JPH07292337A - Adhesive - Google Patents

Abstract

PURPOSE:To obtain an adhesive having the same level of adhesivity to an ordinary epoxy resin and at the same time having high elasticity and excellent moisture resistance by compounding a silane coupling agent, a specific inorganic filler, an epoxy-resin based base polymer and a curing agent. CONSTITUTION:This adhesive is obtained by compounding (A) a silane coupling agent (preferably an ethoxy group-containing epoxysilane, e.g. gamma- glycidoxypropylmethyldiethoxysilane), (B) an inorgapic filler having functional groups containing OH on the surface (preferably a filter obtained by mixing silicon oxide with magnesium oxide), (C) an epoxy-resin based base polymer {preferably a polysulfide modified epoxy resin of formula I [R1 and R3 each is an organic group containing a bisphenol structure; R2 is a polysulfide structure of formula II [(m) is an average content of S and 1-3; (n) is a content of the polysulfide structure and 1-50]]} and (D) a curing agent [preferably a terminal amine-containing compound containing a triazine amine of formula III (R4 is an aliphatic or aromatic hydrocarbon)].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive, and more particularly, to an adhesive which has a large elasticity as well as an adhesive force and is extremely resistant to deterioration of physical properties due to humidity.

[0002]

2. Description of the Related Art Conventionally, epoxy resins have been widely used as adhesives because of their excellent adhesiveness, chemical resistance, durability, and good wettability with various adherends. However, the bisphenol type epoxy resin used for general purpose has a very hard structure after curing and cannot be an elastic material.

Here, there are many cases where an adhesive agent having followability is required depending on the part to be adhered or the material of the adherend, and an epoxy resin having high elasticity has been required.

Therefore, -S is included in the molecular structure of the epoxy resin.
It has been considered that an epoxy resin is modified with polysulfide containing S- (disulfide) so as to have a soft structure while keeping the above-mentioned characteristics of the epoxy resin (Japanese Patent Laid-Open No. 3-273021).

However, the curing mechanism of this method used up to now has not been sufficiently investigated, and the physical properties of the adhesive after curing greatly change depending on the composition of the curing agent. It wasn't done.

In the adhesive strength measurement test, which is a destructive test, the performance of the adhesive cannot be expressed only by the absolute value of the adhesive strength. Even if the values of shear strength and elongation in the tensile test are the same, the performance of the adhesive will greatly differ if the fracture mode is different. Cohesive failure, in which the adhesive layer breaks in tears, is stable with little variation in shear strength in the same material, and because of its excellent adhesion to the adherend, it is an adhesive with a structure that is resistant to microvibration. is there. On the other hand, the cohesive force of the adhesive layer is large, and the interfacial fracture that peels off at the interface between the adherend and the adhesive has a large variation in fracture strength and is unstable, and the strength decreases suddenly. There are many problems in using it for bonding.

As a fatal drawback, it is known that the epoxy resin is inferior in moisture resistance, and the moisture absorption reduces the adhesive strength and the elongation. Usually, if the strength after reduction exceeds the practical strength, it is often possible to use it, but when used as a structural material, it is desirable that the moisture resistance be as high as possible. It is said that it will spread greatly, but it has not yet been obtained that satisfies all the adhesive strength, elasticity, and moisture resistance.

Apart from these, there is also a method of mixing an epoxy resin and a modified silicone to form a micro-separated structure and thereby obtaining an elastic adhesive. However, this method has drawbacks in that it is difficult to balance the combination of the epoxy resin, the modified silicone and the respective curing agents, the cost is increased, and the adhesive strength is inevitably reduced because of elasticity.

[0009]

In view of the above problems, the present invention is a highly elastic adhesive having a large elongation while maintaining an adhesive strength equivalent to that of an ordinary epoxy resin, and excellent in moisture resistance. It is intended to provide an adhesive.

[0010]

In order to achieve the above object, the present invention provides a silane coupling agent, an inorganic filler,
An adhesive comprising a composition containing an epoxy resin base polymer and a curing agent, wherein the inorganic filler has a functional group containing -OH on its surface.

The present invention will be described in detail below.

