JPH01113479A - Filmlike thermosetting adhesive - Google Patents

Abstract

PURPOSE:To obtain the title adhesive excellent in storage stability and properties after being formed into a film, by subjecting the curing agent to be used in an adhesive agent composition comprising a curing agent comprising a reaction product of an imidazole derivative with an epoxy compound, a film-forming resin composition containing an epoxy resin and a solvent to a specified treatment. CONSTITUTION:A curing agent composition is prepared by treating a curing agent comprising a reaction product of an imidazole derivative (e.g., imidazole) with an epoxy compound (e.g., bisphenol A glycidyl ether epoxy resin) with an isocyanate (e.g., tolylene diisocyanate) in a solvent (e.g., toluene) to be used in forming a film. A film-forming resin composition containing 100pts.wt. epoxy resin (e.g., bisphenol A type, liquid curable with this curing agent and a resin (e.g., urethane resin) optionally used for improving the film forming property is mixed with 15-70 pts.wt. said curing agent composition and a solvent (e.g., toluene) to obtain the title adhesive.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a film-like thermosetting adhesive used for assembling electronic parts, etc., and in particular to an epoxy adhesive which has excellent storage stability and physical properties when formed into a film. This invention relates to a resin-based film thermosetting adhesive.

[Prior Art] Film thermosetting adhesives have been proposed as adhesives used, for example, in the assembly of electronic parts. As a conventional adhesive of this type, an epoxy resin-based thermosetting adhesive is widely used.

This epoxy resin-based thermosetting adhesive is adhesive.

Although they have the characteristics of being excellent in strength, corrosion resistance, and electrical insulation, most of them are two-component types and have problems in handling and storage. Therefore, several epoxy resin compositions have been proposed as techniques to solve this problem. These are for example BF.

A latent curing agent such as an amine complex, dicyandiamide, organic acid hydrazide, or imidazole compound is blended with an epoxy resin. However, these have advantages and disadvantages; those with excellent storage stability require high temperatures for curing, and those that can be cured at relatively low temperatures have poor storage stability.

In order to further improve this, a liquid type epoxy resin composition was disclosed in JP-A No. 60-99179, in which an epoxy resin and an imidazole derivative were reacted, and only the surface portion of the product was further inactivated with an isocyanate compound. Disclosed in the official gazette. The reaction between an epoxy resin and an imidazole derivative is expressed by the following formula, taking as an example the reaction between a glycidyl ether type epoxy resin of bisphenol A and 2-methylimidazole.

As can be seen from the above formula, a hydroxyl group is present in the product (1), and this contributes to curing of the resin.

Therefore, if an excessive amount of hydroxyl groups are present, curing occurs during storage, which significantly impairs handling properties as a film adhesive.

Therefore, it has been proposed to previously treat this epoxy resin composition with an isocyanate compound to block some of the hydroxyl groups. For example, when tolylene diisocyanate is used, this reaction is expressed by the following formula.

This reaction is usually carried out in a solvent that does not dissolve the product after it has been pulverized. Therefore, the hydroxyl groups that are blocked are only those present on the surface of the particles of the epoxy resin composition (If). .

[Problems to be solved by the invention] Epoxy resin composition (It) obtained as described above
can be stably stored at room temperature for more than 6 months. However, on the other hand, it has poor solvent resistance, and solid epoxy resin,
Alternatively, when trying to manufacture a film adhesive by blending thermoplastic resins such as urethane resin, acrylic resin, phenoxy resin, polyester resin, etc., if a diluting solvent is added, it will harden in 2 to 3 hours at 40 ° C. This is because the urethane structure layer formed by the bonding of isocyan groups and hydroxyl groups swells, and the active hydroxyl groups present inside the particles are exposed to the surface and come into contact with the epoxy resin to initiate a curing reaction. Conceivable.

If such a curing reaction begins before the application of the epoxy resin composition, the viscosity of the epoxy resin composition increases, resulting in problems such as poor handling and poor storage stability after film formation.

Furthermore, many conventional epoxy resin-based thermosetting adhesives use epoxy resin alone as the resin component, which results in insufficient strength when formed into a film, resulting in seal removal and slits. There are also problems such as stretching and cracking of the film during processing, and uneven coating and running when coating on release paper.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a film-like thermosetting adhesive that solves the above-mentioned problems and has excellent storage stability and physical properties when formed into a film.

