KR102445301B1 - Thermal curable adhesive composition, composite structure having adhesive layer and its preparation method - Google Patents

Abstract

The present invention relates to a thermosetting adhesive composition that enables the formation of an adhesive layer that exhibits improved impact peel strength in a wide temperature range including low temperatures and exhibits long-term reliability in environments exposed to high temperatures, high humidity and salt water, and an adhesive layer formed using the same It relates to a structure comprising a structure and a method for manufacturing the same. The thermosetting adhesive composition may include an epoxy resin; silane-modified epoxy resin; a core-shell structure rubber copolymer comprising a core including a rubber polymer and a shell including a polymer cross-linked or graft-bonded to the core; Polyurethane resin containing a polymer block derived from polyalkylene glycol; and a thermal curing agent.

Description

A thermosetting adhesive composition, a structure including an adhesive layer, and a method for manufacturing the same

The present invention relates to a thermosetting adhesive composition having excellent adhesive strength and enabling the formation of an adhesive layer exhibiting improved impact peel strength in a wide temperature range including low temperatures, a structure including an adhesive layer formed using the same, and a method for manufacturing the same .

Epoxy-based thermosetting adhesives having an epoxy resin as a main component are widely used to bond various substrates such as wood, resin, and metal to each other due to their high heat resistance and excellent adhesive strength.

In particular, recently, the epoxy-based thermosetting adhesive has been widely used for metal-to-metal bonding and metal-to-plastic bonding included in automobile body structures or other mechanical and electronic structures across various products and uses. Among them, in order to reduce the number of welds required for frame manufacturing and reduce overall process cost during the automobile manufacturing process, its application is gradually expanding. Furthermore, in future industrial fields such as aerospace fields and wind power generation fields, interest in the epoxy-based thermosetting adhesive is increasing, and its application is expanding to simplify the overall process and reduce costs.

As such, as the field of application and use of the epoxy-based thermosetting adhesive is expanded, the level of physical properties required for this is gradually increasing. In particular, in the case of automobiles, as actual usage conditions range from a minimum of -40°C to a maximum of 80°C, the adhesive layer formed from the adhesive is required to maintain excellent adhesive strength and impact strength in a wider temperature range.

However, in the case of the epoxy-based adhesive composition developed so far, the impact strength is greatly reduced at a low temperature of the adhesive layer formed therefrom up to -40°C, and its adhesive strength is also insufficient, so its application is limited. Accordingly, research to develop an adhesive that maintains excellent impact strength in a wider temperature range, such as adding a rubber-based reinforcing material, various modified resins, or inorganic fillers to the existing adhesive composition is continuing.

In spite of such continuous research and efforts, an adhesive that exhibits excellent impact strength and adhesive strength at such low temperatures has not yet been properly developed.

The present invention has excellent adhesive strength, exhibits improved impact resistance in a wide temperature range including low temperatures, and exhibits excellent adhesive strength even in environments exposed to high temperatures, high humidity and salt water. To provide an adhesive composition.

In addition, the present invention provides a structure including an adhesive layer formed from the adhesive composition and a method for manufacturing the same.

The present invention is an epoxy resin;

silane-modified epoxy resin;

a core-shell structure rubber copolymer comprising a core including a rubber polymer and a shell including a polymer cross-linked or graft-bonded to the core;

Polyurethane resin containing a polymer block derived from polyalkylene glycol; and

A heat curable adhesive composition comprising a heat curing agent is provided.

The present invention also comprises the steps of applying the thermosetting adhesive composition of the present invention on a substrate; And it provides a method of manufacturing a structure having an adhesive layer comprising the step of thermally curing the applied composition.

In addition, the present invention provides a structure comprising a substrate and an adhesive layer including a cured product of the heat-curable adhesive composition of the present invention. In this structure, the adhesive layer may include a binder layer in which an epoxy resin and a silane-modified epoxy resin are crosslinked via a thermal curing agent, and a core-shell structure rubber copolymer and a polyurethane resin dispersed in the binder layer.

Hereinafter, the thermosetting adhesive composition according to embodiments of the present invention, a structure having an adhesive layer formed therefrom, and a method for manufacturing the same will be described in detail.

Prior to that, unless explicitly stated herein, terminology is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention.

As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.

As used herein, the meaning of 'comprising' specifies a particular characteristic, region, integer, step, operation, element and/or component, and other specific characteristic, region, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of

On the other hand, according to an embodiment of the invention, an epoxy resin; silane-modified epoxy resin; a core-shell structure rubber copolymer comprising a core including a rubber polymer and a shell including a polymer cross-linked or graft-bonded to the core; Polyurethane resin containing a polymer block derived from polyalkylene glycol; And there is provided a heat curable adhesive composition comprising a heat curing agent.

The present inventors researched to develop an adhesive capable of forming an adhesive layer that exhibits excellent impact resistance properties in a wide temperature range, particularly at low temperatures up to -40°C, and exhibits excellent adhesive strength even in environments exposed to high temperature, high humidity and salt water continued.

