KR101809935B1 - Imidazole agent with synthesized copolymers for latent curing of epoxy resin and method of producing the same - Google Patents

Abstract

Disclose imidazole curing agents prepared using copolymers. The present invention is characterized by encapsulating imidazole by using a copolymer of methacrylic acid (MAA) and dodecyl methacrylate (DDMA), and it is possible to construct a system for more effectively delaying an epoxy resin-imidazole system There is an effect.

Description

TECHNICAL FIELD The present invention relates to an imidazole curing agent prepared by using a copolymer for latent curing of an epoxy resin and a method of producing the imidazole curing agent,

The present invention relates to an imidazole curing agent prepared by using a copolymer and a method of preparing the same, and more specifically, by encapsulating imidazole using a specially designed copolymer, The present invention relates to an imidazole curing agent prepared by using a copolymer and a process for producing the same.

Currently, anisotropic conductive films (ACF) are used in the manufacture of LCDs. ACF is made by mixing fine conductive particles with an epoxy adhesive. The conductive particles mixed here are pressed and crushed during the compression and curing process and serve to conduct electricity between the same number of bumpers connected to the liquid crystal plate and more than one million fine bumpers on the back plate. The epoxy adhesive used in this ACF is composed of an epoxy resin and an imidazole curing agent. There are various kinds of curing agents that can be used for epoxy resins. Among them, a combination of an epoxy resin and an imidazole curing agent is known to exhibit the most suitable properties for LCD manufacturing.

However, a very important problem arises here because there is a problem that the epoxy functional group and the imidazole can not be mixed beforehand because the reaction proceeds at room temperature although it is slow.

However, ACF must be manufactured in a pre-mixed form because the epoxy adhesive mixed with the conductive balls in the manufacturing process of the LCD must be made into a film form and be subjected to a waiting time in the manufacturing process for a considerable time. Therefore, the reaction should not occur between the imidazole curing agent and the epoxy functionalities that are mixed.

The property that the reaction occurs at the proper reaction temperature at the desired time while the reaction does not occur at room temperature is called latent curing. Although the formulation of ACF used in the current production process is not known in detail, it is known to encapsulate imidazole particles to inhibit the reaction by using low molecular weight organic substances. However, their encapsulation is incomplete and currently used ACFs must be frozen to completely stop the reaction.

The present inventors have made attempts to form an imidazole-epoxy resin system exhibiting a better latent character. That is, an imidazole-epoxy resin system having storage stability at room temperature was prepared. In these studies, an attempt was made to encapsulate an imidazole hardener with a polycaprolactone (PCL) solvent evaporation method or spray-drying method to have a latent character .

Since PCL has a relatively low melting point at about 60 ° C, it can be easily melted by raising the temperature and easily react with the epoxy resin that has been previously mixed with imidazole. Our previous results show that the encapsulation using PCL has succeeded in showing some delay characteristics. However, the amount of PCL to be used for encapsulation was 1: 1 or more when compared to the amount of imidazole. That is, when using the encapsulated imidazole thus prepared, the PCL is incorporated into the final product in an amount at least equal to the amount of imidazole to be added. PCL has good properties for the encapsulation of imidazole in this study, but the physical properties for ACF are not so good and thus adversely affect the physical properties of the finally formed polymer.

Therefore, in this study, we sought to find a new material for encapsulation that exhibits superior properties to replace PCL. That is, the present inventors sought to find a polymer material for encapsulation having excellent delay characteristics even when encapsulated in a smaller amount than the imidazole used.

 Methacrylate derivatives with long side chains have a comb-like structure. The alkyl chain groups they have are known to self-assemble to form nanodomains.

And polymers formed from methacrylate derivatives with long side chains have very low melting points. Therefore, they are well-preserved and are expected to play a good role in easily dissolving the substance in the desired time.

The carboxylic acid functional group forms a salt with imidazole and is expected to serve as a better barrier. In the present invention, dodecyl methacrylate and meta We have tried to use a copolymer of methacrylic acid as a material to encapsulate imidazole

1. Korean Patent No. 10-0938523 2. Korean Patent No. 10-1234711 3. Korean Patent Publication No. 10-2011-0100235 (September 9, 2011)

The object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide an epoxy resin composition which encapsulates imidazole using a specially designed copolymer, And a process for producing the same.

Another object of the present invention is to provide an imidazole curing agent prepared by using a copolymer capable of constructing a system for more effectively retarding an epoxy resin-imidazole system, and a process for producing the same.

