JP2017132953A - Adhesive composition for structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance viscosity in an electrodeposition coating process having a cleaning process at an atmospheric temperature without reducing adhesiveness and without generating reduction of coating workability by hot apply or reduction of adhesive strength of a junction at low temperature in a weld bond method.SOLUTION: An adhesive composition for structure contains at least an epoxy resin, a core-shell type rubber particle, a reactive diluent and a curing agent, by using a general-purpose epoxy resin and a modified epoxy resin with blended weight ratio in a range of 1:2 to 2:1 as the epoxy resin and blending the core-shell type rubber particle in a range of 45 to 90 pts.wt. and the reactive diluent in a range of 18 to 40 pts.wt. based on 100 pts.wt. of the blended amount of the modified epoxy resin.SELECTED DRAWING: None

Description

  The present invention relates to a structural adhesive composition for use in structural bonding of automobiles, industrial vehicle body panels, and the like, and in particular, structural bonding applied by reducing the viscosity by heating when applied to an object to be coated. It is related with an agent composition.

In recent years, with the aim of improving the fuel efficiency of vehicles such as automobiles with the ultimate goal of suppressing global warming and protecting the global environment, the trend toward lighter fuel consumption has been accelerating. Consideration is being actively attempted. As a means of realizing weight reduction, for example, in a body panel of a vehicle such as an automobile, an attempt to reduce the weight by reducing the thickness of the steel plate or using a lightweight material such as aluminum. Has been made.
On the other hand, in response to the needs of consumers, the performance and upgrading of automobiles are also progressing, and studies have been made to increase the rigidity of the vehicle body for the purpose of improving running performance, operation performance, collision safety, and the like. In order to increase the rigidity of the vehicle body, thickening of the structural member and assembly of the reinforcing plate were conventionally performed. However, thickening of the structural member and assembly of the reinforcing plate led to an increase in the weight of the vehicle body. Could not respond to the trend of weight reduction.

Therefore, as a technique to achieve both weight reduction and rigidity improvement of the vehicle body, a method of strengthening the joining of structural members has been tried. As one of the joining methods, a joining technique using a combination of an adhesive and spot welding ( Weld bond method is attracting attention. In this weld bond method, in general, an adhesive is first applied to a joining portion, and then spot welding is performed. In this spot welding, a plurality of structural members such as steel plates coated with an adhesive (adhesive composition) are overlapped at the joining site, and the structural members such as steel plates are joined by sandwiching them with rod-shaped electrodes. However, this is performed by passing a large current therethrough, and the structural member such as a steel plate is heated at a high temperature and welded by the resistance heat applied between the electrodes.
Epoxy resin-based heat-curing adhesives (structural adhesives) are widely used as adhesives that are applied to joints before spot welding, and the adhesive between joints applied to joints is a spot. Although it is possible to cure by heating immediately after welding, from the viewpoint of reducing man-hours and cost, etc., it is usually an electrodeposition coating film in a coating drying furnace after the electrodeposition coating process performed after the body assembly process At the same time as baking, it is cured using the heat of the paint drying furnace.

By the way, in the electrodeposition coating process performed after the vehicle body assembly process, the vehicle body is generally cleaned as a pretreatment for the base treatment (electrodeposition coating) for the purpose of rust prevention.
Here, as described above, since the adhesive applied to the joining part in the vehicle body assembly process is cured by using the heat of the coating drying furnace after the electrodeposition coating process, the cleaning process in the electrodeposition coating process is performed. In some cases, such an adhesive is in an uncured state.
For this reason, the adhesive applied to the joint site may be broken or destroyed by the force of the water flow (flowing water pressure) used in the cleaning treatment performed in the electrodeposition coating pretreatment in the electrodeposition coating process. , Scattering, deformation (position shift), outflow, dropout, etc.

  In particular, it is preferable that the adhesive applied to the joining portion of the steel plate or the like is applied to the entire surface of the joint so as to protrude from the end of the steel plate from the viewpoint of joining strength, rust prevention, and application state management. Adhesive that protrudes from the joints of the splatters may cause coating defects or contaminate the electrodeposition liquid by adhering to the surface of the vehicle body due to splashing, outflowing, etc. due to flowing water pressure in the cleaning process in the electrodeposition coating process. In addition, when the adhesive is deformed (position misalignment) due to flowing water pressure, there is a risk of causing problems in a later sealer coating process. For this reason, at present, the application of the adhesive is limited to a part of the joining portion.

  Here, as a technique for preventing the scattering of the adhesive due to the flowing water pressure during the cleaning process, for example, after applying the adhesive to the adherend, it is heated at a high temperature in a short time and pseudo-cured before the electrodeposition coating process For example, Patent Document 1 discloses a crosslinkable monomer having an epoxy resin, a core composed of a (meth) acrylate polymer having a glass transition temperature of −30 ° C. or lower, and a glass transition temperature of 70 ° C. or higher. A core-shell type powdery polymer obtained by using a core composed of a (meth) acrylate polymer containing a monomer unit and having a weight average particle diameter of 0.1 to 3.0 μm, and an epoxy resin An epoxy resin-based adhesive composition having pseudo-curability by containing a latent curing agent is disclosed.

  However, such pseudo-curing by preheating requires complicated steps such as preheating work and cooling work after heating, which requires time and labor, and increases man-hours and costs. For this reason, a sufficient heating temperature and time cannot be applied in the process, and there is a limit in preventing the scattering due to the flowing water pressure during the cleaning process by sufficiently curing the adhesive. In addition, epoxy adhesives are highly reactive and tend to foam by heating, so if they are pseudo-cured by preheating that rapidly heats up to a high temperature in a short time, foam is formed inside the adhesive layer. Is likely to occur, which may reduce the adhesive strength.

  Therefore, in response to the scattering, deformation (position shift), outflow, dropout, etc. of the adhesive due to the flowing water pressure during the cleaning process, in the temperature region around 40 ° C. which is the atmospheric temperature in the electrodeposition coating process having the cleaning process. It is conceivable to increase the viscosity of the adhesive.

  However, the atmosphere in the electrodeposition coating process is increased by simply adding a large amount of a high viscosity resin, or by adding a large amount of a filler that imparts thixotropy (thixotropy) such as colloidal calcium carbonate or silica gel. Even if it is designed to increase the viscosity at temperature, the viscosity variation with respect to the temperature change also increases, so the viscosity under the temperature environment condition at the time of coating also becomes high, leading to a decrease in coating workability. become. In addition, the addition of a large amount of filler is expected to adversely affect the adhesive strength.

Here, in addition to being excellent in workability at the time of applying the adhesive and being able to prevent scattering and outflow in the electrodeposition coating process or the subsequent cleaning process, it was synthesized using bisphenol as a raw material. A main epoxy resin that is liquid at 20 ° C., a solid rubber component that is at least one selected from NBR and SBR and does not react with the main epoxy resin, and a latent curing agent for epoxy resin that is activated by heating, JIS- The apparent viscosity measured at a shear rate of 15.5 sec ⁻¹ based on K2220 has an apparent viscosity (V ₂₀ ) at 20 ° C. in the range of 200 to 500 Pa · s, and an apparent viscosity at 40 ° C. (V ₄₀ ). and the value of the ratio of the apparent viscosity _{(V 20) (V 20 /} V 40) is 2.0 or more at 20 ° C. for less than 3.0 It discloses a structural adhesive composition in the range.

  In addition, in Patent Document 3, a core-shell type having a dispersion form in which at least an epoxy resin, primary particles, and secondary aggregates are mixed is assumed to be excellent in flowing water pressure resistance without impairing physical properties such as coating workability and adhesive strength. A structural adhesive composition containing rubber particles and a curing agent is disclosed.

Japanese Patent Laid-Open No. 05-065391 JP 2013-253131 A Japanese Patent Laying-Open No. 2015-108077

  However, in Patent Document 2, it is premised that heating is not performed at the time of coating, and in Patent Document 3, the coating workability at 40 ° C. is used as an evaluation standard in the examples. In view of the above, there is a limit to increasing the viscosity at the atmospheric temperature (around 40 ° C.) in the electrodeposition coating process having the cleaning process.

Here, in general, as the viscosity (material viscosity) of the uncured adhesive is set higher, the viscosity fluctuation with respect to the temperature change becomes larger, so that the viscosity under the atmospheric temperature condition in the electrodeposition coating process becomes higher. When trying to do so, the viscosity in other temperature ranges also increases. For this reason, in the weld bond method in which the above-mentioned adhesive and spot welding are jointly used, in a low temperature in winter, an electrode at the time of spot welding is applied to a structural member such as a steel plate that is laminated by applying an adhesive to the joint part. Even when sandwiched between, the adhesive applied to the joint part of the structural member such as steel plate is difficult to be crushed, thereby causing the energization failure without causing the structural member such as the overlapped steel plate to adhere, and spot welding failure and As a result, there arises a problem that the joint strength of the joint portion is lowered.
In addition, the coating workability can be improved by applying a hot-applied coating by reducing the viscosity by heating at the time of application to the object to be coated. However, if the viscosity is too high, the viscosity is sufficiently reduced by heating at the time of application. It is not possible to ensure good coating workability.

  Therefore, the present invention provides an electrodeposition coating process having a cleaning process without reducing adhesiveness and without causing deterioration in application workability by hot apply and reduction in bonding strength at low temperatures in the weld bond method. An object of the present invention is to provide a structural adhesive composition capable of improving the viscosity at the ambient temperature.

The structural adhesive composition according to claim 1 is a general-purpose epoxy resin as the epoxy resin when the inventors have pursued at least an epoxy resin, core-shell type rubber particles, a curing agent, and a reactive diluent. Resin and modified epoxy resin are used in combination within a blending weight ratio range of 1: 2 to 2: 1 (1: 2 to 2: 1 with 1: 1 as the middle), and the core-shell type rubber particles are 45 to 90 weights. In which the reactive diluent is blended within the range of 18 to 40 parts by weight (18 parts by weight or more and 40 parts by weight or less). It was confirmed.
In addition, said numerical value is not a strict thing but is approximate, and naturally, it is an approximate value including an error due to the type of material, measurement, etc., and does not deny an error of several percent.

According to the experiments by the inventors, the structural adhesive composition according to claim 2 is particularly preferably in the range where the viscosity of the general-purpose epoxy resin and the modified epoxy resin is 5000 to 200000 mPa · s / 25 ° C., respectively. It is what is inside.
Here, the viscosity is measured under a measurement condition of a shear rate of 15.5 s ⁻¹ based on JIS-K2220.
In addition, said numerical value is not a strict thing but is approximate, and naturally, it is an approximate value including an error due to the type of material, measurement, etc., and does not deny an error of several percent.

  The general-purpose epoxy resin of the structural adhesive composition according to claim 3 is a biphenol A type epoxy resin, and the modified epoxy resin is a urethane-modified epoxy resin and / or a rubber-modified epoxy resin.

According to the experiments by the inventors, the structural adhesive composition of claim 4 is particularly preferably a viscosity at 5 ° C. in the range of 5000 to 8000 Pa · s and a viscosity at 40 ° C. of 500 to 700 Pa. It is in the range of s, and the viscosity at 60 ° C. is in the range of 140 to 280 Pa · s.
Here, the viscosity is measured under a measurement condition of a shear rate of 15.5 s ⁻¹ based on JIS-K2220.
In addition, said numerical value is not a strict thing but is approximate, and naturally, it is an approximate value including an error due to the type of material, measurement, etc., and does not deny an error of several percent.