[Means for solving problems]

The film-like thermosetting adhesive according to the present invention has been proposed to achieve the above-mentioned object, and includes a curing agent made of a reaction product of an imidazole derivative and an epoxy compound, and a curing agent that is cured by the curing agent. An adhesive composition consisting of a film-forming resin composition containing an epoxy resin and a solvent that dissolves the film-forming resin composition is formed into a film, and the curing agent is an isocyanate in the solvent used during film formation. It is characterized by being treated with a nato compound.

The above imidazole derivative refers to, for example, an imidazole compound, a carboxylate of an imidazole compound, an adduct of an imidazole compound and an epoxy compound, or an adduct of an imidazole compound with a carboxylate. First, the imidazole compound has the following general formula (where R1 is a hydrogen atom, a carbamoyl alkyl group,
Cyanoalkyl group, carboxyalkyl group.

It represents a diamino-3-triacylalkyl group, preferably a hydrogen atom. R8 represents a hydrogen atom, an alkyl group, or an aryl group; R5 represents a hydrogen atom or an alkyl group; R
4 represents a hydrogen atom or an alkyl group), such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2
-phenylimidazole, 2-dodecylimidazole and the like. Preferably it is 2-methylimidazole.

In addition, as the carboxylate salt of the above imidazole compound,
Acetate, lactate, salicylate, benzoate, adipate, phthalate, citrate.

Tartrates, maleates, trimellidates, etc. can be used.

Further, when the imidazole compound forms an adduct with an epoxy compound, either a monoepoxy compound or a polyepoxy compound can be used as the epoxy compound. Examples of the monoepoxy compound include butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, p-xyl glycidyl ether, glycidyl acetate, glycidyl butyrate, glycidyl hexoate, glycidyl benzoate, and the like. Examples of polyepoxy compounds include glycidyl ether type epoxy resins of bisphenol A, glycidyl ether type epoxy resins of glycerin, and glycidyl ether type epoxy resins of polyalkylene oxide.

Oxybenzoic acid glycidyl ester ether type epoxy resin, dimer acid glycidyl ester type epoxy resin, phenol novolac glycidyl ether type epoxy resin, brominated bisphenol A glycidyl ether type epoxy resin, bisphenol F glycidyl ether type epoxy resin, polybutadiene Examples include alicyclic epoxy resins that are epoxidized with peracetic acid. Preferred is a bisphenol A glycidyl ether type epoxy resin.

The reaction product of an imidazole derivative and an epoxy compound as described above is generally powdered and used as a curing agent. Immediately before use, this curing agent needs to be prepared with an isocyanate compound in a solvent for film formation to inactivate the hydroxyl groups near the surface. Examples of the isocyanate compound include monoisocyanate compounds such as phenyl isocyanate and tolyl isocyanate, and tetramethylene diisocyanate.

Hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isopropylidenecyclohexyl isocyanate, lysine isocyanate, adduct of tolylene diisocyanate and trimethylolpropane, tolylene diisocyanate and pentaerythritol , an adduct of tolylene diisocyanate and polyethylene glycol, an adduct of tolylene diisocyanate and polypropylene glycoal, and a prepolymer of hexamethylene diisocyanate and polyethylene adipate.

Among these, tolylene diisocyanate and diphenylmethane isocyanate are particularly desirable from the viewpoint of curability.

The amount of isocyanate compound used at this time is 100% of the hardening agent.
The amount is 0.01 to 15 parts by weight. If the amount used is less than 0.01 parts by weight, the stability against solvents will be insufficient, and if it is more than 15 parts by weight, the curability upon heating will be significantly reduced.

In addition, the solvent at this time is a non-polar solvent such as xylene, toluene, cyclohexane, hexane, etc., or the above-mentioned non-polar solvent and methyl ethyl ketone.

A mixed solvent with a polar solvent such as ethyl acetate can be used. When using the above mixed solvent, it is desirable that the mixing ratio of the polar solvent be 50% or less.

Since the above solvent is the same as that used to prepare the adhesive and form the film, the epoxy resin or film-forming resin described below is added to this solvent system immediately after the isocyanate treatment. An adhesive composition can be prepared. However, if you want to avoid the effects of residual isocyanate compounds, you can temporarily separate the isocyanate-treated curing agent from the above solvent system and then add new solvent. However, in this case, completely remove the curing agent. It is important not to let it dry out.

