JP6061837B2 - Structural adhesive composition - Google Patents

Description

  The present invention relates to a structural adhesive composition used for structural adhesion of automobiles, industrial vehicle body panels and the like, and more particularly to a structural adhesive composition having excellent resistance to flowing water pressure.

  In the car body assembly process of assembling the car body from the press-formed steel plate, the adhesive composition used for assembling the hemming part and the wheel arch part called doors, hoods, trunk lids, etc. Heat with epoxy resin as the main component because of its excellent adhesive strength to steel sheet, curability in the baking and drying oven of coating film in the electrodeposition coating process after application of adhesive composition, rust prevention and flexibility A curable composition is generally used. This epoxy adhesive composition is generally composed of an epoxy resin, a heat-activatable curing agent such as dicyandiamide, and a filler such as calcium carbonate, and further to an appropriate viscosity or consistency with a thixotropic agent. Prepared. And in the epoxy adhesive composition used for the assembly of these hemming part and wheel arch part, it is applied in the vehicle body assembly process, and the electrodeposition coating film in the coating drying furnace after passing through the electrodeposition coating process. Simultaneously with baking, the curing reaction proceeds so that the adhesive strength is expressed.

On the other hand, in steel plate bonding of structural parts such as automobile roof rails and various pillars, in recent years, in order to ensure the rigidity and strength of the vehicle body, instead of conventional bonding technologies such as welding, bolts and nuts, rivets, etc. In order to reinforce it, a technique (weld bond method) that uses a combination of an adhesive (more precisely, a structural adhesive) and spot welding has attracted attention, and the demand for such an adhesive (structural adhesive) has increased. ing. The “structural adhesive” refers to a highly reliable adhesive (JIS K6800) with little deterioration in adhesive properties even when a large load is applied for a long time.
Here, in the epoxy adhesive composition used for the assembly of the hemming part and the wheel arch part, the material viscosity is generally set low in consideration of the coating workability. When an epoxy adhesive composition is used for joining steel sheets of structural parts such as roof rails and various pillars, the adhesive composition that protrudes from the steel sheet joining part is pre-treated for electrodeposition coating in the electrodeposition coating process. It is destroyed by the force of the water flow (flow water pressure) used in the cleaning process performed in, so that problems such as outer plate adhesion and electrodeposition liquid contamination occur due to dropout, scattering, and outflow.

  Therefore, it is effective to increase the viscosity of the composition as a countermeasure for the destruction (dropout, scattering, outflow, etc.) of the adhesive composition due to the flowing water pressure of the cleaning process. If the viscosity is increased, the coating workability will be adversely affected, and if the viscosity is increased by adding a large amount of a filler that imparts thixotropy (thixotropy) such as colloidal calcium carbonate or silica gel, the adhesive strength will be adversely affected. Is expected to affect.

Here, in patent document 1 and patent document 2, after apply | coating an adhesive composition to a to-be-adhered body, before an electrodeposition coating process, by performing pseudo-curing which heats for a short time, adhesive composition An adhesive composition imparted with pseudo-curing properties has been disclosed as preventing damage (dropout, scattering, outflow, etc.).
Specifically, in Patent Document 1, at least one epoxy resin having an average of more than one epoxy group per molecule, and at least one curing agent for epoxy resin that is activated by heating, Contains at least one amide AM, which is a fatty acid amide or polyamide, having a melting point of 100 ° C. to 145 ° C., and a toughness improving agent such as a block polyurethane polymer, a liquid rubber, an epoxy resin-modified liquid rubber, and a core / shell polymer A one-component thermosetting epoxy resin composition is disclosed, and by containing amide AM, the adhesive strength is not lost even when jet spray cleaning is performed at 60 ° C. after preheating at 125 ° C. for 12 minutes. It is described that it has.
In Patent Document 2, an acrylate polymer containing a core composed of an epoxy resin, a (meth) acrylate polymer having a glass transition temperature of -30 ° C or lower, and a crosslinkable monomer unit having a glass transition temperature of 70 ° C or higher. Epoxy resin adhesive strength containing a core-shell type powdery polymer obtained by using a core having a weight average particle diameter of 0.1 to 3.0 μm and a latent curing agent for epoxy resin. A composition is disclosed, and it is described that pseudo-curability is imparted by blending a core-shell type powdery polymer composed of a (meth) acrylate polymer.

  Furthermore, Patent Document 3 discloses a synthetic rubber having a crosslinkable double bond, a core-shell type acrylic resin, an adhesion imparting agent composed of an epoxy resin and a latent curing agent, a plasticizer, a filler, a dilution, and the like. A curable composition containing an agent is disclosed, and by applying a core-shell type acrylic resin practically used in an acrylic sol to a composition containing synthetic rubber as a main component, in an uncured state, electrodeposition coating can be performed. It is described that the shape retention with respect to the washing shower in the pretreatment process is exhibited.

  Also, with regard to increasing the viscosity of the composition, the resin modification such as toughness enhancement is performed. For example, as disclosed in Patent Document 4 and Patent Document 5, the core-shell type rubber particles are blended in the epoxy resin composition. The method of doing is also known.

Special table 2011-514394 gazette Japanese Patent Laid-Open No. 05-065391 JP 2005-272712 A JP 2010-270204 A Special table 2013-510225 gazette

However, in the techniques of Patent Document 1 and Patent Document 2, the anti-cleaning property is exhibited by performing pseudo-curing by short-time preheating at a high temperature, such as preheating work and cooling work after heating. These complicated processes are required, and time and labor are required. In addition, since the epoxy adhesive composition has a high reactivity and tends to foam by heating, when it is pseudo-cured by preheating that rapidly heats to a high temperature in a short time, the inside of the layer of the composition There is a problem in that foaming is likely to occur, thereby reducing the adhesive strength.
Further, in Patent Document 3, the shower resistance test conditions of the examples are loose and can be easily achieved by the addition of a filler imparting thixotropy, etc., and the water pressure resistance in the washing treatment is insufficient. Expected to be. Further, since the synthetic rubber is blended, a part of the rubber component is likely to be dissolved and remain in the cured epoxy resin phase, thereby causing a problem that the elastic modulus of the cured product is lowered.
Furthermore, in Patent Document 4 and Patent Document 5, although the rubber component is blended in the form of core-shell type rubber particles, although it seems that the deterioration in quality can be suppressed without dissolving in the epoxy resin phase after curing, It is considered that the core-shell type rubber particles are dispersed in the form of primary particles in order to sufficiently exhibit toughness enhancement and the like. According to the experimental study by the present inventors, when the core-shell type rubber particles are in the form of primary particles dispersed, when a strong shear stress is applied during the coating operation, the rheology changes and the physical properties are likely to change. It has been confirmed that the adhesive composition is destroyed by the flowing water pressure equivalent to the treated water.

  Accordingly, the present invention has been made to solve such problems, and does not destroy physical properties such as coating workability and adhesive strength, and does not destroy the adhesive composition due to the flowing water pressure of the cleaning treatment water. An object of the present invention is to provide a structural adhesive composition having excellent pressure properties.

  The structural adhesive composition of the invention of claim 1 is a structural adhesive composition containing at least an epoxy resin, core-shell type rubber particles, and a curing agent, wherein the core-shell type rubber particles are primary particles. And a secondary agglomerate in a dispersed form.