According to the experiments by the inventors, the structural adhesive composition according to claim 5 is particularly preferable when the viscosity at 40 ° C. is in the range of 500 to 700 Pa · s and the viscosity at 40 ° C. The viscosity ratio is in the range of 0.28 to 0.40, and the viscosity ratio of 5 ° C. to the viscosity of 40 ° C. is in the range of 9.3 to 12.3.
Here, the viscosity is measured under a measurement condition of a shear rate of 15.5 s ⁻¹ based on JIS-K2220.
In addition, said numerical value is not a strict thing but is approximate, and naturally, it is an approximate value including an error due to the type of material, measurement, etc., and does not deny an error of several percent.

  According to the structural adhesive composition of the invention of claim 1, it contains at least a general-purpose epoxy resin, a modified epoxy resin, core-shell type rubber particles, a reactive diluent, and a curing agent, The blended weight ratio of the modified epoxy resin is in the range of 1: 2 to 2: 1, and the core shell type rubber particles are blended in the range of 45 to 90 parts by weight with respect to 100 parts by weight of the modified epoxy resin. The reactive diluent is blended in the range of 18 to 40 parts by weight.

  In this way, a general-purpose epoxy resin and a modified epoxy resin are used in combination as an epoxy resin, the blending balance is controlled within a predetermined range, and the blending amount of the core-shell type rubber particles is set to a predetermined amount. By prescribing the compounding amount of the agent to a predetermined amount, the viscosity characteristics under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having the cleaning process are improved, and the viscosity fluctuation with respect to the temperature change is small, and the hot The application workability by applying can be ensured, the bonding strength of the bonded portion by the weld bond method can be ensured even at low temperatures, and the adhesiveness after curing can also be ensured.

  In particular, a modified epoxy resin having high viscosity characteristics is used in combination with a general-purpose epoxy resin, and the blending balance thereof is within a range of general-purpose epoxy resin: modified epoxy resin = 1: 2 to 2: 1. In particular, preferably, the core-shell type rubber particles are within a range of 45 to 90 parts by weight and the reactive diluent is 18 to 40 parts by weight with respect to 100 parts by weight of the modified epoxy resin. Within the range, the viscosity at 40 ° C. can be as high as 500 to 700 Pa · s, and the viscosity ratio at 60 ° C. to the viscosity at 40 ° C. is 0.28 to 0.00, for example. 40, and the viscosity at 60 ° C. is, for example, 140 to 280 Pa · s, and it has an appropriate viscosity characteristic for application at the time of heat application, and good application workability is obtained. Further, the viscosity ratio of 5 ° C. to the viscosity of 40 ° C. can be set to, for example, 9.3 to 12.3, and the viscosity at 5 ° C. is, for example, 5000 to 8000 Pa · s. In the spot welding, the adhesive composition applied to the joining site has a suitable viscosity characteristic to such an extent that the adhesive composition is sufficiently crushed, and without causing poor conduction due to close contact between the structural members to be joined, Good joint strength can be obtained at the joint, and good adhesion after curing can be secured.

Thus, according to the structural adhesive composition of the present invention, although the viscosity at the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having the cleaning process is extremely high, the viscosity fluctuation with respect to the temperature change is small. In addition, it has a viscosity characteristic that can be sufficiently reduced by heating at a temperature that does not cause curing, and is applied to the joint site during spot welding after applying the structural adhesive composition in the weld bond method even at low temperatures. Adhesive composition is sufficiently crushed and the structural members to be joined are brought into close contact with each other so that poor electrical conduction does not occur, good coating workability and bonding strength are obtained, and adhesion is also secured. it can.
That is, the viscosity at the atmospheric temperature in the electrodeposition coating process having a cleaning process without lowering the adhesiveness and without lowering the bonding workability by hot apply and the weld bond method at a low temperature. Can be improved.

  According to the experiments by the inventors, the structural adhesive composition of the invention of claim 2 is particularly preferably that the general-purpose epoxy resin and the modified epoxy resin have a viscosity of 5000 to 200000 mPa · s / 25 ° C., respectively. Within range. If the viscosity of the epoxy resin is in the range of 5000 to 20000 mPa · s / 25 ° C., in addition to the effect of the first aspect, the desired viscosity characteristics can be easily prepared.

  According to the structural adhesive composition of the invention of claim 3, the general-purpose epoxy resin is a biphenol A type epoxy resin, and the modified epoxy resin is a urethane-modified epoxy resin and / or a rubber-modified epoxy resin. In addition to the effects of claim 1 or claim 2, high shear strength and peel strength can be obtained at low cost, and high adhesiveness can be ensured.

According to the structural adhesive composition of the invention of claim 4, according to the experiments by the inventors, the viscosity at 5 ° C. is particularly preferably in the range of 5000 to 8000 Pa · s, and the viscosity at 40 ° C. Is in the range of 500 to 700 Pa · s, and the viscosity at 60 ° C. is in the range of 140 to 280 Pa · s.
The viscosity at 40 ° C. is in the range of 500 to 700 Pa · s, and the viscosity at the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having a cleaning process is extremely high. In addition to the effect described in any one of the above, the resistance to flowing water is extremely high, and the adhesive composition in an uncured state is hardly scattered by the flowing water pressure at the time of cleaning, etc. It is possible to widen or increase the coating thickness. That is, even if the adhesive composition protrudes from the joint end by expanding the application range to the joining site or by increasing the application thickness, the surplus part of the adhesive composition is washed with running water during cleaning. Since the uncured adhesive composition is less likely to scatter due to pressure or the like, there is no risk of adhering to the vehicle body and causing poor coating or contamination of the electrodeposition liquid.
In addition, since the viscosity at 5 ° C. is in the range of 5000 to 8000 Pa · s, the adhesive composition applied to the joining portion is sufficiently crushed and joined at the time of spot welding in the weld bond method even at low temperatures. When the members are brought into close contact with each other, there is no failure in energization, and high bonding strength can be obtained with appropriate fixing properties.
Furthermore, since the viscosity at 60 ° C. is in the range of 140 to 280 Pa · s, it has a viscosity characteristic suitable for coating work by heating at a temperature that does not cause curing, and it is difficult to sag after coating and has high shape retention.

  The structural adhesive composition of the invention of claim 5 has a viscosity at 40 ° C. in the range of 500 to 700 Pa · s, and a viscosity ratio at 60 ° C. to the viscosity at 40 ° C. in the range of 0.28 to 0.40. And a viscosity ratio of 5 ° C. to a viscosity of 40 ° C. is in the range of 9.3 to 12.3.

The viscosity at 40 ° C. is in the range of 500 to 700 Pa · s, and the viscosity at the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having a cleaning process is extremely high. In addition to the effect described in any one of the above, the resistance to flowing water is extremely high, and the adhesive composition in an uncured state is hardly scattered by the flowing water pressure at the time of cleaning, etc. It is possible to widen or increase the coating thickness. That is, even if the adhesive composition protrudes from the joint end by expanding the application range to the joining site or by increasing the application thickness, the surplus part of the adhesive composition is washed with running water during cleaning. Since the uncured adhesive composition is less likely to scatter due to pressure or the like, there is no risk of adhering to the vehicle body and causing poor coating or contamination of the electrodeposition liquid.
Moreover, since the viscosity ratio of 60 ° C. to the viscosity of 40 ° C. is in the range of 0.28 to 0.40, the viscosity characteristic under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having the cleaning process is Even if it is extremely high, the viscosity variation with respect to temperature change is small, so that the adhesive composition applied to the joint site in the weld bond method is sufficiently crushed even at low temperatures, and the structural members to be joined are in close contact with each other It is possible to obtain a high bonding strength without causing energization failure.
Furthermore, since the viscosity ratio of 5 ° C. to the viscosity of 40 ° C. is in the range of 9.3 to 12.3, the viscosity characteristic under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having the cleaning process is Even if it is extremely high, the viscosity fluctuation with respect to temperature change is small, it has a viscosity characteristic that can be sufficiently reduced by heating at a temperature that does not cause curing, it can ensure application workability, and it is difficult to drip after application It has become.

[Embodiment]
Embodiments of the present invention will be described below.
The structural adhesive composition of the present embodiment (hereinafter sometimes abbreviated as “adhesive composition”) includes at least a general-purpose epoxy resin, a modified epoxy resin, core-shell type rubber particles, and a reactive diluent. And a curing agent.

In the present embodiment, a general-purpose epoxy resin and a modified epoxy resin are used in combination as the epoxy resin.
A general-purpose epoxy resin can generally give higher flexibility and strength in a cured product (coating film of an adhesive composition) after curing of the adhesive composition, compared with a modified epoxy resin. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol AP type epoxy resin, bisphenol AD type epoxy resin, bisphenol AF type epoxy resin, bisphenol B type epoxy resin, Examples thereof include bisphenol type bifunctional epoxy resins such as bisphenol BP type epoxy resin, bisphenol C type epoxy resin, bisphenol G type epoxy resin, bisphenol M type epoxy resin and bisphenol P type epoxy resin. These can be used alone or in combination of two or more.
Among them, a bisphenol A type epoxy resin is preferable because it is easily available and inexpensive, can be selected with high viscosity, and can be easily adjusted in viscosity, and from the viewpoint of strength and hardness when cured.

  Modified epoxy resins generally have higher viscosity characteristics than general-purpose epoxy resins and can impart high toughness and plasticity in cured products (coating films). For example, urethane-modified epoxy resins, rubber-modified epoxy resins , Dimer acid-modified epoxy resins, thiocol-modified epoxy resins, and the like. These can be used alone or in combination of two or more. Of these, rubber-modified epoxy resins such as urethane-modified epoxy resins, CTBN-modified epoxy resins, and NBR-modified epoxy resins are excellent in compatibility with general-purpose epoxy resins and curing agents, and are easily available and inexpensive. To preferred.

The urethane-modified epoxy resin may be a resin having a urethane bond and two or more epoxy groups in the molecule, such as a polyhydroxy compound having a hydroxyl group (polyether polyol, polyester polyol, polybutadiene polyol, polyolefin polyol). , Hydroxycarboxylic acid and alkylene oxide adducts) and polyisocyanate compounds having an isocyanate group (tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, etc.) and a compound having a urethane bond, and a bisphenol type epoxy resin ( A resin obtained by reacting with an epoxy compound having a hydroxy group) is used.
The rubber-modified epoxy resin may be an epoxy resin having two or more epoxy groups in the molecule and having a skeleton made of rubber. Examples of the rubber forming the skeleton include polybutadiene and acrylonitrile butadiene rubber (NBR). Butadiene-acrylonitrile rubber having carboxyl groups at both ends (carboxyl-terminated butadiene-nitrile rubber (CTBN)), butadiene-acrylonitrile rubber having amino groups at both ends (amino group-terminated polybutadiene- Acrylonitrile rubber (amino-terminated butadiene-nitrile rubber: ATBN), butadiene-acrylonitrile rubber having carboxyl groups and amino groups at both ends (carboxy group-terminated and amino group-terminated polybutadiene-acrylonitrile rubbers) Etc.

By using such a general-purpose epoxy resin and a modified epoxy resin in combination, the cured product obtained by curing the adhesive composition (coating film of the adhesive composition) has an appropriate strength and flexibility due to the general-purpose epoxy resin. Appropriate toughness and flexibility are imparted by the modified epoxy resin, a predetermined high viscosity is obtained under the atmospheric temperature conditions during the washing step, and good adhesive properties can be secured.
In addition, the general-purpose epoxy resin and the modified epoxy resin are preferably liquid at room temperature from the viewpoint of handleability and preparation of the adhesive composition. The general-purpose epoxy resin that is liquid at room temperature usually has a number average molecular weight of 300 to 1000 and an epoxy equivalent of 150 to 600.
Furthermore, when practicing the present invention, if necessary, in addition to general-purpose epoxy resin and modified epoxy resin, for example, biphenyl type epoxy resin, cresol or phenol / novolak type epoxy resin, chain / alicyclic epoxy It is also possible to blend a polyfunctional epoxy resin having three or more functions such as a resin.

