JPH06256745A - Adhesive resin composition and its production - Google Patents

Abstract

PURPOSE:To obtain a precurable adhesive resin composition excellent in storage stability, useful for e.g. assembling in automobiles, by melt blending each specific powdered polymer, polycaprolactone and curing agent followed by cooling and grinding and by incorporating the resultant powder into a liquid epoxy resin. CONSTITUTION:(A) 10-70 pts.wt. of powdered polymer consisting of a (meth) acrylate 0.05-100 micron in mean particle diameter, (B) 10-100 pts.wt. of a crystalline polycaprolactone and (C) pref. 2-30 pts.wt. (based on 100 pts.wt. of the liquid epoxy resin described below) of a thermally active potential curing agent such as adipoyl dihydrazide are homogeneously melt blended at a temperature not lower than the melting point of the component B, and the resultant blend is cooled and solidified and then ground. The resultant ground product is homogeneously incorporated in 100 pts.wt. of an liquid epoxy resin such as bisphenol A-type epoxy resin to obtain the objective composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive resin composition and a method for producing the same. More specifically, it is used for bonding metal structural members in automobile assembly or filling hemming structures and bonding panels. TECHNICAL FIELD The present invention relates to a one-component structural adhesive which is used for precure and has excellent storage stability, and a method for producing the same.

[0002]

2. Description of the Related Art In an automobile assembly process, for example, doors, hoods, trunk lids, and other panels are coated with an adhesive for the purpose of preventing rust and maintaining the rigidity of the panel at the end of the outer panel. The inner panel is assembled, and the edge of the outer panel is bent to form a hemming structure in which the adhesive is evenly filled. In general, panels such as doors, hoods, and trunk lids are installed in order to prevent the outer panel and inner panel from slipping due to vibration or shock after the hemming process and during transportation to the next process or handling to the vehicle body. It is fixed by spot welding on the hemming part. Alternatively, hot air is jetted to the edge of the panel, or a method of pre-curing the filled adhesive by a heating method using a high-frequency induction heating device to temporarily fix the panel is the current mainstream. Generally, these precureable adhesives differ depending on their composition, but generally, acrylic resin or vinyl chloride resin that swells selectively with the epoxy resin that is the main component of the adhesive when heated to 100 to 120 ° C. The fine powder of is added,
When the temperature of the adhesive rises, these resins appear to be gelled, and are in a dry state to the touch. Panels are temporarily fixed using these characteristics.

[0003]

However, these precureable adhesives contain resin fine powder that swells at 100 to 120 ° C. due to the epoxy resin, which is the main component of the adhesive, and gradually increases even at room temperature. Since it swells and the viscosity increases, storage stability becomes a problem. Especially in summer, the ambient temperature of the adhesive often exceeds 40 ° C in the automobile assembly process. In such a usage environment, the viscosity of the adhesive gradually rises in the pipes, pumps, and nozzles that pump the adhesive to which the resin fine powder that swells due to the epoxy resin is added, and discharges the prescribed amount of adhesive. If it becomes impossible or if it gels completely, the ejection itself becomes impossible. Therefore, it is an important required property of the one-pack type structural adhesive used for vehicle body assembly to secure the storage stability of the pre-curable adhesive at a use environment temperature of 50 ° C. or less. In order to ensure storage stability, the molecular weight of the epoxy resin is adjusted and a specific plasticizer is added, but the present situation is not necessarily an effective means.

Therefore, an object of the present invention is to solve the above problems, to provide an adhesive resin composition which can be pre-cured and is excellent in storage stability, and a method for producing the same.

[0005]

Means for Solving the Problems The present invention satisfying the above-mentioned object is a first step of melting and mixing a specific (meth) acrylic resin, polycaprolactone, and a heat-activatable curing agent at a melting point of polycaprolactone or higher, and further Precure obtained by the second step of crushing the compound after cooling and solidifying, the third step of uniformly mixing and dispersing the obtained pulverized product in a liquid epoxy resin at room temperature, and is extremely excellent in storage stability. The present invention relates to an adhesive resin composition and a method for producing the same.