Here, the core-shell type rubber particles (CSR particles) are a granular material having a rubber-like core layer and a shell layer covering the rubber-like core layer, the core layer has a rubber component, and the rubber-like shape thereof. As long as the shell layer covering the outer side of the core layer is composed of a non-elastic polymer material that does not exhibit rubber elasticity, the substance that forms them is not particularly limited.
These core layer or shell layer, or both core layer and shell layer may be cross-linked (for example, ionic or covalent bond), and the shell layer may be grafted to the core layer.

The core-shell type rubber particles are in a dispersed form in which primary particles and secondary aggregates are mixed.
Here, the dispersion form in which the primary particles and the secondary agglomerates are mixed means that in the composition, the core-shell type rubber particles in the primary particle state and the core-shell type rubber particles in the secondary aggregate state are respectively Shows the state of being distributed and mixed.
Further, the primary particles in the core-shell type rubber particles refer to particles in a single state, and the secondary aggregate refers to an aggregate in a single state in which single particles (primary particles) are connected.
In the composition, the means for mixing the core-shell type rubber particles of the primary particles and the core-shell type rubber particles of the secondary aggregates is not particularly limited, but the control of the blending balance is easy and stable. Since physical properties can be secured, primary particles and secondary aggregates can be mixed by combining core-shell rubber particles in the primary particle state and core-shell rubber particles in the secondary aggregate state. Is preferred.

In the structural adhesive composition of the present invention, the amount of the core-shell type rubber particles is 25 to 45 parts by weight, preferably 30 to 40 parts by weight. .
The blending amount of the core-shell type rubber particles indicates the total amount of core-shell type rubber particles to be blended in the composition regardless of primary particles or secondary aggregates.

In the structural adhesive composition of the present invention , the blending weight ratio of the primary particles of the core-shell type rubber particles to the secondary aggregates is in the range of 2: 3 to 3: 2, preferably 1: 1 in the middle thereof. Are equivalent.

In the core-shell type rubber particle, the structural adhesive composition of the present invention has an average primary particle size in the range of 100 nm to 500 nm.
The above numerical values are not strict, but are approximate, and are naturally approximate values including errors due to measurement and the like, and do not deny errors of several percent.

  The structural adhesive composition according to the invention of claim 1 is a structural adhesive composition containing at least an epoxy resin, core-shell rubber particles, and a curing agent, wherein the core-shell rubber particles are primary. It forms a dispersion form in which particles and secondary aggregates are mixed.

  Here, the inventors have destroyed (dropped off / scattered) the adhesive composition (exactly, the adhesive composition protruding from the adhesion site) due to the flowing water pressure of the cleaning process in the electrodeposition coating process. In order to suppress the outflow, etc., the core-shell type rubber particles in the resin matrix are focused on the dispersion form, and as a result of extensive experimental research, the core-shell type rubber particles in the primary particle state and the secondary aggregate state in the composition The present invention has been completed by discovering that mixing with the core-shell type rubber particles can improve the flow pressure resistance without impairing physical properties such as coating workability and adhesive strength.

  This is because, in addition to the increase in the viscosity resistance of the structural adhesive composition due to the rubber component of the core-shell type rubber particles, when the secondary aggregate of the core-shell type rubber particles is regarded as one particle, the core-shell type is contained in the epoxy matrix. It is presumed that the effect of suppressing the impact due to flowing water pressure was further exhibited by the mixing of the non-uniform particles due to the primary particle state and the secondary aggregate state of the rubber particles, which further increased the structural viscosity resistance.

  And by using the core-shell type rubber particles, an appropriate viscosity characteristic is imparted in the composition, so that the coating workability is not impaired, and the toughness is exhibited in the cured product after curing, and a good adhesive strength is obtained. can get. In addition, since the rubber particles are core-shell type, the rubber component of the rubber particles does not remain dissolved in the epoxy resin phase after curing. For this reason, the elastic modulus is reduced by the rubber component remaining dissolved in the epoxy resin phase. Problems such as these are also unlikely to occur.

  Thus, according to the structural adhesive composition of the present invention, excellent flowing water pressure resistance can be obtained without impairing physical properties such as coating workability and adhesive strength.

According to the structural adhesive composition of the present invention , the compounding amount of the core-shell type rubber particles is in the range of 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin.
As a result of diligent experimental research, the inventors have obtained the best effect of improving the hydraulic pressure resistance with good coating workability and adhesive strength when the blending amount of the core-shell type rubber particles is within this range. The present invention has been completed based on this finding.

That is, when the compounding amount of the core-shell type rubber particles is less than 25 parts by weight with respect to 100 parts by weight of the epoxy resin, the effect of improving the flowing water pressure resistance is not so much obtained in the composition. The increase in the viscosity of the material is increased and the coating workability is reduced. In contrast, the amount of the core-shell type rubber particles by the be in the range of 25 parts by weight to 45 parts by weight, the coating fabric workability and bonding strength is good, and the core-shell type rubber of the primary particle state A high hydrostatic pressure resistance effect is obtained by the core-shell type rubber particles in the state of particles and secondary aggregates.

According to the structural adhesive composition of the present invention , the primary particles and the secondary aggregates of the core-shell type rubber particles are in the range of 2: 3 to 3: 2 in the blending weight ratio.
Here, the more primary particles there are, the rheology changes due to the strong shear stress applied when the composition passes through the pump during the coating operation, and the hydrostatic pressure resistance immediately after the coating operation is reduced. The greater the number of aggregates, the weaker the expression of structural viscosity resistance as a structural adhesive composition against flowing water pressure, and the lowering resistance to flowing water.
Therefore, the weight ratio of the primary particles and secondary agglomerates, 1: 2 and 1 of an equal amount to the intermediate: 3 to 3: that it is in the 2 range, the primary particle state core-shell rubber particles and secondary The most remarkable hydrostatic pressure resistance effect is obtained by the core-shell type rubber particles in the next aggregate state.

According to the structural adhesive composition of the present invention , the average particle size of the primary particles of the core-shell type rubber particles is in the range of 100 nm to 500 nm.
When the average particle diameter of the core-shell type rubber particles in the primary particle state is less than 100 nm, it is difficult to produce, and the primary particles are unstable and easily aggregated, which may reduce the hydrostatic pressure resistance. On the other hand, when the thickness exceeds 500 nm, sufficient toughness cannot be obtained in the cured product after curing, and the peel strength may decrease. Therefore, the average particle diameter of primary particles of the core-shell type rubber particles is within the range of 100 nm to 500 nm, contact Chakukyodo, physical properties such as fluid tight pressure can be obtained stably.

FIG. 1 is a side view and a front view of a schematic diagram for explaining an evaluation test method for resistance to flowing water pressure.

Embodiments of the present invention will be described below.
A structural adhesive composition according to an embodiment of the present invention is a structural adhesive composition containing at least an epoxy resin, core-shell type rubber particles, and a curing agent, wherein the core-shell type rubber particles are primary. The particles and secondary aggregates are mixed to form a dispersed form, that is, the core-shell type rubber particles in the primary particle state and the core-shell type rubber particles in the secondary aggregate state are mixed.