Note that curing agents that have been pretreated with isocyanate compounds are also commercially available and may be used, but in this case, the solvent-based curing agent used to actually prepare the adhesive and form the film must be used. It is necessary to perform isocyanate treatment again.

Next, as the epoxy resin to be cured by the above curing agent, any of the polyepoxy compounds listed as polyepoxy compounds in the above explanation of the imidazole derivatives can be used.

The amount of curing agent added at this time is preferably 15 to 70 parts by weight per 100 parts by weight of the epoxy resin. If the amount of curing agent is less than the above range, the epoxy resin cannot be sufficiently cured, and If the amount of the curing agent is greater than the above range, the curing will proceed excessively and the stability of the film will deteriorate.

The above-mentioned epoxy resin is further blended with other film-forming resins to form a film-forming resin composition for the purpose of improving its film-forming properties. Examples of the film-forming resin include urethane, polyester, phenoxy resin, acrylic rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and the like. The blending ratio of the epoxy resin and the film-forming resin at this time is selected within the range of 95:5 to 10,790.

However, if the epoxy resin has sufficient film-forming ability (for example, in the case of an aliphatic polyepoxy resin), there is no need to add a film-forming resin.

[Effect]

In the present invention, a powdered curing agent made of a reaction product of an imidazole derivative and an epoxy compound is actually dissolved in a solvent for preparing a film-like thermosetting adhesive by dissolving a film-forming resin composition. is treated with an isocyanate compound.

At this time, the powdered curing agent swells in the solvent and the active hydroxyl groups inside the particles are exposed near the surface, but these active hydroxyl groups are immediately inactivated by the isocyanate compound present in the solvent. The epoxy resin does not need to be cured. Therefore, the adhesive composition does not thicken and harden before coating, or harden while it is formed into a film, improving film stability and handling properties. .

The above-described isocyanate treatment is also effective when purchasing and using a curing agent that has been previously treated with isocyanate and is commercially available in a dry state. This is because even if the material has been previously treated with isocyanate, if it is once dried and then put back into the solvent, there is a risk that new active hydroxyl groups will be exposed on the surface, and this will need to be inactivated. It is.

Furthermore, in the present invention, since a film-forming resin is blended in addition to the epoxy resin, the film strength and applicability are improved compared to when the epoxy resin is used alone.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental examples.

First, as a first preliminary experiment, we investigated the storage stability when a commercially available curing agent was further treated with an isocyanate compound in a solvent.In this experiment, the surface of the reaction product of an imidazole compound and an epoxy compound was Powder hardening agent treated with isocyanate compound (product name: HX
3601. (manufactured by Asahi Kasei Co., Ltd.) was used.

First, 100g of the above hardening agent HX3601. A predetermined amount of tolylene diisocyanate (trade name: B-80, manufactured by Sumitomo Bayer Urethane) and toluene were mixed to prepare a mixture with a solid content of 80%. Add this mixture to three-one
The mixture was stirred using a motor for 30 minutes at room temperature until homogeneous. Further, while stirring, the above mixture was heated to 40°C and kept at that temperature for 24 hours to add the hardening agent HX3601.
and tolylene diisocyanate B-80 to prepare a curing agent composition. Due to this reaction, the active hydroxyl groups newly exposed on the surface of the curing agent HX3601 due to the addition of the solvent are converted to tolylene diisocyaner) B-80
is inactivated by

Thereafter, the temperature was maintained at 40° C. and the composition was allowed to stand for a certain period of time, and the properties of the curing agent composition were observed during that time.

Table 1 shows the results of this experiment, where the amount of tolylene diisocyanate B-80 added was 0.005 g.

Three levels were used: 3 g and 18 g, and the relationship between the difference in the amount added and the storage stability was investigated. For comparison, curing agent HX36 which was not treated with tolylene diisocyanate B-80
The results of 01 are also shown.

Note that the 0 mark in the table indicates that the curing agent composition maintains fluidity, and the X mark indicates that the curing agent composition has been cured.

