators, a portion of the curing agent constituting the compound may be blended in the masterbatch preparation process, and the remainder may be blended in a subsequent process. In this case, it is easy to adjust the content of the curing agent in the masterbatch and the compound, and the amount of processing in the masterbatch preparation process is reduced, improving workability.

<Compound manufacturing process>
In the compound preparation step, the master batch, the metal element-containing powder, and the thermosetting resin are mixed. The mixed powder obtained by mixing may be kneaded with a kneader, roll, or the like. By heating and mixing the master batch, the metal element-containing powder, and the thermosetting resin, the master batch and the thermosetting resin adhere to a part or the whole of the surface of the metal element-containing particles constituting the metal element-containing powder to cover the particles, and a part or the whole of the resin such as the epoxy resin in the thermosetting resin becomes a semi-cured product. As a result, a compound is obtained. In the compound preparation step, in addition to the master batch, the metal element-containing powder, and the thermosetting resin, other components constituting the compound may be mixed. Examples of the other components include a coupling agent, a release agent, and an additive. In this specification, the remaining components (non-volatile components) of the components constituting the compound, excluding the metal element-containing powder and the organic solvent used as necessary, may be referred to as a resin composition in some cases. The compound may be obtained by further adding a release agent to the powder obtained by heating and mixing the master batch, the metal element-containing powder, and the thermosetting resin. The resin composition and the release agent may be mixed in advance.

In the kneading, components such as the master batch, metal element-containing powder, thermosetting resin, and coupling agent may be kneaded in a tank. After the metal element-containing powder and coupling agent are charged into the tank and mixed, the master batch and thermosetting resin may be charged into the tank and the raw materials in the tank may be kneaded. A mixed powder of the master batch and thermosetting resin (resin mixed powder) may be prepared in advance, and then the metal element-containing powder and coupling agent may be kneaded to prepare a metal mixed powder, and then the metal mixed powder and the above-mentioned resin mixed powder may be kneaded.

The kneading time depends on the type of kneading machine, the volume of the kneading machine, and the amount of compound produced, but is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 3 minutes or more. The kneading time is preferably 20 minutes or less, more preferably 15 minutes or less, and even more preferably 10 minutes or less. If the kneading time is less than 1 minute, the kneading is insufficient, the moldability of the compound is impaired, and the degree of hardening of the compound may vary. If the kneading time exceeds 20 minutes, for example, the hardening of the resin composition (e.g., epoxy resin and phenolic resin) progresses in the tank, and the fluidity and moldability of the compound are easily impaired. When the raw materials in the tank are kneaded with a kneader while being heated, the heating temperature may be, for example, a temperature at which a semi-cured product such as epoxy resin (B-stage epoxy resin) is generated and the generation of a hardened product such as epoxy resin (C-stage epoxy resin) is suppressed. The heating temperature may be a temperature lower than the activation temperature of the hardening accelerator. The heating temperature is, for example, preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. The heating temperature is preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. When the heating temperature is within the above range, the resin composition in the tank softens and tends to coat the surfaces of the metal element-containing particles that make up the metal element-containing powder, making it easy to produce a semi-cured product such as an epoxy resin, and making it easy to suppress complete curing of the epoxy resin during kneading.

<Compound Overview>
The compound according to the present embodiment contains a master batch (master batch for compound) formed by mixing a urea-based curing accelerator and a curing agent, a metal element-containing powder, and a thermosetting resin. The metal element-containing powder is composed of a plurality (a large number) of metal element-containing particles. The metal element-containing powder may contain at least one selected from the group consisting of simple metals, alloys, and metal compounds. The thermosetting resin may contain an epoxy resin, and may further contain a curing agent such as a phenolic resin. The compound may further contain a coupling agent, a mold release agent, an additive, and the like. As described above, the resin composition is a component that may include a master batch, a thermosetting resin (epoxy resin and a curing agent, etc.), a coupling agent, a mold release agent, and an additive, and is the remaining component (non-volatile component) excluding the organic solvent and the metal element-containing powder. The resin composition may contain another resin in addition to the epoxy resin. The additive is, for example, a flame retardant, a lubricant, or the like. The compound may be a powder (compound powder).

The compound may comprise a metal element-containing powder and a resin composition attached to the surface of each metal element-containing particle constituting the metal element-containing powder. The resin composition may cover the entire surface of the particle, or may cover only a portion of the surface of the particle. The compound may comprise an uncured resin composition and a metal element-containing powder. The compound may comprise a semi-cured product of the resin composition (e.g., a B-stage resin composition) and a metal element-containing powder. The compound may comprise both an uncured resin composition and a semi-cured product of the resin composition. The compound may be composed of a metal element-containing powder and a resin composition.

