JP7606735B2 - Method for handling hardening material and hardening material package - Google Patents

Description

The present invention relates to a method for handling a cured material made of an adhesive or resin before curing. The present invention relates to a cured material package including the cured material and a container capable of storing the cured material. The present invention relates to an adhesive structure bonded by an adhesive.

Epoxy resins, which are often used in two-part epoxy adhesives and the parent phase of fiber-reinforced plastics (FRPs), and benzooxy resins harden when mixed with a curing agent such as an amine, causing the epoxy or benzooxy group to open and polymerize.

However, because the resin itself is hygroscopic and most hardeners are water-soluble, ice grows when frozen and turns into water droplets when returned to room temperature. Alternatively, when the resin is removed from freezer storage, condensation occurs and moisture is encapsulated, attached, or absorbed, causing the hardener to dissolve into the water, resulting in an inconsistency in the resin-hardener equivalence ratio. This results in poor polymerization, which can lead to poor hardening and adhesion.

Similarly, cyanoacrylate adhesives, also known as instant adhesives, are stored in a freezer below the freezing point of water because the presence of moisture causes a polymerization reaction. As a result, if they are used in low-temperature conditions below the dew point without having returned to room temperature, condensation will form, causing rapid hardening and a loss of performance, or they may harden without coming into contact with the object to be adhered, resulting in no adhesive strength.

Typical conventional methods for avoiding the effects of condensation and moisture include blowing dry air or nitrogen gas onto the resin to return it to room temperature, placing it in a dry atmosphere cabinet when removing it from the freezer and waiting until it returns to room temperature, enclosing it with a desiccant, and in the case of vacuum-packed resin, opening it after it has returned to room temperature without opening the pack.

Toray Industries, Inc., "TORAYCA (registered trademark) prepreg," [online], [searched August 3, 2020], Internet: https://www.torayca.com/download/pdf/prepreg.pdf Toagosei Co., Ltd., "Instant Adhesive Aron Alpha (registered trademark)", [online], [searched on August 3, 2020], Internet <http://www.toagosei.co.jp/products/functional/catalog/pdf/index_pdf_01.pdf>

Conventional technology assumes that a dry state is maintained using indirect methods, but does not directly control the amount of moisture in the resin or adhesive or on the surface. For this reason, a method is needed to reliably guarantee a dry state.

Even when condensation and the like were successfully suppressed, the moisture in the resin would collect and freeze in places, but when it thawed, it would turn into a liquid phase and contain liquid droplets, causing adverse effects from the moisture.

Additionally, there was the issue of the high cost of desiccants, dry air and nitrogen.

In view of the above circumstances, the object of the present invention is to reduce the moisture content of the adhesive or resin cured material before curing, prevent condensation, and ensure a dry state inexpensively and easily.

A method for handling a hardening material according to one embodiment of the present invention includes the steps of:
A hygroscopic curing material consisting of an adhesive or resin before being cured by a water-soluble curing agent, or an adhesive or resin before being cured that undergoes a polymerization reaction with moisture, is placed in a vacuum container and vacuum freeze-dried;
After being brought to a temperature above the dew point of the removal environment in the vacuum vessel, the curable material is removed from the vacuum vessel and allowed to cure.

According to the present invention, the moisture content of the hardening material is extremely low because the hardening material is vacuum freeze-dried. Furthermore, the hardening material is hardened at a temperature above the dew point, so the hardening material does not condense. This prevents the hardening material from dissolving in water. As a result, the mechanical properties of the hardened material can be improved.

The process of heating the hardening material in the vacuum vessel to a temperature above the dew point involves heating the hardening material while monitoring the temperature of the hardening material.

According to the present invention, the hardening material is heated while the temperature of the hardening material is monitored, so the hardening material can be easily and stably heated to an appropriate temperature.

The curable material is heated to a temperature above the dew point in the vacuum vessel, then is subjected to secondary heating to around 30°C in the vacuum vessel, after which the curable material is removed from the vacuum vessel and cured.

According to the present invention, the hardening material is subjected to secondary heating, so that moisture in the hardening material can be more reliably removed.

The hardened material that has been subjected to the second heating is removed from the vacuum vessel and transferred directly to the baking process, where it is baked and hardened.

According to the present invention, the hardened material is hardened by firing immediately after removal, thereby improving the mechanical properties of the hardened material after firing.

The curable material is an epoxy adhesive, an epoxy resin, a benzoxy adhesive, a benzoxy resin, a cyanoacrylate resin, or a cyanoacrylate adhesive.

These hardening materials are hygroscopic. Because the hygroscopic hardening materials are vacuum freeze-dried, the moisture content of the hardening materials is extremely low. Furthermore, because the hardening materials are hardened at a temperature above the dew point, the hardening materials do not condense. This prevents the hygroscopic hardening materials from dissolving in water. As a result, the mechanical properties of the hardened materials can be improved.

The epoxy adhesive is a bisphenol A type adhesive.

The bisphenol A type adhesive may contain chlorine.