That is, the first invention of the present invention relates to an adhesive having excellent storage stability, which contains an epoxy resin, a polycaprolactone, a powder polymer composed of (meth) acrylate, and a heat-activatable latent curing agent as essential components. It is a thing.

The epoxy resin used in the present invention is a liquid epoxy resin having at least one epoxy group in the molecule, and examples of such epoxy resin include bisphenol A type epoxy resin and bisphenol F type epoxy resin. . Normally, the number average molecular weight is 300-
1500, epoxy equivalent is 150-900. The epoxy resin mentioned here is preferably a liquid epoxy resin at room temperature, but even a liquid epoxy resin is mixed at room temperature, a liquid epoxy resin is mixed, or a plasticizer is mixed,
There is no problem if the mixture is liquid at room temperature and the epoxy equivalent of the mixture is within the above range. Therefore, in the present invention, the liquid epoxy resin means not only the above epoxy resin which is liquid at room temperature but also the above mixture which is liquid at room temperature. Further, particularly preferably, a bisphenol A type liquid epoxy resin having an epoxy equivalent of 180 to 210 is used because of its excellent workability and curability.

Next, polycaprolactone used in the present invention is an essential component with respect to 100 parts by weight of the above epoxy resin.
10 to 100 parts by weight, particularly preferably 15 to 35 parts by weight are blended. If the compounding amount is less than 10 parts by weight, the composition cannot be pulverized because it does not solidify after being melt mixed at room temperature. If the blending amount exceeds 100 parts by weight, polycaprolactone acts as a plasticizer, and the adhesive resin composition produced by the present invention loses the excellent properties of the epoxy resin.

The number average molecular weight of the above polycaprolactone is
2000-7000 are preferred. Next, the average particle size 0.05 to 100
The powder polymer of micron (meth) acrylate is added in an amount of 10 to 70 parts by weight based on 100 parts by weight of the epoxy resin. Particularly preferably, it is added in an amount of 25 to 50 parts by weight. If the blending amount is less than 10 parts by weight, swelling (dry state to the touch) by the acrylic resin is not sufficient at the time of temporary fixing of the panels, that is, at the time of precure, and the action described in the present invention is not exhibited. On the other hand, if the blending amount exceeds 70 parts by weight, the viscosity of the resin composition after preparation is remarkably increased and the workability is deteriorated.
Examples of the (meth) acrylate polymer include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate and stearyl methacrylate, alkyl acrylates such as methyl acrylate and butyl acrylate, alkyl glycol (meth) acrylates such as butoxyethyl (meth) acrylate, Examples thereof include polymers of alkylene glycol mono (meth) acrylate. A preferred (meth) acrylate is methyl methacrylate. Although not particularly limited, a polyfunctional (meth) acrylate such as trimethylolpropane methacrylate or (poly) ethylene glycol dimethacrylate may be used in combination for adjusting the degree of polymerization.

As the curing agent, a heat-active latent curing agent which is stable at storage and active at high temperature is used, and one having a high adhesive strength to the substrate after curing is preferable. From such a viewpoint, Organic acid dihydrazides and their derivatives such as adipoyl dihydrazide, isophthaloyl dihydrazide, sebacoyl dihydrazide, dicyandiamide, 4,4′-diaminodiphenyl sulfone, or 2
Examples thereof include imidazole derivatives having a triazine ring in the molecule such as methylimidazole triazine salts, acid anhydrides such as trimellitic anhydride, and boron trifluoride complex compounds. In particular, dicyandiamide is preferable because it is excellent in curability after being dispersed and blended in the epoxy resin and in adhesiveness to the substrate. Most preferably, the heat-acting latent curing agent is blended in an amount of 2 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin.