The epoxy equivalent of the epoxy resin may be 180 g/eq or more and 240 g/eq or less, or 190 g/eq or more and 220 g/eq or less. If a resin with a small epoxy equivalent is used, the mechanical strength of the molded body tends to be high.

The content of the metal element-containing powder in the compound is preferably 90% by mass or more and less than 100% by mass with respect to the total mass of the compound. If the content of the metal element-containing powder is high, it becomes difficult to ensure the releasability of the molded body, and workability tends to be poor. From the viewpoint of the electrical properties of the molded body, the content of the metal element-containing powder is preferably 90% by mass or more, more preferably 92% by mass or more, even more preferably 94% by mass or more, and particularly preferably 96% by mass or more. The content of the metal element-containing powder may be 98% by mass or less.

The content of the resin composition in the compound may be 0.2% by mass or more and 10% by mass or less, and preferably 4% by mass or more and 6% by mass or less, based on the mass of the entire compound (e.g., the sum of the masses of the metal element-containing powder and the resin composition).

The content of the masterbatch in the resin composition may be 5% by mass or more and 40% by mass or less, or 10% by mass or more and 30% by mass or less, based on the total amount of the resin composition. When the content of the masterbatch is within the above range, it is easy to achieve both the storage stability of the compound and the mechanical strength of the molded body.

The average particle diameter of the metal element-containing powder is not particularly limited, but may be, for example, 1 μm or more and 300 μm or less. The average particle diameter may be measured, for example, by a particle size distribution analyzer. The shape of each metal element-containing particle constituting the metal element-containing powder is not limited, but may be, for example, spherical, flat, prismatic, or acicular. The compound may include multiple types of metal element-containing powders with different average particle diameters.

Depending on the composition or combination of the metal element-containing powder contained in the compound, the various properties such as the electromagnetic properties of the molded body formed from the compound can be freely controlled, and the molded body can be used as various industrial products or their raw materials. The industrial products manufactured using the compound may be, for example, automobiles, medical equipment, electronic devices, electrical equipment, information and communication devices, home appliances, audio equipment, and general industrial equipment. For example, when the compound contains a permanent magnet such as an Sm-Fe-N alloy or an Nd-Fe-B alloy as the metal element-containing powder, the compound may be used as a raw material for a bonded magnet. When the compound contains a soft magnetic powder such as an Fe-Si-Cr alloy or ferrite as the metal element-containing powder, the compound may be used as a raw material for an inductor (e.g., an EMI filter) or a transformer (e.g., a magnetic core). When the compound contains iron and copper as the metal element-containing powder, the molded body (e.g., a sheet) formed from the compound may be used as an electromagnetic wave shield.

<Compound composition>
(Resin composition)
The resin composition functions as a binder for the metal element-containing particles constituting the metal element-containing powder, and imparts mechanical strength to the molded body formed from the compound. For example, the resin composition contained in the compound fills between the metal element-containing particles when the compound is molded under high pressure using a mold, and binds the particles together. By curing the resin composition in the molded body, the cured resin composition binds the metal element-containing particles together more firmly, improving the mechanical strength of the molded body.

The resin composition contains a thermosetting resin. The thermosetting resin may contain an epoxy resin. The compound contains an epoxy resin, which has relatively excellent fluidity among thermosetting resins, thereby improving the fluidity, storage stability, and moldability of the compound. The compound may also contain other resins in addition to the epoxy resin. For example, the resin composition may contain at least one of a phenolic resin and a polyamide-imide resin as a thermosetting resin. When the resin composition contains both an epoxy resin and a phenolic resin, the phenolic resin may function as a curing agent for the epoxy resin. The resin contained in the compound may be only a thermosetting resin, and the thermosetting resin may be only an epoxy resin or only an epoxy resin and a phenolic resin. The resin composition may contain a thermoplastic resin. The thermoplastic resin may be, for example, at least one selected from the group consisting of an acrylic resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. The resin composition may contain both a thermosetting resin and a thermoplastic resin. The resin composition may contain a silicone resin.

Since epoxy resins have excellent fluidity among thermosetting resins, it is preferable that the resin composition contains an epoxy resin. The epoxy resin may be, for example, a resin having two or more epoxy groups in one molecule.