What is most important in the present invention is to make a material having moisture resistance and having a large elongation without lowering the adhesive strength. In addition, it is an adhesive that has excellent adhesive strength to the adherend and has a fracture mode of cohesive failure.

The silane coupling agent used in the present invention is optional and may be any of those commonly used. For example, vinyl silane, acryl silane, epoxy silane, amino silane, mercapto silane, chloro silane, etc. may be mentioned, but not limited thereto.
Among them, since the base polymer is an epoxy type, epoxysilane and aminosilane are preferable, and epoxysilane is particularly preferable, from the viewpoint of reactivity with the epoxy resin and compatibility. Further, in the silane coupling agent, it is considered that it is easy to form a covalent bond with the inorganic filler,
It is preferable to have an alkoxysilyl group. Such an alkoxy group is also optional, for example, a methoxy group,
Examples thereof include, but are not limited to, an ethoxy group and a β-methoxyethoxy group. Of these, a methoxy group and an ethoxy group are preferable, and an ethoxy group is particularly effective. Furthermore, with an alkoxy group, an epoxy group,
The inclusion of an amino group is particularly preferred because it is compatible with the epoxy resin as the base polymer as it is and can form a crosslinked structure.

The content of the silane coupling agent is preferably 0.1% or more and 10% or less by weight ratio with respect to the inorganic filler. If the amount is less than 0.1% by weight, the effect tends to be insufficient because there are too few bonding groups bonded to the inorganic material. On the other hand, if it exceeds 0.1% by weight, the base polymer may be crosslinked and hardened, and the balance of the crosslinking rate or the degree of crosslinking may be lost, and the initial physical properties such as the adhesive strength or the elongation may be deteriorated.

The method of the silane coupling treatment is arbitrary and any method may be adopted. Examples of the mixing method include a method of adding a silane coupling agent to an inorganic filler and then mixing with a base polymer, a method of mixing a silane coupling agent and a base polymer and then adding an inorganic filler, and a method of simultaneously mixing the three. can give. However, it is preferable to add the silane coupling agent to the inorganic filler and then mix it with the base polymer, and at that time, it is more preferable to perform heat treatment at 50 to 100 ° C. to promote the reaction.

By carrying out this silane coupling treatment, the physical property deterioration caused by swelling due to moisture absorption does not occur at the interface between the inorganic material and the organic agent in the matrix of the cured product of the adhesive or between the chains of the polymer crosslink. .

In the present invention, it is essential to mix an inorganic filler. Inorganic fillers are effective because the adhesive matrix exerts physical properties as structural materials (breaking strength, abrasion resistance, etc.), and some of them form chelates with polymers, and are covalently bonded by a silane coupling agent. Some are doing it. By mixing the inorganic filler, stability of weather resistance such as strength, heat resistance, fatigue resistance, and dimensional stability is improved, and economical efficiency is also improved.

However, in the present invention, in order to effectively exert the effect of the silane coupling treatment, it is necessary that the surface of the inorganic filler has a functional group containing an —OH group. This is because the presence of this OH group makes it possible to covalently bond with the silane coupling agent and improve the physical properties such as moisture resistance, which is the object of the present invention.

The functional group containing an --OH group is not limited to a hydroxyl group, but may be any known functional group such as a carboxylic acid group. Examples of the inorganic filler include silica sand, cement, oxide ceramic particles, metal salts such as calcium carbonate, and aerogel. Among them, the filler that mixed silicon oxide and magnesium oxide,
It is particularly preferably used from the viewpoints of stable strength retention and economy. The mixing ratio of the inorganic filler is preferably 80% by weight or less and 10% by weight or more based on the total weight of the composition. When the inorganic filler mixing ratio is out of the above range,
In some cases, the adhesive may be thickened to make it difficult to apply, or the resin composition and the inorganic filler may not be sufficiently mixed with each other, and the inorganic filler may be peeled off or the coating thickness may be difficult to obtain. Here, the particle size of the inorganic filler is 0.3.
mm or less is preferable. Particularly preferably 0.3 to 0.0
The particle size distribution is such that it is normally distributed in the range of 1 mm. If the particle diameter is too small, the adhesive tends to thicken, and if it is too large, the fluidity of the adhesive becomes insufficient, or particles of the inorganic filler may easily fall off, so they are in the above range. It is preferable. In addition, when the particle size distribution is appropriate, a macro structure in which small particles are embedded between large particles is formed, and the structure is densified without thickening and the strength when adhered and solidified is also improved.