As a result of continuous research by the present inventors, as a result of adding a polyurethane resin having a polymer block derived from a silane-modified epoxy resin and polyalkylene glycol as a reinforcing material to an existing adhesive composition, a wide temperature range including a low temperature of -40°C The invention was completed by discovering that it is possible to form an adhesive layer exhibiting excellent adhesive strength even in an environment exposed to high temperature, high humidity, and salt water along with improved impact resistance in the range.

The reason why the adhesive layer formed from the adhesive composition of one embodiment exhibits such excellent impact resistance and long-term reliability is predicted as follows.

First, the silane-modified epoxy resin forms a binder layer of the adhesive layer together with the epoxy resin, etc., and the alkoxysilane group contained in the silane-modified epoxy resin can be chemically combined with various metal materials such as inorganic fillers that can be added to the binder layer. and a resin portion of the silane-modified epoxy resin may be combined with an epoxy resin and a polyurethane resin. In addition, the silane-modified epoxy resin has excellent compatibility with a rubber copolymer and a polyurethane resin having a core-shell structure, so that it can maintain superior adhesive strength even in harsh environments exposed to low temperature, high temperature, high humidity and salt water. Accordingly, the heat-curable adhesive composition according to the exemplary embodiment appears to be very excellent in impact resistance properties at low temperatures and long-term reliability in harsh environments.

In addition, by adding a polyurethane resin having a relatively large polymer block, that is, a polymer block derived from polyalkylene glycol, compared to the existing polyurethane resin, flexibility and impact resistance can be imparted to the overall adhesive layer. see. As a result, using the adhesive composition of one embodiment, it is predicted that the formation of an adhesive layer that exhibits significantly improved impact resistance in a wide temperature range including low temperatures and long-term reliability even in environments exposed to high temperatures, high humidity and salt water is expected.

Therefore, using the adhesive composition of one embodiment, an adhesive layer that exhibits improved impact peel strength in a wide temperature range up to -40 ° C, and maintains excellent adhesive strength even in an environment exposed to high temperature, high humidity and salt water can be formed. . The adhesive composition of one embodiment can be very preferably used for bonding various substrates in various industrial fields and uses, including automobile bodies.

Hereinafter, the thermosetting adhesive composition of one embodiment will be described in more detail for each component.

First, the composition of one embodiment includes an epoxy resin as a basic resin for exhibiting adhesiveness. This epoxy resin is crosslinked and cured with a heat curing agent to be described later under heat treatment and curing conditions to enable the formation of an adhesive layer.

The kind of such epoxy resin is not particularly limited, and any epoxy resin previously known to be usable in an epoxy-based thermosetting adhesive, for example, saturated, unsaturated, cyclic, acyclic, aliphatic, alicyclic, aromatic or heterocyclic. Any click epoxy resin can be used.

Specific examples of such an epoxy resin include a bisphenol-based epoxy resin, a novolac-based epoxy resin, or an oxazolidone-based epoxy resin derived from bisphenol A or bisphenol F, and two or more selected from these may be used, of course. to be. Among these various epoxy resins, in consideration of excellent adhesive strength and curing properties, bisphenol-based epoxy resins derived from bisphenol A or bisphenol F can be more preferably used, and these bisphenol A epoxy resins and bisphenol F epoxy resins can be used together may be

In the present specification, the epoxy resin is a term encompassing a compound for preparing an epoxy resin, such as bisphenol A diglycidyl ether or bisphenol F diglycidyl ether, and the term epoxy resin may be understood as an epoxy compound.

The epoxy resin may be a bifunctional or polyfunctional epoxy resin having two or more epoxy groups for excellent adhesive properties of the thermosetting adhesive composition.

In addition, the epoxy resin may have an epoxy equivalent of 170 to 600. In a more specific example, as the epoxy resin, one or more bisphenol-based epoxy resins having an epoxy equivalent of 170 or more and less than 300 may be used, along with a bisphenol-based epoxy resin having an epoxy equivalent of 300 or more, or 350 to 600 It can be used by adding.

According to this epoxy equivalent range, the adhesive layer formed from the composition of one embodiment may exhibit appropriate curing properties along with excellent adhesive strength.

The above-described epoxy resin may be included in an amount of 5 to 50% by weight, 5 to 35% by weight, or 10 to 30% by weight based on the total composition of one embodiment. This is in consideration of the adhesive strength and curing properties of the overall composition without deteriorating the functions of other reinforcing materials and additives included in the composition of one embodiment.

On the other hand, the composition of one embodiment described above includes a silane-modified epoxy resin. The silane-modified epoxy resin may be modified by reacting the epoxy resin with a silane compound.

Specifically, in the silane-modified epoxy resin, an alkoxysilane group represented by the following Chemical Formula 1 is introduced into the epoxy resin according to the reaction between the epoxy resin and the silane compound.

[Formula 1]

-R ² -Si(R ¹ ) ₃

In Formula 1,

R ¹ is each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, at least one is an alkoxy group having 1 to 6 carbon atoms,

R ² is a single bond or an alkylene group having 1 to 10 carbon atoms.