Epoxy resins include, for example, biphenyl type epoxy resins, stilbene type epoxy resins, diphenylmethane type epoxy resins, sulfur atom-containing epoxy resins, novolac type epoxy resins, dicyclopentadiene type epoxy resins, salicylaldehyde type epoxy resins, naphthol and phenol copolymer type epoxy resins, epoxidized products of aralkyl type phenolic resins, bisphenol type epoxy resins, epoxy resins containing a bisphenol skeleton, glycidyl ether type epoxy resins of alcohols, glycidyl ether type epoxy resins of paraxylylene and/or metaxylylene modified phenolic resins, glycidyl ether type epoxy resins of terpene modified phenolic resins, etc. The epoxy resin may be at least one selected from the group consisting of glycidyl ether type epoxy resins, cyclopentadiene type epoxy resins, glycidyl ether type epoxy resins of polycyclic aromatic ring modified phenolic resins, glycidyl ether type epoxy resins of naphthalene ring-containing phenolic resins, glycidyl ester type epoxy resins, glycidyl or methylglycidyl type epoxy resins, alicyclic type epoxy resins, halogenated phenol novolac type epoxy resins, orthocresol novolac type epoxy resins, hydroquinone type epoxy resins, trimethylolpropane type epoxy resins, and linear aliphatic epoxy resins obtained by oxidizing olefin bonds with a peracid such as peracetic acid.

In terms of excellent fluidity, the epoxy resin may be at least one selected from the group consisting of biphenyl type epoxy resins, orthocresol novolac type epoxy resins, phenol novolac type epoxy resins, bisphenol type epoxy resins, epoxy resins having a bisphenol skeleton, salicylaldehyde novolac type epoxy resins, and naphthol novolac type epoxy resins.

From the viewpoint of strength of the cured product, the epoxy resin may be at least one selected from the group consisting of biphenylene aralkyl type epoxy resins and orthocresol novolac type epoxy resins.

The epoxy resin may be a crystalline epoxy resin. Although the molecular weight of the crystalline epoxy resin is relatively low, the crystalline epoxy resin has a relatively high melting point and excellent fluidity. The crystalline epoxy resin (highly crystalline epoxy resin) may be, for example, at least one selected from the group consisting of hydroquinone type epoxy resin, bisphenol type epoxy resin, thioether type epoxy resin, and biphenyl type epoxy resin. Commercially available crystalline epoxy resins include, for example, Epicron 860, Epicron 1050, Epicron 1055, Epicron 2050, Epicron 3050, Epicron 4050, Epicron 7050, Epicron HM-091, Epicron HM-101, Epicron N-730A, Epicron N-740, Epicron N-770, Epicron N-775, and Epicron N-86. 5, Epicron HP-4032D, Epicron HP-7200L, Epicron HP-7200, Epicron HP-7200H, Epicron HP-7200HH, Epicron HP-7200HHH, Epicron HP-4700, Epicron HP-4710, Epicron HP-4770, Epicron HP-5000, Epicron HP-6000, N500P-2, and N500P -10 (all trade names of DIC Corporation), NC-3000, NC-3000-L, NC-3000-H, NC-3100, CER-3000-L, NC-2000-L, XD-1000, NC-7000-L, NC-7300-L, EPPN-501H, EPPN-501HY, EPPN-502H, EOCN-1020, EOCN-102S, EOCN-103S, It may be at least one selected from the group consisting of EOCN-104S, CER-1020, EPPN-201, BREN-S, BREN-10S (all trade names manufactured by Nippon Kayaku Co., Ltd.), YX-4000, YX-4000H, YL4121H, and YX-8800 (all trade names manufactured by Mitsubishi Chemical Corporation), and VG-3101L (trade name manufactured by Printec Co., Ltd.).

The resin composition may contain one type of epoxy resin from among the above. The resin composition may contain multiple types of epoxy resins from among the above. Among the above epoxy resins, the resin composition may contain both a biphenylene aralkyl type epoxy resin (NC-3000) and a trifunctional epoxy resin (VG-3101L).

Hardeners are classified into those that harden epoxy resins at low to room temperatures, and heat-curing hardeners that harden epoxy resins when heated. Hardeners that harden epoxy resins at low to room temperatures include, for example, aliphatic polyamines, polyaminoamides, and polymercaptans. Heat-curing hardeners include, for example, aromatic polyamines, acid anhydrides, phenol novolac resins, and dicyandiamide (DICY).