In order to accomplish the above object, an imidazole curing agent prepared by using the copolymer according to the present invention,

1. An imidazole curing agent prepared using a copolymer, wherein the imidazole is encapsulated using a copolymer of methacrylic acid (MAA) represented by the following formula (1) and dodecyl methacrylate (DDMA) represented by the following formula (2).

[Chemical Formula 1] < EMI ID =

[Chemical Formula 2] < EMI ID =

The method for producing an imidazole curing agent using the copolymer according to the present invention comprises:

Preparing a copolymer through polymerization reaction of MAA (Methacrylic acid) and DDMA (dodecyl methacrylate) in a reactor; Dissolving the copolymer and imidazole in dichloromethane (DCM) to prepare a mixed solution; And encapsulating the imidazole in the chamber using a spray drying method.

And a step of using a chain transfer agent for molecular weight control in the copolymer preparation step.

In the spray drying method,

Spraying a mixed solution of the copolymer and imidazole on the opposite wall in a chamber using a spray gun and nitrogen gas; And separating the microcapsules formed on the opposite wall.

According to the present invention, there is an advantage that encapsulation of imidazole using a specially designed copolymer enables effective curing of the epoxy resin effectively.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to construct a system that more effectively has retardation characteristics in the epoxy resin-imidazole system.

1 is a view showing a structural formula of materials used in the present invention.
2 is a SEM photograph of microcapsules according to different copolymer composition ratios.
3 is an SEM photograph of microcapsules obtained by different ratios of copolymer and imidazole.
4 is a DSC curve showing epoxy resin curing behavior according to different copolymer composition ratios.
5 is a DSC curve showing the curing behavior of the epoxy resin with different composition ratios.
6 is a graph showing the transmittance of imidazole through microcapsules.
7 is a graph showing the permeability of 2-methylimidazole through microcapsules.
8 is a graph showing the transmittance of imidazole through a microcapsule made of Co28 copolymer.
9 is a graph showing the transmittance of 2-methylimidazole through microcapsules made of Co28 copolymer.

Hereinafter, an imidazole curing agent prepared using the copolymer according to the present invention and a method for producing the same will be described in detail with reference to the accompanying drawings.

The present invention is to construct a system that has a more effective latent character in an epoxy resin-imidazole system. The present inventors have conducted studies showing the delay characteristics by encapsulating imidazole in various ways using PCL. However, in order to encapsulate imidazole with PCL, at least the same amount of PCL as imidazole was required. In the present invention, attempts have been made to synthesize a new copolymer in order to find a polymer capable of encapsulating imidazole more effectively in place of PCL.

The monomers selected in the present invention are methacrylic acid (MAA) and dodecyl methacrylate (DDMA). The polymers required in the present invention must encapsulate imidazole well, but they must be exposed to imidazole at a desired time, that is, melted and stored at a suitable temperature within a short period of time. Therefore, a polymer having a melting temperature or a molten state at a relatively low temperature is required.

In the present invention, DDMA (dodecyl methacrylate) was selected as such a polymer. This is known as a polymer that does not have a distinct melting point but is molten at very low temperatures. Since methacrylic acid has a carboxylic acid functional group, MMA forms an acid-base salt when mixed with imidazole to inhibit the reaction between the epoxy resin and imidazole very effectively It was expected to be chosen.

In the synthesis of MAA and DDMA, DDTO (1-dodecanethiol) was used as a chain transfer agent, which was added to control the molecular weight. Lowering the molecular weight not only allows the imidazole to be easily dissolved in the solvent in the process of encapsulating the imidazole, but also can help the microcapsule to melt easily and open quickly when the capsule is opened and the reaction is desired to occur.

The composition of the synthesized copolymer was measured by back titration with HCl solution after reacting with KOH solution. The molecular weight of the synthesized copolymer was measured by GPC. The results are shown in Table 1.

The amount of MAA in the copolymer synthesized from the results in Table 1 was slightly higher than the amount actually added. In the case of Co19, the amount of MAA in the copolymer increased by 0.8 mol%. In Co28, the amount of MAA was increased by 1.9 mol%. In the case of Co37, the amount of MAA was increased by 3.5 mol%. The number average molecular weight of the synthesized copolymer measured by GPC was 8,400 ~ 9,400 and the weight average molecular weight was 12,100 ~ 15,200. The molecular weight increased with increasing the proportion of MAA in the copolymer. This means that MAA is better at polymerization than DDMA. The polydispersity values increased with increasing the amount of MAA, that is, with increasing molecular weight, and were found to be relatively low values of polydispersity ranging from 1.44 to 1.62. This low value is considered to be due to the removal of low molecular weight substances using methanol, in addition to the relatively low molecular weight control.