The adhesive resin composition of the present invention is not particularly limited, but may contain an inorganic filler if necessary. Examples of such inorganic fillers include fused silica, crystalline silica, mica, alumina, calcium silicate, aluminum silicate, kaolin clay, calcium carbonate, talc, barium sulfate, magnesium oxide, titanium oxide, zinc oxide, aluminum hydroxide, and trihydrate. Examples include antimony oxide and scaly graphite. These may be used alone or in combination of two or more. Although not particularly limited, the surface of these inorganic fillers may be treated with a silane coupling agent, a titanium coupling agent, a fatty acid, a surfactant or the like.

Next, it is a feature of the method of the present invention that the step for mixing the above-mentioned components into an adhesive resin composition is divided into three steps as described below. Specifically, a powder polymer composed of (meth) acrylate having an average particle size of 0.05 to 100 microns, polycaprolactone having crystallinity, and a heat-activatable latent curing agent within the range of the compounding amount specified in the present invention. The step of uniformly melting and mixing at a temperature equal to or higher than the melting point of polycaprolactone is referred to as the first step. In the first step, the (meth) acrylate does not swell (pseudo-cure) with polycaprolactone even when melt-mixed at a temperature equal to or higher than the melting point of polycaprolactone. After melting and mixing each of these components, polycaprolactone crystallizes in the process of cooling the mixture, and the mixture obtained in the first step becomes completely solid. The step of pulverizing this with a pulverizer such as a pole mill or a feather mill is referred to as a second step. In the second step, the crushed product is preferably crushed using the average particle size of the (meth) acrylate added in the first process as a guide, and the crushed product obtained by repeating classification has an average particle size of 0.1 to 15 microns. It is preferable. Also,
It may be frozen and crushed if necessary. The polycaprolactone added in the first step has a curing point of about 50 to 60 ° C., and the obtained pulverized product does not cause blocking at room temperature. Further, the step of uniformly mixing and dispersing the pulverized product in the liquid epoxy resin at room temperature is the third step. In the third step, the milled product obtained in the second step is uniformly dispersed and mixed in the liquid epoxy resin with a three-roll, planetarium mixer, kneader, extruder, etc. It must be mixed uniformly with the liquid epoxy resin at temperature. When melt-mixed at a temperature above the melting point of polycaprolactone,
The polycaprolactone that has been crystallized and solidified on the surface of the (meth) acrylate or the curing agent is compatible with the epoxy resin, which is the same as when the essential four components of the present invention are melt-mixed at the same time. Not only storage stability is not exhibited, but also epoxy resin is mixed (meta) during mixing.
Acrylate swells and does not form a uniform paste. Therefore, in the third step, it is necessary to prevent the mixture from being heated, and at the same time, to control the temperature so that the heat of the mixture due to shearing during the mixture is equal to or lower than the melting point of polycaprolactone. Therefore, it is preferable that each of the above kneaders is provided with a device for cooling the chamber or cylinder with a cooling medium or the like.

The adhesive resin composition of the present invention is prepared by the above-mentioned steps to obtain a uniform paste state.

[0014]

Next, the operation of the present invention will be described. The adhesive resin composition of the present invention becomes apparently gelled (dry to the touch) due to swelling of the poly (meth) acrylate by the epoxy resin when the composition is heated to 100 ° C. or higher. Therefore, precure is possible and panels can be temporarily fixed. Further, on the surface of the poly (meth) acrylate and the curing agent, polycaprolactone is crystallized and solidified after completion of the first step of producing the adhesive resin composition. Further, the curing agent hardly contacts the epoxy resin, does not increase in viscosity over a long period of time, and exhibits excellent storage stability. Moreover, after coating and filling the desired adhesive site with such an adhesive resin composition, the adhesive resin composition of the present invention is heated to a temperature not lower than the melting point of polycaprolactone (100 to 120 by a high-frequency induction heating device or a hot air blowing device).
By heating to (° C), polycaprolactone, which is crystallized and solidified on the surface of the curing agent and (meth) acrylate, quickly becomes compatible with the epoxy resin, resulting in (meth)
The acrylate is in direct contact with the epoxy resin, and while the epoxy resin is incorporated into the molecular chain, the acrylate swells rapidly and becomes dry to the touch. With such a mechanism, the adhesive resin composition of the present invention can be pre-cured, and the panels can be fixed.