When a curing agent that cures epoxy resins in the range of low to room temperature is used, the glass transition point of the cured epoxy resin is low and the cured epoxy resin tends to be soft. As a result, the molded body formed from the compound also tends to be soft. On the other hand, from the viewpoint of improving the heat resistance of the molded body, the curing agent may preferably be a heat-curing type curing agent, more preferably a phenolic resin, and even more preferably a phenolic novolac resin. In particular, by using a phenolic novolac resin as a curing agent, it is easy to obtain a cured epoxy resin with a high glass transition point. As a result, the heat resistance and mechanical strength of the molded body are easily improved.

The phenolic resin may be at least one selected from the group consisting of aralkyl-type phenolic resin, dicyclopentadiene-type phenolic resin, salicylaldehyde-type phenolic resin, novolac-type phenolic resin, copolymerized phenolic resin of benzaldehyde-type phenol and aralkyl-type phenol, paraxylylene- and/or metaxylylene-modified phenolic resin, melamine-modified phenolic resin, terpene-modified phenolic resin, dicyclopentadiene-type naphthol resin, cyclopentadiene-modified phenolic resin, polycyclic aromatic ring-modified phenolic resin, biphenyl-type phenolic resin, and triphenylmethane-type phenolic resin. The phenolic resin may be a copolymer composed of two or more of the above. As a commercially available phenolic resin, for example, Tamanol 758 manufactured by Arakawa Chemical Industries Co., Ltd. or HP-850N manufactured by Hitachi Chemical Co., Ltd. may be used.

The phenol novolac resin may be, for example, a resin obtained by condensing or co-condensing phenols and/or naphthols with aldehydes under an acid catalyst. The phenols constituting the phenol novolac resin may be, for example, at least one selected from the group consisting of phenol, cresol, xylenol, resorcin, catechol, bisphenol A, bisphenol F, phenylphenol, and aminophenol. The naphthols constituting the phenol novolac resin may be, for example, at least one selected from the group consisting of α-naphthol, β-naphthol, and dihydroxynaphthalene. The aldehydes constituting the phenol novolac resin may be, for example, at least one selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde.

The curing agent may be, for example, a compound having two phenolic hydroxyl groups in one molecule. The compound having two phenolic hydroxyl groups in one molecule may be, for example, at least one selected from the group consisting of resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenol.

The resin composition may contain one type of phenolic resin from among the above. The resin composition may contain multiple types of phenolic resins from among the above. The resin composition may contain one type of curing agent from among the above. The resin composition may contain multiple types of curing agents from among the above.

The ratio of active groups (phenolic OH groups) in the curing agent that react with epoxy groups in the epoxy resin may be preferably 0.5 to 1.5 equivalents, more preferably 0.6 to 1.4 equivalents, and even more preferably 0.8 to 1.2 equivalents per equivalent of epoxy groups in the epoxy resin. Here, the above ratio includes the active groups in the curing agent contained in the master batch. If the ratio of active groups in the curing agent is less than 0.5 equivalents, it is difficult to obtain a sufficient elastic modulus of the resulting cured product. On the other hand, if the ratio of active groups in the curing agent exceeds 1.5 equivalents, the mechanical strength of the molded product formed from the compound after curing tends to decrease. However, even if the ratio of active groups in the curing agent is outside the above range, the effects of the present invention can be obtained.

The resin composition contains a master batch. The master batch is a mixture of a urea-based curing accelerator and a curing agent. The curing agent can be the same as the curing agent used in the thermosetting resin described above.

The urea-based curing accelerator is a component that accelerates the curing of thermosetting resins. When the thermosetting resin contains an epoxy resin, the urea-based curing accelerator reacts with the epoxy resin to accelerate the curing of the epoxy resin. By using the urea-based curing accelerator in a masterbatch form, the storage stability, moldability, and demoldability of the compound are easily improved. In addition, by using the urea-based curing accelerator in a masterbatch form, the mechanical strength of molded bodies (e.g., electronic components) manufactured using the compound can be improved.

The urea-based curing accelerator is not particularly limited as long as it is a curing accelerator having a urea group, but from the viewpoint of improving storage stability, an alkylurea-based curing accelerator having an alkylurea group is preferable. Examples of alkylurea-based curing accelerators having an alkylurea group include aromatic alkylureas and aliphatic alkylureas, and commercially available products include U-CAT3512T (product name, manufactured by San-Apro Ltd., aromatic dimethylurea) and U-CAT3513N (product name, manufactured by San-Apro Ltd., aliphatic dimethylurea).