The alkyl group having 1 to 6 carbon atoms may be a methyl group, an ethyl group, or a straight chain, branched chain or cyclic alkyl group having 3 to 6 carbon atoms, and the alkoxy group having 1 to 6 carbon atoms is a methoxy group, an ethoxy group, or a straight chain having 3 to 6 carbon atoms. , may be a branched chain or cyclic alkoxy group, and the alkylene group having 1 to 10 carbon atoms is a methylene group, 1,1-ethylene group, 1,2-ethylene group, or a straight chain, branched chain or cyclic group having 3 to 10 carbon atoms. It may be an alkylene group.

For example, in Formula 1, R ¹ is each independently a methyl group, an ethyl group, a propyl group, a methoxy group, an ethoxy group, or a propoxy group, but at least one is a methoxy group, an ethoxy group or a propoxy group, and R ² may be a propylene group, a butylene group, a 2,2-dimethylpropylene group, a 2,2-dimethylbutylene group, or a 3,3-dimethylbutylene group.

The silane-modified epoxy resin may be obtained by reacting the above-described epoxy resin with a silane compound represented by the following Chemical Formula 2 or the following Chemical Formula 3.

[Formula 2]

NHR ³ -R ² -Si(R ¹ ) ₃

In Formula 2, R ¹ and R ² are as defined in Formula 1, and R ³ is hydrogen, an alkyl group having 1 to 6 carbon atoms, or an aminoalkyl group having 1 to 6 carbon atoms.

[Formula 3]

OCN-R ² -Si(R ¹ ) ₃

In Formula 3, R ¹ and R ² are as defined in Formula 1 above.

The aminoalkyl group having 1 to 6 carbon atoms may be an aminomethyl group, 2-aminoethyl group, 1-aminoethyl group, or a linear, branched or cyclic aminoalkyl group having 3 to 6 carbon atoms.

For example, R ³ may be hydrogen, an aminomethyl group, an aminoethyl group, or an aminopropyl group.

Various silane-modified epoxy resins can be provided by mixing and reacting the epoxy resin with an appropriate amount according to the number of epoxy groups included in the epoxy resin using the silane compound.

The above-described silane-modified epoxy resin may be included in an amount of 2 to 50% by weight, or 5 to 50% by weight, based on the total composition of one embodiment. Within this content range, the adhesive strength and long-term reliability of the overall composition may be improved without deteriorating the functions of other reinforcing materials and additives included in the composition of one embodiment.

The composition of one embodiment also includes a core-shell structure rubber copolymer including a core including a rubber polymer and a shell including a polymer cross-linked or graft-bonded to the core. The core-shell structure rubber copolymer is a reinforcing material added to improve overall impact resistance of the adhesive layer formed of the adhesive composition of one embodiment.

In the rubber copolymer having a core-shell structure, the core may include a diene-based rubber polymer such as butadiene rubber and/or isoprene rubber, or a diene-based rubber copolymer obtained by copolymerizing the diene-based rubber polymer with another monomer or the like.

In a specific example, the diene-based rubber copolymer includes the above-described diene-based rubber, an aromatic vinyl monomer such as styrene, a vinyl cyanide monomer such as (meth)acrylonitrile, and an alkyl (meth)acrylate-based monomer such as methyl acrylate. It may be a copolymer obtained by copolymerizing one or more monomers selected from the group consisting of.

In addition, the shell grafted or cross-linked to the core may include an aromatic vinyl monomer such as styrene; vinyl cyanide monomers such as (meth)acrylonitrile; vinyl acetate-based monomers; halogenated vinyl monomers such as vinyl chloride; glycidyl (meth)acrylate-based monomers such as glycidyl methacrylate; and methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, or t-butyl methacrylate formed from one or more monomers selected from the group consisting of alkyl (meth) acrylate-based monomers It may include a (co)polymer that is used, and the (co)polymer of this shell may be grafted or crosslinked to the core.

The rubber copolymer having the core-shell structure may be prepared by a method such as copolymerizing them by an emulsion polymerization method in the presence of a monomer to form the core and the shell after preparing the above-mentioned core. However, such a manufacturing method may follow conventional manufacturing conditions for manufacturing a core-shell structure rubber copolymer, and specific conditions thereof are also described in Synthesis Examples to be described later, so an additional description thereof will be omitted.

On the other hand, in the above-described core-shell structure of the rubber copolymer, the core may have a glass transition temperature (Tg) of -30°C or less, or -100°C to -30°C, and the shell is 50°C or more, or It may have a Tg of 60°C to 120°C. Accordingly, it is possible to more effectively reinforce the impact strength and mechanical properties of the adhesive layer formed of the composition of one embodiment.

In addition, the core-shell structure rubber copolymer may have a number average particle diameter of 250 to 500 nm, and the core has a core particle diameter ratio of 0.8 to 0.99 to the total particle diameter of the core-shell structure rubber copolymer. It can have a particle size that becomes More specifically, the core may have a number average particle diameter of 200 to 495 nm, or 230 to 450 nm, and may have a structure in which a thin shell surrounds the core.