As described above, the adhesive resin composition of the present invention is
Due to polycaprolactone crystallized and solidified on the surface of the (meth) acrylate resin and the curing agent, not only the (meth) acrylate resin does not swell in the epoxy resin, but also the curing agent does not come into contact with the epoxy resin, so that almost no reaction occurs. However, it is characterized by exhibiting excellent storage stability. Moreover, once such an adhesive resin composition is once heated to a temperature (100 to 120 ° C.) higher than the melting point of polycaprolactone, the (meth) acrylate resin swells rapidly with the epoxy resin, resulting in excellent precure performance. It is characterized by showing.

[0016]

The present invention will be described with reference to the following examples and comparative examples. Examples and Comparative Examples (Preparation of Sample) Polymer of acrylic acid (number average molecular weight 50,000) obtained by finely pulverizing a polymer of methyl methacrylate into 0.3 μm by spray drying, and polycaprolactone (number average molecular weight 2000, melting point 55 ° C .: Praxel 220, number average molecular weight 4
000, melting point 58 ° C: Praxel 240, number average molecular weight 6000
0, melting point 60 ° C .: Praxel H7, all manufactured by Daicel Chemical Industries, Ltd. and hardener dicyandiamide (H3636S: manufactured by AR Co., Ltd.) in the proportions shown in Table 1 respectively. At a temperature equal to or higher than the melting point of polycaprolactone, the mixture was kneaded with a triple roll three times to obtain a paste composition. This composition gradually increased in viscosity after being left at room temperature, and became completely solid 20 minutes after the completion of kneading. This solid composition was pulverized with a feather mill, and the obtained pulverized product was repeatedly classified to obtain a fine powder having an average particle size of 10 microns. This fine powder was blended with a bisphenol A type epoxy resin (epoxy equivalent 190: manufactured by Epikote 828 Yuka Shell Epoxy Co., Ltd.) in the proportions shown in Table 1, and defoamed with a Brabender type kneader for 20 minutes. The mixture was kneaded to obtain uniform paste-like adhesive resin compositions of sample numbers 1 to 7.

[0017]

[Table 1]

Next, as a comparative example, unlike the production method of the present invention, a composition obtained by simultaneously blending the above acrylic resin polymer, polycaprolactone and a curing agent dicyandiamide, and a liquid epoxy resin in the proportions shown in Table 2. Was mixed with a Brabender type kneader for 20 minutes at a temperature equal to or higher than the melting point of polycaprolactone while defoaming to obtain paste compositions of sample numbers 8 to 14. Some of these compositions became solid after standing. The compositions of sample Nos. 15 to 18 in Table 3 were obtained by melt-mixing acrylic resin, dicyandiamide, and polycaprolactone, and then pulverizing and blending them into a liquid epoxy resin. Although similar, the compounding amount is out of the range of the present invention.

[0019]

[Table 2]

[0020]

[Table 3]

(Evaluation of Characteristics) (1) Confirmation of Precure Performance As shown in FIG. 1, the obtained paste-like composition 2 was
A bead diameter of 5 mm was applied onto an oil surface steel plate (SPCC-SD) 1 having a thickness of 0.8 mm, and the tip of the hot air injection nozzle 5 of the hot air injection device 4 was kept 5 cm from the back surface of the steel plate 1 of the composition 2 applied. Then, hot air at 400 ° C. was jetted onto the surface of the steel sheet. After the hot air injection was finished, it was confirmed that the applied composition was in a dry state to the touch (pre-cured state). The precure temperature at this time was measured by embedding a thermocouple in the bead shape applied and measuring the temperature. When the composition reached 120 ° C., hot air injection was stopped. The state in which it solidified completely and did not adhere to the finger after the end of heating was defined as "good" in terms of precure property, and the state in which it adhered to the finger was defined as "bad". Furthermore, thickness is 1.6 mm and width is 25 m.
Using a shear test piece of m, length 100 mm, and dimensions (SPCC-SD), an adhesive joint having an adhesive length of 12 mm was prepared. Figure 2
As shown in, the center of the bonded portion was heated by the same hot air blowing device 4 with hot air of 400 ° C., and the heating was terminated when the temperature of the bonded portion reached 120 ° C. The shear strength under this precure condition was measured. If the shear bond strength is 1.0 MPa or more, the pre-cure performance is “good” and the shear bond strength is
Precuring performance was rated as "poor" if the pressure was less than 1.0 MPa. The precure temperature at this time was measured by embedding a thermocouple in the bonded portion.