Next, what is important in the present invention is that
It is to make a material having a large elongation without lowering the adhesive strength. In addition, it is an adhesive that has excellent adhesive strength to the adherend and has a fracture mode of cohesive failure. This physical property is mainly determined by the base polymer.

The base polymer used in the present invention is optional, and any epoxy resin type may be used. However, since the physical properties after curing are particularly balanced, the following polysulfide-modified epoxy resin is particularly preferable. preferable.

The polysulfide-modified epoxy resin is represented by the following general formula.

[0023]

[Chemical 3] In the above general formula, R ₁ and R ₃ are organic groups containing a bisphenol skeleton, and R ₂ is a polysulfide skeleton.
Examples of the organic groups R ₁ and R ₃ containing the bisphenol skeleton include bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, phenol novolac type epoxy resin, brominated phenol novolac type epoxy resin, cresol novolac type epoxy resin, etc. Can be mentioned.

The polysulfide skeleton R ₂ is represented by the general formula (-C ₂ H ₄ OCH ₂ OC ₂ H ₄ -S _m ) _n- , and the average content m of S is in the range of 1 to 3, It is preferably 1.5 to 2.5. Further, the average content n of the polysulfide skeleton is 1 to 50, preferably 2 to 30.
Is. When the average content n of the polysulfide skeleton is less than 1, it has the same physical properties as that of a normal bisphenol A type epoxy resin but low elasticity, and n is 50.
If it is more than the above, the viscosity tends to increase, and it tends to be difficult to handle as an adhesive. As such a polysulfide-modified epoxy resin, one having a viscosity at 25 ° C. of not more than 3000 poise is preferable from the viewpoint of handleability, and for example, “Flep” manufactured by Toray Thiokol Company can be mentioned. These polysulfide-modified epoxy resins have excellent adhesive strength and have a very flexible structure. This is the intrinsic physical property of a polymer that is derived from a linear molecular structure that is linked by disulfide.

The hardener for this base polymer is also optional, and any known method may be used, but an amine-based hardener is mentioned as an efficient one. Among them,
The most preferable one for achieving the object of the present invention is a curing agent containing at least a triazine-based amine in a compound having an amino group at a terminal. By adding this, the physical properties after curing greatly differ. First, it becomes a soft structure with large elongation, and then the fracture mode becomes cohesive failure. This is because the triazine structure is connected to the main chain part of the molecular structure where the cross-linking has been advanced by the amino group, which shows flexibility more than the benzene ring and can have a more dense cross-linking structure than the aliphatic system. Is.

Here, the content ratio of the triazine amine is 10 to 50% by weight in the compound having an amino group at the terminal.
Is preferable, and particularly preferably 15 to 30% by weight. If this range is exceeded, the effect of the compound having an amino group at the other end will increase, the curing of the polymer will progress, and the fracture morphology will be interface fracture, or conversely, the polymer will be too soft and have a low shear strength. This is because it may become

Here, the aromatic and aliphatic hydrocarbons (R ⁴ ) attached to the triazine ring are optional and are not particularly limited, but if they are too large, a crosslinked structure is difficult to form, and if they are too small. A benzene ring that is compact and has a large volume is preferable because it is difficult for the resin to have a large volume and the thixotropy tends to be poor.

The compound having an amino group at the terminal other than the triazine-based amine is optional, and any compound commonly used may be used. Examples thereof include alicyclic polyamines, aliphatic polyamines, polyamidoamines, main chain modified amines, and the like, and mixtures thereof. Specific examples thereof include xylenediamine, N- (2-cyanoethyl) -m xylenediamine, and trimethylamine, but are not limited thereto.

