KR20210052087A - 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 having excellent adhesive strength and enabling the formation of an adhesive layer providing 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. The thermosetting adhesive composition includes: an epoxy resin; an inorganic filler having a secondary particle form in which a plurality of primary particles are aggregated; liquid rubber; a polyurethane resin including a polymer block derived from polytetrahydrofuran; and a thermal curing agent curable at a temperature of 80 deg. C or higher.

Description

A structure including a thermosetting adhesive composition, an adhesive layer, and a manufacturing method thereof {THERMAL CURABLE ADHESIVE COMPOSITION, COMPOSITE STRUCTURE HAVING ADHESIVE LAYER AND ITS PREPARATION METHOD}

The present invention relates to a thermosetting adhesive composition that has excellent adhesive strength and enables 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 of manufacturing the same. .

Epoxy-based thermosetting adhesives containing 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 high heat resistance and excellent adhesive strength.

In particular, in recent years, the epoxy-based thermosetting adhesive has been widely used for metal-metal bonding and metal-plastic bonding included in automobile body structures, 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 overall process cost during the automobile manufacturing process, the application of the epoxy-based thermosetting adhesive is gradually expanding. Further, even in future industrial fields such as aerospace field and wind power field, interest in the epoxy-based thermosetting adhesive is increasing and its application is expanding in order to simplify the overall process and reduce cost.

As the application fields and uses of the epoxy-based thermosetting adhesive are expanded as described above, the level of physical properties required for this is gradually increasing. In particular, in the case of automobiles, according to the name, the actual conditions of use are from -40°C to 80°C, it is required that the adhesive layer formed from the adhesive maintains excellent adhesive strength and impact peel strength in a wider temperature range.

However, in the case of the epoxy-based adhesive composition developed so far, the impact peel strength is greatly reduced at a low temperature of -40°C in the adhesive layer formed therefrom, and the adhesive strength thereof is also insufficient, so that its application is facing a limit. .

Accordingly, research to develop an adhesive that maintains excellent impact peel 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 being continued.

Despite such continuous research and efforts, an adhesive that exhibits excellent impact peel strength and adhesive strength at low temperatures as described above has not yet been properly developed.

An object of the present invention is to provide a thermosetting adhesive composition capable of forming an adhesive layer that has excellent adhesive strength and exhibits more improved impact peel strength in a wide temperature range including low temperatures.

In addition, the present invention is to provide a structure including an adhesive layer formed from the adhesive composition and a method of manufacturing the same.

The present invention

Epoxy resin;

An inorganic filler having a secondary particle form in which a plurality of primary particles are aggregated;

Liquid rubber;

Polyurethane resin including a polymer block derived from polytetrahydrofuran; And

Thermal curing agent capable of curing at temperatures above 80 ℃

It provides a heat curable adhesive composition comprising a.

The present invention also includes the steps of applying the heat curable adhesive composition of the present invention on a substrate; And it provides a method of manufacturing a structure comprising the step of forming an adhesive layer by thermally curing the applied composition at a temperature of 80 °C or higher.

In addition, the present invention provides a structure comprising a substrate and an adhesive layer including a cured product of the thermosetting adhesive composition of the present invention. In this structure, the adhesive layer may include a binder layer in which an epoxy resin is crosslinked through a thermal curing agent, and an inorganic filler, a liquid rubber, and a polyurethane resin dispersed in the binder layer.

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

Unless expressly stated in the specification, terminology is only intended to refer to specific embodiments and is not intended to limit the present invention.

The singular forms used in the present specification also include plural forms unless the phrases clearly indicate the opposite meaning.

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

On the other hand, according to one embodiment of the invention,

Epoxy resin; An inorganic filler having a secondary particle form in which a plurality of primary particles are aggregated; Liquid rubber; Polyurethane resin including a polymer block derived from polytetrahydrofuran; And there is provided a heat curable adhesive composition comprising a heat curing agent curable at a temperature of 80° C. or higher.

The present inventors continued their research to develop an adhesive capable of forming an adhesive layer exhibiting excellent impact peel strength in a wide temperature range, particularly at low temperatures up to -40°C.

