JP6981794B2 - Epoxy adhesive - Google Patents

Description

The present disclosure relates to epoxy adhesives.

Epoxy adhesives are generally used in a wide range of fields such as automobiles, machinery, electronic engineering, ships, space, civil engineering, and construction because of their good adhesive properties, mechanical strength, chemical resistance, and heat resistance. .. Adhesives for these applications may be required to have high reliability even under high temperature conditions. For example, adhesives for fixing between members in articles such as motors that may become hot during use are required to have high reliability under high temperature conditions.

For example, in a DC motor including a winding (for example, a copper wire) and a rotor having a commutator connected to the end of the winding, and a stator having a permanent magnet. Around the commutator, for the purpose of ensuring the reliability of the motor by preventing the electrical connection from being damaged due to the movement of the copper wire such as heat, vibration, and loosening of the copper wire during use, and the disconnection of the copper wire. The adhesive is arranged so as to fix, reinforce, and seal (potting) the winding part of the. DC motors are widely used in many applications such as automobiles, electronic engineering products, household products, and general-purpose industrial products. For example, in a DC motor used around an automobile engine, the temperature near the adhesive may be as high as about 120 ° C. or higher, so that particularly high reliability is required under high temperature conditions.

Patent Document 1 describes a composition containing a liquid bisphenol type epoxy resin, a latent curing agent, and a urea compound having a specific structure, wherein the latent curing agent consists of solid particles having an average particle size of 3 to 14 μm. Describes a one-component epoxy resin composition comprising solid particles having an average particle size of 2 to 15 μm.

Patent Document 2 is an epoxy resin composition containing an inorganic filler containing (A) epoxy resin, (B) phenol resin, (C) curing accelerator, and (D) hollow inorganic filler as essential components. The content of the hollow inorganic filler is 50% by volume or more with respect to the total composition, the content of the total inorganic filler is 68% by volume or more with respect to the total composition, and the dielectric constant of the cured product is 3. A epoxy resin composition for encapsulating a semiconductor, which is characterized by having a value of 5.5 or less, is described.

Japanese Unexamined Patent Publication No. 9-316171 Japanese Unexamined Patent Publication No. 2005-041937

As a general means for obtaining a highly heat-resistant adhesive, the use of a curable material having a high glass transition temperature (Tg) can be mentioned. The epoxy resin compositions described in Patent Documents 1 and 2 use an epoxy resin, which has a relatively high Tg. However, curable materials with high Tg often tend to be rigid and brittle, and therefore adhesives obtained with such curable materials often have the problem of cracking due to stress concentration due to external forces during use. Examples of the causes of stress concentration as described above include thermal expansion or contraction of the adhesive due to a temperature change during use of the adhesive, and vibration. However, the techniques described in Patent Documents 1 and 2 apply an adhesive in which cracks are sufficiently suppressed even when the adhesive is subjected to thermal expansion or contraction (that is, thermal shock) due to a large temperature change during use. It wasn't something to do.

One object of the present invention is to solve the above-mentioned problems and to provide an epoxy adhesive in which thermal expansion or contraction of the adhesive due to a temperature change during use of the adhesive and generation of cracks due to vibration are suppressed. And.

One aspect of the disclosure is
Contains epoxy and filler,
The epoxy contains a trifunctional or higher functional liquid epoxy.
The filler provides an epoxy adhesive containing hollow particles.
Another aspect of the disclosure is
Provided is an adhesive for fixing a winding of a motor with a DC brush, which comprises an epoxy adhesive according to one aspect of the present disclosure.

According to some aspects of the present disclosure, there is provided an epoxy adhesive that is not excessively dense and that suppresses the generation of cracks due to thermal shock during use.

It is a figure which shows the dynamic viscoelasticity measuring apparatus (DMA) measurement result in Examples 5 and 6, and Comparative Examples 1 and 2.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these aspects, and it is intended that the present invention includes any modifications that do not deviate from the spirit and scope of the claims. .. Unless otherwise specified, each measurement referred to in the present disclosure is intended to be performed by the method described in the section [Examples] or a method understood by those skilled in the art to be equivalent thereto.

<Epoxy adhesive>
One aspect of the disclosure is
Contains epoxy and filler,
The epoxy contains a trifunctional or higher functional liquid epoxy.
The filler provides an epoxy adhesive containing hollow particles.
The inclusion of the filler in the epoxy adhesive is advantageous in terms of improving the mechanical strength of the epoxy adhesive. The filler contains hollow particles. The hollow particles contribute to the good thermal impact resistance of the adhesive by providing an epoxy adhesive having a relatively low storage elastic modulus while functioning as a filler. The use of hollow particles is also advantageous in that it provides a low-density epoxy adhesive (for example, a lightweight adhesive which is advantageous in terms of energy saving when used in a moving body such as an automobile). Therefore, according to the epoxy adhesive of the present disclosure, it is possible to obtain an epoxy adhesive having desired properties in which cracks are less likely to occur even when subjected to a thermal impact without excessively increasing the density of the epoxy adhesive.