The total amount of the compound having an amino group at the terminal including the triazine-based amine varies depending on the epoxy equivalent of the polysulfide-modified epoxy resin and the active hydrogen equivalent of the compound having an amino group at the terminal. It is preferably about 0.3 to 3.0 times the active hydrogen equivalent per mol. If the content deviates from this range, the reaction balance between the polysulfide-modified epoxy resin and the compound having an amino group at the end tends to be upset, and many unreacted substances remain in the system, and physical properties such as adhesion and weather resistance may deteriorate. .

Here, a solvent or a diluent may be added in order to improve the compatibility of the polymer and the inorganic filler and adjust the viscosity of the adhesive. The solvent is not particularly limited, but examples thereof include aromatic hydrocarbons such as toluene, xylene, hexane, and cyclohexane, ketones such as acetone and methyl ethyl ketone, and halogenated hydrocarbons. However, in terms of workability, it is preferable to add a diluent rather than a solvent. As the diluent, a reactive agent having an epoxy group at the terminal such as phenyl glycidyl ether, n-butyl glycidyl ether, allyl glycidyl ether, or polyethylene glycidyl ether is used. It is optional, such as an aromatic non-reactive one, and there is no problem in using it depending on the purpose.

The substrate using the adhesive obtained in the present invention is not limited and is arbitrary. For example, ceramic-based slate, cement siding board, asbestos siding board, wooden boards and synthetic resin boards other than ceramics, or metal plates, inorganic tiles, inorganic boards, etc. However, it is possible to use it for building materials, which have been considered difficult to apply adhesives, but the present invention is not limited to this.

In the present invention, the method of applying the adhesive is arbitrary, and there is no problem in using a generally widely used method. For example, a roll coater method, a knife coater method, a curtain flow coater method, and the like, and an air spray method in which the viscosity is adjusted to allow spraying, and the like can be used, but are not limited thereto.

The coating thickness of the adhesive is preferably 0.1 to 5 mm, particularly preferably 0.3 to 0.8 mm. This is because if the coating thickness is too thin, there is a concern that the adhesive layer that absorbs external force will not grow sufficiently after adhesion and solidification, and the adherend may peel off.If the coating thickness is too thick, the amount of adhesive applied per unit area will increase. Therefore, the burden on the substrate becomes large and the cost tends to increase.

Examples are shown below, but the present invention is not limited to these.

[0035]

【Example】

Example 1 A commercially available silane coupling agent (γ-glycidoxypropylmethyldiethoxysilane, trade name KBE-402: manufactured by Shin-Etsu Silicone Co., Ltd.) was added to 60 parts by weight of sufficiently dried silica sand.
1.2 parts by weight was added dropwise, and the mixture was sufficiently stirred and then heat-treated at 80 ° C. for 2 hours.

Next, 30 parts by weight of a commercially available polysulfide-modified epoxy resin (trade name "Flep-60" manufactured by Toray Thiokol Co., Ltd.) was mixed with heat-treated silica sand, and 2
-4-diamino-6-phenyl-1,3,5-triazine: m-xylenediamine: N- (2-cyanoethyl)
-M-xylylenediamine: N, N'-bis (2-cyanoethyl) -m-xylylenediamine (20: 29: 4)
10 parts by weight of the curing agent mixed in 4: 7), 2 parts by weight of phenyl glycidyl ether and a diluent (trade name "SAS
The viscosity was adjusted with 2 parts by weight of -296 "manufactured by Nisseki Chemical Co., Ltd.

As shown in FIG. 1, raw stainless steel plate 2 (thickness: 1 mm, length: 10 cm, width: 2.2) washed with acetone.
5 cm) and the porcelain tile 1 are adhered with the adhesive (adhesive layer: thickness, 0.5 mm) obtained as described above, and a pressure of 1 kg / cm ² is applied from above to 20 ° C. and 50% RH. 12
After leaving for a while, the pressure and the mold were removed, and curing was continued for 7 days. Then, tensile strength and stretch were measured with Autograph AG-10TE (manufactured by Shimadzu Corporation).

Also, this sample was taken from the 8th day at 50 ° C. for 9 days.
The sample was kept in a high temperature and high humidity tank at 5% RH and taken out from the high temperature and high humidity tank 15 days later, and 20 ° C. and 50% RH
A tensile test similar to the above was also performed on the sample that had been allowed to stand at, and the moisture resistance was examined.