As a result of continuous research of the present inventors, as a reinforcing material was added to the existing adhesive composition, an inorganic filler in the form of secondary particles in which primary particles were agglomerated and a polyurethane resin having a polymer block derived from polytetrahydrofuran was added as a reinforcing material,- It was found that it was possible to form an adhesive layer exhibiting excellent adhesive strength with improved impact peeling strength in a wide temperature range including a low temperature of up to 40°C, and the invention was completed.

The reason why the adhesive layer formed from the adhesive composition of one embodiment exhibits such excellent impact peel strength and the like is predicted as follows.

First, as the inorganic filler has an aggregated secondary particle shape and thus an irregular surface/particle shape, it is predicted that the impact applied thereto in the adhesive layer can be more effectively buffered. In addition, the inorganic filler in the form of agglomerated secondary particles appears to act as a buffer to absorb energy while the particles in the agglomerated form are temporarily separated from each other by an external impact.

In addition, compared to the existing polyurethane resin, by adding a polyurethane resin having a relatively long-chain polymer block, that is, a polymer block derived from polytetrahydrofuran, it is possible to impart flexibility to the entire adhesive layer. see. As a result, it is predicted that when the adhesive composition of one embodiment is used, it is possible to form an adhesive layer exhibiting significantly improved impact peel strength over a wide temperature range including low temperatures.

Therefore, when the adhesive composition of one embodiment is used, an adhesive layer that maintains excellent adhesive strength while exhibiting improved impact peel strength in a wide temperature range of -40°C can be formed. The adhesive composition of this embodiment may be preferably used to bond 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.

The thermally curable adhesive composition according to an embodiment is a basic resin for exhibiting adhesiveness, and includes an epoxy resin. These epoxy resins are crosslinked and cured with a thermal curing agent to be described later under heat treatment and curing conditions to enable formation of an adhesive layer.

The type of the epoxy resin is not particularly limited, and any epoxy resin previously known to be usable in an epoxy-based heat-curable adhesive, for example, saturated, unsaturated, cyclic, acyclic, aliphatic, alicyclic, aromatic or heterocyclic. All click epoxy resins can be used.

Specific examples of such epoxy resins include bisphenol-based epoxy resins derived from bisphenol A or bisphenol F, novolac-based epoxy resins, or oxazolidone-based epoxy resins, and two or more selected from them may be used. 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 addition, such an epoxy resin may have an epoxy equivalent of 170 to 600 in terms of adhesiveness of the overall composition. In a more specific example, the epoxy resin may be one or more bisphenol-based epoxy resins having an epoxy equivalent weight of 170 or more and less than 300, and a bisphenol-based epoxy resin having an epoxy equivalent weight of 300 or more, or 350 to 600 may be used. Can be used in addition.

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

The epoxy resin may be included in an amount of 20 to 70% by weight, or 20 to 65% by weight, or 25 to 60% by weight, or 25 to 50% 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 function of other reinforcing materials and additives included in the composition of the embodiment.

The thermosetting adhesive composition according to an embodiment includes an inorganic filler having a secondary particle form in which a plurality of primary particles are aggregated.

As described above, as the inorganic filler in the form of aggregated secondary particles is included in the composition of one embodiment, the adhesive layer may exhibit improved impact peel strength in a wide temperature range including low temperatures.

The inorganic filler may be manufactured or commercially available in the form of the secondary particles, and may include any inorganic material capable of reinforcing mechanical properties of the adhesive layer.

As a non-limiting example, such an inorganic material may include calcium oxide (CaO), magnesium oxide (MgO), alumina (Al ₂ O ₃ ), calcium carbonate (CaCO ₃ ), or silica (SiO ₂ ), and these Inorganic fillers formed so that at least one inorganic material selected from among them has a secondary particle shape may be used.

Among these various inorganic fillers, calcium oxide (CaO) in the form of secondary particles that can function as a moisture absorbing material or the like in the adhesive layer while further improving the impact peel strength of the adhesive layer may be preferably used.

In order that the inorganic filler can further mitigate the impact in the adhesive layer and exhibit excellent moisture absorption properties, the inorganic filler is a plurality of particles having a particle diameter of 1 nm to 20 µm, or 1 nm to 15 µm, or 1 nm to 10 µm. The primary particles of may have a form of aggregated secondary particles, and these secondary particles may have a number average particle diameter (D50) of 1 µm to 200 µm, or 1 µm to 150 µm, or 1 µm to 100 µm. have.