  Here, the epoxy resin may generally be a compound having two or more epoxy groups. For example, bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AD Type, bisphenol AF type, biphenyl type epoxy compound having bisphenyl group, polyalkylene glycol type, alkylene glycol type etc. epoxy compound, naphthalene ring epoxy compound, fluorene group epoxy compound etc. Glycidyl ether type epoxy resin, phenol novolak type, orthocresol novolak type and other novolak type epoxy resin, polyfunctional glycidyl ether, tetraphenylol ethane type and other polyfunctional type glycidyl ether type epoxy resin Synthetic fatty acid glycidyl ester type epoxy resin such as dimer acid, N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (TGDDM), tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, N, Aromatic epoxy resins having a glycidylamino group such as N-diglycidylaniline, trishydroxyphenylmethane type epoxy resins, epoxy compounds having a tricyclodecane ring (for example, cresols or phenols such as dicyclopentadiene and m-cresol) Epoxy compounds obtained by a production method in which epichlorohydrin is reacted after polymerizing the polymer), trishydroxyphenylmethane type epoxy resin, sorbitol type epoxy resin, polyglycerol type epoxy resin, glycine Glycol ester type epoxy resins, heterocyclic epoxy resins, diaryl sulfone type epoxy resin, pentaerythritol type epoxy resin, trimethylol propane type epoxy resin and the like, is selected in accordance with the Shito such compositions. Among these, bisphenol A type and bisphenol F type are preferable. This is because the viscosity of the composition can be easily adjusted. The bisphenol A type epoxy resin is a polycondensation compound of bisphenol A and epichlorohydrin, and the bisphenol A skeleton increases the heat resistance and also improves the toughness to increase the tensile shear adhesive strength. The ether group improves chemical resistance, and the methylene chain increases flexibility. This bisphenol A type epoxy resin can be used from liquid to solid depending on the molecular weight, but is preferably liquid to semi-solid at room temperature, particularly liquid. This is because the handling property and the application workability of the composition become easy. Moreover, the thing whose epoxy equivalent is in the range of 180-300 g / eq is suitable. In addition, an epoxy equivalent means the gram number of the resin containing 1 gram equivalent of an epoxy group (unit: g / eq).

Furthermore, it is also possible to use modified epoxy resins such as urethane-modified epoxy resin and dimer acid modification as the epoxy resin. As the urethane-modified epoxy resin, the structure is not particularly limited as long as it has a urethane bond and two or more epoxy groups in the molecule. From the point that it can be introduced into the molecule, a resin obtained by reacting a urethane bond-containing compound having an isocyanate group with a hydroxy group-containing epoxy compound is preferable.
These epoxy resins can be used alone or in combination of two or more.

The core-shell type rubber particle is a granular material having a structure having at least two layers of a rubber-like core layer and a shell layer.
Here, the core layer of the core-shell type rubber particle means an inner portion of the core-shell type rubber particle and can form a domain inside the core-shell type rubber particle. The core layer may be a rubber-like substance, and is typically an elastomer. For example, a polymer obtained by polymerizing a conjugated diene and / or a lower alkyl acrylate, or a monomer copolymerizable therewith. It is preferably made of a copolymerized copolymer, polysiloxane rubber or the like, and more preferably insoluble in an epoxy resin.
Examples of the conjugated diene include butadiene, isoprene, chloroprene and the like. Among them, butadiene is particularly preferable because it can be obtained at a low cost, and the resulting polymer has good properties as a rubber and can be easily polymerized.
Examples of the lower alkyl acrylate include ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate. Among these, n-butyl acrylate and 2-ethylhexyl acrylate are obtained. This is particularly preferable because the properties of the combined rubber are good and polymerization is easy.

Examples of the monomer copolymerizable with the conjugated diene or alkyl acrylate include aromatic vinyl such as styrene, vinyl toluene, vinyl naphthalene, and α-methyl styrene, vinyl cyanide and cyanide such as aromatic vinylidene, acrylonitrile, and methacrylonitrile. And alkyl methacrylates such as vinylidene chloride, methyl methacrylate, and butyl methacrylate, aromatic (meth) acrylates such as benzyl (meth) acrylate, phenoxyethyl acrylate, ethyl (meth) acrylate, and butyl methacrylate, vinyl acetate, and vinyl chloride. .
In addition, a monomer having a functional group such as an epoxy group, a carboxyl group, a hydroxyl group, and an amino group can be copolymerized. For example, examples of the monomer having an epoxy group include glycidyl methacrylate, examples of the monomer having a carboxyl group include methacrylic acid, acrylic acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2- Examples thereof include hydroxy methacrylate and 2-hydroxy acrylate.
Furthermore, as a component constituting the core, crosslinkable monomers (polyfunctional) such as divinylbenzene, butanediol di (meth) acrylate, triallyl (iso) cyanurate, allyl (meth) acrylate, diallyl itaconate, diallyl phthalate Monomers), grafting monomers having two or more unsaturated sites with unequal reactivity, such as diallyl maleate, monoallyl fumarate, and allyl methacrylate, and at least one of the reactive sites is non-conjugated. it can. When such a crosslinkable monomer or grafting monomer is used in a small amount, preferably 10% by weight or less of the entire core-shell type rubber particle, a bond between layers is obtained, and the particle is not easily deformed even when heated. It becomes. Further, silicone rubber can be used as a monomer copolymerizable with conjugated diene or alkyl acrylate.
In addition, in place of, or in combination with, a monomer copolymerizable with such a conjugated diene or alkyl acrylate, alkyl or allyl disubstituted silyloxy such as dimethylsilyloxy, methylphenylsilyloxy, diphenylsilyloxy, etc. Polysiloxane rubber composed of units can also be used. When such a polysiloxane rubber is used, if necessary, by partially using a polyfunctional alkoxysilane compound at the time of polymerization or by radically reacting a silane compound having a vinyl reactive group. It is preferable to introduce a crosslinked structure into the polysiloxane in advance.

  The rubber-like core layer is preferably a substance having a glass transition point (Tg) of −20 ° C. or lower. This is because the elastic modulus at low temperature can be lowered and the peel strength can be increased. Incidentally, the glass transition point (Tg) refers to the temperature of the peak value of tan δ in dynamic viscoelasticity measurement.

  On the other hand, the shell layer of the core-shell type rubber particles forms the outer part of the core-shell type rubber particles, and usually forms the outermost part of the core-shell type rubber particles, and has an affinity (compatibility) for the epoxy resin. Have. The material constituting the shell layer is not particularly limited as long as it is a material that does not exhibit rubber elasticity. However, a polymer obtained by polymerizing monomers of methyl methacrylate and / or styrene, or a copolymerizable monomer thereof is copolymerized. It preferably consists of a copolymer. These can be obtained at a low cost, can have both good graft polymerizability and affinity for epoxy resins, and have good adhesive strength over a wide range of temperatures.

  Examples of monomers copolymerizable with methyl methacrylate or styrene include alkyl acrylates such as ethyl acrylate and butyl acrylate, alkyl methacrylates such as ethyl methacrylate and butyl methacrylate, vinyltoluene, α-methylstyrene, monochlorostyrene, and 3,4-dichlorostyrene. And vinyl polymerizable monomers such as aromatic vinyl such as bromostyrene, aromatic vinylidene, vinyl acetate, vinyl chloride, acrylonitrile and methacrylonitrile, and vinyl cyanide and vinylidene cyanide. Of these, ethyl acrylate or acrylonitrile is preferred.

  Further, as a monomer copolymerizable with methyl methacrylate or styrene, by copolymerizing a monomer having an epoxy group and / or a functional group that reacts with the epoxy group, for example, a carboxyl group, a hydroxyl group, an amino group, or the like. The shell layer surface may be modified with an epoxy group and / or a functional group that reacts with the epoxy group. For example, examples of the monomer having an epoxy group include glycidyl methacrylate, examples of the monomer having a carboxyl group include methacrylic acid, acrylic acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2- Examples thereof include hydroxy methacrylate and 2-hydroxy acrylate.