In addition, as the rubber copolymer of the core-shell structure, in addition to having a number average particle diameter of 250 to 500 nm as described above, if necessary, a rubber copolymer having a small particle diameter of less than 250 nm, and/or more than 500 nm It may further include a rubber copolymer having a large particle diameter of. The particle diameter range and the degree of addition of the core-shell structure rubber copolymer may be determined by those skilled in the art in consideration of the field or use in which the composition of one embodiment is used, and the level of impact strength required.

The above-described core-shell structure rubber copolymer may be included in an amount of 5 to 30% by weight, or 10 to 25% by weight, based on the total composition of one embodiment. Accordingly, it is possible to improve the impact resistance properties and long-term reliability of the overall composition at low temperature without deteriorating the functions of the above-described silane-modified epoxy resin and other additives.

Additionally, the composition of one embodiment includes a polyurethane resin including a polymer block derived from polyalkylene glycol. In general, a polyurethane resin is formed by reacting a polyol and a polyvalent isocyanate as shown in the following general formula 1, and includes a polyol-derived residue (R') and a polyvalent isocyanate-derived residue (R), respectively, and has a urethane linking group connecting them It contains repeating unit structures.

[General formula 1]

Conventional polyurethane resins are typically prepared using ethylene glycol or propylene glycol as the polyol. However, the composition of one embodiment includes a polymer block in the form of a relatively long-chain polymer derived from polyalkylene glycol as the polyol-derived residue.

Therefore, the polyurethane resin included in the composition of one embodiment is a polyalkylene glycol, for example, poly (alkylene glycol having 2 to 3 carbon atoms), or a polymer block derived from branched polyalkylene glycol, It may have a repeating unit structure including a residue derived from polyvalent aliphatic isocyanate and a urethane linkage connecting them.

As such, as the adhesive composition of one embodiment includes a polyurethane resin having a long-chain polymer block, that is, a polymer block derived from polyalkylene glycol, it seems that flexibility and impact resistance can be imparted to the overall adhesive layer. , As a result, it seems that the adhesive layer formed from the composition of one embodiment can exhibit more improved impact resistance in a wide temperature range including low temperatures. In particular, as the polyurethane resin has a polymer block derived from branched polypropylene glycol among polyalkylene glycols, the adhesive layer may exhibit more improved impact resistance and moisture resistance and salt water resistance at low temperatures.

Such polyurethane can be obtained by polymerizing a polyol containing polyalkylene glycol and a polyvalent isocyanate of divalent or higher in the presence of a urethane curing catalyst. An example of the reaction conditions thereof is also described in Synthesis Examples to be described later.

The above-described polyurethane may be obtained by using a polyalkylene glycol having an OH equivalent of 400 to 2,000, or 400 to 1,500, and may have a total weight average molecular weight of 5,000 or more or 8,000 or more, and 100,000 or less. Thereby, while the low-temperature impact peel strength of the adhesive layer is further improved, it is possible to suppress a decrease in other physical properties of the adhesive layer, such as basic adhesive strength.

In addition, the polyurethane may be prepared by using a general polyvalent aliphatic isocyanate of divalent or higher, and specific examples thereof include hexamethylene diisocyanate, isophorone diisocyanate or methylenedicyclohexyl diisocyanate, or two or more selected from these. can be heard

In addition, the polyurethane may have a structure in which an isocyanate group at the terminal is capped with an amine compound, an alcohol compound, or an oxime compound. The alcohol compound may be a compound including a -OH group, such as a phenol compound, benzyl alcohol, or a bisphenol compound. Due to such an end capping structure, it is possible to prevent the basic physical properties of the adhesive layer from being lowered or the impact strength of the adhesive layer from being sufficiently improved due to the addition of polyurethane.

In addition, the polyurethane resin is a method of controlling the number of functional groups of the polyvalent isocyanate, or additionally using various branching agents or chain extenders, etc., to have a linear structure or a branched structure, or to have a structure in which they are mixed. it might be

The above-described polyurethane resin may be included in an amount of 2 to 25% by weight, or 5 to 20% by weight, based on the total composition of one embodiment. Thereby, the impact peel strength under a wide temperature range of the adhesive layer can be further improved, and it can suppress that the adhesive strength of an adhesive layer, etc. fall due to the addition of the said polyurethane resin.

On the other hand, the composition of one embodiment includes a thermal curing agent together with each component described above. It is preferable that the thermosetting agent be curable at a temperature of 80°C or higher, or 100°C or higher. This thermal curing agent is a component that crosslinks and cures with the epoxy resin and the silane-modified epoxy resin under the application of heat to form an adhesive layer, and a temperature of 80° C. or higher to form an appropriate adhesive layer while reducing damage to the substrate to be bonded may react with the epoxy resin to cause crosslinking and curing reactions.

The type of the thermal curing agent is not particularly limited, and any thermal curing agent previously known to be usable in the epoxy-based thermal curing composition may be used. Specific examples thereof include a dicyandiamide-based curing agent; Melamine-type hardening|curing agents, such as a melamine; diallyl melamine-based curing agent; guanamine-based curing agents such as acetoguanamine or benzoguanamine; aminotriazole-based curing agents such as 3-amino-1,2,4-triazole; hydrazide-based curing agents such as adipic acid dihydrazide, stearic acid dihydrazide or isophthalic acid dihydrazide; Cyanoacetamide-based curing agent; Alternatively, an aromatic polyamine-based curing agent such as diaminodiphenylsulfone may be used, and two or more selected from these may be mixed and used.