In the present invention, encapsulation of imidazole was carried out by spray-drying method. The shape of the microcapsules once formed was examined by SEM. The morphological changes according to the composition ratio of the copolymer were examined with the ratio of imide (Im) to the copolymer used being 1.0 / 1.0. The results are shown in Fig.

The result of Fig. 2 shows that Co19, Co28 and Co37 were well formed into spherical microcapsules. Compared to the case of Co28, microcapsules of relatively uniform shape were formed. The same results were obtained in three replicate experiments, which suggests that the solubility of Co28 in the solvents used is better than that of the copolymers with different composition ratios. The microcapsules thus formed had an average size of 156 mu m for Co19, 124 mu m for Co28, and 156 mu m for Co37.

Next, SEM photographs of the microcapsules formed by copolymerizing Co28 with Co28 and Im in the ratio of 1.0 / 0.8, 1.0 / 1.0 and 1.0 / 1.2 were obtained. The results are shown in Fig.

In the results of Fig. 3, 1.0 / 0.8 and 1.0 / 1.0 showed similar results with no significant difference, but at 1.0 / 1.2, microcapsules slightly larger and slightly larger in size were formed. The average size of the formed microcapsules was 124 占 퐉 for 1.0 / 0.8, 124 占 퐉 for 1.0 / 1.0 and 145 占 퐉 for 1.0 / 1.2, respectively.

The amount of imidazole actually contained in the microcapsules was calculated using the ratio of carbon to nitrogen measured using EA. The results are shown in Table 2.

The results of Table 2 show that the ratio of imidazole is almost the same as the ratio we put in. In the meantime, the method of encapsulating imidazole was spray-drying method and solvent evaporation method. In the solvent evaporation method, the imidazole leaks into the water during the encapsulation process and the ratio of the imidazole in the microcapsule formed is lower than the feed ratio. However, in the spray drying method, the imidazole is contained in the microcapsules at about the same ratio as the supply ratio without such concerns.

DSC was used to determine the curing behavior of these microcapsules when they were mixed with epoxy resin. The copolymer used was Co28, and the ratio of copolymer / imidazole was 1.0 / 1.0. The results are shown in Fig.

In FIG. 4, the shapes of the DSC curves show that the curing behavior using only pure imidazole (Im) is almost the same as the curing behavior using microcapsules. This means that the reaction mechanism when using pure imidazole is the same as the reaction mechanism when using microcapsules. Although the shapes are almost the same, it can be seen that microcapsules have a slightly lower kick-off temperature and peak temperature in a detailed comparison. And 2MI (2-methylimidazole) showed almost the same phenomenon. The results are shown in FIG. This is because the copolymer used in the encapsulation plays a role in slowing down the reaction between the imidazole and the epoxy resin.

Curing behaviors of epoxy resin with DSC were investigated by using Im and 2MI as curing agents and Co19, Co28 and Co37 as copolymers. The results are shown in Table 3. In this experiment, we adjusted the amount of microcapsules added to give the same amount of imidazole that was finally added.

Table 3 shows that the peak temperature was increased by 3 ~ 15 ℃ in the case of Im, and by 5 ~ 15 ℃ in the case of 2MI when the pure imidazole was used. This is because the copolymer contained in the microcapsule interferes with the reaction between the epoxy resin and the imidazole to some extent. The peak temperature increases from Co19 to Co37 because the amount of MAA contained in the copolymer increases. That is, the amount of the carboxylic acid functional group in the copolymer is increased to form a salt with imidazole in the microcapsule. And in each case the increase in the amount of imidazole relative to the amount of copolymer serves to lower the peak temperature.

Currently, most LCD manufacturing is conducted at 180 ° C. Therefore, we measured the curing time of epoxy resin with microcapsules prepared at 180 ℃. This curing time has a significant impact on manufacturing costs because it determines how quickly the manufacturing can be done. And since attempts are underway to lower the manufacturing temperature, the results at 150 ° C were also measured. Lowering the manufacturing temperature also has a significant effect on the manufacturing cost. Table 4 shows the results of the measurement of the curing time at each temperature. In order to investigate the delay characteristics of our microcapsules, which is our final research objective, we measured the shelf life at 20 ℃, ie, the time taken for the hardening reaction to proceed. The results are also shown in Table 4.