If the particle diameter range of the primary particles of the inorganic filler and/or the average particle diameter of the secondary particles is out of the range, the low-temperature impact peel strength of the adhesive layer is insufficient, or the dispersibility of the inorganic filler decreases, so that the overall adhesive strength of the adhesive layer is lowered. Can be.

The inorganic filler in the form of agglomerated secondary particles can be prepared by agglomerating the inorganic filler in the form of primary particles by a known method, or can be obtained commercially.

The above-described inorganic filler may be included in an amount of 1 to 20% by weight, or 3 to 10% by weight, based on the total composition of one embodiment. When the content of the inorganic filler is too small, the impact peel strength of the adhesive layer may not be sufficient, and when the content of the inorganic filler is too large, the dispersibility in the adhesive layer may decrease, and the adhesive strength of the adhesive layer may decrease.

The heat curable adhesive composition according to an embodiment includes a liquid rubber.

The liquid rubber is a reaction product of butadiene or butadiene-acronitrile copolymer and an epoxy resin. That is, the liquid rubber may be a rubber-modified epoxy resin.

In the liquid rubber, the rubber is a homopolymer or copolymer of a conjugated diene, in particular a diene-nitrile copolymer. The conjugated diene rubber is preferably butadiene or isoprene, and butadiene is particularly preferred. The nitrile is preferably acrylonitrile. Preferred such copolymers are butadiene-acrylonitrile copolymers.

In the liquid rubber, the rubber contains an average of 1.5 to 2.5, or 1.8 to 2.2 epoxy reactive end groups per molecule. The epoxy reactive end group may be an amino group or a carboxyl group. The rubber has a number average molecular weight (Mn) of 2000 to 8000 g/mol, or 2000 to 6000 g/mol.

As a non-limiting example, commercially available rubbers include Hycar 2000X162, Hycar 1300X31, Hycar 1300X8, Hycar 1300X9, Hycar 1300X18 from CVC Thermoset Specialties.

The liquid rubber can be obtained by reacting an excess of epoxy and the rubber. As the epoxy resin, the general epoxy resin described above may be used. Preferably, as the epoxy resin, a bisphenol A or bisphenol F bisphenol epoxy resin may be used.

As a non-limiting example, the commercially available liquid rubber is Polydis 3619 from S&S.

The above-described liquid rubber may be included in an amount of 5 to 50% by weight, or 10 to 45% by weight, or 20 to 45% by weight, based on the total composition of one embodiment. As a result, it is possible to improve the impact peel strength of the overall composition without deteriorating the functions of other reinforcing materials and additives such as the above-described inorganic filler.

The heat curable adhesive composition according to an embodiment may additionally include a rubber copolymer having a core-shell structure.

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

In such a core-shell structured rubber copolymer, the core may include a diene rubber polymer such as butadiene rubber and/or isoprene rubber, or a diene rubber copolymer in which the diene rubber polymer is copolymerized with other monomers.

In a specific example, the diene-based rubber copolymer is 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.

The shell grafted or crosslinked to the core is 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 monomers such as glycidyl methacrylate; And at least one (co) selected from the group consisting of alkyl (meth)acrylate-based monomers such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate or t-butyl methacrylate A polymer may be included, and the (co)polymer of such a shell may be grafted or crosslinked to the core.

The core-shell structured rubber copolymer can be prepared by a method such as copolymerizing the above-described core by means of emulsion polymerization in the presence of a monomer to form the core and the shell. However, such a manufacturing method may follow the conventional manufacturing conditions for manufacturing the core-shell structured rubber copolymer, and specific conditions thereof are also described in the synthesis examples to be described later, so an additional description thereof will be omitted.

In the above-described core-shell structured rubber copolymer, the core may have a glass transition temperature (Tg) of -30°C or less, or -60°C to -30°C, and the shell is 50°C or more, or 60°C. It may have a Tg of to 120 ℃. As a result, it is possible to more effectively reinforce the impact peel strength and mechanical properties of the adhesive layer formed of the composition of one embodiment.

The core-shell structured rubber copolymer may have a number average particle diameter of 250 to 500 nm, and the core has a particle size in which a core particle size ratio to the total particle size of the core-shell structured rubber copolymer is 0.8 to 0.99 Can have. 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.