The core-shell type rubber particle is a granular material having a structure in which at least two layers of a core layer having rubber characteristics or elasticity and a non-rubber elastic shell layer are contained, and the central core layer is enclosed by the 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 an elastic rubber material, and is typically an elastomer. For example, a polymer obtained by polymerizing a conjugated diene and / or a lower alkyl (meth) acrylate, or copolymerizable therewith. It is preferably made of a copolymer obtained by copolymerization with a monomer, polysiloxane rubber, or the like, and is preferably unnecessary for the epoxy resin.

Examples of the conjugated diene include butadiene, isoprene, chloroprene, and the like. Among them, butadiene is particularly preferable because it is available at a low price, and the resulting polymer has good rubber properties and is easily polymerized.
Examples of lower alkyl (meth) acrylates include ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Among them, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable because the properties of the resulting polymer as rubber are good and polymerization is easy.

Examples of monomers copolymerizable with conjugated dienes or alkyl (meth) acrylates include, for example, aromatic vinyl such as styrene, vinyltoluene, vinylnaphthalene, and α-methylstyrene, cyanidation such as aromatic vinylidene, acrylonitrile, and methacrylonitrile. Vinyl / vinylidene cyanide, alkyl (meth) acrylates such as methyl (meth) acrylate and butyl (meth) acrylate, aromatic (meth) acrylates such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, vinyl acetate, chloride Examples include vinyl and silicone rubber.
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 (meth) acrylate, and examples of the monomer having a carboxyl group include (meth) acrylic acid, maleic acid, itaconic acid, and the like. , 2-hydroxy (meth) acrylate and the like.

In addition, alkyl or allyl such as dimethylsilyloxy, methylphenylsilyloxy, diphenylsilyloxy, etc., instead of, or in combination with, monomers copolymerizable with such conjugated dienes or alkyl (meth) acrylates Polysiloxane rubber composed of disubstituted silyloxy 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.
Furthermore, as a component constituting the core of the core-shell type rubber particles, crosslinkability such as divinylbenzene, butanediol di (meth) acrylate, triallyl (iso) cyanurate, allyl (meth) acrylate, diallyl itaconate, diallyl phthalate, etc. Use a grafting monomer that has two or more unsaturated sites with unequal reactivity, such as monomer (polyfunctional monomer), diallyl maleate, monoallyl fumarate, etc., and at least one of the reactive sites is unconjugated You can also. 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.

  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 shell of the core-shell type rubber particles, and has an affinity for the epoxy resin (compatibility). 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 price, can have both good graft polymerizability and affinity for epoxy resins, and can have good adhesive strength over a wide range of temperatures.

  Examples of monomers copolymerizable with methyl methacrylate or styrene include alkyl (meth) acrylates such as ethyl (meth) acrylate and butyl (meth) acrylate, vinyltoluene, α-methylstyrene, monochlorostyrene, and 3,4-dichloro. Examples thereof include vinyl polymerizable monomers such as aromatic vinyl such as styrene and bromostyrene, aromatic vinylidene, vinyl acetate, vinyl chloride, acrylonitrile and methacrylonitrile, and vinyl cyanide and vinylidene cyanide. Of these, ethyl (meth) 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 (meth) acrylic acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2- Hydroxy (meth) acrylate etc. are mentioned.

  In addition, when calculating | requiring the chemical reactivity with the other component which comprises an adhesive composition when an adhesive composition hardens | cures in a shell layer, hydroxyalkyl (meth) acrylate, epoxy alkyl (meth) acrylate, etc. (Meth) acrylic acid esters having reactive side chains, epoxy alkyl vinyl ethers, (meth) acrylamides (including N-substituents), α, β-unsaturated acids, α, β-unsaturated acid anhydrides, and A copolymer obtained by copolymerizing at least one component selected from the monomer group consisting of maleimide derivatives and the like is more preferable. 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, and maleic imide. Moreover, the reactivity (interaction property) is improved by including the reactive group which reacts with an epoxy resin, a hardening | curing agent, etc., for example, the glycidyl group provided by monomers, such as glycidyl methacrylate, an epoxy group, etc. in a shell layer. It is also possible.

  The shell layer may be grafted and / or cross-linked to the core layer, and a crosslinkable monomer or grafting monomer may be used at 10% by weight or less as a monomer copolymerizable with methyl methacrylate or styrene. is there. Bonding between layers is obtained, and the particles are difficult to deform 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 rubbery core layer is preferably a material having a glass transition point (Tg) of −20 ° C. or lower, and the shell layer is preferably a material having a glass transition point (Tg) of 50 ° C. or higher. This is because the elastic modulus at low temperature can be lowered and the peel strength can be increased, and high adhesiveness and flexibility can be obtained even at high temperature. Incidentally, the glass transition point (Tg) refers to the temperature of the peak value of tan δ in dynamic viscoelasticity measurement.
Furthermore, in the case of carrying out the present invention, the core-shell type rubber particles are constituted by more than two layers if the core layer showing rubber elasticity is covered with a shell layer not showing rubber elasticity. It may be. 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 inside thereof, or may be surrounded by a second core layer made of a different rubber-like material. Good. Further, the rubbery core layer may be surrounded by two or more shell layers having different chemical compositions and / or properties, such as a soft (soft) core layer, a hard (hard) shell layer, a soft shell layer, A structure of a hard shell layer or the like is also possible.

Such a core-shell type rubber particle is not particularly limited with respect to its production method. For example, it is possible to use a commercial product produced by a technique such as emulsion polymerization, turbid polymerization, or microsuspension polymerization. It is.
The dispersion form of the core-shell type rubber particles in the adhesive composition is dispersed in a primary particle state as a single particle and / or a secondary aggregate state in which the single particles are aggregated into an irregular aggregate state. Is done. The core-shell type rubber particles may be added to the adhesive composition in a dry powder state, or may be added in a state dispersed in an epoxy resin. The primary average particle diameter of preferable core-shell type rubber particles is in the range of 100 nm to 500 nm, and within this range, the dispersibility is good, and physical properties such as adhesive strength and viscosity characteristics can be stably obtained.

  As the reactive diluent, an epoxy-based diluent having an epoxy group is used. Specifically, monofunctional n-butanol glycidyl ether, butyl glycidyl ether, butylphenyl glycidyl ether, hexyl glycidyl ether, 2- Ethylhexyl glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl glycidyl ether, furfuryl glycidyl ether, trimethoxysilyl glycidyl ether, other higher alcohol glycidyl ether, methacrylic acid glycidyl ester, etc., polyfunctional 1,4-butane Diol / diglycidyl ether, 1,6-hexanediol / diglycidyl ether, trimethylolpropane / triglycidyl ether, polyethylene glycol / diglycidyl ether, Examples include dimer acid and diglycidyl ester.

Further, in the structural adhesive composition of the present embodiment, a curing agent is blended, and the curing agent is activated by heating, for example, heating at a high temperature simultaneously with baking after the electrodeposition coating process of the vehicle body. It is supposed to be cured.
As the curing agent, a latent curing agent that is usually used as a curing agent for epoxy resins, that is, a co-reactive type (multifunctional type) of a heat activated type (generally activated at 80 to 250 ° C.). Any catalyst known as a catalytic curing agent (also called a curing catalyst, a curing accelerator, or a curing aid) can be used, as long as it is activated by heating and functions catalytically. Also included. For example, polyamines such as dicyandiamide (DICY), 4,4′-diaminodiphenylsulfone (DDS), imidazole compounds such as 2-n-heptadecylimidazole, adipic acid dihydrazide, stearic acid dihydrazide, isophthalic acid dihydrazide, dibasic acid Organic acid hydrazide compounds such as hydrazide, urea compounds such as N, N-dialkylurea derivatives and N, N-dialkylthiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, semicarbazide, cyanoacetamide, diaminodiphenylmethane, isophorone Amine compounds such as diamine, m-phenylenediamine and tertiary amine, aminotriazoles such as 3-amino-1,2,4-triazole, N-aminoethylpiperazine, melamines, acetoguanamine and benzoguanamine Guanamines, guanidines, dimethylureas, boron trifluoride complex compounds, boron trichloride complex compounds, liquid phenols such as trisdimethylaminomethylphenol, polythiols, triphenylphosphine, ketimine compounds, sulfonium salts, onium salts, phenols A co-reactive (polyfunctional) curing agent that reacts with an epoxy group such as a novolak resin, an amine (for example, 3- (3,4-dichlorophenyl) -N, N-dimethylurea (DCMU), a tertiary amine, Amine complexes such as monoethylamine trifluoride, amine trichloride complexes, amine adduct compounds, etc.), imidazole series (for example, 2-peptadecylimidazole (C17Z), 2-undecylimidazole (C11Z), 2-phenylimidazole ( 2PZ), 1,2-dimethylimidazole (1 2DMZ), 2-phenyl-4-methylimidazole, imidazole adduct compounds, etc.), hydrazide compounds (for example, adipic acid dihydrazide, dodecanedioic acid dihydrazide), urea compounds (for example, 1,1 ′-(4-methyl-1, 3-phenylene) bis (3,3-dimethylurea), phenyl-dimethylurea, methylene-diphenyl-bisdimethylurea, 3-phenyl-1,1-dimethylurea, 3- (3-chloro-4-methylphenyl) Urea derivatives such as -1,1-dimethylurea, and catalytic curing agents such as phenyldimethylurea (PDMU) can be used. These may be used alone or in combination of two or more. Among these, dicyandiamide or a derivative thereof (for example, polyepoxide addition-modified product, amidation-modified product, Mannich-modified product, Michael addition-modified product) is preferable from the viewpoint of adhesive strength, storage stability, pot life, and the like.

  In addition, although a hardening | curing agent is mix | blended suitably according to the epoxy resin (epoxy equivalent, compounding quantity etc.) to be used, curing conditions, etc., for example with respect to 100 weight part of total compounding quantities of a general purpose epoxy resin and a modified epoxy resin , Within the range of 0.1 to 40 parts by weight. If it is in the range of 0.1 to 40 parts by weight, high physical properties such as desired adhesive strength required for the structural adhesive composition can be obtained. More preferably, it is in the range of 1 to 30 parts by weight.

  Furthermore, when implementing this invention, it is also possible to mix | blend a thixotropic agent (thixotropic agent) for the handleability improvement at the time of adhesive composition preparation. As such a thixotropic agent (thixotropic agent), for example, carbon black such as ketjen black, silica, fine calcium carbonate, sepiolite and the like can be used, and these can be used alone or in combination of two or more. You may combine.

  In addition, a filler can be blended for adjusting the viscosity of the adhesive composition, improving the mechanical properties after curing, and reducing the cost. 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, anorthite (sienite), chlorite, bentonite, montmorillonite, barite, cristobalite, dolomite, quartz, diatomaceous earth, aluminum silicate, barium carbonate, magnesium carbonate, zinc carbonate, mineral fiber, 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, cellulose, cement, poly Resin powder such as Tylene, 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, glass beads Examples thereof include metal powders and bitumen substances. These may be used alone or in combination of two or more. Among these, calcium carbonate is preferable from the viewpoint of dispersibility and viscosity adjustment.

  In addition, various additives as required, such as reaction retardants, anti-aging agents, antioxidants, pigments, dyes, plasticizers, silane coupling agents, adhesion promoters, flame retardants, antistatic agents, UV absorption An agent, a surfactant, a dispersant, a dehydrating agent, a solvent, a thermosetting resin other than an epoxy resin, a thermoplastic resin, or the like can be used in appropriate combination.