As can be seen from the results of DSC analysis in Table 3, the curing time at 180 ° C is increased by 1 to 10 seconds compared with the use of pure imidazole (Im). As shown in Table 3, the hardening time increased from Co19 to Co37. This is also due to the increase in the amount of carboxylic acid functional groups in the copolymer as shown in Table 3 above. These results were similar when using 2MI. The results of the shelf life at 20 ° C show that the curing reaction proceeds in 1 day when pure Im is used, but it increases to 10-18 days when microcapsules are used, Respectively. In case of 2MI, it also increased to 8 ~ 14 days and showed sufficient delay characteristics. This delay characteristic was also better from Co19 to Co37.

From the above results, it is presumed that the microcapsules prepared using Co46 will have better delay characteristics. Therefore, although Co 46 was synthesized and tried to manufacture microcapsules, it failed to solve the solvent problem and failed to produce microcapsules.

To see how well the microcapsules we synthesized are encapsulated, we looked at how well the microcapsules are permeated into the water when imidazole is added. Co 19, Co 28 and Co 37 were compared with those of Im and 1: 1 microcapsules. The results are shown in Fig.

The results of FIG. 6 show that Co 19 <Co 28 <Co 37 shows a higher degree of permeability. In the case of Co37, almost all of the release occurred in about 40 minutes. In the case of Co28, the release was completed in 60 minutes. In the case of Co19, the release was complete in 90 minutes.

It is considered that this is due to the influence of the MAA component contained in the copolymer component. The MAA moiety has good compatibility with water, so if the content of this moiety is increased, it can be well compatible with water. Therefore, the Co37 copolymer having the highest content has the highest permeability. A similar result was obtained for 2MI. The results are shown in Fig. At this time, permeability of microcapsules prepared with 2MI and 1: 1 for Co19, Co28 and Co37 were also compared.

As shown in Fig. 7, the transmittance of Co19 <Co28 <Co37 was larger than that of Co19. That is, Co37 having the highest content of MAA showed the fastest permeability.

In the case of Co28, the difference in permeability according to the content of imidazole was examined. The result in the case of Im is shown in Fig. The results of Fig. 8 show that the highest transmittance was obtained when the content of Im was 1.0 / 1.2, which was the highest, and the lowest transmittance was 1.0 / 0.8 when the content was small. The results in the case of 2MI were also measured and the results are shown in Fig. The results were almost similar to those of Im. This is because the difference in the amount of the copolymer due to the relative ratio difference causes the difference in the thickness to be surrounded.

Hereinafter, a method of preparing an imidazole curing agent prepared using the copolymer according to the present invention will be described in detail.

Example 1 Synthesis of Copolymer of MAA and DDMA

In the present invention, three compositions were used, and the molar ratios of MAA and DDMA were 1: 9, 2: 8, and 3: 7, respectively. Of these, the ratio of 2: 8 molar was introduced below. First, 1.72 g (0.0200 mol) of MAA and 20.35 g (0.0800 mol) of DDMA were added to the reactor, and 200 mL of 2-butanone was added thereto to prepare a solution. And 0.328 g (2.00 x ^10-3 mol) of an AIBN initiator was added to the monomer solution. Then 0.405 g (2.00 x ^10-3 mol) of 1-dodecanethiol (DDTO) was added to the chain transfer agent to control the molecular weight. The polymerization reaction was carried out under nitrogen gas at 80 DEG C for 8 hours. After completion of the polymerization reaction, the reaction product was poured into an excess amount of methanol to obtain a polymer in the form of a precipitate. After filtering the formed copolymer, it was washed several times with methanol and then dried under vacuum. (yield: 14.8 g, 67.1%) (IR: CH stretch 2922 cm ^-1 , 2850 cm ^-1 , ester C = 1732 cm ^-1 , carboxylic acid C = 1710 cm ^-1 ). The molar ratios of MAA: DDMA were 1: 9 and 3: 7, respectively.

[Chemical Formula 1] &lt; EMI ID =

[Chemical Formula 2] &lt; EMI ID =

Example 2: Encapsulation method of imidazole using a spray-drying method

1.0 g of imidazole and 1.0 g of the copolymer were dissolved in 15 mL of dichloromethane. The solution was sprayed with nitrogen gas (3 atm) in a small chamber (60 cm x 60 cm x 60 cm) with one side open. The distance from the spray gun to the opposite wall was 100 cm. The shape and size of the microcapsules formed were observed using SEM and the amount of imidazole in the microcapsules was calculated using EA (Elemental analysis) data.

The imidazole curing agent prepared in Examples 1 and 2 was reacted with an epoxy resin and, as a comparative example, pure imidazole (Im) or 2-methylimidazole (2MI) was reacted with an epoxy resin, Are described in detail in Table 4 above.