It was confirmed that the silica sand used contained sufficient -OH groups from the peaks appearing at 3696 to 3620 cm ^-1 in the surface FT-IR measured previously. The results are shown in Table 1.

Example 2 The same test as in Example 1 was conducted except that the silane coupling agent was changed to (γ-glycidoxypropyltrimethoxysilane, trade name KBM-403: manufactured by Shin-Etsu Silicone Co., Ltd.).

The results are shown in Table 1.

Example 3 The same test as in Example 1 was carried out except that the silane coupling agent was changed to γ-aminopropyltriethoxysilane (trade name KBE-903: manufactured by Shin-Etsu Silicone Co., Ltd.).

The results are shown in Table 1.

Comparative Example 1 The same test as in Example 1 was carried out except that silica sand was used without being subjected to a silane coupling treatment and was simply dried.

The results are shown in Table 1.

Comparative Example 2 The same test as in Example 1 was conducted except that silica sand was not mixed and only the polysulfide-modified epoxy resin, the curing agent and the silane coupling agent were mixed.

The results are shown in Table 1.

Comparative Example 3 The same test as in Example 1 was carried out except that carbon powder (inorganic filler having no —OH group on the surface) was used in place of silica sand.

The results are shown in Table 1.

[0050]

[Table 1] From these results, it has elasticity (spreading) that can absorb the difference in the adhesive force as an adhesive and the expansion coefficient of the adherend, and the fracture mode is a reliable cohesive fracture and is practical. It has been found that the method of the present invention is very effective in obtaining a moisture resistant adhesive.

[0051]

EFFECTS OF THE INVENTION According to the present invention, the adhesive strength is high, the elasticity is high, and the failure mode is reliable cohesive failure.
Moreover, an excellent adhesive having practical moisture resistance was obtained. By using this adhesive, it is possible to bond to applications where it was impossible with conventional hard adhesives, such as between different materials with completely different thermal expansion coefficients or where the adhesive interface is susceptible to peeling due to vibration. It is possible, and application to large-scale structural materials, for which joining with an adhesive is impossible, is also considered. In addition to this, it has become possible to apply it to places that were previously unusable for epoxy adhesives, such as high humidity locations and outdoors.

[Brief description of drawings]

FIG. 1 is a drawing of a test piece in which a stainless steel plate and a porcelain tile are bonded together according to the present invention.

[Explanation of symbols]

 1: Porcelain tile 2: Stainless steel plate 3: Adhesive

Claims (9)

[Claims] 1. An adhesive comprising a composition containing a silane coupling agent, an inorganic filler, an epoxy resin base polymer and a curing agent, wherein the inorganic filler has a functional group containing --OH on its surface. And adhesives. 2. The adhesive according to claim 1, wherein the silane coupling agent has an alkoxy group. 3. The adhesive according to claim 2, wherein the silane coupling agent has an epoxy group or an amino group together with an alkoxy group. 4. The adhesive according to claim 2, wherein the alkoxy group is an ethoxy group. 5. The adhesive according to claim 1, wherein the content of the silane coupling agent is 0.1% or more and 10% or less by weight ratio with respect to the inorganic filler. 6. The adhesive according to claim 1, wherein the weight ratio of the inorganic filler is 80% or less and 10% or more in the total composition. 7. The epoxy resin-based base polymer has at least the general formula: [However, R ₁ and R ₃ are organic groups containing a bisphenol skeleton, and R ₂ is (—C ₂ H ₄ OCH ₂ OC ₂ H ₄
The polysulfide skeleton represented by -S _m ) _n- (where m is 1 to 3 and represents the average content of S in the polysulfide skeleton, n is 1 to 50, and the average content of the polysulfide skeleton in one molecule is It represents). ] The adhesive agent of Claim 1 which is a polysulfide modified epoxy resin shown by these. 8. The curing agent has at least the general formula: (R ₄ represents an aliphatic or aromatic hydrocarbon group.)
The adhesive according to claim 1, which is a compound having an amino group at a terminal, including the triazine-based amine represented by 9. The adhesive according to claim 8, wherein the content ratio of the triazine-based amine is 10% by weight or more and less than 50% by weight in the compound having an amino group at the terminal.