  In addition, when calculating | requiring the chemical reactivity at the time of epoxy resin hardening of a shell layer, (meth) acrylic acid ester and epoxy alkyl which have reactive side chains, such as hydroxyalkyl (meth) acrylate and epoxyalkyl (meth) acrylate, One or more components selected from a monomer group consisting of vinyl ether, (meth) acrylamide (including N-substituents), α, β-unsaturated acid, α, β-unsaturated acid anhydride, maleimide derivatives, and the like A copolymer obtained by copolymerization is more preferred. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, styrene, α-methylstyrene, (meth) acrylonitrile, (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, Examples thereof include glycidyl (meth) acrylate, glycidyl vinyl ether, (meth) acrylamide, maleic anhydride, maleic imide and the like. It is also possible to increase the reactivity by including a reactive group that reacts with an epoxy resin or a curing agent, for example, a glycidyl group provided by a monomer such as glycidyl methacrylate in the shell layer.

  Further, the shell layer is preferably grafted and / or cross-linked to the core layer, and a crosslinkable monomer or grafting monomer can be used at 10% by weight or less as a monomer copolymerizable with methyl methacrylate or styrene. It is. This is because bonding between layers is obtained and the particles are hardly deformed even during heating. Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene, alkane polyol polyacrylates such as hexanediol diacrylate, butylene glycol dimethacrylate, norbornene dimethylol dimethacrylate, and the like. Examples thereof include unsaturated carboxylic acid allyl esters such as allyl methacrylate.

  The shell layer is preferably a substance having a glass transition point (Tg) of 50 ° C. or higher. This is because high adhesive strength can be obtained at high temperatures.

Such a core-shell type rubber particle is not particularly limited with respect to its production method, and a commercially available product can be used.
The preferable core / shell ratio (weight ratio) of the core-shell type rubber particles is in the range of 50/50 to 95/5, more preferably in the range of 60/40 to 90/10. When the core / shell ratio (weight ratio) exceeds 50/50 and the core layer ratio decreases, the viscosity in the composition may decrease and the coating workability may decrease. If the ratio of the shell layer is reduced, primary particles are difficult to obtain, the handling and operability are likely to be hindered, and stable physical properties may not be obtained.

  In the case of carrying out the present invention, the core-shell type rubber particles may be composed of more than two layers as long as the core layer showing rubber elasticity is covered with a shell layer not showing rubber elasticity. Good. For example, the central core layer made of one rubber-like material may be provided with another layer made of an inelastic material on the inner side thereof, or may be surrounded by a second core layer made of a different rubber-like material. Good. Further, the rubber-like core layer may be surrounded by two or more shell layers having different chemical compositions and / or characteristics, such as a soft core layer, a hard shell layer, a soft shell layer, a structure of a hard shell layer, etc. It is also possible.

In the present embodiment, the core-shell type rubber particles are used in combination with a primary particle state as a single particle and a secondary aggregate state in which the single particles are aggregated into an irregular aggregate state. Blend in. That is, by mixing and dispersing two types of core-shell type particles in a primary particle state and core-shell type particles in a secondary aggregate state in an epoxy resin, the primary particles of the core-shell type particles and the secondary aggregates of the core-shell type particles are obtained. It is set as the composition which makes the dispersion form disperse | distributed and mixed in an epoxy resin.
In particular, when using a core-shell type particle in a secondary aggregate state as a commercial product, as described later, by kneading the core-shell type particle in a secondary aggregate state into an epoxy resin using a kneader or the like. It is possible to disperse the core-shell type particles in the epoxy resin by breaking up the aggregates of the secondary aggregates to the state of primary particles. The epoxy resin containing the core-shell type particles dispersed in the primary particle state thus prepared and the core-shell type rubber particles in the secondary aggregate state are mixed in the epoxy resin not containing these core-shell type rubber particles. Thus, it is possible to stably secure a dispersion form in which the core-shell type particles in the primary particle state and the secondary aggregate state are mixed in the epoxy resin in a balanced state. That is, as a means for mixing the primary particles and the secondary aggregates in the composition, the core-shell type rubber particles dispersed in the primary particle state in the epoxy resin and the core-shell type rubber particles in the secondary aggregate state are used in combination. By blending, the control operation of the blending amount of the primary particles and the secondary aggregates and the blending balance can be easily controlled.

Here, the average particle diameter of the primary particles of the core-shell type rubber particles, that is, the primary average particle diameter of the core-shell type rubber particles is preferably in the range of 100 nm to 500 nm. Those having a thickness of less than 100 nm are difficult to produce, and the primary particles are unstable and easily aggregate, which may reduce the resistance to flowing water pressure. On the other hand, when it exceeds 500 nm, sufficient toughness cannot be obtained in the cured product after curing, and the peel strength may be reduced.
In the structural adhesive composition of the present invention, the core-shell type rubber particles of the secondary aggregate are essential components in addition to the core-shell type rubber particles of the primary particles. The core-shell type rubber particles of the secondary aggregate are only required to have a secondary aggregate shape, and ordinary commercially available products can be used. For this reason, an average particle diameter of 0.1 μm to 2000 μm can be used, but 0.5 μm to 1000 μm is preferable because good characteristics can be easily obtained comprehensively.
Thus, the core-shell type rubber particles of primary particles and secondary aggregates are dispersed and contained in the structural adhesive composition, and the average particle size of the primary particles is within the range of 100 nm to 500 nm, which is stable. Physical properties such as resistance to flowing water and adhesive strength can be secured.

  In addition, the numerical value of the average particle diameter of the core-shell type rubber particles is not strict but is approximate, and is naturally an approximate value including an error due to measurement or the like, and does not deny an error of several percent.

The total amount of the core-shell type rubber particles to be blended as a dispersion form in the primary particle state and the secondary aggregate state is preferably in the range of 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin. More preferably, it is in the range of 30 to 40 parts by weight.
When the blending amount of the core-shell type rubber particles is less than 25 parts by weight, the effect of improving the hydrostatic pressure resistance is hardly obtained in the composition, and the toughness is low and the peel strength is lowered. This is because the increase in the viscosity of the material increases and the coating workability decreases.

Further, the blending weight ratio of the primary particles and the secondary aggregates in the core-shell type rubber particles is preferably in the range of 2: 3 to 3: 2 with the equivalent of 1: 1 in the middle. When the primary particles and secondary aggregates are outside this range, the more primary particles, the more rheology changes due to the strong shear stress applied when the composition passes through the pump during the coating operation. This is because the pressure resistance decreases, and the more secondary aggregates, the weaker the expression of structural viscosity resistance as a structural adhesive composition against flowing water and the lower the resistance to flowing water. For this reason, when the weight ratio of the primary particles to the secondary aggregates is in the range of 2: 3 to 3: 2 with the equivalent of 1: 1 in the middle, the most remarkable hydrostatic pressure resistance effect is obtained.
In this way, the core-shell type rubber particles dispersed in the primary particle state and the core-shell type rubber particles in the secondary aggregate state are mixed in the epoxy resin and the mixing balance is controlled to control the hydrostatic pressure resistance and coating operation. Properties such as properties and adhesive strength can be stably obtained.
Particularly, the reason why the resistance to flowing water pressure is improved is presumed that the shape effect in which the primary particles having the particle shape and the secondary aggregate having the irregular shape complement each other in shape is influenced.