(A) Epoxy The epoxy adhesive of the present disclosure is a thermosetting adhesive, and (A) epoxy is contained in the epoxy adhesive as a thermosetting component. (A) Epoxy contains a trifunctional or higher functional liquid epoxy. In the present disclosure, the liquid epoxy means an epoxy having a viscosity of 0.01 Pa · s or more and 50 Pa · s or less at a rotation speed of ^{200 seconds-1} when measured at 70 ° C. with a conical flat plate viscometer. The trifunctional or higher functional liquid epoxy may be one kind or a combination of two or more kinds of compounds. The trifunctional or higher functional liquid epoxy contributes to increasing the Tg of the epoxy adhesive of the present disclosure. In some embodiments, the trifunctional or higher liquid epoxy also provides the advantage of lowering the viscosity of the epoxy adhesive. Further, in some embodiments, trifunctional or higher functional epoxies contribute to the realization of good adhesion performance in adhesion between adherends made of various materials due to the contribution of the large number of functional groups they possess. ..

In a preferred embodiment, the epoxy equivalent of the trifunctional or higher liquid epoxy (the number of grams of the resin containing 1 gram equivalent of the epoxy group) is about 60 or more, or about 70 or more, or about 80 from the viewpoint of availability and reactivity. From the viewpoint of heat resistance of the epoxy adhesive after curing and high Tg, it is about 1000 or less, about 500 or less, or about 300 or less.

A preferred example of a trifunctional or higher functional liquid epoxy is a glycidylamine type epoxy resin having at least one aromatic ring in one molecule from the viewpoint of satisfactorily imparting high Tg and low viscosity to the epoxy adhesive of the present disclosure. Examples thereof include glycidylphenol type epoxy resin. Examples of the glycidylamine type epoxy resin include triglycidylaminophenol type epoxy compound, triglycidylaminocresol type epoxy compound, tetraglycidyldiaminodiphenylmethane type epoxy compound, tetraglycidylmethoxylylylene diamine type epoxy compound, and tetraglycidylbisaminomethylcyclohexane type epoxy. Examples thereof include compounds, tetraglycidyl glycol uryl type epoxy compounds and the like. Examples of the glycidyl phenol type epoxy resin include phenol novolac type epoxy compounds and triphenylmethane triglycidyl ether type compounds.

A preferred example of a liquid epoxy composed of trifunctional or higher-functional aliphatics is an ether in the skeleton from the viewpoint of imparting low viscosity to the epoxy adhesive of the present disclosure and good heat resistance to some extent without reducing the crosslink density. Examples thereof include trimethiol propanetriglycidyl ether, trimethiol ethanetriglycidyl ether, castor oil modification and glycerol-modified polyglycidyl ether having a bond. Preferred examples of the tetrafunctional or higher include pentaerythritol polyglycidyl ether and sorbitol-modified polygusidyl ether. The usable ones are not limited to the above.

で表されるトリグリシジルｐ−アミノフェノール、及び下記式（２）：

で表されるトリクレジルｍ−アミノフェノールである。 A preferred example of the triglycidylaminophenol type epoxy compound is the following formula (1) :.

Triglycidyl p-aminophenol represented by, and the following formula (2):

It is a tricresyl m-aminophenol represented by.

で表されるトリグリシジルアミノクレゾールである。 A preferred example of the triglycidylaminocresol type epoxy compound is the following formula (3) :.

It is a triglycidyl aminocresol represented by.

で表されるトリフェニルメタントリグリシジルエーテルである。 A preferred example of the triphenylmethane triglycidyl ether type compound is the following formula (4) :.

It is a triphenylmethane triglycidyl ether represented by.

で表されるテトラグリシジルジアミノジフェニルメタン（４，４’−メチレンビス［Ｎ，Ｎ−ビス（オキシラニルメチル）アニリン］）である。 A preferred example of the tetraglycidyl diaminodiphenylmethane type epoxy compound is the following formula (5):

It is tetraglycidyldiaminodiphenylmethane (4,4'-methylenebis [N, N-bis (oxylanylmethyl) aniline]) represented by.

で表されるテトラグリシジルメタキシリレンジアミンである。 A preferred example of the tetraglycidylmethoxylylylenediamine type epoxy compound is the following formula (6) :.

It is a tetraglycidylmethoxylylenediamine represented by.

で表されるテトラグリシジルビスアミノメチルシクロヘキサンである。 A preferred example of the tetraglycidyl bisaminomethylcyclohexane type epoxy compound is the following formula (7):

It is tetraglycidylbisaminomethylcyclohexane represented by.

で表されるテトラグリシジルグリコールウリルである。 A preferred example of the tetraglycidyl glycol uryl type epoxy compound is the following formula (8) :.

It is a tetraglycidyl glycol uryl represented by.

（式中、ｎは２以上である。）
で表される化合物である。 Further, a preferable example of the phenol novolac type epoxy compound is the following formula (9) :.

(In the formula, n is 2 or more.)
It is a compound represented by.

In a preferred embodiment, the trifunctional or higher liquid epoxy comprises a trifunctional epoxy, a polyfunctional epoxy containing a tetrafunctional or higher, or a combination thereof. Further, in a preferred embodiment, the trifunctional or higher functional epoxy is a trifunctional epoxy, a tetrafunctional epoxy, or a combination thereof.

The content of the trifunctional or higher liquid epoxy is preferably about 30% by mass or more, or about 40% by mass or more, or about 40% by mass or more based on (A) 100% by mass of epoxy from the viewpoint of obtaining a high Tg epoxy adhesive. It is 50% by mass or more, or about 60% by mass or more, and is preferably about 95% by mass or less, or about 85% by mass or less, or about 75% by mass or less from the viewpoint of giving good adhesive properties and low viscosity. be.