Among these various thermal curing agents, in consideration of appropriate curing properties and processability of the adhesive composition and excellent adhesive strength of the adhesive layer, dicyandiamide, isophthalic acid dihydrazide, adipic acid dihydrazide, or 4,4' Diaminodiphenylsulfone etc. can be used preferably.

The above-described thermal curing agent may be used in an amount of 1.5 to 15% by weight, or 2.5 to 10% by weight, or 2.5 to 7% by weight, based on the total composition, and the content thereof is the content of the epoxy resin and the silane-modified epoxy resin. A person skilled in the art can appropriately determine it in consideration.

On the other hand, the composition of one embodiment described above, in addition to each component described above, a curing catalyst, a general inorganic filler in the form of primary particles, a reactive diluent having a mono-epoxy group, a plasticizer, a non-reactive diluent, a coupling agent, a flow control agent, a thixotropy regulator It may further include one or more additives selected from the group.

As each of these additives, any additive applied to the epoxy-based heat-curable adhesive may be used without any particular limitation.

For example, as the curing catalyst for controlling the curing rate and temperature of the adhesive composition, p-chlorophenyl-N,N-dimethylurea or 3-phenyl-1,1-dimethyl urea, 3,4- urea catalysts such as dichlorophenyl-N,N-dimethylurea; tertiary-acryl or alkylene amine catalysts such as benzyldimethylamine or 2,4,6-tri(dimethylaminomethyl)phenol; piperidine-based catalysts; Alternatively, an imidazole-based catalyst such as C1-C12 alkylene imidazole or N-aryl imidazole may be used.

The curing catalyst may be included in an appropriate amount in consideration of the required curing rate and temperature, for example, may be included in an amount of 0.1 to 2.0% by weight in the total composition.

In addition, the composition of one embodiment may further include a general inorganic filler in the form of a primary particle that has been generally used.

These general inorganic fillers may be used for additional control of basic properties of the adhesive composition, rheological properties, etc., and may have various particle shapes such as angular, spherical, plate, and needle-shaped. Examples of such general inorganic fillers include silicate-like inorganic fillers of quartz powder, alumina, calcium carbonate, calcium oxide, aluminum hydroxide, magnesium calcium carbonate, barite, or aluminum magnesium calcium silicate. In addition, as another example of the general inorganic filler, there may be mentioned silica fine particles that can be added to control the viscosity of the composition of one embodiment, brittleness, and the like. As the silica fine particles, either hydrophobic or hydrophilic particles may be used, and more preferably, hydrophobic silica fine particles may be used.

The general inorganic filler may be included in an amount appropriately determined by a person skilled in the art within a content range of 2 to 20% by weight based on the total composition, for example, in the case of silica fine particles, it may be included in an amount of 0.5 to 7% by weight. .

In addition, the composition of one embodiment may further include additives such as a reactive diluent or non-reactive diluent having a mono-epoxy group, a plasticizer, a coupling agent such as a silane coupling agent, a fluidity control agent, or a thixotropy control agent, and the types of these additives and The amount that can be added is known to those skilled in the art. For example, the reactive diluent having a mono epoxy group may be included in an amount of 5 wt% or less based on the total composition.

Meanwhile, the above-described adhesive composition may be prepared by mixing each of the above-described components according to a general method. For example, an epoxy resin, a modified silane epoxy resin, and the rubber copolymer of the core-shell structure are first mixed, and the remaining inorganic fillers and additives except for the polyurethane resin, the thermal curing agent and the curing catalyst are mixed, and then finally After lowering the temperature, it can be prepared by mixing a polyurethane resin, a thermal curing agent and a curing catalyst.

The heat-curable adhesive composition thus prepared may be used to form various structures or composites by bonding various substrates such as wood, metal, and plastic. Accordingly, according to another embodiment of the invention, applying the above-described heat-curable adhesive composition on a substrate; and heat curing the applied composition to form an adhesive layer.

In this case, the adhesive composition may be applied to various substrates through a mechanical application method of an extrusion method, a jet spray method such as swirl or streaming, etc. according to a method well known in the art. When there are a plurality of substrates to be bonded, the adhesive composition may be applied to only one of the substrates, or may be applied to both or both.

In addition, the type of the substrate to which the adhesive composition is applied is not particularly limited, and may be applied for adhesion or bonding of various substrates including wood, coated or uncoated metal, aluminum, plastic, or plastic containing glass fiber. More suitably, the adhesive composition is a steel sheet, for example, a cold-rolled steel sheet, an electro-galvanized steel sheet, a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet, or a zinc/nickel/magnesium coated steel sheet, aluminum, or It can be applied to these metal substrates for adhesion or bonding of aluminum alloys.

After the adhesive composition is applied, heat of 80° C. or more, or 100° C. or more, or 80 to 220° C. may be applied to thermally cure the adhesive composition, and as a result, an adhesive layer is formed on the substrate to adhere various substrates Or it can be joined.