Thus, the structural adhesive composition of the present embodiment contains at least a general-purpose epoxy resin, a modified epoxy resin, core-shell type rubber particles, a reactive diluent, and a curing agent.
Here, in order to increase the material viscosity of the adhesive composition, even if the blending of a high-viscosity epoxy resin, a filler such as calcium carbonate, or core-shell type rubber particles is increased, the relative amount is increased accordingly. In addition, the adhesiveness after curing decreases. In general, the higher the viscosity, the greater the viscosity fluctuation with respect to temperature change. Therefore, it is also possible to design a higher viscosity at the ambient temperature (around 40 ° C) in the electrodeposition coating process that has a cleaning process. Also, because the viscosity in other temperature ranges becomes high, poor conduction may occur at the time of spot welding in the weld bond method at low temperatures, and it may be difficult to apply due to insufficient viscosity reduction even when heated during application. To do.

  Therefore, in the structural adhesive composition of the present embodiment, a general-purpose epoxy resin that imparts appropriate strength and flexibility in the cured product (coating film of the adhesive composition) after curing, and higher than the general-purpose epoxy resin A modified epoxy resin that has viscosity characteristics and imparts appropriate toughness and flexibility in the cured product is used in combination, and the blending balance of the general-purpose epoxy resin and the modified epoxy resin is controlled to a predetermined amount. By defining the blending amount of the particles and the blending amount of the reactive diluent to a predetermined amount, it has a high viscosity characteristic under the ambient temperature conditions (around 40 ° C.) in the electrodeposition coating process having a cleaning process through their cooperation. However, good adhesiveness is ensured in the cured product, viscosity fluctuation with respect to temperature change is small, and sufficient viscosity reduction can be achieved by heating at a predetermined temperature during application. However, even at such a low temperature, the adhesive composition applied to the joining site in the weld bond method is sufficiently crushed, and during spot welding after application of the adhesive composition. The structural members such as the steel plates to be joined are sufficiently adhered to each other so that good application workability by hot apply and good joint strength by the weld bond method can be obtained without causing a failure of current conduction. In other words, it improves the viscosity at the ambient temperature (around 40 ° C) in the electrodeposition coating process that has a cleaning process, but it also has a viscosity characteristic suitable for hot apply and an adhesive composition applied to the bonding site even at low temperatures in the weld bond method. The object was sufficiently crushed so that the viscosity characteristics suitable for spot welding could be controlled.

  Here, by using a modified epoxy resin and a general-purpose epoxy resin together, while securing adhesive strength with a general-purpose epoxy, high-viscosity characteristics can be secured with a modified epoxy resin. When the amount of the general-purpose epoxy resin is relatively increased and the amount of the modified epoxy resin is decreased, the desired high viscosity characteristic at the atmospheric temperature (around 40 ° C.) in the electrodeposition coating process having a cleaning treatment, that is, at the time of cleaning Even if the resistance to flowing water pressure is improved and the range of application to the joint site is expanded, high viscosity characteristics cannot be obtained to such an extent that scattering, outflow, etc. are effectively prevented. On the other hand, when the amount of the modified epoxy resin is relatively increased and the amount of the general-purpose epoxy resin is decreased, the viscosity fluctuation with respect to the temperature change becomes large. Especially in the low temperature environment in winter, the joint part is used during the spot welding in the weld bond method. Since the viscosity of the adhesive composition applied to the surface is too high, even when the electrode for spot welding is sandwiched, it is not sufficiently crushed and the structural members to be joined cannot be in close contact with each other. It becomes impossible to obtain a sufficient bonding strength.

  According to the experiments by the inventors, it is particularly preferable that the blending weight ratio of the general-purpose epoxy resin and the modified epoxy resin is in the range of 1: 2 to 2: 1 with the equivalent of 1: 1 in between. It has a good balance between viscosity characteristics and adhesiveness, and the desired high viscosity can be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process having a cleaning process. A structure that is small and has a suitable viscosity characteristic so that the adhesive composition applied to the joining site in the weld bond method can be sufficiently crushed when sandwiching the electrode for spot welding even at low temperatures in winter The members can be brought into close contact with each other, and good bonding strength can be obtained without causing poor conduction. Note that the above numerical values are not necessarily required to be strict, and even if the numerical values are slightly changed in relation to the type of epoxy resin to be used, other materials constituting the adhesive composition, etc. There is no denial.

The viscosities of the general-purpose epoxy resin and the modified epoxy resin are selected according to the types (properties, etc.) of the resin component so that a desired viscosity characteristic can be obtained. It was confirmed that the desired viscosity characteristics can be easily adjusted by adjusting the content within the range of s / 25 ° C. to 200000 (mPa · s / 25 ° C.).
If the general-purpose epoxy resin is a biphenol A-type epoxy resin and the modified epoxy resin is a urethane-modified epoxy resin and / or a rubber-modified epoxy resin, high shear strength and peel strength can be obtained at low cost and high adhesiveness. Can be secured.

  In addition, the structural adhesive composition of the present embodiment contains core-shell rubber particles, thereby increasing the viscosity and elasticity of the adhesive composition, and resistance to flowing water that collides with the adhesive composition during the cleaning process. Can increase the sex. Furthermore, the viscosity fluctuation with respect to the temperature change can be weakened. Moreover, toughness is exhibited in the cured product after curing, and good adhesive strength is obtained.

  Here, when the blending amount of the core-shell type rubber particles is too small, the desired high viscosity characteristic under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having a cleaning process, that is, the flowing water pressure at the time of cleaning. Even if the resistance is improved and the range of application to the bonding site is widened, high viscosity characteristics cannot be obtained to such an extent that scattering, outflow, etc. are effectively prevented. Moreover, high shear strength is not obtained in the cured product, and the adhesiveness is lowered. On the other hand, when there is too much compounding quantity, adhesiveness will fall in hardened | cured material because the compounding quantity of another material becomes relatively small. Moreover, there is a risk of reducing plasticity and the like. Furthermore, the increase in the viscosity of the material is large, and even if it is heated at a predetermined temperature during application, it cannot be sufficiently reduced in viscosity, and the application workability is lowered. In addition, under the low temperature environment in winter, the adhesive composition applied to the joint site in the weld bond method cannot be brought into close contact with each other without being sufficiently crushed. Decreases.

According to the experiments by the inventors, it is particularly preferable that the amount of the core-shell type rubber particles is within the range of 45 to 90 parts by weight with respect to 100 parts by weight of the modified epoxy resin. The desired high viscosity can be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process having treatment, and the water pressure resistance can be further improved. Appropriate workability is obtained with moderate viscosity characteristics, and it is sufficient when the electrode composition for spot welding is sandwiched between the adhesive composition applied to the joint site in the weld bond method even at low temperatures in winter. It has an appropriate viscosity characteristic to such a degree that it can be crushed, it can adhere the structural members to be joined together, and can obtain good joint strength without causing poor electrical conduction. That.
Note that the above numerical values are not necessarily required to be strict, and even if the numerical values are slightly changed in relation to the type of core-shell type rubber particles to be used, other materials constituting the adhesive composition, etc. It does not deny implementation.

In particular, according to the experimental study by the present inventors, when a large amount of a single rubber is compounded in order to increase the viscosity under the atmospheric temperature condition (around 40 ° C.) during the cleaning process, the crosslinking reaction of the epoxy resin is inhibited. When the elastic modulus after curing is reduced, the adhesiveness of the cured product is lowered, and the dispersion is easily affected by the mixing conditions and difficult to disperse, so the storage stability is poor and stable physical properties can be secured. However, there is a limit to increasing the viscosity under the ambient temperature condition (around 40 ° C.) during the cleaning process.
On the other hand, in the structural adhesive composition of the present embodiment, since the core-shell type rubber particles in which the rubber particles are the core-shell type are blended, the dispersibility is good and the reactivity with the epoxy resin is small. Storage stability is also good, and the rubber component of the rubber particles does not remain dissolved in the epoxy resin phase after curing, and the physical properties such as elastic modulus are reduced by the rubber component remaining dissolved in the epoxy resin phase. In addition, a higher viscosity can be stably secured under the ambient temperature conditions (around 40 ° C.) in the electrodeposition coating process having a cleaning process, and the reliability becomes high.

  Furthermore, the viscosity fluctuation | variation with respect to a temperature change can also be made small by containing a reactive diluent. Here, when the amount of the reactive diluent is too small, the viscosity variation of the material with respect to the temperature change becomes large, and it is not possible to sufficiently reduce the viscosity even when heated at a predetermined temperature at the time of coating, and the coating workability is improved. descend. In addition, in a low temperature environment such as in winter, the adhesive composition applied to the bonding site in the weld bond method has a high viscosity, so that the structural members to be bonded without being sufficiently crushed cannot be spotted. Failure to conduct electricity easily occurs during welding, resulting in a decrease in bonding strength. On the other hand, if the blending amount is too large, the blending amount of other materials becomes relatively small, and the desired high viscosity is obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process having a cleaning process. May not be obtained, or the adhesiveness of the cured product may be reduced.

According to the experiments by the inventors, it is particularly preferable that the reactive diluent is washed if it is in the range of 18 to 40 parts by weight with respect to 100 parts by weight of the modified epoxy resin. Even if the desired high viscosity is obtained under the atmospheric temperature conditions (around 40 ° C.) during the process, when applying the adhesive by hot apply, it has an appropriate viscosity characteristic for application and good application workability is obtained. Even at low temperatures, the adhesive composition applied to the joining site in the weld bond method has an appropriate viscosity characteristic to the extent that it is sufficiently crushed when sandwiching the electrode for spot welding, and the structural members to be joined together Good bonding strength can be secured without causing poor electrical conduction, and adhesion of the cured product can be secured.
Note that the above numerical values are not necessarily required to be strict, and even if the numerical values are slightly changed depending on the type of reactive diluent used, other materials constituting the adhesive composition, etc. It does not deny implementation.

  As described above, according to the structural adhesive composition of the present embodiment, the blended weight ratio of the general-purpose epoxy resin and the modified epoxy resin is preferably in the range of 1: 2 to 2: 1, and the modified epoxy resin is used. The core-shell type rubber particles are blended in the range of 45 to 90 parts by weight with respect to 100 parts by weight (including a modified epoxy resin as a dispersion medium for the core rubber-type particles), and a reactive diluent is added. By blending within the range of 18 parts by weight to 40 parts by weight, even if the viscosity under the ambient temperature condition (around 40 ° C.) during the cleaning process is improved, the viscosity variation with respect to the temperature change is small, so However, the adhesive composition applied to the joining site in the weld bond method without being too high in viscosity is sufficiently crushed and the structural members to be joined are brought into close contact with each other, which may cause poor conduction during spot welding. Ku, also has a sufficiently thinning capable viscosity characteristics by heating at a temperature not causing curing, good coating workability and the bonding strength is obtained, further, it can be ensured adhesion after curing. In other words, application workability by hot apply, bonding strength by weld bond method, adhesiveness of cured products and high viscosity characteristics at ambient temperature (around 40 ° C) during the cleaning process are made possible, and viscosity fluctuation with temperature change Excellent balance.

The structural adhesive composition of the present embodiment having such a composition is prepared by mixing known ingredients with a known mixing and dispersing machine such as a planetary mixer, a disper, a Henschel mixer, a kneader, an ink roll, an extruder, and a change can type mixer. It is prepared by mixing and stirring uniformly.
The prepared structural adhesive composition according to the present embodiment is applied to an adherend by a known method such as spraying, sealer gun, or brushing.

  At this time, as described above, according to the structural adhesive composition of the present embodiment, at least the general-purpose epoxy resin, the modified epoxy resin, the core-shell type rubber particles, the reactive diluent, and the curing agent. Preferably, the blending weight ratio of the general-purpose epoxy resin and the modified epoxy resin is in the range of 1: 2 to 2: 1, and the core-shell type rubber particles are added to 100 parts by weight of the total blended amount of the modified epoxy resin. By blending within the range of 45 parts by weight to 90 parts by weight, and by blending the reactive diluent within the range of 18 parts by weight to 40 parts by weight, a high viscosity is obtained at the ambient temperature conditions (around 40 ° C.) during the washing step. Since it has the characteristics, at the time of coating, the coating workability is ensured by heating at a predetermined temperature to reduce the viscosity (a hot apply type).