  The core-shell type rubber particles to be blended as a dispersion form of primary particles and secondary aggregates may be used alone, or the chemical composition and functional group of the core layer or shell layer, and the glass transition temperature, etc. It is also possible to use a mixture of two or more different in characteristics and particle size. For example, the core-shell type rubber particles dispersed in the form of primary particles can be stabilized in the form of primary particles by using the core-shell type rubber particles formed with a shell layer having sufficient affinity for the epoxy resin. For the core-shell type rubber particles that can be dispersed in the form of secondary particles, the core-shell type rubber particles formed with a shell layer with poor affinity for the epoxy resin can be used to form secondary aggregates. It can be stably dispersed in the form.

  Further, the curing agent contained in the structural adhesive composition of the present embodiment may be any one that is usually used as a curing agent for epoxy resins, that is, has an active group that can react with an epoxy group. For example, imidazole compounds such as dicyandiamide, 4,4′-diaminodiphenylsulfone, 2-n-heptadecylimidazole, organic compounds such as adipic acid dihydrazide, stearic acid dihydrazide, isophthalic acid dihydrazide, dibasic acid hydrazide, and isophthalic acid dihydrazide Acid hydrazide compounds, urea compounds such as N, N-dialkylurea derivatives and N, N-dialkylthiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, semicarbazide, cyanoacetamide, diaminodiphenylmethane, tertiary amines, polyamines , Isophoronediamine, m-phenyle Amine compounds such as diamine, aminotriazoles such as 3-amino-1,2,4-triazole, N-aminoethylpiperazine, melamines, guanamines such as acetoguanamine and benzoguanamine, guanidines, dimethylureas, trifluoride Boron bromide complex compounds, boron trichloride complex compounds, liquid phenols such as trisdimethylaminomethylphenol, polythiols, triphenylphosphine, ketimine compounds, sulfonium salts, onium salts, phenol novolac resins, and the like can be used. These may be used alone or in combination of two or more. Among these, dicyandiamide is preferable from the viewpoints of the adhesive strength, storage stability, pot life, and the like of the composition.

In addition, it is preferable that the compounding quantity of a hardening | curing agent exists in the range of 5 weight part-30 weight part with respect to 100 weight part of epoxy resins. When the blending amount of the curing agent is less than 5 parts by weight, the curing rate of the composition tends to be slow or the curing is insufficient and physical properties such as adhesive strength tend to be lowered, while on the other hand, it exceeds 30 parts by weight. And it becomes difficult to obtain desired physical properties required for the structural adhesive composition. Therefore, the more preferable amount of the curing agent is in the range of 7 to 30 parts by weight.
The curing agent is preferably solid particles having an average particle diameter measured by a laser diffraction / scattering method in the range of 3 μm to 15 μm. If the average particle size is less than 3 μm, the storage stability of the composition may be lowered. On the other hand, if it exceeds 15 μm, the curing rate becomes slow and impractical.

Further, in the present embodiment, a thixotropic agent can be blended for improving the handleability. As such a thixotropic agent, for example, carbon black such as ketjen black, silica, fine calcium carbonate, sepiolite and the like can be used. These thixotropic agents can be used alone or in combination of two or more.
In addition, it is suitable that the compounding quantity of a thixotropic agent shall be 10 weight part or less with respect to 100 weight part of epoxy resins. This is because when the amount of the thixotropic agent exceeds 10 parts by weight, the coating workability and the adhesive strength are lowered. In particular, in the present embodiment, the core-shell type rubber particles have an appropriate viscosity characteristic without blending a large amount of thixotropic agent.
As the thixotropic agent, it is preferable to use solid particles having an average particle diameter measured by a laser diffraction / scattering method in a range of 0.01 μm to 0.1 μm. This is because if the average particle size is less than 0.01 μm, the viscosity becomes high and the handleability may be deteriorated. On the other hand, if it exceeds 0.1 μm, the coating workability and the adhesive strength may be lowered.

In addition, a filler can be blended for adjusting the viscosity of the composition and improving mechanical properties. Such fillers include calcium carbonate, talc, magnesia, calcium silicate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, alumina, zircon, graphite, barium sulfate, clay, mica, kaolin, wollastonite, Mica, feldspar, feldspar (sienite), chlorite, talc, bentonite, montmorillonite, barite, dolomite, quartz, diatomaceous earth, calcium silicate, aluminum silicate, barium carbonate, magnesium carbonate, zinc carbonate, textile fiber , Silica such as glass fiber, aramid pulp, boron fiber, carbon fiber, phosphate, crystalline silica, amorphous silica, fused silica, fumed silica, calcined silica, precipitated silica, ground (fine powder) silica, wax, Silica sand, cristobalite, cellulose Resin powder such as cement, polyethylene, calcium oxide, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, titanium dioxide, hollow ceramic beads, hollow inorganic beads such as hollow glass beads, hollow organic beads such as polyester resin, Examples thereof include glass beads, metal powder, and bituminous substances. These may be used singly or in combination of two or more, but calcium carbonate is preferred from the viewpoint of dispersibility and the like.
In addition, it is suitable that the compounding quantity of a filler shall be 80 weight part or less with respect to 100 weight part of epoxy resins. This is because when the amount of the filler exceeds 80 parts by weight, the coating workability and the adhesive strength are lowered.
Moreover, when a filler is particulate, it is preferable that the average particle diameter measured by the laser diffraction / scattering method exists in the range of 0.05 micrometer-500 micrometers. If the average particle size is less than 0.05 μm, the viscosity may increase and the handleability may deteriorate, and if it exceeds 500 μm, the filler tends to settle and the uniformity may decrease.

The structural adhesive composition according to the present embodiment is prepared by uniformly mixing and stirring these blended components with a known mixing and dispersing machine such as a planetary mixer, a disper, a Henschel mixer, and a kneader. .
In particular, when using commercially available core-shell type rubber particles (powder) in a secondary aggregate state, for example, by adding core-shell type rubber particles (powder) in a secondary aggregate state to an epoxy resin, After heating and stirring at a temperature of ˜200 ° C. or high-speed shearing stirring, kneading is carried out with a kneading machine such as a hot roll, an intermixer, a kneader, or a three-roll mill, whereby core-shell type rubber particles are secondary agglomerates in the epoxy resin It is possible to disperse the aggregates as primary particles dissociated. Then, by mixing the epoxy resin in which the core-shell type rubber particles in the primary particle state are dispersed, the core-shell type rubber particles in the secondary aggregate state, a curing agent, and the like, in an epoxy resin not containing these, It can be set as the structural adhesive composition which forms the dispersion | distribution form in which the core-shell type rubber particle of a primary particle state and the secondary aggregate state core-shell type rubber particle were mixed.

In this way, the core-shell type rubber particles dispersed in the primary particle state in the epoxy and the core-shell type rubber particles in the secondary aggregate state are blended together, and the primary particles and secondary aggregates are mixed in the composition. This makes it easy to control the blending amount of primary particles and secondary aggregates and control the blending balance, and can stably obtain physical properties such as resistance to flowing water, coating workability, and adhesive strength, and mass production. It is also possible to obtain a stable quality.
However, when carrying out the present invention, the means for blending the core-shell type rubber particles and mixing the primary particles and the secondary particles is not particularly limited as described above.