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

The above-described core-shell structured rubber copolymer may be included in an amount of 5 to 30% by weight, or 5 to 20% by weight, based on the total composition of one embodiment. As a result, it is possible to improve the impact peel strength of the overall composition without deteriorating the functions of other reinforcing materials and additives such as the above-described inorganic filler.

The thermosetting adhesive composition according to an embodiment includes a polyurethane resin including a polymer block derived from polytetrahydrofuran.

In general, a polyurethane resin is formed by reflecting 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 a repeating unit structure.

[General Formula 1]

Conventional polyurethane resins are typically prepared using ethylene glycol or propylene glycol as the polyol. In contrast, the polyurethane resin included in the composition of one embodiment includes a polymer block derived from polytetrahydrofuran and formed in the form of a relatively long-chain polymer as the polyol-derived moiety.

Accordingly, the polyurethane resin included in the composition of the embodiment has a repeating unit structure including a polymer block derived from polytetrahydrofuran, a residue derived from a polyvalent aliphatic isocyanate, and a urethane linking group connecting them, and in some cases , It may further include a residue derived from an alkylene glycol having 2 to 5 carbon atoms, such as ethylene glycol or propylene glycol.

As described above, as the adhesive composition of one embodiment contains a polyurethane resin having a long-chain polymer block, that is, a polymer block derived from polytetrahydrofuran, it appears that flexibility can be imparted to the entire adhesive layer. It appears that the adhesive layer formed from the composition of one embodiment can exhibit more improved impact peel strength in a wide temperature range including low temperatures.

Such a polyurethane resin can be obtained by polymerizing polytetrahydrofuran and a polyol containing optionally alkylene glycol, a polyhydric isocyanate having a divalent or higher value, 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 polyurethane resin may be obtained using polytetrahydrofuran having an OH equivalent of 400 to 2200, or 450 to 1000, and may have a weight average molecular weight (Mw) of 5000 to 500000 g/mol as a whole. As a result, while the low-temperature impact peeling strength of the adhesive layer is further improved, it is possible to suppress other physical properties of the adhesive layer such as basic adhesive strength from deteriorating.

As a non-limiting example, the weight average molecular weight (Mw) may be measured using an Agilent PL-GPC 220 instrument equipped with a 300 mm long PolarGel MIXED-L column (Polymer Laboratories). The measurement temperature is 65°C, tetrahydrofuran or dimethylformamide is used as a solvent, and the flow rate is measured at a rate of 1 mL/min. The sample is prepared to a concentration of 10 mg/10 mL, and then supplied in an amount of 100 μL. The Mw value and Mn value are derived with reference to the calibration curve formed using the polystyrene standard. The molecular weight (g/mol) of the polystyrene standard is 580/ 3,940/ 8,450/ 31,400/ 70,950/ 316,500/ 956,000/ 4,230,000.

The polyurethane resin including the polymer block derived from the polytetrahydrofuran may be prepared using a general polyhydric aliphatic isocyanate having a divalent or higher value. For example, the polyvalent aliphatic isocyanate may be one or more compounds selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylenedicyclohexyl diisocyanate.

In addition, the polyurethane resin may have a structure in which the terminal isocyanate group is end-capped with an amine compound, an alcohol compound, a phenol compound, an oxime compound, or a bisphenol compound. Due to such an end capping structure, it is possible to prevent the addition of the polyurethane resin from lowering the basic physical properties of the adhesive layer or not sufficiently improving the impact peel strength of the adhesive layer.

The polyurethane resin is a method in which the number of functional groups of the polyvalent isocyanate is adjusted or various branching agents or chain extenders are additionally used, and the polyurethane resin is provided to have a linear, branched or crosslinked structure, or a mixed structure thereof. May be.

The 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 peeling strength under a wide temperature range of the adhesive layer can be further improved, and it is possible to suppress a decrease in the adhesive strength of the adhesive layer due to the addition of the polyurethane resin.

The thermally curable adhesive composition according to an embodiment includes a thermal curing agent capable of curing at a temperature of 80° C. or higher or 100° C. or higher.

The thermal curing agent is a component that forms an adhesive layer by crosslinking and curing with the epoxy resin under the application of heat, and the epoxy resin and the epoxy resin at a temperature of 80° C. or higher to form an appropriate adhesive layer while reducing damage to the substrate to be adhered. It can react and cause crosslinking and curing reactions.

The type of the thermal curing agent is not particularly limited, and any thermal curing agent known to be usable in the epoxy-based thermal curable composition may be used.