The heating temperature at the time of application is appropriately set to a temperature at which the viscosity can be reduced to a level that can be applied (for example, a level that can be discharged by a pump, etc.) depending on the content and viscosity of the adhesive composition. If the heating temperature at that time is too high, the curing reaction proceeds and good coating workability cannot be obtained. Therefore, the temperature is usually set to 45 ° C. to 60 ° C. in consideration of the safety of the coating work.
According to the structural adhesive composition of the present embodiment, due to the above-mentioned blending, there is little viscosity variation with respect to temperature change even if it has high viscosity characteristics under the atmospheric temperature conditions (around 40 ° C.) during the cleaning process. Thus, the viscosity does not become too high even under conditions of 50 ° C. to 60 ° C., and good coating workability is ensured.

  As described above, the structural adhesive composition of the present embodiment is applied by heating at a predetermined temperature to reduce the viscosity at the time of application, and the heating at this time causes the curing to proceed. Since the heating is performed at a low temperature without any heat treatment and the heat treatment is not performed at a high temperature in a short time as in the case of pseudo-curing, the adhesive strength is hardly lowered due to the foaming of the epoxy resin. In addition, the low heating temperature makes it possible to apply heat by, for example, improving the degree to which a simple heater is attached to a general-purpose pump facility. There is nothing.

And in the structural adhesive composition of this Embodiment, after application | coating, the viscosity characteristic according to atmospheric temperature conditions is shown by the temperature dependence of a viscosity, and a viscosity rises.
At this time, when the adherend to which the structural adhesive composition of the present embodiment is applied is a structural member of a vehicle body, by performing spot welding as appropriate after applying the adhesive composition as a weld bond method, Bonding can be strengthened.

  In particular, according to the structural adhesive composition of the present embodiment, even if the composition described above has a high viscosity characteristic under the atmospheric temperature condition (around 40 ° C.) during the cleaning process, the viscosity variation with respect to the temperature change occurs. With less, the viscosity does not become too high even at low temperatures in winter, and the adhesive composition applied to the joint site in the weld bond method is sufficiently crushed and the structural members to be joined are brought into close contact with each other and are energized during spot welding. It does not cause defects, has good spot weldability, ensures the bonding strength by the weld bond method even at low temperatures in winter, and has high bonding reliability.

  The structural adhesive composition of the present embodiment contains an epoxy resin curing agent and is cured by heating. For example, the structural adhesive composition of the present embodiment is applied. When the adherend is a structural member of a vehicle body, the adhesive composition is applied in the vehicle body assembly process, and after being subjected to a cleaning process in the electrodeposition coating process, the electrodeposition coating is performed. The process of baking the electrodeposition coating film in a paint drying oven is followed, and during this baking, the adhesive composition is heat-cured (for example, at a temperature of about 150 ° C. to about 220 ° C. for about 20 minutes to about 60 minutes). Is done.

  At this time, the adhesive composition applied to the adherend is exposed to a cleaning process in the electrodeposition coating process in an uncured state, but according to the structural adhesive composition of the present embodiment, As described above, it contains at least a general-purpose epoxy resin, a modified epoxy resin, core-shell type rubber particles, a reactive diluent, and a curing agent, preferably a blending weight ratio of the general-purpose epoxy resin and the modified epoxy resin Is within the range of 1: 2 to 2: 1, and the core-shell type rubber particles are blended within the range of 45 parts by weight to 90 parts by weight with respect to 100 parts by weight of the modified epoxy resin, and the reactive diluent is added. By blending in the range of 18 parts by weight to 40 parts by weight, the atmospheric temperature during the cleaning process without impairing properties such as coating workability with hot apply, bonding strength by weld bond method, adhesion of cured product, etc. conditions( Since it has a high viscosity properties at near 0 ° C.), even without the pre-heating that could lead to a decrease in adhesive strength (pseudo cure), it exhibits high resistance to washing when the flow water pressure. That is, even in an uncured state, shape retention and fixability to the adherend are exhibited, and the scattering, outflow, deformation (position shift), and the like of the adhesive composition are effectively prevented. Therefore, it is possible to prevent coating failure due to scattering, outflow, deformation (position shift), etc. of the adhesive composition, contamination of the electrodeposition liquid, and processing failure in the later sealer coating process.

  In addition, high viscosity characteristics can be obtained under the atmospheric temperature conditions (around 40 ° C.) during the cleaning process without impairing characteristics such as hot-apply coating workability, weld bond strength by weld bonding, and adhesiveness of the cured product. The structural adhesive composition according to the present embodiment can be used, for example, as an adhesive for structural members in automobiles, vehicles (bullet trains, trains), civil engineering, architecture, electronics, ships, aircraft, space industry, and the like. . Especially in automobiles, structural parts such as roof rails, various pillars, doors, hoods, trunk hemming parts of inner panels and outer panels, wheel arch parts, side sills, outer sills, etc. Useful as a structural adhesive. And high joint strength to a structure part is securable by combined use (weld bond method) with spot welding etc. which used an electrode etc. Moreover, since it has a high viscosity characteristic in the atmospheric temperature conditions (around 40 degreeC) at the time of a washing | cleaning process, it is useful for adhesion | attachment of the member exposed to flowing water after the application to a to-be-adhered body.

[Example]
Next, examples of the structural adhesive composition according to the embodiment of the present invention will be specifically described.
First, adhesive compositions according to Examples 1 to 8 were prepared with the contents shown in Table 1 as the composition of the structural adhesive composition of the present embodiment. Moreover, the adhesive composition concerning the comparative example 1 thru | or the comparative example 4 was also prepared for the comparison. The composition of each Example and each Comparative Example is shown in the upper part of Table 1.

In this example and comparative example, as a general-purpose epoxy resin, a bisphenol A type epoxy resin that is liquid at room temperature (manufactured by ADEKA Corporation: “Adeka Resin EP-4100”, viscosity: 13,000 <mPa · s / 25 ° C. >)It was used.
As the modified epoxy resin, urethane-modified epoxy resin (ADEKA Co., Ltd .: “Adeka Resin EPU-78-11”) or rubber (NBR) modified epoxy resin (ADEKA Co., Ltd .: “Adeka Resin EPR-2007”). ”, Viscosity: 120,000 <mPa · s / 25 ° C.>).

The core-shell type rubber particles have a two-layer structure in which a 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) (Aika Industry ( Co., Ltd .: “ZEFIAC F-351”) was used.
As the reactive diluent, glycidyl ether (manufactured by ADEKA Corporation: “ADEKA GLYCIROL ED-503”) was used.
In addition, as a curing agent for the epoxy resin, dicyandiamide (Japan Epoxy Resin Co., Ltd .: “Jer Cure DICY15”) is used, and as its curing catalyst, an amine adduct system (Ajinomoto Fine Techno Co., Ltd .: “Amicure”). PN50 ") was used.

  In Examples and Comparative Examples, silica (Nihon Aerosil Co., Ltd .: “Aerosil # 380”) was added as a thixotropic agent, and heavy calcium carbonate (Takehara Chemical Industries, Ltd.) was added as a filler.

  As shown in Table 1, in all of Examples 1 to 8 and Comparative Examples 1 to 4, the amount of dicyandiamide as a curing agent was 15 parts by weight, and the amount of amine adduct catalyst was 5 Part by weight, 10 parts by weight of silica as a thixotropic agent, and 120 parts by weight of calcium carbonate as a filler are unified, and the contents of epoxy resin, core-shell rubber particles, and reactive diluent are as follows: The blending amount is changed.

  Specifically, in Example 1, as the epoxy resin, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, and bisphenol A type epoxy resin is 100 parts by weight, urethane modified epoxy resin. 100 parts by weight, 60 parts by weight of core-shell type rubber particles, and 25 parts by weight of glycidyl ether as a reactive diluent.

  In the blending of Example 1, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended at a ratio of 1: 1 by weight. Further, the blending amount of the core-shell type rubber particles is 60 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 25 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Example 2, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin rubber (NBR) modified epoxy resin are used in combination as an epoxy resin, and 100 parts by weight of bisphenol A type epoxy resin and rubber (NBR). ) 100 parts by weight of the modified epoxy resin, 60 parts by weight of the core-shell type rubber particles, and 25 parts by weight of glycidyl ether as the reactive diluent.

  Even in the blending of Example 2, the bisphenol A type epoxy resin as a general-purpose epoxy resin and the rubber (NBR) -modified epoxy resin as a modified epoxy resin are blended at a ratio of 1: 1 by weight. Further, the blending amount of the core-shell type rubber particles is 60 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 25 parts by weight with respect to 100 parts by weight of the rubber (NBR) -modified epoxy resin as the modified epoxy resin. Yes. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the rubber (NBR) modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 wt. The amount of glycidyl ether as a reactive diluent is 12.5 parts by weight.

  In Example 3, a general-purpose epoxy resin bisphenol A-type epoxy resin and a modified epoxy resin urethane-modified epoxy resin are used in combination as an epoxy resin, 133 parts by weight of bisphenol A-type epoxy resin, and 67 parts by weight of urethane-modified epoxy resin. In addition, 60 parts by weight of core-shell type rubber particles and 25 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the blending of Example 3, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended in a ratio of 2: 1 by weight. Further, the blending amount of the core-shell type rubber particles is 90 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 37 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Example 4, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin were used in combination as an epoxy resin, 67 parts by weight of bisphenol A type epoxy resin, and 133 parts by weight of urethane modified epoxy resin. In addition, 60 parts by weight of core-shell type rubber particles and 25 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the blending of Example 4, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended at a weight ratio of 1: 2. Further, the blending amount of the core-shell type rubber particles is 45 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 18 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Example 5, as the epoxy resin, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, and the bisphenol A type epoxy resin is 100 parts by weight and the urethane modified epoxy resin is 100 parts by weight. In addition, 50 parts by weight of core-shell type rubber particles and 25 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the blending of Example 5, bisphenol A type epoxy resin as a general-purpose epoxy resin and urethane-modified epoxy resin as a modified epoxy resin are blended at a weight ratio of 1: 1. Further, the blending amount of the core-shell type rubber particles is 50 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 25 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. In addition, when the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 25 parts by weight. The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Example 6, as the epoxy resin, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, and the bisphenol A type epoxy resin is 100 parts by weight and the urethane modified epoxy resin is 100 parts by weight. In addition, 70 parts by weight of core-shell type rubber particles and 25 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the blending of Example 6, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended at a weight ratio of 1: 1. Further, the blending amount of the core-shell type rubber particles is 70 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 25 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. In addition, when the total compounding amount of the bisphenol A type epoxy resin as the general-purpose epoxy resin and the urethane-modified epoxy resin as the modified epoxy resin is 100 parts by weight, the compounding amount of the core-shell type rubber particles is 35 parts by weight. The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Example 7, as the epoxy resin, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, and the bisphenol A type epoxy resin is 100 parts by weight and the urethane modified epoxy resin is 100 parts by weight. In addition, 60 parts by weight of core-shell type rubber particles and 30 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the blending of Example 7, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended at a ratio of 1: 1 by weight. Further, the blending amount of the core-shell type rubber particles is 60 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 30 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 15 parts by weight.

  In Example 8, as the epoxy resin, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, and the bisphenol A type epoxy resin is 100 parts by weight and the urethane modified epoxy resin is 100 parts by weight. Then, 60 parts by weight of core-shell type rubber particles and 40 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the formulation of Example 8, a bisphenol A type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin are blended at a weight ratio of 1: 1. Further, the blending amount of the core-shell type rubber particles is 60 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 40 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The blending amount of glycidyl ether as a functional diluent is 20 parts by weight.