(Left below) Table 1 shows that the curing agent compositions containing 3 g or 18 g of tolylene diisocyanate B-80 have excellent storage stability. However, tolylene diisocyaner) B-
It was found that the material to which 3g of 80 was added cured in about 15 minutes when heated to 170°C, whereas the material to which 18g was added took longer to harden. In addition, the product to which 0.005g of tolylene diisocyaner (tolylene diisocyaner) B-80 was added had slightly better storage stability than the product to which it was not added at all, but it hardened after being left at 40'C for 12 hours, and the surface It was found that the hydroxyl group was not sufficiently inactivated.

Next, as a second preliminary experiment, we investigated the stability when the curing agent treated with isocyanate as described above was actually blended with an epoxy resin and formed into a film.The isocyanate compound used in the experiment are the above-mentioned tolylene diisocyanate B-80 and triisocyanate (product name: T
-100, manufactured by Toshi Co., Ltd.), and the epoxy resins include bisphenol A type liquid epoxy resin (product name: Ebikoat 1007, manufactured by Yuka Shell Co., Ltd.) and bisphenol A type solid epoxy resin (product name: Epicoat 828).
゜Yuka Shell Co., Ltd.) was used.

First, 100 g (7) 3 g of the above curing agent HX3601
(7)) Lylene diisocyanate B-80 or triisocyanate T-100 was mixed, and toluene was further added to prepare a mixture with a solid content of 80%. This mixture was reacted according to the method described above to prepare each curing agent composition.

The above liquid epoxy resin Epicoat 1 is added to the above curing agent composition.
007 and solid epoxy resin Epicoat 82B were added to prepare an adhesive composition, and after aging at 30°C for 24 hours, the adhesive composition was coated to prepare film adhesives (1) and (II). For comparison, a film adhesive (Ill) was similarly prepared using a curing agent composition that was not subjected to isocyanate treatment. The component ratios in each of these film adhesives are shown in Table 2. All numbers represent parts by weight.

Table 2 further shows these film adhesives (r) to (I[I)
was left at 40°C for a predetermined number of days, and the stability of the film was examined.

Table 3 shows the results of this experiment. Here, the film stability is 0 days after the start of leaving at 40''C.

The solubility of each film in methyl ethyl ketone was evaluated on the 5th day, the 10th day, the 15th day, and the 30th day, and those that melted were marked O, and those that had already hardened and did not dissolve were marked X. .

Furthermore, in order to compare and study the stability in the case where no aging was performed, each of the above film adhesives (1) to (III)
) was left at 40° C. immediately after preparation, and the stability of the film was observed every time the same number of days as above had passed.

The results are also shown in Table 3.

(The following is a margin.) Looking at this table, film adhesive (1) and film adhesive (It) maintain good film stability over the entire observation period regardless of the presence or absence of aging. On the other hand, in the film adhesive (III) in which the curing agent composition is not treated with an isocyanate compound,
It can be seen that in the case of no aging, the stability begins to deteriorate after 15 days, and that this number of days becomes even faster when aging is carried out. This indicates that there was no isocyanate compound to block the exposed hydroxyl groups when the curing agent powder was swollen in the solvent, so the curing reaction progressed while the curing agent powder was left in the form of a film. ing. If curing has already progressed in this film-formed state, it will no longer function as an adhesive when it is finally cured by heating.

The above preliminary experiments confirmed the effect of isocyanate treatment on the curing agent composition and film adhesive. It is characterized by the addition of a film-forming resin to improve the physical properties of the film.

Examples of the film-like thermosetting adhesive according to the present invention will be described below.

Example 1-Implementation NI2 In this example, six types of epoxy resins are used.

Curing agent HX360 treated with five types of film-forming resins and tolylene diisocyanate B-80
1 to prepare each thermosetting adhesive composition,
This was coated with or without aging under the conditions described above and formed into a film to prepare a film-like thermosetting adhesive.

The composition of each of these film-like thermosetting adhesives is as shown in Table 4. All numbers in the table represent parts by weight.

This table also shows the compositions of Comparative Examples 1 to 9, which will be described later.

Next, regarding each of these film-like thermosetting adhesives,
Curing time when press hardening is performed at 170°C (time when insoluble matter in methyl ethyl ketone becomes 90% or more [
), film stability at 40″C of film thermosetting adhesive prepared without aging (days)
The film stability (days) at 40° C., seal removal property, and coating property of the film thermosetting adhesive prepared through aging were evaluated. These results are shown in Table 5.

In the table, the ○ mark in the seal removal property column indicates that the seal can be removed satisfactorily, and the X mark indicates that the film may be cut due to insufficient strength.