The structure thus formed has a structure including a substrate and an adhesive layer including a cured product of the heat-curable adhesive composition described above. In this structure, the adhesive layer is a binder in which an epoxy resin and a silane-modified epoxy resin are crosslinked via a heat curing agent. A layer and a core-shell structure dispersed in the binder layer may have a form including a rubber copolymer and a polyurethane resin.

In such a structure, the adhesive layer exhibits improved impact peel strength in a very wide temperature range including low temperatures up to -40°C, and can maintain excellent adhesive strength together even in environments exposed to high temperatures, high humidity and salt water. Accordingly, such a structure may be a structure/composite included in an automobile body, or various resin/metal structure/composite materials applied in various future industrial fields such as aerospace fields and wind power generation fields.

According to the present invention, a thermosetting adhesive that exhibits improved impact peel strength over a very wide temperature range, including low temperatures up to -40°C, and enables the formation of an adhesive layer that maintains excellent adhesive strength even in environments exposed to high temperatures, high humidity and salt water A composition is provided.

This adhesive composition exhibits significantly improved impact peel strength at wide temperatures, including very low temperatures, where conventional adhesives did not properly implement impact resistance properties, and has excellent moisture resistance and salt water resistance in environments exposed to high temperature, high humidity and salt water. As it also exhibits excellent long-term reliability, it can be very preferably used for bonding various substrates in various industrial fields and uses, including automobile bodies and various future industrial fields.

Hereinafter, preferred embodiments are presented to help the understanding of the present invention. However, the following examples are only for illustrating the invention, and the present invention is not limited thereto.

Synthesis Example 1: Preparation of a core-shell structure rubber copolymer

Core manufacturing

80 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 65 parts by weight of 1,3-butadiene as a monomer, 1.0 parts by weight of sodium dodecylbenzene sulfonate as an emulsifier, 0.85 parts by weight of calcium carbonate, 0.28 parts by weight of tertiary dodecylmercaptan , 0.28 parts by weight of potassium persulfate as an initiator were each added, and the reaction was carried out at 75° C. until a polymerization conversion rate of 30 to 40%. After that, 0.3 parts by weight of sodium dodecylbenzene sulfonate is added, and 20 parts by weight of 1,3-butadiene is additionally added, and then the temperature is raised to 80° C. and the reaction is terminated when the polymerization conversion rate is 95%. Rubber latex used as a core got

The gel content of the core thus prepared is determined by coagulating the rubber latex using a dilute acid or metal salt, washing it, and drying it in a vacuum oven at 60° C. for 24 hours. At this time, 1 g of the obtained rubber is put in 100 g of toluene for 48 hours After storage in the dark at room temperature, the sol and the gel were separated and measured.

Preparation of core-shell structure rubber copolymer

After putting 75 parts by weight of the rubber latex prepared above into a sealed polymerization reactor, the temperature was raised to 75° C. after filling with nitrogen, and then 0.1 parts by weight of sodium pyrophosphate, 0.2 parts by weight of dextrose and 0.002 parts by weight of ferrous sulfide were added to the polymerization reactor. Wealth was put in batches.

In a separate mixing device, 26 parts by weight of methyl methacrylate, 3.0 parts by weight of styrene, 0.5 parts by weight of sodium dodecylbenzene sulfonate as an emulsifier, 0.1 parts by weight of cumene hydroperoxide, and 20 parts by weight of ion-exchanged water were mixed to prepare a monomer emulsion. did.

The monomer emulsion was continuously introduced into the polymerization reactor over 3 hours, and then, after 30 minutes, 0.03 parts by weight of hydroperoxide was added and aged at the same temperature for 1 hour to complete the reaction when the polymerization conversion rate was 96%.

An antioxidant was added to the reactant, and Magne?? After agglomeration with sulfate, dehydration and drying were performed to prepare a rubber copolymer having an agglomerated core-shell structure.

Synthesis Example 2: Preparation of a polyurethane resin including a polymer block derived from polyalkylene glycol

In a nitrogen-substituted polymerization reactor, 100 g of branched polypropylene glycol having an OH equivalent of 1000, 22.23 g of isophorone diisocyanate, 13.4 g of allylphenol, and 0.1 g of a tin catalyst are mixed and added, and the polypropylene is reacted at 75°C. A urethane resin was prepared.

Synthesis Example 3: Preparation of silane-modified epoxy resin

100 g of bisphenol A epoxy resin having an epoxy equivalent of 190 and 1 g of 3-aminopropyltrimethoxysilane were mixed and added to a nitrogen-substituted polymerization reactor and reacted at 100° C. to prepare a silane-modified epoxy resin.

Examples 1, 2 and Comparative Examples 1 to 4: Preparation of heat-curable adhesive composition

The heat-curable adhesive compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared according to the components and compositions summarized in Table 1, and the following method.