In contrast to the blending examples, in Comparative Example 1, the blending of the core-shell type rubber particles was reduced to 30 parts by weight, and the other blending contents were blended in the same manner as in Example 1, but various materials were blended.
That is, in Comparative Example 1, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, bisphenol A type epoxy resin is 100 parts by weight, urethane modified epoxy resin is 100 parts by weight, and In addition, 30 parts by weight of core-shell type rubber particles and 25 parts by weight of glycidyl ether as a reactive diluent are blended.

  In the formulation of Comparative Example 1, bisphenol A type epoxy resin as a general-purpose epoxy resin and urethane-modified epoxy resin as a modified epoxy resin are blended at a ratio of 1: 1 by weight, and urethane as a modified epoxy resin. The blending amount of the core-shell type rubber particles is 30 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 25 parts by weight with respect to 100 parts by weight of the modified epoxy resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 15 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

Moreover, in Comparative Example 2, the reactive diluent was not blended, and other materials were blended in the same manner as in Example 1 except that various materials were blended.
In Comparative Example 2, a general-purpose epoxy resin bisphenol A type epoxy resin and a modified epoxy resin urethane modified epoxy resin are used in combination, bisphenol A type epoxy resin 100 parts by weight, urethane modified epoxy resin 100 parts by weight, and core shell The mold rubber particles are blended in 30 parts by weight.

  In Comparative Example 3, although a general-purpose epoxy resin bisphenol A-type epoxy resin and a modified epoxy resin urethane-modified epoxy resin are used in combination, a bisphenol A-type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin The blending weight ratio was 1: 3. Other ingredients were blended in the same manner as in Example 1 and various materials were blended.

That is, in Comparative Example 3, 50 parts by weight of bisphenol A type epoxy resin, 150 parts by weight of urethane-modified epoxy resin, 60 parts by weight of core-shell type rubber particles, and 25 parts by weight of glycidyl ether as a reactive diluent. The composition of the part.
In the blending of Comparative Example 3, the blending ratio of the bisphenol A type epoxy resin as the general-purpose epoxy resin and the urethane-modified epoxy resin as the modified epoxy resin is 1: 3 by weight, and the urethane-modified epoxy as the modified epoxy resin. The amount of the core-shell type rubber particles is 40 parts by weight and the amount of glycidyl ether as the reactive diluent is 22 parts by weight with respect to 100 parts by weight of the resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  In Comparative Example 4, although a general-purpose epoxy resin bisphenol A-type epoxy resin and a modified epoxy resin urethane-modified epoxy resin are used in combination, a bisphenol A-type epoxy resin as a general-purpose epoxy resin and a urethane-modified epoxy resin as a modified epoxy resin The blending weight ratio was 3: 1. Other ingredients were blended in the same manner as in Example 1 and various materials were blended.

That is, in Comparative Example 4, 150 parts by weight of bisphenol A type epoxy resin, 50 parts by weight of urethane-modified epoxy resin, 60 parts by weight of core-shell type rubber particles, and 25 parts by weight of glycidyl ether as a reactive diluent. The composition of the part.
In the composition of Comparative Example 4, the blending ratio of the bisphenol A type epoxy resin as the general-purpose epoxy resin and the urethane modified epoxy resin as the modified epoxy resin is 3: 1 by weight, and the urethane modified epoxy as the modified epoxy resin. The amount of the core-shell type rubber particles is 120 parts by weight and the amount of the glycidyl ether as the reactive diluent is 50 parts by weight with respect to 100 parts by weight of the resin. When the total blending amount of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin is 100 parts by weight, the blending amount of the core-shell type rubber particles is 30 parts by weight, reaction The amount of glycidyl ether as a functional diluent is 12.5 parts by weight.

  And various materials are mix | blended with the compounding quantity shown in Table 1 in this way, and it mixes using a high-speed mixer at room temperature, Various adhesive composition (Example 1 thru | or Example 8 and Comparative Example 1 thru | or) Comparative Example 4) was prepared.

Here, about the adhesive composition concerning these each compounding, application to the joining of structural members, such as a steel plate of an automobile body (use as a structural adhesive), and measurement evaluation of viscosity under a predetermined temperature condition The shear strength was measured and evaluated.
As for the viscosity, using a SOD viscometer (manufactured by Kogyo Co., Ltd .: “Cat. No. 860R-01M”), based on the JIS-K2220, the measurement condition was a shear rate of 15.5 s ⁻¹ . The viscosity (material viscosity) of the adhesive composition at each of the three levels of 5 ° C., 40 ° C., and 60 ° C. (temperature control with a circulating high-temperature bath or heater) was measured.

  In the body assembly line in which spot welding is performed after the adhesive composition is applied to the structural member in consideration of the use of the weld bond method for joining the structural member, the temperature is close to 5 ° C. in winter. Therefore, if the viscosity at 5 ° C. assuming winter is within the range of 4,500 Pa · s to 8,000 Pa · s (4,500 Pa · s or more, 8,000 Pa · s or less), Even when the temperature was low, the adhesive composition applied to the joining site in the weld bond method was sufficiently crushed and the structural members to be joined were brought into close contact with each other, and evaluated as “◯” because no poor conduction occurred during spot welding. The low viscosity of less than 4,500 Pa · s has a problem that the fluidity is high and the bonding strength is inferior. On the other hand, the high viscosity of more than 8,000 Pa · s is too high and the weld is weak. In the bond method, the adhesive composition applied to the bonding site was not sufficiently crushed and the structural members to be bonded could not be closely adhered to each other.

  In addition, the viscosity at 40 ° C. assuming the ambient temperature in the cleaning process in the electrodeposition coating process after the body assembly process is in the range of 500 Pa · s to 900 Pa · s (500 Pa · s or more and 900 Pa · s or less). If present, it can sufficiently resist the flowing water pressure in the cleaning treatment, has higher resistance to flowing water pressure to prevent scattering of the adhesive composition, etc., and is sufficient as a viscosity required for the structural adhesive composition. Therefore, it was evaluated as “Good”. Those having a low viscosity of less than 500 Pa · s were evaluated as “x” because the resistance to flowing water pressure could not be made higher than before.

  Furthermore, when applying to an object to be applied (adhered object), assuming a heating temperature at which the adhesive composition is hardened by applying a reduced viscosity by heating (hot application) at 60 ° C., If the viscosity at 60 ° C. is in the range of 100 Pa · s to 300 Pa · s (100 Pa · s or more and 300 Pa · s or less), good coating workability is obtained, and the evaluation is “◯”. About what exceeded 300 Pa.s, even if it heated, it was evaluated as x, since the discharge | emission defect etc. would arise without being sufficiently reduced in viscosity, and coating workability | operativity will fall. In addition, about the thing with a low viscosity of less than 100 Pa * s, it evaluated as x from a viewpoint that generation | occurrence | production of sagging or a dripping at the time of discharge may be anxious at 60 degreeC.

The shear strength was measured according to JIS K6850. That is, an adhesion test body was prepared using each of the adhesive compositions of Examples and Comparative Examples, and then a tensile shear adhesive strength test was performed to measure the shear strength (shear adhesive strength).
Specifically, 10 mm × 100 mm × 1.6 mm steel plates are prepared as a set as a test panel, and each adhesive is bonded over a length range of 10 mm from one longitudinal end of the one panel. The adhesive composition was applied at a thickness of 0.15 mm, and one end of the other panel was overlapped on the surface to which the adhesive composition was applied, and adhered in a straight line (adhesive layer between joints of both panels: 10 mm × 10 mm × thickness 0.15 mm). Next, each adhesive composition was heat-cured in a hot air oven under conditions of 170 ° C. × 30 minutes in the same manner as the baking conditions for a general electrodeposition coating film on a vehicle body, and a completely cured adhesive composition layer was formed. The adhesion test body joined via the was produced. Both ends of this adhesion test body were pulled in the longitudinal direction at a tensile speed of 10 mm / min using a tensile tester (manufactured by Shimadzu Corporation), and the shear strength was measured at room temperature (20 ° C.).
If the shear strength at this time is 25 MPa or more, the adhesiveness required for the structural adhesive composition is sufficiently high, so it was evaluated as “good”, and those having less than 25 MPa were evaluated as “poor” because the adhesiveness was low. .

  The results of the measurement evaluation of the viscosity and the measurement evaluation of the shear strength are as shown in the lower part of Table 1. Further, the ratio of the viscosity at 5 ° C. to the viscosity at 40 ° C. and the ratio of the viscosity at 60 ° C. to the viscosity at 40 ° C. were calculated, and the values are shown in Table 1.

  As shown in Table 1, in Examples 1 to 8, the viscosity at 40 ° C. is as high as 500 Pa · s to 700 Pa · s, but the viscosity at 5 ° C. is 5000 Pa · s to 8000 Pa · s. The viscosity ratio of the 5 ° C. viscosity to the 40 ° C. viscosity is 9.3 to 12.3, and the viscosity at 60 ° C. is 140 Pa · s to 280 Pa · s. The viscosity ratio of the viscosity is 0.28 to 0.40. That is, although the viscosity at 40 ° C. is as high as 500 Pa · s to 700 Pa · s, the viscosity fluctuation with respect to the temperature change is small. Furthermore, the shear strength after curing is also as good as 26 to 30 MPa.

That is, in Examples 1 to 8, the viscosity at 40 ° C. is as high as 500 Pa · s to 700 Pa · s, and shows high viscosity characteristics under the atmospheric temperature during the cleaning process, but 60 ° C. assuming hot apply. The viscosity is 140 Pa · s to 280 Pa · s, suitable for hot-applying workability, and the viscosity at 5 ° C assuming winter is 5000 Pa · s to 8000 Pa · s. Even under low temperatures, the adhesive composition applied to the joint site in the weld bond method is sufficiently crushed and the structural members to be joined are brought into close contact with each other, making it suitable for spot welding without causing energization failure during spot welding. It turns out that it becomes a viscosity characteristic.
Furthermore, the shear strength after heating under the general baking conditions for electrodeposition coating on the vehicle body and complete curing is sufficiently high.

On the other hand, in Comparative Example 1, the amount of the core-shell type rubber particles is less than that of the example, and the amount of the core-shell type rubber particles is 30 parts per 100 parts by weight of the urethane-modified epoxy resin as the modified epoxy resin. It is a part by weight.
In Comparative Example 1 having such a composition, the viscosity at 40 ° C. is as low as 300 Pa · s due to the small amount of the core-shell rubber particles, and when the viscosity is as low as 300 Pa · s, the adhesive composition is applied. If the range is widened or the coating thickness is increased, it will not be able to sufficiently resist the flowing water pressure during the cleaning process, resulting in a lot of scattering, displacement (displacement), outflow, etc. of the adhesive composition. It easily causes contamination of the electrodeposition liquid. Moreover, the viscosity at 5 ° C. is 3500 Pa · s and the viscosity at 60 ° C. is 90 Pa · s, which causes a decrease in bonding strength due to dripping after coating. Further, in Comparative Example 1, the shear strength is also inferior.

In Comparative Example 2, glycidyl ether as a reactive diluent is not blended.
In Comparative Example 2 having such a blend, although the viscosity at 40 ° C. is as high as 800 Pa · s and the shear strength is good, glycidyl ether as a reactive diluent is not blended, so that 5 ° C. The viscosity ratio of 5 ° C. to 40 ° C. viscosity is 31.3 at a viscosity of 25000 Pa · s, and the viscosity ratio of 60 ° C. viscosity to 40 ° C. viscosity at 350 ° C. is 0.44. Yes, the viscosity variation with temperature change is large.
Therefore, even if it is heat-treated at the time of application, it cannot be sufficiently reduced in viscosity, and even if it is difficult to apply or even if it can be applied, it is bonded in a weld bond method at low temperatures such as in winter. The adhesive composition applied to the site is not sufficiently crushed and the structural members to be joined cannot be brought into close contact with each other.