(A) The epoxy may contain an additional epoxy component in addition to the trifunctional or higher functional liquid epoxy. Examples of the additional epoxy component include any epoxy compound not included in the trifunctional or higher liquid epoxy, such as glycidyl ether, aliphatic, aniline type or glycidylated aliphatic, alicyclic and aromatic hydroxyl compounds. Examples thereof include glycidyl esters obtained by glycidylizing aromatic carboxylic acids, glycidyl amines obtained by glycidylizing aniline and toluidine, and the like. Specific examples include, for example, bisphenol A type epoxy resin, dimer acid-modified bisphenol A type epoxy resin, bisphenol epoxy resin such as bisphenol F type epoxy resin, epoxy resin having an aliphatic skeleton such as hexanediol diglycidyl ether, and phenol novolac. It has a novolak epoxy resin such as an epoxy resin and a cresol novolak epoxy resin, a brominated epoxy resin, an alicyclic epoxy resin, an epoxidized ether such as polyethylene glycol glycidyl ether and a polypropylene glycol glycidyl ether, a glycidyl neodecanoate, and an isocyanurate ring. Examples thereof include triglycidyl isocyanurate, phenoxy resin, glycidyl ether having a monofunctional or higher naphthalene skeleton, glycidyl ether having a biphenyl skeleton, and the like, which are not included in the trifunctional or higher functional liquid epoxy.

In some embodiments, the additional epoxy component comprises, as a reactive diluent or reactive plasticizer, a low viscosity epoxy compound such as an alkyl monoglycidyl ether, an alkyl diglycidyl ether, an alkylphenol monoglycidyl ether.

The amount of (A) epoxy with respect to 100% by mass of the epoxy adhesive is preferably about 15% by mass or more, or about 20% by mass or more, or about 25% by mass or more, from the viewpoint of obtaining good adhesive performance. B) From the viewpoint of satisfactorily obtaining the advantages of other components such as fillers, it is preferably about 60% by mass or less, or about 55% by mass or less, or about 50% by mass or less.

(B) Filler (B) The filler contains hollow particles. In the present disclosure, "hollow particle" means a particle having a cavity inside (typically one cavity per particle). Examples of the material of the hollow particles include inorganic substances such as glass, aluminosilicate and silica, and organic substances whose shell is generally a thermoplastic resin typified by polyacrylonitrile and whose inside is hollow.

The true density (g / cm ³ ) of the hollow particles is preferably about 0.5 or less, or about 0.4 or less, from the viewpoint of obtaining an epoxy adhesive having a low storage elastic modulus and a low density. On the other hand, when the hollow particles are used in an environment accompanied by a sudden thermal change due to their hollow structure, it is desirable that the hollow particles have a high compressive strength because they are less likely to cause cracks in the cured product at the time of thermal shock. The true density of the hollow particles is preferably about 0.2 or more, or about 0.3 or more, from the viewpoint of making it difficult to cause cracks at the time of thermal shock by obtaining good compressive strength. The compressive strength (90% remaining) (that is, the strength using the pressure as an index when pressure is applied to the hollow particles to reduce the volume by 10%) is preferably about 30 MPa or more, or about 50 MPa or more, or about. It is 70 MPa or more. Hollow particles may provide thermal insulation in the epoxy adhesive due to their hollow structure. When the epoxy adhesive is used under high temperature conditions, it is desirable that such a heat insulating effect is small in terms of preventing deterioration of the adhesive.

In a preferred embodiment, the hollow particles are hollow microspheres. In the present disclosure, the "hollow microsphere" means a hollow particle having an average particle size (d50) of 100 μm or less. The average particle size (d50) is preferably about 50 μm or less, more preferably about 30 μm or less, from the viewpoint of mechanical strength.

Commercially available products of hollow particles and hollow microspheres include glass bubbles (iM16K, 3M Japan Co., Ltd.) as hollow fine particles of soda lime borosilicate glass, and silicon dioxide (silicon dioxide produced by heating volcanic ash silas at high temperature). Shirasu balloon (Winlight, MSB-3011, Axies Co., Ltd.) consisting of composite components such as silica) and alumina, and organic / inorganic hybrid filler (EMC-) in which fine calcium carbonate is adhered to the surface of plastic microspheres. 40, Nippon Ferrite Co., Ltd.) and the like can be exemplified.

In a preferred embodiment, the filler further contains a filler component other than the hollow particles (hereinafter, also referred to as an additional filler component). Additional filler components include fillers of inorganic substances such as aluminum, alumina, silica, glass, boron nitride, aluminum nitride, magnesium hydroxide, aluminum hydroxide, calcium carbonate, barium sulfate, and (meth) acrylic acid esters and Examples thereof include fillers of organic substances such as styrene, phenol, silicone and nylon. The additional filler component may be one kind or a combination of two or more kinds. The additional filler component may be porous particles, but is typically particles that are substantially free of voids (ie, solid particles).

Hollow particles have the advantage as a filler that improves the mechanical strength of the cured epoxy adhesive, as well as the effect of suppressing and reducing the significant increase in the storage elastic modulus of the epoxy adhesive in the glass state and the storage elastic modulus in the rubber region. It can give the effect of suppressing a large decrease in the amount of rubber and the advantage of contributing to the reduction of density. On the other hand, the additional filler component satisfactorily contributes to the improvement of the mechanical strength of the cured epoxy adhesive. The inclusion of a combination of hollow particles and additional filler components in the filler adjusts the total amount of filler to a sufficient amount to maintain good mechanical strength and adhesive performance of the epoxy adhesive, while using the amount of hollow particles. Is advantageous in that the amount of the adhesive can be adjusted to a suitable range in which the effect of reducing the storage elastic modulus and the effect of reducing the density can be obtained and the heat insulating effect is unlikely to occur.