First, the rubber copolymer of the core-shell structure, the epoxy resin and the silane-modified epoxy resin are put in a planetary mixer and mixed at 80° C. for 5 hours, and then the remaining inorganic fillers except for the polyurethane resin, the thermal curing agent and the curing catalyst, and Additives were put in a planetary mixer and stirred at 80° C. for 3 hours. Finally, the temperature was lowered to 40° C., a heat curing agent, a curing catalyst, and a polyurethane resin were mixed, further mixed for 1 hour, and the kneading was terminated by further lowering the temperature to room temperature.

Thus, the thermosetting adhesive compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Silane-modified epoxy resin ¹ 35 35 35 35 epoxy resin Bisphenol A Epoxy ² 10 15 40 45 Bisphenol F Epoxy ³ 6 16 16 16 21 16 Core-Shell Rubber ⁴ 15 15 15 15 15 polyurethane resin Resin A ⁵ 10 15 10 Resin B ⁶ 10 10 reactive diluent Mono Epoxy Resin ⁷ 1.6 1.6 1.6 1.6 1.6 1.6 colorant ⁸ 0.05 0.05 0.05 0.05 0.05 0.05 heat curing agent ⁹ 5.35 5.35 5.35 5.35 5.35 5.35 curing catalyst ¹⁰ One One One One One One inorganic filler CaCO ₃ 8 8 8 8 8 8 CaO 5 5 5 Fumed Silica ¹¹ 3 3 3 3 3 3

(Unit: % by weight)

In Table 1, specific types and physical properties of each component are as follows:

1: Silane-modified epoxy resin prepared in Synthesis Example 3

2: Bisphenol A epoxy resin with an epoxy equivalent of 190 (manufactured by Kukdo Chemical, product name: YD-128)

3: Bisphenol F epoxy resin with an epoxy equivalent of 170 (manufactured by Kukdo Chemical, product name: YDF-170)

4: Core-shell structured rubber copolymer prepared in Synthesis Example 1 (number average particle diameter of core 300 nm; number average particle diameter of all copolymers 330 nm)

5: Polyurethane resin prepared in Synthesis Example 2 (Mw: 13,000)

6: Huntzman DY965 polyurethane resin

7: Reactive diluent of NC513 from Cardolite

8: Pigment violet 23 colorant

9: Airproduct's 1200G thermal curing agent (specific ingredient name: dicyandiamide)

10: Curing catalyst of Amicure UR7/10 from Evonik

11: Fumed silica from Cabot's TS720

Test Example: Formation of an adhesive layer and evaluation of physical properties

1. Impact peel strength test

In the following method, an adhesive layer was formed from the compositions of Examples and Comparative Examples, and the impact peel strength thereof was measured and evaluated. The impact peel strength was evaluated as the average value of the impact peel strength measured by producing five specimens.

As the substrate, cold-rolled steel having a length of 90 mm, a width of 25 mm, and a thickness of 1.6 mm, and a strength of 440 MPa, was used. It was kept at 0.2 mm.

Each adhesive composition was applied to the bonding region of the substrate, and cured at 180° C. for 20 minutes to form an adhesive layer having a thickness of 2 mm. At a temperature of -40°C, a 45 kg weight was freely dropped on the specimen from a height of 1.5 m to measure the impact peel strength, and the measurement results are shown in Table 2 below.

2. Shear strength (adhesive strength) experiment

An adhesive layer was formed from the compositions of Examples and Comparative Examples, and the shear strength thereof was measured and evaluated. The shear strength was evaluated as the average value of the shear strength measured by producing five specimens.

An aluminum alloy (Al 6061) having a length of 100 mm, a width of 25 mm, and a thickness of 3 mm was used as the substrate, the bonding area of the substrate was 25 x 10 mm, and the interval between bonding areas was 0.2 mm using glass beads. kept.

Each adhesive composition was applied to the bonding region of the substrate, and cured at 180° C. for 20 minutes to form an adhesive layer having a thickness of 2 mm.

The sample thus prepared was sprayed with brine (pH: 6.5 to 7.2 mixed salt solution (0.9 wt% NaCl aqueous solution + 0.1 wt% CaCl ₂ aqueous solution + 0.075 wt% NaHCO ₃ aqueous solution)) at a temperature of 23 ° C over 4 hours, and , the obtained specimen was aged for 4 hours at a temperature of 23° C. and a relative humidity of 50%, and then aged for 16 hours at a temperature of 40° C. and a relative humidity of 100%, as 1 cycle, and 30 cycles were repeated. And the shear strength (adhesive strength) of the adhesive layer was measured at 23° C. under a condition of 10 mm/min for the obtained specimen, and the measurement results are shown in Table 2 below.

Impact Peel Strength (-40°C; Units: N/mm) Shear strength (23°C; unit: MPa) Example 1 35 25 Example 2 37 26 Comparative Example 1 X ^a 25 Comparative Example 2 15 12 Comparative Example 3 X ^a 12 Comparative Example 4 8 26

a: The adhesive layer was peeled off before the impact was applied at a low temperature, and the impact peel strength could not be measured.

Referring to Table 2, it is confirmed that the adhesive layer formed of the composition of Examples exhibits very good impact peel strength even at a low temperature of -40°C and excellent shear strength even after the complex salt water test.