Further, in Comparative Example 3, the mixing ratio of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin was 1: 3 by weight, and urethane as a modified epoxy resin was used. The blending amount of the core-shell type rubber particles is 40 parts by weight and the blending amount of glycidyl ether as the reactive diluent is 22 parts by weight with respect to 100 parts by weight of the modified epoxy resin.
In Comparative Example 3 having such a composition, the viscosity at 40 ° C. is as high as 700 Pa · s, and the viscosity at 60 ° C. is 220 Pa · s, which is also suitable for application workability by hot apply and has good shear strength. However, the viscosity ratio at 5 ° C. is 12000 Pa · s and the viscosity ratio of the 50 ° C. viscosity to the 40 ° C. viscosity is 17.1, and the viscosity variation with respect to the temperature change is large on the low temperature side. In the construction method, the adhesive composition applied to the joining site is not sufficiently crushed and the structural members to be joined cannot be brought into close contact with each other.

In Comparative Example 4, the mixing ratio of the bisphenol A type epoxy resin as a general-purpose epoxy resin and the urethane-modified epoxy resin as a modified epoxy resin was 3: 1 by weight, and urethane as a modified epoxy resin was used. In 100 parts by weight of the modified epoxy resin, the amount of the core-shell type rubber particles is 120 parts by weight, and the amount of the glycidyl ether as the reactive diluent is 50 parts by weight. Although a high shear strength can be obtained, the viscosity at 40 ° C. is as low as 400 Pa · s, and when the application range of the adhesive composition is widened or the application thickness is increased, it is sufficient for the flowing water pressure during the cleaning process. It cannot resist, and the adhesive composition often scatters, displaces (displaces), flows out, etc., and easily causes poor coating or contamination of the electrodeposition liquid. Further, since the viscosity at 5 ° C. is 4000 Pa · s and the viscosity at 60 ° C. is 95 Pa · s, the bonding strength is reduced due to dripping after coating.

  Thus, the blending balance of the general-purpose epoxy resin and the modified epoxy resin is controlled within the range of 1: 2 to 2: 1 by weight ratio, and further, the core-shell type rubber with respect to 100 parts by weight of the modified epoxy resin. In Examples 1 to 8, in which the particles were blended in the range of 45 to 90 parts by weight and the reactive diluent was blended in the range of 18 to 40 parts by weight, the viscosity at 40 ° C. was 500 Pa.・ Since it has a high viscosity of s to 700 Pa · s and high viscosity characteristics are obtained, the resistance to flowing water pressure during washing (flowing water pressure resistance) is extremely high, and the adhesive is uncured due to the flowing water pressure during washing, etc. Since the composition is less likely to scatter, it is possible to widen the application range to the bonding site or increase the application thickness. That is, even if the adhesive composition protrudes from the joint end by expanding the application range to the joining site or by increasing the application thickness, the surplus part of the adhesive composition is washed with running water during cleaning. Since it is difficult to scatter due to pressure or the like, there is no possibility of adhering to the vehicle body and causing a coating failure, contamination of a pre-painting treatment liquid (such as an electrodeposition liquid), or a processing failure in a later sealer process. In addition, since it has such a high viscosity, it is possible to easily remove the excess part of the adhesive composition protruding from the adhesion site even in an uncured state, and the adhesive composition can be removed by removing the excess part. Can prevent coating defects due to spraying, etc., resulting in poor coating, contamination of the pre-painting treatment liquid, etc., and subsequent processing failures in the sealer process.

Even if the viscosity at 40 ° C. is 500 Pa · s to 700 Pa · s and the viscosity property is high, the viscosity ratio at 60 ° C. to the viscosity at 40 ° C. is within the range of 0.28 to 0.40. Since the viscosity at ° C is in the range of 140 Pa · s to 280 Pa · s, it has a viscosity characteristic that can be sufficiently reduced by heating at a temperature that does not cause curing, and the application workability is also good. Even when the discharge amount is varied, stable coating quality can be obtained. Furthermore, it is difficult to sag after coating, and has high shape retention and fixability to an adherend.
In addition, the viscosity ratio at 5 ° C to the viscosity at 40 ° C is within the range of 9.3 to 12.3, and the viscosity at 5 ° C is within the range of 5000 to 8000 Pa · s. The structural members to be joined are sufficiently crushed and bonded to each other, and good spot weldability can be secured without causing poor electrical conduction during spot welding, and high joint strength can be obtained at the joint. Therefore, the bonding reliability is high. In addition, the adhesion of the adhesive composition to the spot gun electrode during spot welding is small, and workability can be improved.

  And according to the structural adhesive composition of a present Example, even if it preserve | saves for a long period of time, a viscosity fluctuation with time is few, can maintain a predetermined viscosity, and its storage stability is high. This is presumed to be because the viscosity variation with respect to the temperature change is small in spite of the extremely high viscosity characteristics at the atmospheric temperature (around 40 ° C.) in the electrodeposition coating process having the cleaning process as described above. In addition, the rubber particles are core-shell type and have low reactivity with the epoxy resin, there is little increase in viscosity due to the rubber component being dissolved in the epoxy resin, and there is no need for heating when preparing the adhesive composition. The lack of progress is also considered as a factor.

  Further, in the experimental study of the present inventors, according to the structural adhesive composition of this example of such a formulation, not only the shear strength after curing but also the peel strength is high, and the rubber particles are core-shell type Therefore, the cured product shows a high elastic modulus because the rubber component does not remain dissolved in the epoxy resin phase. Therefore, high adhesive force is maintained even in an environment with a large amount of moisture, and the adhesion reliability is high.

  Furthermore, according to the structural adhesive composition of this example having such a composition, the glass transition temperature after heat-curing is kept high, the heat resistance is high, and the shear strength and the like are increased even at a high temperature (for example, 80 ° C.). Excellent peel strength and high adhesive strength. Therefore, for example, when the vehicle travels, such as the roof rails of automobiles, parts such as various billers, and hemming parts of parts called lids (opening parts) such as hoods, doors, trunk lids, etc. It is also useful for application to high temperature sites. The glass transition temperature is high due to the use of general-purpose epoxy resin and modified epoxy resin, and because the rubber particles are core-shell type, the rubber component does not dissolve in the cured epoxy resin phase and the glass transition temperature decreases. It is speculated that there is also a reason for not doing it.

In addition, according to the structural adhesive composition of this example having such a composition, curing at a low temperature is possible due to the high viscosity, and the adhesive strength is reduced even if the temperature when curing is low. In other words, for example, a temperature distribution range of about 20 minutes to about 60 minutes at a temperature of about 150 ° C. to about 220 ° C. is expanded.
And in the present Example, since the viscosity was improved, it was possible to reduce the flow down due to the decrease in the viscosity of the adhesive at the initial stage of the heat treatment when curing, and to reduce the adhesion failure. In particular, the incorporation of silica as a filler prevents dicyandiamide from precipitating and heterogeneous due to a decrease in viscosity during heat curing, and also prevents interfacial breakage caused by dicyandiamide precipitating and heterogeneous. .

Further, according to the experimental study by the present inventors, in the structural adhesive composition of this example having such a composition, the volume resistivity ρ after curing was measured by the double ring electrode method based on IEC600093. 1 × 10 ¹³ Ωcm and high insulation properties, and when the structural adhesive composition of this example is used for joining different metal members such as iron and aluminum, for example, galvanic corrosion (dissimilar metal contact corrosion) It was confirmed that there is an inhibitory effect.

  As described above, the structural adhesive composition of the present example includes a bisphenol A type epoxy resin as a general-purpose epoxy resin, a urethane-modified epoxy resin or a rubber-modified epoxy resin as a modified epoxy resin, and a core-shell type rubber. Containing particles, glycidyl ether as reactive diluent, dicyandiamide and amine catalyst as curing agent, silica as thixotropic agent, calcium carbonate as filler, bisphenol A type epoxy resin and urethane modified epoxy The resin / rubber modified epoxy resin is blended in a weight ratio of 1: 2 to 2: 1, and 45 to 90 core-shell type rubber particles are added to 100 parts by weight of the urethane modified epoxy resin / rubber modified epoxy resin. In the range of parts by weight, glycidyl ether was blended in the range of 18 to 40 parts by weight. Than is. In the structural adhesive composition of this example, the core-shell type rubber particles are 25 to 35 parts by weight with respect to 100 parts by weight in total of the bisphenol A type epoxy resin and the urethane-modified epoxy resin / rubber-modified epoxy resin. In the range of parts, the reactive diluent is in the range of 12.5 parts by weight to 20 parts by weight.

  According to the structural adhesive composition of this example, a general-purpose epoxy resin and a modified epoxy resin are used in combination as an epoxy resin, the blending balance is controlled within a predetermined range, and the blending of core-shell type rubber particles is also performed. By setting the amount to be a predetermined amount and further defining the amount of the reactive diluent to be a predetermined amount, the viscosity characteristic at the atmospheric temperature (around 40 ° C.) in the electrodeposition coating process having a cleaning process is extremely high, Moreover, the viscosity variation with respect to the temperature change is small, the application workability by hot application can be ensured, the bonding strength by the weld bond method can be ensured even at a low temperature, and the adhesiveness after curing is also good. That is, when the adhesive composition is heated and applied, the adhesive composition has an appropriate viscosity characteristic and does not deteriorate the workability of the application, and the adhesive composition applied to the bonding site in the weld bond method even at a low temperature is sufficient. The structural members that are crushed and joined are brought into close contact with each other, there is no poor conduction during spot welding, stable spot weldability is obtained without reducing joint strength, and the ambient temperature conditions during the cleaning process Then, it has a high viscosity characteristic and high flowing water pressure resistance is obtained, and adhesion of a cured product after curing can be secured.

Here, when the blending amount of the core-shell type rubber particles is small, the blending amount of the core-shell type rubber particles is less than 45 parts by weight with respect to 100 parts by weight of the modified epoxy resin based on the comparison between Example and Comparative Example 1. And the desired high viscosity characteristics at the atmospheric temperature (around 40 ° C) in the electrodeposition coating process with cleaning treatment, that is, the resistance to flowing water pressure during cleaning is improved, and the application range to the joint is expanded. Even if the coating thickness is increased, high viscosity characteristics cannot be obtained to such an extent that the scattering or outflow is effectively prevented. Moreover, in the hardened | cured material which the structural adhesive composition hardened | cured, high shear strength is not obtained and adhesiveness falls.
On the other hand, if the amount of the core-shell type rubber particles is too large, according to the experimental study by the present inventors, the amount of the core-shell type rubber particles exceeds 90 parts by weight with respect to 100 parts by weight of the modified epoxy resin. And the adhesiveness falls because the compounding quantity of other materials becomes relatively small. Furthermore, the increase in the viscosity of the material is so great that even if it is heated at a predetermined temperature during application, it cannot be sufficiently reduced in viscosity, so that the workability of the application is reduced or the weld bond method is used in a low temperature environment such as winter. The strength also decreases.

  If the blending amount of the core-shell type rubber particles is within the range of 45 to 90 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin / rubber-modified epoxy resin that is a high-viscosity resin, the cleaning treatment is performed. The desired high viscosity characteristics can be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process, and the resistance to flowing water pressure can be further improved, and the adhesive composition can be applied by hot apply. Structural members to be joined that have viscosity characteristics and that have appropriate viscosity characteristics to such an extent that the adhesive composition applied to the bonding site is sufficiently crushed even at low temperatures during spot welding in the weld bond method. Good application workability and bonding strength can be obtained without causing poor electrical conduction during spot welding, and high shear strength can be ensured.