From the viewpoint of obtaining a low-viscosity epoxy adhesive, the shape of the additional filler component is preferably spherical, but on the other hand, it also affects the surface condition and specific surface area of the filler, and is not limited thereto. The particle size of the additional filler component is preferably about 10 μm or more, or about 15 μm or more from the viewpoint of not excessively increasing the viscosity of the epoxy adhesive, while it is preferably about 30 μm or less from the viewpoint of mechanical strength. Or it is about 20 μm or less, or about 15 μm or less.
It is also effective to blend two or more kinds of particles having different particle sizes from the viewpoint of optimal filling into the epoxy adhesive and a balance of viscosity.

In the present disclosure, the "average particle size (d50)" referring to the filler means a medium diameter (d50) based on the particle distribution obtained by the light scattering method. The particle distribution obtained by the light scattering method measures the amount of scattered light and the number of scattered particles under conditions where the relationship with the amount of turbulent light is known, based on the scattering phenomenon that occurs when light hits particles floating in the fluid. It is the particle size distribution obtained by the above, or it is the particle distribution obtained by measuring the diffraction pattern based on the fact that the diffraction pattern due to the minute particles of the laser light changes depending on the size of the particles. The medium diameter (d50) means the particle size when the number of particles larger than a certain particle size occupies 50% of the total particles in the particle size distribution of the particles.

(A) The amount of the filler (B) with respect to 100 parts by mass of the epoxy is preferably about 20 parts by mass or more, or about 50 parts by mass or more, or about 100 parts by mass or more from the viewpoint of obtaining a good effect by using the filler. From the viewpoint of good cured physical properties, it is preferably about 360 parts by mass or less, or about 300 parts by mass or less, or about 250 parts by mass or less.

The amount of the filler with respect to 100% by volume of the epoxy adhesive is preferably about 20% by volume or more, about 34% by volume or more, or about 41% by volume or more, which is good from the viewpoint of obtaining a good effect by using the filler. From the viewpoint of the cured physical properties, it is preferably about 80% by volume or less, about 70% by volume or less, or about 60% by volume or less.

(A) The amount of hollow particles with respect to 100 parts by mass of epoxy is preferably about 0.1 part by mass or more, about 10 parts by mass or more, or about 15 parts by mass from the viewpoint of obtaining a good effect by using the hollow particles. From the viewpoint of making it difficult for the hollow particles to cause a heat insulating effect and maintaining the strength, the content is preferably about 60 parts by mass or less, about 50 parts by mass or less, or about 40 parts by mass or less.

The amount of the hollow particles in the filler (B) is preferably about 1% by mass or more, about 5% by mass or more, or about 10% by mass or more from the viewpoint of obtaining a good effect by using the hollow particles. From the viewpoint of making it difficult for the hollow particles to cause a heat insulating effect and maintaining the strength, it is preferably about 55% by mass or less, about 45% by mass or less, or about 35% by mass or less.

(C) Core-shell toughening agent In a preferred embodiment, the epoxy adhesive of the present disclosure further contains (C) a core-shell toughening agent. (C) The core-shell toughening agent includes any kind of core-shell toughening agent that is understood by those skilled in the art to be usable as a toughening agent as a resin modifier. In a typical embodiment, the (C) core-shell toughening agent is a composite material in which the inner core portion and the outer shell portion are made of different materials. Here, the "different materials" are intended to be materials having different compositions and / or properties from each other, and thus include, for example, materials of the same type but having different molecular weights.

From the viewpoint of obtaining a good toughening effect on the epoxy adhesive, the Tg of the shell portion is preferably higher than the Tg of the core portion. In this case, the core portion, which has a relatively low Tg, acts as a stress concentration point to impart flexibility to the cured epoxy adhesive, while the shell portion causes undesired aggregation of core-shell toughening agents. The core-shell toughening agent can be controlled to evenly disperse in the epoxy adhesive. Therefore, it is possible to impart toughness without impairing the cured physical properties of the adhesive. It is also useful from the viewpoint of dispersion of internal stress such as curing shrinkage.

In an exemplary embodiment, the core portion and the shell portion have a Tg of about −110 ° C. or higher and about −30 ° C. or lower, and a Tg of the shell portion of about 0 ° C. or higher and about 200 ° C. or lower. You can choose the material. In the present disclosure, Tg of the material of the core portion and the material of the shell portion is defined as the temperature of the peak value of tan δ in the dynamic viscoelasticity measurement.

The core-shell toughening agent is a polymer of conjugated diene such as butadiene, isoprene, 1,3-pentadiene, cyclopentadiene, dicyclopentadiene, and non-conjugated diene such as 1,4-hexadiene, etilidennorbornene; these conjugated or non-conjugated. Diene and aromatic vinyl compounds such as styrene, vinyltoluene and α-methylstyrene, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxybutyl acrylate and glycidyl. Copolymer with (meth) acrylate such as methacrylate and butoxyethyl methacrylate; Acrylic rubber such as polybutyl acrylate; Silicone rubber; With core portion containing rubber component such as IPN type composite rubber composed of silicone and polyalkyl acrylate , A core-shell type graft copolymer having a shell portion formed by copolymerizing a (meth) acrylic acid ester around the core portion may be used. Polybutadiene, butadiene-styrene copolymer and acrylic-butadiene rubber-styrene copolymer can be advantageously used as the core portion, and those formed by graft-copolymerizing methyl (meth) acrylate as the shell portion can be advantageously used. .. The shell portion may be layered, and the shell portion may be composed of one layer or a plurality of layers.