Hereinafter, the materials and apparatuses used in the process for preparing imidazole curing agents according to the present invention will be described in detail, and various measurement methods will be described.

<Material and equipment used>

The structures of the compounds used are shown in Fig. The diglycidyl ether of bisphenol F (YDF-170) was purchased from Kukdo Chemical. Aldrich products were used for methacrylic acid (MAA), dodecyl methacrylate (DDMA), azobisisobutyronitrile (AIBN), imidazole (Im), 2-methylimidazole (2MI), 2-butanone, tetrahydrofuran (THF) for HPLC, and dichloromethane .

Differential scanning calorimetry (DSC) was measured in a nitrogen atmosphere using a differential scanning calorimeter (Scinco DSC N-650) to investigate the curing behavior of the epoxy resin. Calorimeter was calibrated using high purity indium. All samples (~ 10 mg) were used after sealing using an aluminum DSC pan. The DSC was measured between 15 ° C and 200 ° C and the heating rate was 10 ° C / min. Scanning electron microscopy (SEM) analysis was performed using Hitachi S-2500C or Hitachi S-5200V scanning electron microscopes. Elemental analysis (EA) was measured using an elemental analyzer (EA 1110, CE Instruments) and IR spectroscopy was measured using an FTIR spectrometer (Bruker IFS 66 V / S). The molecular weight and molecular weight distribution of the polymer were measured by gel permeation chromatography (GPC) (Viscotek TDA302). THF was used as the eluant when using GPC and the RI detector was used at 35C. For the calculation of the number average molecular weight and weight average molecular weight, polystyrene standard reagents were used.

&Lt; Measurement of Amount of MAA in Synthesized Copolymer >

The amount of MAA in the synthesized copolymer was measured by the back titration method. Dissolve 0.500 g of the synthesized copolymer in 20 mL of THF, add 20 mL of 0.100 M KOH solution, and stir well for 5 minutes. Then centrifuge at 3,000 rpm for 1 minute to precipitate all precipitates, then remove 20 mL of the above solution and titrate with 0.100 M HCl solution to determine the amount of KOH reacted with the carboxylic acid functional groups in the copolymer Respectively.

&Lt; Measurement of curing time &

The curing time was measured by the continuous indentation method. After raising the temperature of the reaction vessel to the desired temperature, a mixture of epoxy resin and microcapsules was added thereto. Then, every second, the surface of the mixture was pierced using a pin to measure the time that the pin could not penetrate the surface.

&Lt; Measurement of transmittance of microcapsules >

100 mL of distilled water was added to a 250 mL round bottomed flask, and 0.100 g of the synthesized microcapsules was added thereto. The solution was stirred very slowly at a rate of one revolution per second using a magnetic bar while maintaining the temperature of the entire system at 35 ° C. After the sample was sampled at the above time intervals at predetermined time intervals, the amount of imidazole exiting to the outside was measured using HPLC.

In the present invention, a new method for encapsulating imidazole has been sought in order to have a delay characteristic in an epoxy resin-imidazole system, which is an essential system for anisotropic conduction films (ACF). In the present invention, MAA and DDMA were copolymerized to prepare a copolymer, which was then used to encapsulate imidazole. This method was able to encapsulate imidazole using a much smaller amount than the conventional method, and exhibited excellent delay characteristics. It is considered that the carboxylic acid functional group of MAA plays an important role in the delay characteristics.

Claims (4)

1. An imidazole curing agent prepared using a copolymer, wherein the imidazole is encapsulated using a copolymer of methacrylic acid (MAA) represented by the following formula (1) and dodecyl methacrylate (DDMA) represented by the following formula (2).
[Chemical Formula 1] &lt; EMI ID =

[Chemical Formula 2] &lt; EMI ID =

Preparing a copolymer through polymerization reaction of MAA (Methacrylic acid) and DDMA (dodecyl methacrylate) in a reactor;
Dissolving the copolymer and imidazole in dichloromethane (DCM) to prepare a mixed solution; And
And encapsulating the imidazole in the chamber using a spray drying method. 3. The method of claim 2,
In the copolymer preparation step,
A method for preparing an imidazole curing agent using a copolymer, the method comprising the step of using a chain transfer agent for molecular weight control. 3. The method of claim 2,
In the spray drying method,
Spraying a mixed solution of the copolymer and imidazole on the opposite wall in a chamber using a spray gun and nitrogen gas; And
And separating the microcapsules formed on the opposite side wall of the microcapsules.

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