For example, the thermal curing agent may include a dicyandiamide-based curing agent; Melamine-based curing agents such as 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, it may be an aromatic polyamine-based curing agent such as diaminodiphenylsulfone. The thermal curing agent may include one or more compounds selected from the group consisting of the exemplified compounds.

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

The above-described thermal curing agent may be used in an amount of 1.5 to 10% 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 appropriately determined by those skilled in the art in consideration of the content of the epoxy resin. You can decide.

On the other hand, the heat curable adhesive composition according to an embodiment, in addition to each of the above-described components, a curing catalyst, a general inorganic filler in the form of a primary particle, a reactive diluent having a mono epoxy group, a plasticizer, a non-reactive diluent, a coupling agent, a flow control agent, thixotropic It may further include one or more additives selected from the group consisting of a modulator.

As each of these additives, any additives 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-acrylic or alkylene amine catalysts such as benzyldimethylamine or 2,4,6-tri(dimethylaminomethyl)phenol; Piperidine catalyst; Alternatively, an imidazole-based catalyst such as C1-C12 alkylene imidazole or N-arylimidazole may be used.

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

In addition to the aforementioned inorganic filler in the form of agglomerated secondary particles, the composition of one embodiment may further include an inorganic filler in the form of primary particles that have been generally used.

These general inorganic fillers may be used for additional control of the basic properties or rheological properties of the adhesive composition, and may have various particle shapes such as angular shape, spherical shape, plate shape, and needle shape. Examples of such general inorganic fillers include silica powder, alumina, calcium carbonate, calcium oxide, aluminum hydroxide, magnesium calcium carbonate, barite, or aluminum magnesium calcium silicate type silicate-like inorganic filler. In addition, as another example of the general inorganic filler, silica fine particles that can be added to control the viscosity or tooth plasticity of the composition of the embodiment may be mentioned. These silica fine particles may be hydrophobic or hydrophilic particles, and more suitably, 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 the content range of 0.1 to 20% by weight based on the total composition. For example, the composition may contain 0.5 to 7% by weight of silica fine particles.

In addition, the composition of one embodiment may further include additives such as a reactive diluent having a mono epoxy group, a non-reactive diluent, a plasticizer, a coupling agent such as a silane coupling agent, a rheology control agent, or a thixotropic control agent. The amount that can be added is obviously known to those skilled in the art.

Meanwhile, the thermosetting adhesive composition may be prepared by mixing the above-described components according to a general method.

For example, after mixing the epoxy resin and the liquid rubber first, mixing the remaining inorganic fillers and additives excluding the polyurethane resin, the thermal curing agent, and the curing catalyst, and finally lowering the temperature, polyurethane resin, heat It can be prepared by mixing a curing agent and a curing catalyst.

The thermosetting adhesive composition thus prepared may be used to form various structures or composites by bonding various substrates such as wood, metal, and plastic.

According to another embodiment of the invention, applying the above-described heat curable adhesive composition on a substrate; And forming an adhesive layer by thermally curing the applied composition at a temperature of 80° C. or higher.

According to another embodiment of the present invention, there is provided a structure including the substrate and an adhesive layer including a cured product of the thermosetting adhesive composition.

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, 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 all of two or more substrates.

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, aluminium, plastic or glass fiber-containing plastic.

Suitably, the adhesive composition is used for adhesion of 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, or of an aluminum or aluminum alloy. It can be applied to these metal substrates for adhesion or bonding.

After the adhesive composition is applied, heat of 80° C. or higher, 100° C. or higher, or 80 to 220° C. may be applied to thermally cure the adhesive composition. 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 above-described thermosetting adhesive composition.

In the above structure, the adhesive layer may have a form including a binder layer in which an epoxy resin is crosslinked through a thermal curing agent, and an inorganic filler, a liquid rubber, and a polyurethane resin dispersed in the binder layer.

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. Accordingly, such a structure may be a structure/composite included in an automobile body, or various resin/metal structures/composites applied in various future industrial fields such as aerospace field or wind power generation field.

According to the present invention, there is provided a thermosetting adhesive composition that exhibits improved impact peel strength in a very wide temperature range including low temperatures up to -40°C, and enables formation of an adhesive layer maintaining excellent adhesive strength.