Examples of such a core-shell toughening agent include methyl methacrylate-butadiene copolymer, methyl methacrylate-butadiene-styrene copolymer, methyl methacrylate-acrylonitrile-butadiene-styrene copolymer, and methyl methacrylate-acrylic rubber copolymer. Methyl methacrylate-acrylic rubber-styrene copolymer, methyl methacrylate-acrylic butadiene rubber copolymer, methyl methacrylate-acrylic butadiene rubber-styrene copolymer, methyl methacrylate- (acrylic silicone IPN rubber) copolymer, etc. However, but not limited to these. As the core-shell toughening agent, a methyl methacrylate-butadiene copolymer, a methyl methacrylate-butadiene-styrene copolymer, and a methyl methacrylate-acrylic butadiene rubber-styrene copolymer can be advantageously used.

The core-shell toughening agent is usually in the form of fine particles, and the average value (weight average particle size) of the primary particle size is generally about 0.05 μm or more or about 0.1 μm or more, about 5 μm or less, or about 1 μm or less. In the present disclosure, the average value of the primary particle size of the core-shell toughening agent is determined from the value obtained by the zeta potential particle size distribution measurement.

In a preferred embodiment, the core-shell toughening agent may be used in a dispersed state in the matrix. The core-shell toughening agent dispersed in the matrix is advantageous because it can be well dispersed in the epoxy adhesive. (A) A matrix having a good affinity with epoxy is particularly preferable from the viewpoint of good dispersion of the core-shell toughening agent in the epoxy adhesive. As such a matrix, an epoxy resin (for example, bisphenol A or the like) can be exemplified.

As the core-shell toughening agent, a commercially available product supplied as a resin modifier or the like may be used. For example, as a methyl methacrylate-butadiene-styrene (MBS) -based core-shell resin, BTA751 (commercially available from Dow Chemical Co., Ltd.) may be used. As a core-shell resin in which the resin is dispersed in epoxy, MX-153 (methyl-butadiene-styrene (MBS), which is commercially available from Kaneka Co., Ltd.) is contained in bisphenol A diglycidyl ether. As the acrylic core-shell resin, F351 (available on the market from Aika Kogyo Co., Ltd.) and the like can be exemplified.

(C) The amount of the core-shell toughening agent used is (A) from the viewpoint of reducing cracks during curing shrinkage, reducing brittleness such as peel strength and toughness, and obtaining thermal shock resistance in the epoxy adhesive after curing. ) Based on 100 parts by mass of epoxy, it is preferably about 1 part by mass or more, about 5 parts by mass or more, or about 10 parts by mass or more, and preferably about 60 parts by mass from the viewpoint of adhesive properties and an increase in adhesive viscosity. It is less than a part, or about 50 parts by mass or less, or about 40 parts by mass or less.

(D) Latent Curing Agent As the latent curing agent, various compounds generally used as a latent curing agent for a one-component epoxy adhesive can be used. The latent curing agent does not have the activity of curing the epoxy resin at room temperature, but can be activated by heating to cure the epoxy resin. For example, conventionally known fine-grained latent curing agents are insoluble in epoxy resins at room temperature, and can be solubilized when heated to cure epoxy resins. The epoxy adhesives of the present disclosure do not preclude the use of curing agents other than (D) latent curing agents to the extent that they do not impair the purposes of the present disclosure, but in typical embodiments, the epoxy adhesives contain a curing agent. The agent consists of (D) a latent curing agent.

The latent curing agent used as the (D) latent curing agent can be used alone or in combination of two or more depending on the type of the epoxy (A), the desired properties of the cured product of the epoxy adhesive, and the like. .. The (D) latent curing agent in the present disclosure includes compounds involved in curing an epoxy resin. In some embodiments, (D) the latent curing agent is used in combination with a curing accelerator and / or a cross-linking agent.

(D) Examples of the compound that can be used as a latent curing agent include dicyandiamide (DICY) and its derivatives, hydrazide compounds (for example, organic acid dihydrazide), boron trifluoride-amine complex (for example, boron trifluoride monoethylamine), and imidazole compounds. (For example, those finely granular at room temperature, for example, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric acid. Additives), amineimides, polyamines, tertiary amines, amine compounds (eg alkylurea, etc.); reaction products of amine compounds with epoxy compounds (amine-epoxy adducts), reaction products of amine compounds with isocyanate compounds. And so on. These can be used alone or in combination of two or more.