Claims (22)

5 to 50% by weight of an epoxy resin;
2 to 50 wt% of a silane-modified epoxy resin;
5 to 30% by weight of a rubber copolymer having a core-shell structure comprising a core including a rubber polymer and a shell including a polymer cross-linked or graft-bonded to the core;
2 to 25% by weight of a polyurethane resin including a polymer block derived from polyalkylene glycol; and
A thermally curable adhesive composition comprising 1.5 to 15% by weight of a thermal curing agent.
The thermosetting adhesive composition according to claim 1, wherein the epoxy resin comprises at least one selected from the group consisting of a bisphenol-based epoxy resin, a novolak-based epoxy resin, and an oxazolidone-based epoxy resin.
The thermosetting adhesive composition according to claim 1, wherein the epoxy resin has an epoxy equivalent weight of 170 to 600.
According to claim 1, wherein the silane-modified epoxy resin is a thermosetting adhesive composition in which an alkoxy silane group represented by the following formula (1) is bonded to the epoxy resin:
[Formula 1]
-R ² -Si(R ¹ ) ₃
In Formula 1,
R ¹ is each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, at least one is an alkoxy group having 1 to 6 carbon atoms,
R ² is a single bond or an alkylene group having 1 to 10 carbon atoms.
5. The method of claim 4, wherein in Formula 1, R ¹ is each independently a methyl group, an ethyl group, a propyl group, a methoxy group, an ethoxy group or a propoxy group, at least one is a methoxy group, an ethoxy group or a propoxy group,
R ² is a propylene group, a butylene group, a 2,2-dimethylpropylene group, a 2,2-dimethylbutylene group, or a 3,3-dimethylbutylene group, the thermosetting adhesive composition.
The thermosetting adhesive composition of claim 1, wherein the core comprises a diene-based rubber polymer or copolymer.
According to claim 6, wherein the diene-based rubber copolymer is a diene-based rubber; and
A thermosetting adhesive composition, which is a copolymer obtained by copolymerizing one or more monomers selected from the group consisting of aromatic vinyl monomers, vinyl cyanide monomers, and alkyl (meth)acrylate-based monomers.
According to claim 1, wherein the shell is selected from the group consisting of an aromatic vinyl monomer, a vinyl cyanide monomer, a vinyl acetate monomer, a halogenated vinyl monomer, a glycidyl (meth) acrylate monomer, and an alkyl (meth) acrylate monomer. A heat curable adhesive composition comprising a polymer formed from one or more monomers.
The thermosetting adhesive composition according to claim 1, wherein the core-shell structure rubber copolymer comprises a core having a Tg of -100°C to -30°C and a shell having a Tg of 50°C to 120°C.
The rubber copolymer of claim 1, wherein the core-shell structure rubber copolymer has a number average particle diameter of 250 to 500 nm, and the core has a ratio of 0.8 to 0.99 to the total particle diameter of the core-shell structure rubber copolymer. A thermosetting adhesive composition having a particle size.
The thermosetting adhesive composition of claim 1, wherein the polyurethane resin has a polymer block derived from polyalkylene glycol, a residue derived from a polyvalent aliphatic isocyanate, and a repeating unit including a urethane linkage connecting them.
The thermosetting adhesive composition according to claim 11, wherein the polyurethane resin comprises a polymer block derived from branched polyalkylene glycol.
The thermosetting adhesive composition according to claim 11, wherein the polyurethane resin has terminal isocyanate groups end-capped with an amine compound, an alcohol compound, or an oxime compound.
The thermosetting adhesive composition according to claim 11, wherein the polyvalent aliphatic isocyanate comprises at least one selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate and methylenedicyclohexyl diisocyanate.
12. The thermosetting adhesive composition of claim 11, wherein the polyalkylene glycol has an OH equivalent weight of 400 to 2,000, and the polyurethane resin has a weight average molecular weight of 5,000 to 500,000.
According to claim 1, wherein the thermal curing agent is a dicyandiamide-based curing agent, a melamine-based curing agent, a diallylmelamine-based curing agent, a guanamine-based curing agent, an aminotriazole-based curing agent, a hydrazide-based curing agent, a cyanoacetamide-based curing agent and at least one selected from the group consisting of aromatic polyamine-based curing agents.
delete According to claim 1, wherein at least one additive selected from the group consisting of a curing catalyst, a general inorganic filler in the form of primary particles, a reactive diluent having a mono-epoxy group, a plasticizer, a non-reactive diluent, a coupling agent, a flow control agent, and a thixotropic agent is further added A thermosetting adhesive composition comprising.
applying the heat curable adhesive composition of claim 1 on a substrate; and
A method of manufacturing a structure comprising the step of thermally curing the applied composition to form an adhesive layer.
A structure comprising a substrate and an adhesive layer comprising a cured product of the heat-curable adhesive composition of claim 1 .
The structure according to claim 20, wherein the substrate is made of wood, metal or plastic.
The method according to claim 20, wherein the adhesive layer comprises: a binder layer in which an epoxy resin and a silane-modified epoxy resin are crosslinked through a thermal curing agent;
A structure comprising a rubber copolymer and a polyurethane resin having a core-shell structure dispersed in the binder layer.