The content of the urea-based curing accelerator in the compound is not particularly limited as long as it is an amount that can provide a curing acceleration effect. However, from the viewpoint of improving the storage stability, curability, and fluidity of the compound in a well-balanced manner, the content of the urea-based curing accelerator is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, per 100 parts by mass of the epoxy resin. If the content of the urea-based curing accelerator is less than 0.1 parts by mass, it is difficult to obtain a sufficient curing acceleration effect. If the content of the urea-based curing accelerator exceeds 30 parts by mass, the storage stability of the compound is likely to decrease. However, even if the content of the urea-based curing accelerator is outside the above range, the effect of the present invention can be obtained. From the same viewpoint, the content of the urea-based curing accelerator is preferably 0.001 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the total amount of the thermosetting resin (including the curing agent contained in the master batch) contained in the compound.

The master batch and/or compound may contain other curing accelerators other than the urea-based curing accelerator, as long as the effect of the present invention is not significantly impaired. The other curing accelerators are not limited as long as they are components that accelerate the curing of the thermosetting resin. Examples of the other curing accelerators include imidazoles such as alkyl group-substituted imidazoles and benzimidazoles, and phosphorus-based curing accelerators. The other curing accelerators may be used alone or in combination of two or more.

From the viewpoint of fully obtaining the effects of the present invention, the proportion of the urea-based curing accelerator in the curing accelerator is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass, based on the total amount of the curing accelerator.

The resin composition may contain a coupling agent. The coupling agent improves the adhesion between the resin composition and the metal element-containing particles constituting the metal element-containing powder, and improves the flexibility and mechanical strength of the molded body formed from the compound. The coupling agent may be, for example, at least one selected from the group consisting of silane-based compounds (silane coupling agents), titanium-based compounds, aluminum compounds (aluminum chelates), and aluminum/zirconium-based compounds. The silane coupling agent may be, for example, at least one selected from the group consisting of epoxy silane, mercapto silane, amino silane, alkyl silane, ureido silane, acid anhydride silane, and vinyl silane. In particular, aminophenyl-based silane coupling agents are preferred. The resin composition may contain one of the above coupling agents, or may contain multiple of the above coupling agents.

The resin composition may contain a wax. The wax increases the fluidity of the compound during molding (e.g., transfer molding) of the compound and also functions as a mold release agent. The wax may be at least one of a fatty acid such as a higher fatty acid and a fatty acid ester.

Waxes include, for example, fatty acids such as montanic acid, stearic acid, 12-hydroxystearic acid, and lauric acid, or esters thereof; fatty acid salts such as zinc stearate, calcium stearate, barium stearate, aluminum stearate, magnesium stearate, calcium laurate, zinc linoleate, calcium ricinoleate, and zinc 2-ethylhexanoate; stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bislauric acid amide, distearyl adipate amide, ethylene bisoleic acid amide, dioleyl adipate amide, N-stearyl stearic acid amide, fatty acid amides such as butyl stearate, N-oleyl stearamide, N-stearyl erucamide, methylol stearamide, and methylol behenamide; fatty acid esters such as butyl stearate; alcohols such as ethylene glycol and stearyl alcohol; polyethers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and modified products thereof; polysiloxanes such as silicone oil and silicone grease; fluorine compounds such as fluorine-based oil, fluorine-based grease, and fluorine-containing resin powder; and waxes such as paraffin wax, polyethylene wax, amide wax, polypropylene wax, ester wax, carnauba wax, and microwax.

The wax content in the compound may be 0.08% by mass or more and 0.20% by mass or less, or 0.10% by mass or more and 0.15% by mass or less, based on the total amount of the compound. When the wax content is equal to or more than the lower limit of the above range, the fluidity and releasability of the compound are more likely to be improved, and when the wax content is equal to or less than the upper limit, the decrease in mechanical strength of the molded body produced using the compound is more likely to be suppressed.

For the purpose of improving the environmental safety, recyclability, moldability, and low cost of the compound, the compound may contain a flame retardant as an additive. The flame retardant may be, for example, at least one selected from the group consisting of bromine-based flame retardants, bulb flame retardants, hydrated metal compound-based flame retardants, silicone-based flame retardants, nitrogen-containing compounds, hindered amine compounds, organometallic compounds, and aromatic engineering plastics. The resin composition may contain one type of flame retardant among the above, or may contain multiple types of flame retardants among the above.