In some embodiments, when a latent curing agent having a relatively high reaction initiation temperature (eg, polyamine compound, dicyandiamide, etc.) is used, the latent curing agent is combined with the curing accelerator from the viewpoint of good progress of the curing reaction. It is preferable to be done. Examples of the curing accelerator include imidazole compounds, boron trifluoride, tertiary amines, urea compounds (for example, 1,1'-(4-methyl-m-phenylene) bis (3,3-dimethyl) urea, 3-( p-chlorophenyl) -1,1-dimethylurea, etc.) can be used. As is known to those skilled in the art, some of the compounds that can be used as a curing accelerator include latent curing such as the above-mentioned imidazole compound, boron trifluoride, amine-epoxy compound, tertiary amine and the like. Some can also function as agents. Examples of the combination of the latent curing agent and the curing accelerator include a combination of dicyandiamide and an imidazole compound and / or a urea compound and / or a tertiary amine, a combination of a polyamine compound and a urea compound, and the like. In some embodiments, the latent curing agent (D) may contain dicyandiamide from the viewpoint of imparting good heat resistance and peeling strength to the epoxy adhesive in the present disclosure. Examples thereof include a combination of dicyandiamide as a latent curing agent and an imidazole and / or a urea compound as a curing accelerator, and an imidazole compound as a latent curing agent.

In general, high Tg curable materials tend to require higher curing temperatures for complete curing. However, from the viewpoint of preventing stress concentration during curing due to the influence of the coefficient of thermal expansion, thermal curing conditions at a lower temperature are preferable. The composition of the (D) latent curing agent, which is preferable from the viewpoint of lowering the thermosetting temperature, includes dicyandiamide as a latent curing agent and imidazole and / or a urea compound and / or a tertiary amine as a curing accelerator. Examples include combinations, imidazole compounds and / or tertiary amines as latent curing agents.

(D) The amount of the latent curing agent to be used should be selected in consideration of the curability of the epoxy adhesive, the heat resistance and the moisture resistance of the cured epoxy adhesive, and the like. From the viewpoint of promoting curing well and increasing the Tg of the epoxy adhesive, preferably about 1 part by mass or more, about 2 parts by mass or more, or about 3 parts by mass based on (A) 100 parts by mass of epoxy. The amount is preferably about 50 parts by mass or less, about 40 parts by mass or less, or about 30 parts by mass or less from the viewpoint of suppressing the increase in viscosity of the mixture and not impairing the heat resistance of the cured product. ..

When a curing accelerator and / or a crosslinking agent is used, the amount used thereof should be selected in consideration of the type and amount of the latent curing agent to be used. From the viewpoint of promoting curing well, the amounts of the curing accelerator and the cross-linking agent are, for example, about 1 part by mass or more, about 2 parts by mass or more, or about 3 parts by mass or more, respectively, based on 100 parts by mass of the epoxy. It can be, for example, about 20 parts by mass or less, or about 15 parts by mass or less, or about 10 parts by mass or less from the viewpoint of suppressing the increase in viscosity of the mixture and the storage stability.

(E) Optional component The epoxy adhesive may further contain an optional component. Optional components include: rheology modifiers such as fumed silica, amide-based, calcium carbonate fine particles; antioxidants such as phenol-based and sulfur-based; silane coupling agents such as epoxy-modified alkoxysilane; flame retardants; colorants; leveling. Agents; antifoaming agents; solvents; dispersants and the like can be exemplified.

The amount of the optional component used can be appropriately determined as long as the effect of the present invention is not impaired. The dispersant should be selected according to the type of filler from the viewpoint of reducing the viscosity. Based on the total mass of 100 parts by mass of the filler, the amount is about 10 parts by mass or more, about 20 parts by mass or more, or about 50 parts by mass or more, and about 500 parts by mass or less, about 300 parts by mass or less, or about 200 parts by mass or less. Can be used in.

The leology adjuster is about 0.1% by mass or more, about 0.2% by mass or more, or about 0.5% by mass or more, and about 15% by mass or less, based on the total mass of 100% by mass of the epoxy adhesive. It can be used in an amount of 10% by mass or less, or about 5% by mass or less.

The epoxy adhesive can be prepared, for example, by mixing the above components with a mixer while heating as necessary and defoaming as necessary.

In a preferred embodiment, the viscosity of the epoxy adhesive as measured by a conical flat plate viscometer at 25 ° C. and a rotation speed of 200 seconds- ¹ is about 10 Pa · s or more and about 200 Pa · s or less. From the viewpoint of operability of the epoxy adhesive, the viscosity is preferably about 15 Pa · s or more, or about 20 Pa · s or more, or about 25 Pa · s or more, and about 180 Pa · s or less, or about 170 Pa · s or less. Or it is about 160 Pa · s or less.

In a preferred embodiment, the glass transition temperature (Tg) when the measurement sample obtained by curing the epoxy adhesive is measured by a dynamic viscoelasticity measuring device is about 160 ° C. or higher. The glass transition temperature (Tg) is preferably about 160 ° C. or higher, or about 180 ° C. or higher, or about 190 ° C. or higher, or about 200 ° C. or higher, and is used for the epoxy adhesive, from the viewpoint of good heat resistance. From the viewpoint of suppressing the increase in viscosity and promoting the cross-linking of the epoxy resin as much as possible under a curing temperature that does not affect the surrounding members and the adherend, it is preferably about 350 ° C. or lower, or about 330 ° C. ° C or lower, or about 300 ° C or lower.

In a preferred embodiment, the storage elastic modulus when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device is about 1 GPa or more, or about 2 GPa or more at 25 ° C. from the viewpoint of having good rigidity of the adhesive. , Or about 3 GPa or more, and from the viewpoint of good thermal impact resistance of the adhesive, it is about 9.5 GPa or less, or about 8.5 GPa or less, or about 7.5 GPa or less.