Further, in the coating property column, an O mark indicates excellent adhesion to the release paper, and an X mark indicates that coating unevenness or running occurs.

This table also shows the characteristics of Comparative Examples 1 to 9, which will be described later.

(Left below) Comparative Examples 1 to 9
In this comparative example, the curing agent composition, epoxy resin, and
- Does not contain any of the film-forming resins or
Either the amount of the compound is inappropriate or the amount of hardening is insufficient.
(This is an example where the acid compound is not treated with isocyanate.The film prepared in each comparative example
The composition of the one-muth thermosetting adhesive is shown in Table 4 above.
1 is as shown.
We also conducted similar evaluations for each of these film-like thermosetting adhesives. The results are shown in Table 5 (
As shown.

In addition, those with a horizontal line in the curing time column indicate that no curing radiation was applied, and also indicate film stability (age).
Those with a horizontal line in the column ``with 2 rings'' are coach-in.
Each represents that Og was impossible,
These Examples 1 to 12 and Comparative Examples 1 to
Let's consider 19 all together.
Consistently, all examples exhibited fast curing times and good film stability, seal removal properties, and coach-in removal properties. Here, the film stability is stated to be 530 days, but it goes without saying that this indicates the upper limit of the observation period and does not indicate the upper limit of film stability.

In Example 5, no film-forming resin was used, but this is because Dinacol 614, which is used as an epoxy resin, also functions as a film-forming resin.

On the other hand, all of the comparative examples have some problems.

First, since Comparative Examples 1 to 4 have the same epoxy eyelid composition and film-forming resin composition as Example 1, they are all excellent in seal removal properties and coating properties. However, because the curing agent composition was not treated with isocyanate, for example, in Comparative Example 11, the film stability decreased after aging, and in Comparative Example 2, the film stability decreased regardless of the presence or absence of aging. In addition, in Comparative Example 3 and Comparative Example 4, the hardening agent ■
Since the acid is a conventionally used type of compound, the film stability is reduced and the curing time is significantly extended, and especially in Comparative Example 4, even coating is not possible after aging. be.

Comparative Example 5 and Comparative Example 6 are examples in which there is no problem in terms of composition, but the content of the curing agent composition is inappropriate. The appropriate content range is 15 to 70 parts by weight, but in Comparative Example 5, it was lower than the above range, so 170 parts by weight was used.
Hardening does not occur even when pressed at ℃, and seal removal properties are also poor. In addition, in Comparative Example 6, since the temperature was higher than the above range, curing progressed too much before pressing.

In Comparative Example 7, although an appropriate amount of the isocyanate-treated curing agent composition was used, the film-forming resin was not contained, so that the seal removal properties and coating properties were deteriorated.

In Comparative Example 8, the content of the film-forming resin was too low, resulting in poor seal removal properties.

In Comparative Example 9, the content of the epoxy resin was so low that curing did not occur.

〔Effect of the invention〕

As is clear from the above explanation, in the film thermosetting adhesive according to the present invention, a powdered curing agent made of a reaction product of an imidazole derivative and an epoxy compound is used to actually prepare the adhesive. By treatment with an isocyanate compound in a solvent for curing, active hydroxyl groups near the surface of the curing agent are inactivated. This results in
Not only does the storage stability of the above-mentioned curing agent alone improve, but also the storage stability when mixed with an epoxy resin and a film-forming resin to form a thermosetting adhesive composition, and the coating improves the storage stability of the thermosetting adhesive composition. The stability of the film when used as a curable adhesive is greatly improved.

Furthermore, in the present invention, instead of using an epoxy resin alone, other resins having excellent film-forming properties are mixed, thereby improving seal removal properties and coating properties when formed into a film.

Therefore, it is possible to provide a film-like thermosetting adhesive that is excellent in handleability and economical efficiency.

Patent applicant: Ka-Kemi*S Co., Ltd. Agent Patent Attorney Mi Koike Between Sakae Tamura Same as Masaru Sato

Claims (1)

[Claims] An adhesive comprising a curing agent made of a reaction product of an imidazole derivative and an epoxy compound, a film-forming resin composition containing an epoxy resin that is cured by the curing agent, and a solvent that dissolves the film-forming resin composition. 1. A film-like thermosetting adhesive, characterized in that the curing agent is treated with an isocyanate compound in a solvent used during film formation.