(Metal element-containing powder)
The metal element-containing powder may contain at least one selected from the group consisting of, for example, a metal element, an alloy, and a metal compound. The specific gravity (density) of the metal element-containing powder may be, for example, 5 g/cm ³ or more. The metal element-containing powder may be, for example, at least one selected from the group consisting of a metal element, an alloy, and a metal compound. The alloy may include at least one selected from the group consisting of a solid solution, a eutectic, and an intermetallic compound. The alloy may be, for example, stainless steel (Fe-Cr alloy, Fe-Ni-Cr alloy, etc.). The metal compound may be, for example, an oxide such as ferrite. The metal element-containing powder may contain one type of metal element or multiple types of metal elements. The metal element contained in the metal element-containing powder may be, for example, a base metal element, a precious metal element, a transition metal element, or a rare earth element. The compound may contain one type of metal element-containing powder, or may contain multiple types of metal element-containing powder.

The metal element-containing powder is not limited to the above composition. The metal element contained in the metal element-containing powder may be at least one selected from the group consisting of, for example, iron (Fe), copper (Cu), titanium (Ti), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), tin (Sn), chromium (Cr), barium (Ba), strontium (Sr), lead (Pb), silver (Ag), praseodymium (Pr), neodymium (Nd), samarium (Sm) and dysprosium (Dy). The metal element-containing powder may contain elements other than the metal element. The metal element-containing powder may contain, for example, oxygen (O), beryllium (Be), phosphorus (P), boron (B), or silicon (Si). The metal element-containing powder may be a magnetic powder. The metal element-containing powder may be a soft magnetic alloy or a ferromagnetic alloy. The metal element-containing powder may be, for example, a magnetic powder consisting of at least one selected from the group consisting of Fe-Si alloys, Fe-Si-Al alloys (Sendust), Fe-Ni alloys (Permalloy), Fe-Cu-Ni alloys (Permalloy), Fe-Co alloys (Permendur), Fe-Cr-Si alloys (electromagnetic stainless steel), Nd-Fe-B alloys (rare earth magnets), Sm-Fe-N alloys (rare earth magnets), Al-Ni-Co alloys (Alnico magnets), and ferrite. The ferrite may be, for example, spinel ferrite, hexagonal ferrite, or garnet ferrite. The metal element-containing powder may be a copper alloy such as a Cu-Sn alloy, a Cu-Sn-P alloy, a Cu-Ni alloy, or a Cu-Be alloy. The metal element-containing powder may contain one of the above elements and compositions, or may contain multiple of the above elements and compositions.

The metal element-containing powder may be Fe alone. The metal element-containing powder may be an alloy containing iron (Fe-based alloy). The Fe-based alloy may be, for example, an Fe-Si-Cr-based alloy or an Nd-Fe-B-based alloy. The metal element-containing powder may be at least one of an amorphous iron powder and a carbonyl iron powder. When the metal element-containing powder contains at least one of Fe alone and an Fe-based alloy, it is easy to produce a compact having a high space factor and excellent magnetic properties from the compound. The metal element-containing powder may be an Fe-amorphous alloy. As a commercially available product of Fe amorphous alloy powder, for example, at least one selected from the group consisting of AW2-08, KUAMET-6B2 (all trade names of Epson Atmix Corporation), DAP MS3, DAP MS7, DAP MSA10, DAP PB, DAP PC, DAP MKV49, DAP 410L, DAP 430L, DAP HYB series (all trade names of Daido Steel Co., Ltd.), MH45D, MH28D, MH25D, and MH20D (all trade names of Kobe Steel, Ltd.) may be used.

<Molded body>
The molded article according to the present embodiment may include the above-mentioned compound. The molded article according to the present embodiment may include a cured product of the above-mentioned compound. The molded article may consist of only the compound. The molded article may include at least one selected from the group consisting of an uncured resin composition, a semi-cured product of the resin composition (a B-stage resin composition), and a cured product of the resin composition (a C-stage resin composition).

<Method of manufacturing molded body>
The method for producing a molded body according to the present embodiment may include a step of pressurizing the compound in a mold. The method for producing a molded body may include only a step of pressurizing the compound in a mold, or may include other steps in addition to the step. The method for producing a molded body may include a first step, a second step, and a third step. Each step will be described in detail below.

In the first step, the compound is prepared using the method described above.

In the second step, the compound is pressed in a mold to obtain a molded body (B-stage molded body). Here, the resin composition fills the spaces between the individual metal element-containing particles that make up the metal element-containing powder. The resin composition then functions as a binding material (binder) to bond the metal element-containing particles together.