In a preferred embodiment, the ratio of the storage elastic modulus at 225 ° C. to the storage elastic modulus at 25 ° C. when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device (storage elastic modulus at 225 ° C./25 ° C.). From the viewpoint of good thermal shock resistance of the adhesive, the storage elastic modulus) is about 2.2% or more, or about 3.0% or more.
In a preferred embodiment, the difference between the storage elastic modulus at 25 ° C. and the storage elastic modulus at 225 ° C. when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device is the good thermal shock resistance of the adhesive. From the viewpoint of, it is about 7.3 GPa or less, or about 7.0 GPa or less.

In a preferred embodiment, the density of the epoxy adhesive is about 1.2 or more, or about 1.3 or more, or about 1.4 or more from the viewpoint of good mechanical strength of the adhesive, and the weight of the adhesive is light. From the viewpoint of conversion, it is about 2.0 or less, or about 1.9 or less, or about 1.7 or less.

<Use of epoxy adhesive>
The epoxy adhesives of the present disclosure can bond adherends of various materials including metals, coated metals, plastic and filled plastic substrates, glass fiber, wood and the like to each other. The epoxy adhesive can be applied to the adherend while heating as needed. Then, by heating, the epoxy adhesive is cured and adheres between the adherends. The curing conditions of the epoxy adhesive vary depending on the formulation of the adhesive, but in one embodiment, for example, about 100 ° C. or higher, or about 110 ° C. or higher, or about 120 ° C. or higher, and about 250 ° C. or lower, or about 230 ° C., Alternatively, it can be cured at a curing temperature of about 200 ° C. or lower, and a curing time of, for example, about 5 minutes to about 90 minutes, or about 10 minutes to about 60 minutes. More typical examples of the curing conditions include 140 ° C. × 30 minutes or 180 ° C. × 10 minutes.

The epoxy adhesive of the present disclosure has an advantage that the generation of cracks due to thermal shock during use is suppressed. Such epoxy adhesives are particularly preferably applied to members where large temperature changes are applied to the adhesive. Such members include automobile members (for example, motor winding fixing, magnet fixing, member fixing near the engine room, adhesion of the reactor core material arranged in the boost converter in the interval unit, etc.), and other automobile members. (For example, adhesion of the core material of the reactor arranged in the boost converter in the inverter unit for automobiles, etc.) and the like. Examples of the motor include a motor with a DC brush and a brushless motor. Used in DC motors that have a rotor (rotor) with a winding (eg copper wire) and a commutator connected to the end of the winding, and a stator with a permanent magnet. The winding part around the commutator is fixed, reinforced and wound for the purpose of preventing the electrical connection from being damaged due to heat, vibration, loosening of the copper wire, etc., and preventing the disconnection of the copper wire to ensure the reliability of the motor. The adhesive is arranged so as to fix the wires.

In the present disclosure, a DC brushed motor is a rotor (rotor) having a winding (for example, a copper wire) and a commutator (commutator) connected to the end of the winding, and a stator (fixed) having a permanent magnet. It means a DC motor equipped with a child). The brushless motor means a motor including a rotor (rotor) having a permanent magnet, a winding (for example, a copper wire), and a stator (stator) to which the end of the winding is connected. In a motor with a DC brush, the rotor with a structure to which the windings are connected rotates, so an adhesive that can maintain good electrical connection with the windings even after the rotation of the rotor due to long-term motor use is desired. Is done.

Another aspect of the present disclosure provides an adhesive for fixing, reinforcing and sealing a winding of a DC brushed motor, including the epoxy adhesive of the present disclosure. In a typical embodiment, the winding is copper wire. The epoxy adhesive of the present disclosure is particularly useful as an adhesive for fixing the windings of a DC brushed motor, and particularly useful for fixing the windings of a DC brushed motor located near the engine room of an automobile. Is. In addition to vibration, the conditions for using a motor used near the engine room of an automobile are, for example, a temperature that is negative in degrees Celsius (for example, the temperature at which it starts to be used in cold regions) and a high temperature of about 120 ° C or higher (for example, when the accelerator is fully open). Accompanied by rapid and large temperature changes such as temperature changes between. Even under such harsh usage conditions, the epoxy adhesives of the present disclosure can achieve good electrical connection of windings.

Hereinafter, embodiments of the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

1. 1. Materials The materials shown in Table 1 were used.

2. 2. Evaluation method (1) Thermal impact test An Olifant washer test piece was prepared and subjected to a thermal impact test. The epoxy adhesive was injected into a metal can (made of tin) with an outer diameter of about 39 mm and a height of 11 mm installed in the cavity in the center of the Olifant washer, and cured at 120 ° C. for 60 minutes to obtain a cured product. .. The measurement conditions are as follows.
Measurement conditions: -40 ° C x 30 minutes ⇔ 160 ° C x 30 minutes Number of cycles: 50 cycles and 100 cycles It was confirmed that cracks occurred after a predetermined number of cycles.

(2) Specific gravity The weight of the glass bottle (W1) g and the weight of water filled in the glass bottle at a standard temperature (W2) g were taken. Similarly, an adhesive adjusted to a standard temperature was injected to obtain a filled weight (W3) g.
The specific gravity was calculated by the following formula.
(W3-W1) / (W2-W1)
The value obtained by calculation was used as the specific weight.

(3) Glass transition temperature (Tg) and storage elastic modulus (E')
The glass transition temperature (Tg) and storage elastic modulus (E') of the cured product obtained by curing the epoxy adhesive at 150 ° C. for 30 minutes were measured by a dynamic viscoelasticity measuring device (DMA). The measurement conditions are as follows.
Specimen: 5 mm x 10 mm x 0.03 mm
Measurement mode: Tension mode Strain frequency: 10Hz
Rate of temperature rise: 4 ° C./min The glass transition temperature was obtained as the temperature of the peak of tan δ defined by the storage elastic modulus (E') / loss elastic modulus (E ″).