The structural adhesive composition according to the present embodiment thus prepared is applied to an adherend by a known method such as spraying, gunning, or brushing. In particular, the structural adhesive composition of the present embodiment has an appropriate viscosity characteristic due to the core-shell type rubber particles, and therefore has good dischargeability when applied by a pump or the like, and good application workability is obtained. Furthermore, it has a sagging resistance that does not easily sag after coating, and has good fixability and shape retention to an adherend in an uncured state.
Further, warm application at 35 ° C. to 40 ° C. is also possible during application. In addition, it is also possible to enhance the bondability of the adherend by using spot welding after application (weld bond method).
When the adherend is a vehicle body part or the like, it is applied in the body assembly process and then subjected to a cleaning process in the electrodeposition coating process.

  At this time, in the structural adhesive composition of the present embodiment, the core-shell type rubber is obtained by forming a dispersed form in which the core-shell type rubber particles in the primary particle state and the core-shell type rubber particles in the secondary aggregate state are mixed. Electrodeposition provides excellent flow resistance due to structural viscous resistance (particle resistance), which is manifested by the shape effect of the primary particles and secondary aggregates of the particles, and the viscous resistance due to the rubber component of the core-shell type rubber particles. The destruction (dropout, scattering, outflow, etc.) of the composition due to the flowing water pressure of the cleaning process in the painting process is prevented.

After the cleaning process is performed in the electrodeposition coating process, the electrodeposition coating is performed, and then the electrodeposition coating is baked in the coating drying furnace and simultaneously heat-cured (for example, a temperature of about 180 ° C. to about 215 ° C. For about 20 minutes to about 60 minutes).
In the structural adhesive composition of the present embodiment, the core-shell type rubber particles exhibit toughness in the cured product after curing, and good adhesive strength is obtained.

  In this embodiment, since the rubber particles are core-shell type, the rubber component of the rubber particles does not remain dissolved in the epoxy resin phase after curing, and the rubber component remains dissolved in the epoxy resin phase. There is no decrease in physical properties such as elastic modulus. In addition, a large amount of high viscosity resin (for example, high molecular weight semi-solid to solid bis-A type epoxy resin) that causes a decrease in coating workability and adhesive strength due to high viscosity, Preheating, which may cause a decrease, can also be omitted.

  Thus, according to the structural adhesive composition of the present embodiment, excellent flowing water pressure resistance can be obtained without impairing physical properties such as coating workability and adhesive strength.

  In the present invention, various additives, for example, a catalyst, a curing accelerator, a plasticizer, a reactive diluent, a reaction retarder, an antiaging agent, an antioxidant, a pigment, a dye, and a coloring agent, as necessary. Agent, coupling agent, leveling agent, thixotropic agent, adhesion imparting agent, flame retardant, antistatic agent, conductivity imparting agent, lubricant, slidability imparting agent, ultraviolet absorber, surfactant, dispersant, A dispersion stabilizer, an antifoaming agent, a dehydrating agent, a crosslinking agent, a rust inhibitor, a solvent, and the like can be blended.

  In addition, the structural adhesive composition of the present embodiment having high flow-water pressure resistance without impairing physical properties such as coating workability and adhesive strength can be used for automobiles, vehicles (Shinkansen, trains), civil engineering, for example. It can be used as an adhesive for structural members in the fields of architecture, electronics, ships, aircraft, space industry and the like. At this time, high joint strength to the structural part can be ensured by the combined use (weld bond method) such as spot welding using an electrode or the like. In addition, it can also be used as an adhesive for general office work, medical use, and electronic materials, but since it has excellent resistance to flowing water, it is particularly suitable for members exposed to flowing water after application to the adherend. Useful for bonding.

Next, examples of the structural adhesive composition according to the embodiment of the present invention will be specifically described.
In the structural adhesive composition of this example, as the epoxy resin, a liquid bisphenol A type epoxy resin (manufactured by ADEKA Corporation: “Adeka Resin EP-4100”; epoxy equivalent: 190) or urethane-modified epoxy Resin (manufactured by ADEKA Corporation: “Adeka Resin EPU-7812A”; polyol component: polypropylene glycol (PPG), polyisocyanate component: tolylene diisocyanate (TDI)), carbon black (Ketjen Black: “Carbon ECP”), heavy calcium carbonate (manufactured by Takehara Chemical Industry Co., Ltd .; average particle size 2 μm to 4 μm) as filler, and dicyandiamide (manufactured by Japan Epoxy Resin Co., Ltd.) as a curing agent: “Jer Cure DICY15”) was used.
As the secondary aggregate of the core-shell type rubber particles, the core layer made of a rubber-like polymer (n-butyl acrylate polymer) is coated with a shell layer made of a glass-like polymer (methyl methacrylate polymer). Structure (Aika Kogyo Co., Ltd .: “ZEFIAC F-351”; secondary aggregate average particle size = 1 μm; shell layer glass transition temperature: 100 ° C. to 120 ° C., core layer glass transition temperature: −50 ° C. to −60 ° C.) was used.

  The core-shell type rubber particles (in powder form) in the secondary aggregate state are added to the epoxy resin, heated and stirred at 80 ° C., and then mixed in a three-roll kneader. The core-shell type rubber particles were dispersed as primary particle states of 100 nm to 500 nm in which the aggregation of the secondary aggregates was released. An epoxy resin in which the core-shell type rubber particles in the primary particle state are dispersed in an epoxy resin in which nothing is mixed, the core-shell type rubber particles in the secondary aggregate state, a thixotropic agent, a filler, A curing agent was added and mixed using a high-speed mixer, and blended and prepared as shown in Table 1 to prepare various structural adhesive compositions (Examples 1 to 3).

More specifically, as Example 1, a part of 100 parts by weight of a liquid bisphenol A type epoxy resin as an epoxy resin and a core shell type rubber particle of “ZEFIAC F-351” manufactured by Aika Industry Co., Ltd. (Secondary aggregate state) After mixing 15 parts by weight and heating and stirring at 80 ° C., the core-shell type rubber particles are in a state of primary particles in a bisphenol A type epoxy resin by a kneading machine of three rolls. Dispersed. In this case, the amount of the liquid bisphenol A type epoxy resin is preferably high viscosity in order to dissociate the core-shell type rubber particles from the secondary aggregate state to the primary particles by kneading three rolls, and this high viscosity is obtained. For this purpose, it is advantageous to use a smaller amount, for example, 50 parts by weight or less.
Then, an epoxy resin in which the core-shell type rubber particles of the primary particles are dispersed, 15 parts by weight of core-shell type rubber particles in a secondary aggregate state, 4 parts by weight of ketjen black as a thixotropic agent, and a weight as a filler. 60 parts by weight of calcium carbonate, 8 parts by weight of dicyandiamide as a curing agent, and the remaining amount of 100 parts by weight of liquid bisphenol A type epoxy resin were mixed and prepared using a high-speed mixer.

  In Example 2, in the liquid bisphenol A type epoxy resin, the blending amount of the core-shell type rubber particles in the primary particle state and the blending amount of the core-shell type rubber particles in the secondary aggregate state are both 20 parts by weight. Were prepared in the same manner as in Example 1 in various amounts.

  As Example 3, various amounts of materials were prepared in the same manner as Example 1 except that urethane-modified epoxy resin was used.

For comparison, various materials were blended and prepared with the blending composition shown in Table 1 to prepare adhesive compositions according to Comparative Examples 1 to 5.
Comparative Example 1 was carried out except that the amount of the primary particle state core-shell type rubber particles and the amount of the secondary aggregate state core-shell type rubber particles in the liquid bisphenol A type epoxy resin were both 10 parts by weight. In the same manner as in Example 1, various materials were blended and prepared.