The thermosetting adhesive composition exhibits significantly improved impact peel strength at a wide temperature including very low temperatures where conventional adhesives did not exhibit sufficient impact peel strength, and thus various industrial fields and uses including automobile bodies and various future industries It can be very preferably used to bond a variety of substrates in.

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

Synthesis Example 1: Preparation of a polyurethane resin containing a polymer block derived from polytetrahydrofuran

To a nitrogen-substituted polymerization reactor, 109.76 g of polytetrahydrofuran having an OH equivalent of 500, 36.92 g of hexamethylene diisocyanate, 2.51 g of propylene glycol, 22.75 g of t-butylphenol, and 0.1 g of a tin catalyst were mixed and added to the polymerization reactor. 75 The reaction was carried out at °C to prepare a polyurethane resin.

Examples 1 and 2 and Comparative Examples 1 to 4: Preparation of thermosetting adhesive composition

According to the components and compositions summarized in Table 1 below and the following method, the thermosetting adhesive compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared.

First, liquid rubber and epoxy resin are put into a planetary mixer and mixed at 80° C. for 5 hours. Additionally, the remaining fillers and additives excluding the polyurethane resin, the thermal curing agent and the curing catalyst were added to the planetary mixer and stirred at 80° C. for 3 hours. Finally, the temperature was lowered to 40° C., a thermal curing agent, a curing catalyst, and a polyurethane resin were added, and after mixing for 1 hour, the temperature was further lowered to room temperature to terminate the kneading. Thus, the thermosetting adhesive compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared.

Content (% by weight) Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Epoxy resin Bisphenol A ¹ 10 - 40 10 10 10 Bisphenol F ² 16 26 16 16 16 16 Liquid rubber ³ 40 35 - 40 40 40 Polyurethane Susie A ⁴ 10 15 - 10 10 - Suzy B ⁵ - - 20 - - 10 Core-shell rubber copolymer ⁶ 5.6 5.6 5.6 5.6 5.6 5.6 Colorant ⁷ 0.05 0.05 0.05 0.05 0.05 0.05 Thermal curing agent ⁸ 6 6 6 6 6 6 Curing catalyst ⁹ One One One One One One weapon
Filler CaCO ₃ 3 3 3 8 3 3 CaO ¹⁰ 5 5 5 - - - CaO ¹¹ - - - - 5 5 Fumed silica ¹² 3 3 3 3 3 3 Silane coupling agent ¹³ 0.35 0.35 0.35 0.35 0.35 0.35

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

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

2. Bisphenol F epoxy resin with an epoxy equivalent of 170 (Kukdo Chemical, product name: YDF-170)

3. Liquid rubber (S&S, product name: Polydis3619, reactant of carboxyl terminal butadiene-acrylonitrile copolymer and epoxy resin)

4. Polyurethane resin A: polyurethane resin prepared in Synthesis Example 1 (Mw: 13000 g/mol)

5. Polyurethane resin B: DY965 from Huntzman

6. Core-shell rubber copolymer: MX 153 from kaneka

7. Colorant: Pigment violet 23

8. Thermal curing agent: Airproduct 1200G (ingredient name: dicyandiamide)

9. Curing catalyst: Evonik's Amicure UR7/10

10. CaO (particle agglomerated structure): Uni-Ox of Youyeong Materials (a secondary particle form in which primary particles having a particle diameter of 0.5 µm are aggregated, and the number average particle diameter of the secondary particles is 40 µm)

11. CaO: Yoshizawa's HALP_P_Z (primary particle form with a particle diameter of 3 μm)

12. Fumed silica: TS720 from Cabot

13. Silane coupling agent: A-187 from GE Advanced Materials

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

(1) Impact peel strength test

Specimens including an adhesive layer formed from the compositions of Examples and Comparative Examples were prepared, and the impact peel strength was measured and evaluated by the following method.

Five specimens having a length of 90 mm, a width of 25 mm, and a thickness of 1.6 mm were prepared. Cold-rolled steel having a strength of 440 MPa was used as the substrate for the specimen. The bonding area was set to be 25 mm x 30 mm, and the adhesive layer was maintained at 0.2 mm intervals using glass beads. Each adhesive composition was applied to the substrate and cured at 180° C. for 20 minutes to form an adhesive layer.

At a temperature of -40 °C, a weight of 45 kg was freely dropped on the adhesive layer of the specimen at a height of 1.5 m to measure and evaluate the impact peel strength of each adhesive layer.