In the third step, the molded body is cured by heat treatment to obtain a molded body in the C stage. The heat treatment temperature may be any temperature at which the resin composition in the molded body is sufficiently cured. The heat treatment temperature may be preferably 100°C or more and 300°C or less, more preferably 150°C or more and 250°C or less. In order to suppress oxidation of the metal element-containing powder in the molded body, it is preferable to perform the heat treatment in an inert atmosphere. If the heat treatment temperature exceeds 300°C, the metal element-containing powder may be oxidized or the resin cured product may deteriorate due to the trace amount of oxygen inevitably contained in the heat treatment atmosphere. In order to sufficiently cure the resin composition while suppressing oxidation of the metal element-containing powder and deterioration of the resin cured product, the heat treatment temperature may be held for a period of preferably several minutes to 10 hours, more preferably 5 minutes to 8 hours.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

(Ingredients used)
The components used in the resin compositions of the Examples and Comparative Examples are shown below.
[Epoxy resin]
Biphenyl aralkyl type epoxy resin (epoxy equivalent: 265 to 285 g/eq)
Polyfunctional aromatic epoxy resin (epoxy equivalent: 210 g/eq)

[Curing agent]
Phenol aralkyl type phenolic resin (OH equivalent: 204-208 g/eq)
Triphenolmethane type phenolic resin (OH equivalent: 103 g/eq)

硬化促進剤Ｂ（イミダゾール系硬化促進剤）
硬化促進剤Ｃ（リン系硬化促進剤） [Curing accelerator]
Curing accelerator A (aromatic dimethylurea represented by the following formula (I), melting point: about 185° C.)

Curing accelerator B (imidazole-based curing accelerator)
Curing accelerator C (phosphorus-based curing accelerator)

[Coupling Agent]
Coupling Agent A (3-mercaptopropyltrimethoxysilane, molecular weight 196)
Coupling Agent B (8-methacryloxyoctyltrimethoxysilane, molecular weight 319)
Coupling Agent C (3-glycidoxypropyltrimethoxysilane, molecular weight 236)

[Release agent]
Release agent A (zinc laurate)
Release agent B (Montanic acid wax, melting point: approx. 99°C)

[Additive]
Silicon-containing block polymer

[Magnetic powder]
Amorphous iron powder (average particle size 24 μm)
FeSiCr iron powder (average particle size: approx. 2 μm)

Example 1
[Preparation of master batch]
4 parts by mass of a curing agent (phenol aralkyl type phenol resin) was placed in a stirrer and heated to 130 to 150° C. to melt the curing agent. 1 part by mass of a urea-based curing accelerator (aromatic dimethylurea represented by the above formula (I), product name: U-CAT3512T, manufactured by San-Apro Co., Ltd.) was added little by little to the heated and melted curing agent, and the mixture was stirred and mixed until no lumps or spots were present. The resulting mixture was discharged from the stirrer and cooled to room temperature, and then pulverized to a particle size of about 2 mm or less using a pulverizer to obtain a master batch for compounding.

[Preparation of Compound]
The master batch, epoxy resin, hardener, release agent, and additives shown in Table 1 were put into a poly bag in the amounts (unit: parts by mass) shown in the table. These materials were mixed in a poly bag for 1 minute to prepare a resin mixture. The resin mixture corresponds to all other components of the resin composition except the coupling agent. In addition, two types of magnetic powder and a coupling agent were mixed in a poly bag for 1 minute to prepare a metal powder mixture. The amorphous iron powder (average particle size 24 μm) and the FeSiCr iron powder (average particle size about 2 μm) were mixed in a ratio of amorphous iron powder:FeSiCr iron powder = 82:18 (mass ratio) when preparing the metal element-containing powder. The above resin mixture and metal powder mixture were combined and mixed for 1 minute to obtain a mixed powder of the compound.

A roll (two-roller manufactured by Kodaira Manufacturing Co., Ltd.) was heated to 90°C, and while maintaining that temperature, the mixed powder of the compound was melted and kneaded for 10 minutes. The kneaded product obtained by melting and kneading was cooled to room temperature, and then crushed with a hammer until the particle size was about 2 mm. Note that the above "melt" refers to the melting of at least a portion of the resin composition of the contents. The metal element-containing powder in the compound does not melt during the compound preparation process.

The compound of Example 1 was prepared using the above method. The content of metal element-containing powder in the compound was 96.4 mass%.

(Comparative Examples 1 to 3)
The compounds of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1, except that a master batch was not prepared, and a resin mixture was prepared by blending the epoxy resin, curing agent, curing accelerator, release agent, and additives shown in Table 1 in the blending amounts (unit: parts by mass) shown in the same table.