  Comparative Example 2 was carried out except that the blending amount of the primary particle state core-shell type rubber particles and the blending amount of the secondary aggregate state core-shell type rubber particles in the liquid bisphenol A type epoxy resin were both 25 parts by weight. In the same manner as in Example 1, various materials were mixed and prepared.

  In Comparative Example 3, all the core-shell type rubber particles in the composition were in a primary particle state. That is, a part of 100 parts by weight of a liquid bisphenol A type epoxy resin as an epoxy resin and a core-shell type rubber particle (secondary aggregate state) of “ZEFIAC F-351” manufactured by Aika Kogyo Co., Ltd. After mixing and heating and stirring at 80 ° C., the core-shell type rubber particles were dispersed in the state of primary particles in the bisphenol A type epoxy resin by a three-roll kneader. Then, an epoxy resin in which the core-shell type rubber particles in the primary particle state are dispersed, 4 parts by weight of ketjen black as a thixotropic agent, 60 parts by weight of heavy calcium carbonate as a filler, and dicyandiamide 8 as a curing agent. The remaining amount of 100 parts by weight of liquid parts and 100 parts by weight of liquid bisphenol A type epoxy resin was mixed and prepared.

  In Comparative Example 4, all the core-shell type rubber particles in the composition were in a secondary aggregate state. That is, 100 parts by weight of a liquid bisphenol A type epoxy resin as an epoxy resin, 30 parts by weight of core-shell type rubber particles of “ZEFIAC F-351” manufactured by Aika Kogyo Co., Ltd. used as a secondary aggregate state, and a thixotropic agent 4 parts by weight of Ketjen Black, 60 parts by weight of heavy calcium carbonate as a filler, and 8 parts by weight of dicyandiamide as a curing agent were mixed and prepared.

  Comparative Example 5 includes 100 parts by weight of a liquid bisphenol A type epoxy resin as an epoxy resin, 4 parts by weight of ketjen black as a thixotropic agent, and heavy carbonic acid as a filler without compounding core-shell type rubber particles. 120 parts by weight of calcium and 8 parts by weight of dicyandiamide as a curing agent were mixed and prepared.

And about the adhesive composition concerning each of these mixing | blendings, the evaluation test of flowing water pressure resistance, application | coating workability | operativity, and adhesive strength was done.
With respect to the evaluation test for resistance to flowing water pressure, the test setting was performed on the assumption of the cleaning treatment status in the electrodeposition coating process after assembling the parts to which the actual adhesive composition was applied to the vehicle body. Specifically, on the 1 mm thick steel plate (SCGA steel plate) a, the adhesive compositions of the examples and comparative examples described above were applied in a bead shape with a length of 45 mm in a 2 mm width using a pump and a hand gun. It was attached. In Table 1, the result of evaluation with the pump applied using the pump is “after application work”, and the result of evaluation with the hand gun applied without using the pump is “initial” in Table 1. .
Thereafter, a steel plate b having a length of 15 mm, a width of 70 mm, and a thickness of 1.0 mm is placed on the surface of the structural adhesive composition, and the horizontal direction of the steel plate b is aligned with the width direction of the structural adhesive composition, that is, along the bead shape. Then, the structural adhesive composition is located in the center in the longitudinal direction of the steel plate b, and the structural adhesive composition is joined in a state where a part of the structural adhesive composition protrudes. At this time, it is assumed that the adhesive composition protruding from the bonding site is represented by A.
Then, the steel plates a and b coated with the structural adhesive composition are fixed on the test panel c. At this time, in a state where the test panel c is inclined at 45 degrees with respect to the horizontal, the direction in which the structural adhesive composition A protrudes is upward. From the hose d having a diameter of 12 mm set at a height of 400 mm upward from above the steel plate a with respect to a position 50 mm away from the end face in the direction in which the structural adhesive composition A of the steel plate a protrudes. 40 ° C. warm water was allowed to flow out at a flow rate of 20 L / min for 5 seconds, and the splashed structural water composition and the displacement of the steel sheet b joined to the structural adhesive composition A were observed by the warm water that flowed out. To do. A state where there was no scattering and displacement was marked with ◯, a state where there was no scattering but displacement was seen as Δ, and a state where scattering and displacement were seen were marked with ×.

For the evaluation of the coating workability, the viscosity of the structural adhesive composition at a measurement temperature of 40 ° C. and a shear rate of 15.5 s ⁻¹ was measured with an SOD viscometer, and 500 (Pa · s) or more was determined to be rejected. did.

Further, regarding the adhesive strength, the peel strength by a 90 ° peel test was measured according to JIS K6854-3. The test product was a 200 mm × 25 mm × 0.8 mm SPCC-SD steel plate that was bent at 90 ° with a length of 150 mm and degreased. The structural adhesive composition of the example was applied and bonded, and the structural adhesive composition was heated at 170 ° C. for 20 minutes to cure the structural adhesive composition. In addition, the thickness of the structural adhesive composition for a test product is 0.15 mm.
The test product produced in this way was set in a tensile tester (manufactured by Shimadzu Corp., autograph), pulled under conditions of a temperature of 20 ° C. and a tensile speed of 200 mm / min, and the peel strength (N) was measured. If the peel strength is 100 N or more, the peel strength required for the structural adhesive is sufficient.

  The composition of each example and comparative example and the blending amount (parts by weight) of each component are shown in the upper part of Table 1, and the evaluation test results of each water pressure resistance, application workability, and adhesive strength are shown in the lower part of Table 1. Shown in

  As shown in Table 1, with respect to 100 parts by weight of the epoxy resin, the dispersion state of the core-shell type rubber particles was blended in a mixed state of primary particles and secondary aggregates (blending weight ratio 1: 1). In Example 1 and Example 3, and in Example 2 in which 40 parts by weight in total were blended, the coating workability was good, and good flowing water pressure resistance was obtained, and the peel strength in the cured product after curing was also 130 N to 150 N The adhesive strength was also good.

On the other hand, although the core-shell type rubber particles are blended and the dispersion form is a mixed state of primary particles and secondary aggregates (blending weight ratio 1: 1), the blending amount is 100 parts by weight of the epoxy resin. In Comparative Example 1, which was 20 parts by weight, the coating workability and the adhesive strength were good, but the flowing water pressure resistance was insufficient.
Moreover, although the core-shell type rubber particles are blended and the dispersion form is a mixed state of primary particles and secondary aggregates (blending weight ratio 1: 1), the blending amount is 50 with respect to 100 parts by weight of the epoxy resin. In Comparative Example 2, which was parts by weight, the resistance to flowing water was good and the adhesive strength was also good. However, the viscosity of the structural adhesive composition increased and the coating workability was poor.

  Next, in Comparative Example 3 in which only 30 parts by weight of the primary particles are blended with 100 parts by weight of the epoxy resin, the flow-water pressure resistance in the initial state before being applied to the coating apparatus was good. After the application work with the pump, the resistance to flowing water deteriorated, and it was found that the rheological change was large only with the primary particles.

Further, in Comparative Example 4 in which only 30% by weight of the secondary agglomerate was blended with 100 parts by weight of the epoxy resin core-shell type rubber particles, the coating workability and the adhesive strength were good, but the resistance to flowing water pressure was insufficient. It was.
From the results of Comparative Example 3 and Comparative Example 4, it is considered that the change in rheology due to pump coating greatly changes as the primary particle state or the amount of secondary aggregates increases. Therefore, it is preferable that the blending weight ratio between the primary particles and the secondary aggregate is in the range of 2: 3 to 3: 2.