In addition, from Comparative Example 2, if a reactive diluent is not blended, the viscosity variation of the material with respect to the temperature change becomes large, and even when heated at a predetermined temperature during application, it cannot be sufficiently reduced in viscosity. Workability is reduced. Furthermore, as a result of investigation by the present inventors, when the blending amount of the glycidyl ether as the reactive diluent is less than 18 parts by weight with respect to the blending amount of the modified epoxy resin of 100 parts by weight, good coating workability is ensured. Is difficult. In addition, during spot welding in the weld bond method, the viscosity is high in a low temperature environment such as in winter, so that the adhesive composition applied to the joining site is not sufficiently crushed and the structural members to be joined are not in close contact with each other. As a result, the energization is poor and the bonding strength is reduced.
On the other hand, if the amount of the reactive diluent is too large, according to the experimental study by the present inventors, the amount of glycidyl ether as the reactive diluent is 100 parts by weight of the modified epoxy resin. If it exceeds 40 parts by weight, the desired high viscosity characteristics can be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process having a cleaning process because the blending amount of other materials becomes relatively small. Or the adhesiveness after curing decreases.

  If the compounding amount of the reactive diluent is in the range of 18 parts by weight to 40 parts by weight with respect to 100 parts by weight of the urethane-modified epoxy resin / rubber-modified epoxy resin, the ambient temperature during the washing step (40 The desired high viscosity characteristics can be obtained at around (° C.), and the adhesive composition can be applied by hot-applying. It is suitable for spot welding in the weld bond method even at low temperatures. The adhesive composition has adequate viscosity characteristics to such an extent that it can be sufficiently crushed, and the structural members to be joined can be brought into close contact with each other without causing poor electrical conduction during spot welding, resulting in good coating workability and bonding strength. Furthermore, the adhesiveness after curing can be secured.

  Further, from Comparative Example 3, when the amount of urethane-modified epoxy resin / rubber-modified epoxy resin is relatively increased and the amount of bisphenol A type epoxy resin is decreased, the viscosity variation with respect to the temperature change is increased particularly on the low temperature side. In the low temperature environment, the weld bond method has a high viscosity during spot welding, and the adhesive composition applied to the joining site is not sufficiently crushed, and the structural members to be joined are not in close contact with each other. Good bonding strength cannot be obtained.

On the other hand, as shown in Comparative Example 4, the amount of the bisphenol A type epoxy resin is relatively increased in the blending relationship between the bisphenol A type epoxy resin and the urethane modified epoxy resin / rubber modified epoxy resin. When the amount of the rubber-modified epoxy resin is reduced, the desired high viscosity characteristic cannot be obtained under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having a cleaning treatment.
That is, if the blending weight ratio of the bisphenol A type epoxy resin and the urethane-modified epoxy resin / rubber-modified epoxy resin deviates from 1: 2 to 2: 1, a good bonding strength cannot be obtained in the weld bond method, or a cleaning process is performed. The desired high viscosity characteristic may not be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process.

  Washing is performed when the blending weight ratio of the general-purpose epoxy resin and the modified epoxy resin is within a range of 1: 2 to 2: 1 (including 1: 2 and 2: 1) with an equivalent of 1: 1 in between. The desired high viscosity characteristics can be obtained under the atmospheric temperature conditions (around 40 ° C.) in the electrodeposition coating process with treatment, and the resistance to flowing water pressure can be reliably improved, and the viscosity variation with temperature change It has a small viscosity characteristic when applied with hot-apply adhesive, and the adhesive composition applied to the joint area is sufficiently crushed even at low temperatures during spot welding in the weld bond method. Therefore, it is possible to adhere the structural members to be joined to each other and to obtain good application workability and bonding strength of the joint without causing poor electrical conduction.

  In the structural adhesive composition of this example, a modified epoxy resin having high viscosity characteristics is used in combination with a general-purpose epoxy resin, and the blending balance thereof is bisphenol A type epoxy resin: urethane modified epoxy resin / rubber modified epoxy resin = 1. : In the range of 2 to 2: 1, and further, the core-shell type rubber particles are in the range of 45 to 90 parts by weight with respect to the total of 100 parts by weight of the urethane-modified epoxy resin and rubber-modified epoxy resin. When the diluent is in the range of 18 parts by weight to 40 parts by weight, the viscosity at 40 ° C. is 500 to 700 Pa · s, high viscosity characteristics can be obtained, good adhesiveness can be secured, and 40 ° C. The viscosity ratio at 60 ° C. with respect to the viscosity can be 0.28 to 0.40, and the viscosity at 60 ° C. is 140 to 280 Pa · s. Having. Furthermore, the viscosity ratio of 5 ° C. to the viscosity of 40 ° C. can be set to 9.3 to 12.3, the viscosity at 5 ° C. is 5000 to 8000 Pa · s, and the adhesive is used in the weld bond method even at low temperatures in winter. Adhesive composition applied to the joint site during spot welding after application of the composition has an appropriate viscosity characteristic so that the structural members to be joined can be brought into close contact with each other without causing poor electrical conduction. .

  Thus, by obtaining a high viscosity characteristic with a viscosity at 40 ° C. of 500 to 700 Pa · s, the resistance to flowing water becomes extremely high, and the uncured adhesive composition is scattered by the flowing water pressure at the time of washing, etc. Since it is difficult to displace (displacement), outflow, dropout, etc., it is possible to widen the application range and apply the entire joint area, or to expand the application range. It becomes applicable to. Furthermore, even after the application of the adhesive composition to the adherend site and before the baking process (heat curing process), not only the cleaning process but also the processes such as bending, cutting, and acid treatment are performed. At this time, it is difficult for the adhesive composition in an uncured state to scatter, and contamination of the pre-coating treatment liquid due to outflow of the adhesive composition, deterioration of the working environment, and the like are prevented.

Moreover, as a viscosity characteristic with a viscosity at 40 ° C. of 500 to 700 Pa · s, the viscosity ratio at 60 ° C. with respect to the viscosity at 40 ° C. within the range of 140 to 280 Pa · s at 60 ° C. is 0.28 to 0.8. Since it is within the range of 40, the viscosity does not become too high even when heating is performed at a temperature condition (for example, 50 to 60 ° C.) that does not cause curing, and the viscosity is sufficiently reduced by heating and is suitable for coating. It has the characteristics, the coating workability is good, it is difficult to sag after coating, and the shape retention and fixing property to the adherend are high.
Further, as a high viscosity characteristic having a viscosity at 40 ° C. of 500 to 700 Pa · s, the viscosity ratio at 5 ° C. with respect to the viscosity at 40 ° C. is within the range of 9.3 to 12. 3 is within the range, the viscosity does not become too high at the time of spot welding after applying the adhesive composition in the weld bond method even at low temperatures, and the adhesive composition applied to the joint site is sufficiently crushed. In this way, the structural members to be joined are brought into close contact with each other, so that a poor electrical conduction is not caused, and good joining strength is obtained with an appropriate fixing property.
In addition, even if the viscosity is increased under the ambient temperature condition (around 40 ° C.) during the cleaning step, sufficient shear bond strength can be maintained without affecting the shear bond strength after curing.
Note that the numerical values of the viscosity (Pa · s) and the viscosity ratio have been made suitable by the experimental study by the inventors as described above in the viscosity evaluation, and are not necessarily required to be strict. Even if the numerical values are changed slightly, the implementation is not denied.

Further, in the structural adhesive composition of this example, the viscosity of the bisphenol A type epoxy resin and the urethane-modified epoxy resin / rubber-modified epoxy resin is 5000 (mPa · s / 25 ° C.) to 200000 (mPa · s /), respectively. 25.degree. C.) and because they are liquid at room temperature, they are easy to handle and easy to prepare without the need for heat treatment during preparation.
Furthermore, the general-purpose epoxy resin is a biphenol A type epoxy resin, and the modified epoxy resin is a urethane-modified epoxy resin and / or a rubber-modified epoxy resin, so that high shear strength and peel strength can be obtained at low cost and high adhesion. Have sex.

Thus, according to the structural adhesive composition of the present invention, although the viscosity characteristics under the atmospheric temperature condition (around 40 ° C.) in the electrodeposition coating process having the cleaning process are extremely high, the viscosity fluctuation with respect to the temperature change It has a small viscosity characteristic that can be sufficiently reduced by heating at a temperature that does not cause curing, and has an appropriate viscosity characteristic for spot welding after applying the adhesive composition in the weld bond method even at low temperatures. In addition, the adhesive composition applied to the joining portion is sufficiently crushed and the structural members to be joined are brought into close contact with each other, so that poor conduction is not caused and good coating workability and joining strength are obtained. Furthermore, adhesion can be secured.
That is, the atmospheric temperature in the electrodeposition coating process having a cleaning process without lowering the adhesiveness and without lowering the bonding strength at low temperatures by the weld bond method or lowering the coating workability by hot apply. The viscosity in can be improved.

  Therefore, the structural adhesive composition of the present invention is a structural member for automobiles, vehicles (bullet trains, trains), civil engineering, architecture, electronics, aircraft, space industry, etc. (for example, organic materials / polymers such as metal materials and plastics). In addition to adhesives for materials, inorganic materials such as concrete), adhesives for medical, general office, and electronic materials (for example, interlayer adhesives for multilayer substrates such as build-up substrates, die bonding agents, It can also be used as a semiconductor adhesive such as underfill, BGA reinforcing underfill, anisotropic conductive film (ACF), anisotropic conductive paste (ACP), etc. Applicable. In addition, not only as an adhesive, but as an epoxy resin composition for general use, such as paints, coating agents, molding materials (including sheets, films, FRP, etc.), insulating materials (printed boards, wire coatings) Etc.), sealant (for example, potting for capacitors, transistors, diodes, light emitting diodes, ICs, LSIs, etc., dipping, transfer mold sealing, ICs, LSIs for COB, COF, TAB, etc.) It is also possible to apply to underfill for flip-flops, etc., sealing when mounting IC packages such as QFP, BGA, and CSP).

  When practicing the present invention, the composition, components, blending amount, adjustment method, and the like of other parts of the structural adhesive composition are not limited to the above-described embodiments. Furthermore, the numerical values given in the embodiments and examples of the present invention are not all critical values, and certain numerical values indicate preferred values suitable for implementation, so the numerical values are slightly changed. However, it does not deny the implementation.

Claims (5)

A structural adhesive composition containing at least an epoxy resin, core-shell type rubber particles, a reactive diluent, and a curing agent,
As the epoxy resin, a general-purpose epoxy resin and a modified epoxy resin are used in combination within a weight ratio of 1: 2 to 2: 1,
The core-shell type rubber particles are blended in the range of 45 to 90 parts by weight and the reactive diluent is blended in the range of 18 to 40 parts by weight with respect to 100 parts by weight of the modified epoxy resin. Structural adhesive composition.   The structural adhesive composition according to claim 1, wherein the general-purpose epoxy resin and the modified epoxy resin have a viscosity in a range of 5000 to 200000 mPa · s / 25 ° C.   3. The structural epoxy resin according to claim 1, wherein the general-purpose epoxy resin is a bisphenol A type epoxy resin, and the modified epoxy resin is a urethane-modified epoxy resin and / or a rubber-modified epoxy resin. Adhesive composition.   The structural adhesive composition has a viscosity at 5 ° C. in the range of 5000 to 8000 Pa · s, a viscosity at 40 ° C. in the range of 500 to 700 Pa · s, and a viscosity at 60 ° C. of 140 to 280 Pa · s. The structural adhesive composition according to any one of claims 1 to 3, wherein the structural adhesive composition is within a range of s.   The structural adhesive composition has a viscosity of 40 ° C. within a range of 500 to 700 Pa · s, a viscosity ratio of 60 ° C. to a viscosity of 40 ° C. within a range of 0.28 to 0.40, and The structural adhesive composition according to any one of claims 1 to 3, wherein the viscosity ratio at 5 ° C to the viscosity at 40 ° C is in the range of 9.3 to 12.3. .