<Bending test: Measurement of mechanical strength>
The compounds obtained in Example 1 and Comparative Examples 1 to 3 were transfer molded under the conditions of a mold temperature of 140°C, a molding pressure of 13.5 MPa, and a molding time of 360 seconds to obtain test pieces. The dimensions of the test pieces were 80 mm long x 10 mm wide x 3.0 mm thick. A three-point support bending test was performed on the test pieces using an autograph AGS-500A manufactured by Shimadzu Corporation. In the bending test, one side of the test piece was supported by two supports F arranged at an interval of 64 mm. A load W was applied to the center position between the two supports F on the other side of the test piece. The load at which the test piece broke was measured as bending strength (unit: MPa). The bending test was performed at room temperature (25°C). The higher the bending strength value, the better the mechanical strength.

<Evaluation of storage stability>
The compounds obtained in Example 1 and Comparative Examples 1 to 3 were stored for a predetermined time (24 hours, 48 hours, 72 hours) under an environment of 25°C and 50% RH. The fluidity of the compounds before (initial) and after storage for a predetermined time was evaluated by the following method using a flow tester CFT-100 manufactured by Shimadzu Corporation. First, 7 g of the compound was molded to prepare a cylindrical tablet with a diameter of about 10 mm and a height of about 12 mm. Using this tablet, the stroke length (plunger push-in distance, unit: mm) and the minimum melt viscosity (Pa·s) were measured under conditions of 130°C, 20 seconds of preheating, and 100 kg load, and the fluidity was evaluated. The ratio (%) of the stroke length of the compound after storage for a predetermined time when the stroke length of the initial compound was taken as 100% was calculated as the stroke length retention rate. In addition, the ratio (%) of the minimum melt viscosity of the compound after storage for a specified time, when the minimum melt viscosity of the initial compound was taken as 100%, was calculated as the minimum melt viscosity retention rate. These measured values were used as indicators of fluidity. Here, it can be said that the greater the stroke length and the lower the minimum melt viscosity, the higher the fluidity. And, the smaller the change in the fluidity of the compound after storage for a specified time compared to the fluidity of the initial compound (the closer the stroke length retention rate and the minimum melt viscosity retention rate are to 100%), the better the storage stability can be determined. The results are shown in Table 1.

The compound manufacturing method according to the present invention is of great industrial value since it is possible to produce a molded article having excellent mechanical strength and a compound having excellent storage stability.

Claims (15)

A step of mixing a urea-based curing accelerator and a curing agent to prepare a master batch;
mixing the master batch, a metal element-containing powder, and a thermosetting resin;
Equipped with
the curing agent comprises a phenolic resin;
a mass ratio of the curing agent to the urea-based curing accelerator in the master batch is 3.4 to 5.0;
A method for producing a compound , wherein in the step of preparing the master batch, the components are mixed while being heated to a temperature at which the curing agent melts. The method for producing the compound according to claim 1, wherein the thermosetting resin comprises an epoxy resin. The method for producing the compound according to claim 2, wherein the thermosetting resin further comprises a phenolic resin. The method for producing a compound according to claim 2 or 3, wherein the epoxy resin comprises at least one selected from the group consisting of biphenylene aralkyl type epoxy resins and orthocresol novolac type epoxy resins. The method for producing a compound according to any one of claims 1 to 4 , wherein the content of the metal element-containing powder in the compound is 90 mass% or more and less than 100 mass% based on the total amount of the compound. The method for producing a compound according to any one of claims 1 to 5 , wherein the thermosetting resin contains an epoxy resin, and the content of the urea-based curing accelerator in the compound is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the epoxy resin. A urea-based curing accelerator and a curing agent are mixed while being heated to a temperature at which the curing agent melts ,
the curing agent comprises a phenolic resin;
A compound master batch , wherein a mass ratio of the curing agent to the urea-based curing accelerator is 3.4 to 5.0 . A compound comprising the compound masterbatch according to claim 7 , a metal element-containing powder, and a thermosetting resin. The compound of claim 8 , wherein the thermosetting resin comprises an epoxy resin. 10. The compound of claim 9 , wherein the thermosetting resin further comprises a phenolic resin. The compound according to claim 9 or 10 , wherein the epoxy resin comprises at least one selected from the group consisting of biphenylene aralkyl type epoxy resins and orthocresol novolac type epoxy resins. The compound according to any one of claims 8 to 11 , wherein the content of the metal element-containing powder is 90% by mass or more and less than 100% by mass. The compound according to any one of claims 8 to 12 , wherein the thermosetting resin contains an epoxy resin, and the content of the urea-based curing accelerator is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the epoxy resin. A molding comprising the compound according to any one of claims 8 to 13 . A cured product of the compound according to any one of claims 8 to 13 .