(2) Shear strength (adhesive strength) test

The same specimen as in the impact peel strength test was prepared.

The specimen was allowed to stand at 23° C. and 60 RH for 1 week, and then the shear strength (adhesion strength) of the adhesive layer was measured five times at 23° C. under the condition of 10 mm/min, and the average value was taken.

Impact peel strength
(-40 ℃; Unit: N/mm) Shear strength
(23 ℃; Unit: N/mm) Example 1 30 40 Example 2 33 39 Comparative Example 1 Very low strength, not measurable 35 Comparative Example 2 5 20 Comparative Example 3 5 37 Comparative Example 4 Very low strength, not measurable 35

Referring to Table 2, it was confirmed that the adhesive layer formed of the composition of the Example exhibits very excellent impact peel strength even at a low temperature of -40°C, and exhibits a room temperature adhesive strength equal to or higher than that of the Comparative Example.

In contrast, it was confirmed that the adhesive layer formed of the composition of Comparative Example exhibits very poor impact peel strength at low temperatures.

Claims (17)

Epoxy resin;
An inorganic filler having a secondary particle form in which a plurality of primary particles are aggregated;
Liquid rubber;
Polyurethane resin including a polymer block derived from polytetrahydrofuran; And
Thermal curing agent capable of curing at temperatures above 80 ℃
Containing, heat curable adhesive composition.
The method of claim 1,
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 method of claim 1,
The epoxy resin has an epoxy equivalent of 170 to 600, heat curable adhesive composition.
The method of claim 1,
The inorganic filler has a secondary particle form in which a plurality of primary particles having a particle diameter of 1 nm to 20 μm are aggregated,
The secondary particles have a number average particle diameter (D50) of 1 μm to 200 μm,
Thermosetting adhesive composition.
The method of claim 1,
The liquid rubber is a reaction product of butadiene or butadiene-acronitrile copolymer and an epoxy resin, a thermosetting adhesive composition.
The method of claim 1,
The polyurethane resin has a repeating unit including a polymer block derived from polytetrahydrofuran, a residue derived from a polyvalent aliphatic isocyanate, and a urethane linking group connecting them.
The method of claim 6,
The polyurethane resin further comprises a residue derived from an alkylene glycol having 2 to 5 carbon atoms, a thermosetting adhesive composition.
The method of claim 6,
The polyurethane resin is a thermally curable adhesive composition in which the terminal isocyanate group is end-capped with an amine compound, an alcohol compound, a phenol compound, an oxime compound, or a bisphenol compound.
The method of claim 6,
The polyhydric aliphatic isocyanate includes at least one selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylenedicyclohexyl diisocyanate.
The method of claim 6,
The polytetrahydrofuran has an OH equivalent of 400 to 2200,
The polyurethane resin has a weight average molecular weight of 5000 to 500000 g/mol,
Thermosetting adhesive composition.
The method of claim 1,
The thermal curing agent is dicyandiamide curing agent, melamine curing agent, diallyl melamine curing agent, guanamine curing agent, aminotriazole curing agent, hydrazide curing agent, cyanoacetamide curing agent, and aromatic polyamine curing agent A thermosetting adhesive composition comprising at least one selected from the group consisting of.
The method of claim 1,
20 to 70% by weight of the epoxy resin;
1 to 20% by weight of the inorganic filler;
5 to 50% by weight of the liquid rubber;
2 to 25% by weight of the polyurethane resin; And
1.5 to 10% by weight of the thermal curing agent
Containing, heat curable adhesive composition.
The method of claim 1,
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 rheology control agent, and a thixotropic control agent Adhesive composition.
Applying the heat curable adhesive composition of claim 1 on a substrate; And
Forming an adhesive layer by thermally curing the applied composition at a temperature of 80° C. or higher
Containing, the method of manufacturing a structure.
A structure comprising a substrate and an adhesive layer comprising a cured product of the thermosetting adhesive composition of claim 1.
The method of claim 15,
The substrate is made of wood, metal or plastic, a structure.
The method of claim 15,
The adhesive layer includes a binder layer in which an epoxy resin is crosslinked through a thermal curing agent,
A structure comprising an inorganic filler, a liquid rubber, and a polyurethane resin dispersed in the binder layer.