  And in the comparative example 5 which did not mix | blend a core-shell type rubber particle, although the viscosity of a structural adhesive composition is raised and the improvement of flowing water pressure resistance is aimed at by mixing | blending a large quantity of fillers, coating workability | operativity is improved. Even if the viscosity is increased until it is inferior, sufficient water pressure resistance cannot be obtained, and the adhesive strength is not sufficient.

  As described above, in the above examples, good flow resistance was obtained because the core-shell type rubber particles in the primary particle state and the core-shell type rubber particles in the secondary aggregate state are mixed. Therefore, when the secondary aggregate of the core-shell type rubber particles is regarded as one particle in addition to the viscosity resistance given by the rubber component of the core-shell type rubber particles, the core-shell type is contained in the epoxy matrix. It is presumed that the effect of suppressing the impact caused by the flowing water pressure was exhibited by further increasing the structural viscous resistance by mixing non-uniform particles due to the primary particle state and the secondary aggregate state of the rubber particles.

  In addition, in Examples 1 to 3, the cured product has a high peel strength of 100 N or higher, indicating a high adhesive strength. This is considered to be due to the fact that toughness is imparted by the rubber component of the core-shell type rubber particles, thereby improving the absorption relaxation of stresses such as bending stress, tensile stress and impact stress.

From the above results, the total amount of the core-shell type rubber particles to be blended as the dispersed form in the primary particle state and the secondary aggregate state is in the range of 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin. It is preferable that In Comparative Example 1 in which the blending amount of the core-shell type rubber particles is less than 25 parts by weight, the effect of improving the hydrostatic pressure resistance is not so much obtained in the structural adhesive composition, and the toughness is small and the peel strength is slightly lowered. Yes. On the other hand, in Comparative Example 2 exceeding 45 parts by weight, the increase in the viscosity of the structural adhesive composition is large and the coating workability is lowered. For this reason, by making the total amount of the core-shell type rubber particles within the range of 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin, the coating workability and the adhesive strength are good, and the primary A good hydrostatic pressure resistance effect is obtained by the core-shell type rubber particles in the particle state and the core-shell type rubber particles in the secondary aggregate state.
Furthermore, in Examples 1 to 3, the most remarkable hydrostatic pressure resistance effect is obtained when the blending weight ratio of the primary particles and the secondary aggregates of the core-shell type rubber particles is 1: 1. .

Further, according to the experimental study by the present inventors, the structural adhesive compositions of Examples 1 to 3 have a high glass transition point and high heat resistance. Furthermore, at high temperatures, for example, It has been confirmed that even at 80 ° C., it has excellent shear strength and peel strength and exhibits high adhesive strength.
In addition, there is little decrease in the glass transition point, corrosion resistance, and high joint strength using spot welding even at low temperatures, for example, at -5 ° C, assuming winter in the body assembly process. It is possible to secure.

In the structural adhesive compositions of Examples 1 to 3, the rubber particles are blended in the form of a core-shell type, thereby suppressing an increase in viscosity due to dissolution of the rubber component in the epoxy resin during storage. Therefore, the storage stability is high, and even in the cured product, the rubber component of the core-shell type rubber particles does not remain dissolved in the epoxy resin phase and has a high cured product elastic modulus.
For this reason, it is applicable to a wide field as a structural adhesive.

  As described above, the structural adhesive composition of the embodiment of the present invention is a structural adhesive composition containing an epoxy resin, core-shell type rubber particles, a curing agent, a thixotropic agent, and a filler. In addition, the core-shell type rubber particles form a dispersion form in which primary particles and secondary aggregates are mixed.

Therefore, according to the structural adhesive composition of the embodiment of the present invention, in addition to the increase in viscosity resistance due to the rubber component of the core-shell type rubber particles, the core-shell type rubber particles are mixed with primary particles and secondary aggregates. Due to the dispersion form, the primary particle state and the secondary aggregate state particles of the core-shell type rubber particles are mixed in the epoxy matrix, and the structural viscosity resistance is increased, and the water flow resistance is high.
Further, by using the core-shell type rubber particles, the increase in the material viscosity is moderate and the coating workability is good, and the toughness is exhibited in the cured product after curing, and good adhesive strength is obtained. In addition, since the rubber particles are of the core-shell type, the rubber component of the rubber particles does not remain dissolved in the epoxy resin phase after curing. For this reason, the elastic modulus and heat resistance generated when the rubber component dissolves in the epoxy resin phase. There is also no decrease in the glass transition temperature.

  Thus, according to the structural adhesive composition of the examples of the present invention, it is possible to obtain excellent water pressure resistance without impairing physical properties such as coating workability and adhesive strength.

In particular, in the examples of the present invention, the core-shell type rubber particles in the secondary aggregate state are mixed with the epoxy resin and stirred, and then kneaded with a kneader to obtain the core-shell type in the epoxy resin. It is possible to stably disperse the particles as primary particles in which the aggregates of the secondary agglomerates are released, and in the secondary agglomerate state with the epoxy resin containing the core-shell type particles dispersed as the primary particle state By mixing the core-shell type particles in the epoxy resin not containing these core-shell type particles, it is possible to stably ensure the balance between the primary particle state and the secondary aggregate state of the core-shell type particles. .
Then, using the core-shell type rubber particles in the secondary aggregate state as described above, the epoxy resin containing the core-shell type rubber particles in which the primary particles are dispersed is dispersed into the primary particle state in the epoxy and the secondary resin. When mixing primary particles and secondary aggregates in a composition by mixing them into a single epoxy resin that is not mixed with core-shell type rubber particles in an aggregate state, primary particles and secondary particles It is easy to control the blending amount of the aggregate, and the blending balance between the primary particles and the secondary aggregate can be easily controlled. Therefore, it is suitable for mass production, and physical properties such as resistance to flowing water can be stably obtained.

However, when practicing the present invention, the means for mixing primary particles and secondary aggregates in the structural adhesive composition is not limited to the above, and the primary particles and secondary aggregates are not limited to the above. It is not limited to the same kind. The main point of the present invention is to improve the hydrostatic pressure resistance by increasing the structural viscosity due to the shape effect, and it is considered that this effect is similarly exerted even when the primary particles and the secondary aggregates are used as different materials. Further, in the above examples, a filler (calcium carbonate) and a thixotropic agent (carbon black) are used, but it is not always necessary to use them, and a thermosetting resin other than an epoxy resin, a thermoplastic resin, a plasticizer. Etc. may be added as appropriate.
Further, the composition, components, and blending amount of other parts of the structural adhesive composition are not limited to the above embodiment.

A Structural adhesive composition a, b Steel plate c Test panel d Hose

Claims (1)

A structural adhesive composition containing at least an epoxy resin, core-shell type rubber particles, and a curing agent,
The core-shell type rubber particles have a dispersed form in which primary particles having an average particle diameter in the range of 100 nm to 500 nm and secondary aggregates having an average particle diameter in the range of 0.5 μm to 1000 μm are mixed.
The compounding amount of the core-shell type rubber particles is in the range of 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin,
The core-shell type rubber particle is a structural adhesive composition characterized in that the blending weight ratio of primary particles and secondary aggregates is in the range of 2: 3 to 3: 2 .

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