3. 3. Experiment [Examples 1 to 7, Comparative Examples 1 to 2]
The compounding ingredients shown in Table 1 were mixed with a mixer to obtain an epoxy adhesive. The performance of the obtained epoxy adhesive was evaluated by the above procedure.
The results are shown in Table 2.

The volume ratio was calculated by calculating the volume of each component of the adhesive from the density or specific gravity value of each raw material.

Although the adhesives of Examples 1 to 7 all had low densities, they showed high thermal shock resistance under severe temperature change conditions of -40 ° C to 160 ° C. On the other hand, in Comparative Examples 1 and 2 (examples in which hollow particles were not used), the thermal impact resistance was low.

FIG. 1 is a diagram showing the measurement results of the dynamic viscoelasticity measuring device (DMA) in Examples 5 and 6 and Comparative Examples 1 and 2. Especially in the glass region near 25 ° C., the storage elastic modulus of Examples 5 and 6 is lower than the storage elastic modulus of Comparative Examples 1 and 2, and conversely, in the rubber region near 225 ° C., the storage elastic modulus of Comparative Examples 1 and 2. The rate is higher than in Examples 5 and 6. In other words, the epoxy adhesives according to Examples 5 and 6 show relatively low elasticity in the glass state, while having a relatively high elastic modulus in the rubber-like region, so that the storage elastic modulus is temperature-dependent. Is a relatively small epoxy adhesive. It is considered that this not only suppresses the change in hardness in the cycle test between the low temperature region and the high temperature region, but also suppresses the generation of cracks and the movement of the copper wire by reducing the stress during the thermal cycle.

The epoxy adhesive according to the present disclosure can be suitably applied to various applications including automobile members such as motors with DC brushes. A part of the embodiment of the present invention is described in the following aspects 1-9.
[Aspect 1]
Contains epoxy and filler,
The epoxy contains a trifunctional or higher functional liquid epoxy.
An epoxy adhesive in which the filler contains hollow particles.
[Aspect 2]
The epoxy adhesive according to embodiment 1, wherein the amount of the hollow particles with respect to 100 parts by mass of the epoxy is 0.1 part by mass to 60 parts by mass.
[Aspect 3]
The epoxy adhesive according to aspect 1 or 2, wherein the amount of the filler with respect to 100 parts by mass of the epoxy is 20 parts by mass to 360 parts by mass.
[Aspect 4]
The epoxy adhesive according to any one of aspects 1 to 3, wherein the amount of the hollow particles is 55% by mass or less based on 100% by mass of the total amount of the filler.
[Aspect 5]
The epoxy adhesive according to any one of aspects 1 to 4, wherein the amount of the trifunctional or higher liquid epoxy is 30% by mass to 95% by mass with respect to 100% by mass of the epoxy.
[Aspect 6]
The epoxy adhesive according to any one of aspects 1 to 5, wherein the amount of the filler is 34% by volume to 80% by volume with respect to 100% by volume of the epoxy adhesive.
[Aspect 7]
The epoxy adhesive according to any one of aspects 1 to 6, wherein the stored elastic modulus at 25 ° C. when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device is 1 GPa or more and 7.5 GPa or less. ..
[Aspect 8]
Ratio of storage elastic modulus at 225 ° C to storage elastic modulus at 25 ° C when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device (storage elastic modulus at 225 ° C / storage elasticity at 25 ° C) The epoxy adhesive according to any one of aspects 1 to 7, wherein the rate) is 2.2% or more.
[Aspect 9]
An adhesive for fixing windings of a motor with a DC brush, which comprises the epoxy adhesive according to any one of aspects 1 to 8.

Claims (6)

Contains epoxies, fillers and core-shell toughening agents ,
The epoxy contains a trifunctional or higher functional liquid epoxy.
The filler, the inorganic hollow particles seen including,
The amount of the inorganic hollow particles with respect to 100 parts by mass of the epoxy is 0.1 part by mass to 60 parts by mass.
The amount of the filler with respect to 100 parts by mass of the epoxy is 20 parts by mass to 360 parts by mass.
An epoxy adhesive in which the amount of the inorganic hollow particles is 55% by mass or less based on 100% by mass of the total amount of the filler. The epoxy adhesive according to claim 1, wherein the amount of the trifunctional or higher liquid epoxy with respect to 100% by mass of the epoxy is 30% by mass to 95% by mass. The amount of the filler for the epoxy adhesive 100 vol%, 34% by volume to 80% by volume, an epoxy adhesive any crab according to claim 1 or 2. The item according to any one of claims 1 to 3 , wherein the storage elastic modulus at 25 ° C. when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device is 1 GPa or more and 7.5 GPa or less. Epoxy adhesive. Ratio of storage elastic modulus at 225 ° C to storage elastic modulus at 25 ° C when the epoxy adhesive is measured using a dynamic viscoelasticity measuring device (storage elastic modulus at 225 ° C / storage elasticity at 25 ° C) The epoxy adhesive according to any one of claims 1 to 4 , wherein the rate) is 2.2% or more. An adhesive for fixing windings of a motor with a DC brush, which comprises the epoxy adhesive according to any one of claims 1 to 5.

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