(2) Confirmation of Storage Stability The obtained resin composition was stored at 25 ° C. for 180 days and at 50 ° C. for 30 days.
It was held and the change in viscosity was examined. Relative humidity in each case
Hold at 70%. The viscosity was measured with a B-type viscometer. The storage stability was evaluated by increasing the viscosity after the end of the retention with respect to the initial viscosity, and the storage stability of the sample having less than 10% was “good”,
A sample having a viscosity increase of 10% or more after the end of holding was designated as "poor" in storage stability.

As is clear from the examples of Table 1, samples obtained within the scope of the present invention and by the manufacturing method (Sample No. 1)
7 to 7) all show excellent precure property and storage stability. On the other hand, in the comparative example of Table 2, although the sample is within the scope of the present invention, the manufacturing method is different from that of the present invention, and thus the characteristics of the present invention cannot be obtained. Sample number 8
Although Nos. 9 and 9 have good pre-cure properties, they have a problem in storage stability, and the viscosity increase rate when kept at 50 ° C for 30 days is 500.
% Is exceeded for practical use. Further, since the sample Nos. 10 to 14 have a large amount of polycaprolactone added, they are in a paste form after the kneading is completed, but after being left at room temperature, the viscosity gradually increases and finally becomes a solid form. In addition, since sample numbers 15 to 18 are outside the range specified by the present invention, the sample numbers 16 to 18 are added.
Is not dispersible, and other samples do not satisfy precuring performance and / or storage stability.

[0024]

INDUSTRIAL APPLICABILITY As described above, the adhesive resin composition and the method for producing the same according to the present invention have a powder polymer made of (meth) acrylate in an epoxy resin, a heat-acting latent curing agent, and crystallinity. Polycaprolactone is blended in a specific amount ratio, and the production method thereof is an acrylic resin, a curing agent, and polycaprolactone are melt-kneaded at a temperature equal to or higher than the melting point of polycaprolactone. It is characterized by adding to. The adhesive resin composition of the present invention produced in this manner has good pre-curability and excellent storage stability. By using such an adhesive resin composition, the panels can be easily temporarily fixed by heating. Further, even in the summer, the discharge amount does not change due to the increase in viscosity, so that there is no need to manage viscosity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a hot-air jetting device arranged on a sample piece for confirming the pre-cure property (dry state to the touch) in an example of the present invention.

FIG. 2 is a cross-sectional view of a hot-air jetting device arranged on a sample piece for confirming shear strength during pre-cure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel plate 2 Adhesive resin composition 3 Thermocouple 4 Hot air injection device 5 Hot air injection nozzle of hot air injection device

Claims (2)

[Claims] 1. An epoxy resin having at least one epoxy group in a molecule, which is liquid at room temperature, 100 parts by weight, polycaprolactone having crystallinity of 10 to 100 parts by weight, (meth).
An adhesive resin composition comprising 10 to 70 parts by weight of a powder polymer made of acrylate and a heat-activatable latent curing agent. 2. A powder polymer of (meth) acrylate having an average particle diameter of 0.05 to 100 microns, polycaprolactone having crystallinity, and a heat-acting latent curing agent are uniformly melt-mixed at a temperature higher than the melting point of polycaprolactone. And a second step of pulverizing the obtained mixture after cooling and solidifying the mixture, and a third step of uniformly mixing and dispersing the pulverized product in a liquid epoxy resin at room temperature. The method for producing the adhesive resin composition according to claim 1.