The hardening material package according to one aspect of the present invention comprises:
A vacuum freeze-dried cured material having hygroscopic properties, the cured material being made of an adhesive or resin before curing that is cured by a water-soluble curing agent, or an adhesive or resin before curing that undergoes a polymerization reaction with moisture;
and a vacuum container capable of storing the hardened material in a vacuum frozen state.

This allows the hardening material package to be transported to the location where the hardening material is to be used, and at the location where the hardening material is to be used, the hardening material package can be removed from the vacuum container and used. This means that the hardening material can be used at the location where it is to be used without any deterioration.

The freeze-dried hardened material has a fracture toughness value 1.2 times or more after hardening compared to a hardened material that has been hardened without going through the vacuum freeze-drying process.

Vacuum freeze drying of the hardened material improves the fracture toughness value of the hardened material after hardening.

The freeze-dried hardened material is a bisphenol A type adhesive.

The adhesive structure according to one embodiment of the present invention comprises:
The bonded structure is bonded with a bisphenol A type adhesive, and has a fracture toughness value 1.2 times or more as compared to the hardened material hardened without going through a vacuum freeze-drying process.

The present invention reduces the moisture content of the adhesive or resin curing material before curing, preventing condensation and ensuring a dry state inexpensively and easily.

The effects described here are not necessarily limited to those described herein, and may be any of the effects described in the present invention.

1 is a flow chart illustrating a method for handling hardening material according to one embodiment of the present invention. 1 shows a schematic diagram of how to handle a hardening material. 1 shows an example of a hardenable material package.

The following describes an embodiment of the present invention with reference to the drawings.

I. First embodiment

1. How to handle hardening materials

Figure 1 is a flow chart showing a method for handling a hardening material according to one embodiment of the present invention. Figure 2 shows a schematic diagram of the method for handling a hardening material.

Step S1: Preparation of hardening material

Prepare a curable material. The curable material is hygroscopic. The curable material is made of an adhesive or resin before curing that is cured by a water-soluble curing agent. Alternatively, the curable material is made of an adhesive or resin before curing that undergoes a polymerization reaction with moisture. The curable material is a synthetic resin, an adhesive, a film-like adhesive, or an instant adhesive. Specifically, the curable material is an epoxy adhesive, an epoxy resin, a benzoxy adhesive, a benzoxy resin, a cyanoacrylate resin, or a cyanoacrylate adhesive. The epoxy adhesive is a bisphenol A type adhesive. The bisphenol A type may contain chlorine. The curable material is, for example, a CFRP (Carbon Fiber Reinforced Plastics) prepreg roll. The CFRP prepreg roll is a roll-shaped CFRP prepreg (a sheet-shaped material in which carbon fibers are impregnated with resin) wound around a bobbin (core material). Prepreg is a material used for main structural members such as the fuselage, main wings, and tail of an aircraft, and for propellers of ships and submarines.

Step S2: Freezing the hardened material

The hardening material is frozen so that it does not harden. Specifically, the hardening material is frozen by storing it in a freezer at about -18°C to -24°C. The hardening material may be frozen at about -18°C or below. The hardening material can be stored in a freezer at about -18°C for about six months. Preferably, the hardening material is frozen at -20°C or below.

Step S3: Vacuum freeze-drying (freeze-drying) of the hardened material

The hardening material is removed from the freezer. The hardening material is placed in a vacuum container. The vacuum container is a container (packaging container) that can store the hardening material in a vacuum-packed state by vacuum freezing. A temperature sensor (e.g., a thermocouple) is attached to a predetermined position of the frozen hardening material. The frozen hardening material with the temperature sensor attached is placed in a vacuum freeze dryer. The vacuum freeze dryer is depressurized by a vacuum pump. Then, in the vacuum freeze dryer, the ice contained in the frozen hardening material sublimes into water vapor, and the moisture contained in the hardening material is removed. The vacuum freeze dryer has a cold trap (also called a cooling trap). The cold trap may be part of the freezer. The cold trap removes the water vapor in the vacuum freeze dryer. The vacuum freeze dryer is gradually heated while monitoring the temperature of the hardening material using a temperature sensor. After confirming that the temperature of the hardening material has exceeded the dew point (dew point in the vacuum freeze dryer), secondary heating (secondary drying) is performed to about 30°C (a temperature that does not affect the hardening material). The secondary heating evaporates the water remaining in the hardened material (water bound between molecules), further removing the moisture contained in the hardened material. This causes the hardened material placed in the vacuum container to be vacuum lyophilized (freeze-dried). As a result, a hardened material package is produced.

Figure 3 shows an example of a hardening material package.

The hardening material package 10 is a package in which the hardening material 11 that has been vacuum freeze-dried is sealed in a vacuum container 12. When the hardening material before vacuum freeze-drying is a gel-like resin such as prepreg, the hardening material 11 that has been vacuum freeze-dried has fine porous exhaust flow paths. The hardening material 11 is a roll of CFRP prepreg wound around a bobbin (core material).

Step S4: Remove

The cured material package is removed from the freeze dryer. The cured material may be transported to the point of use.

Step S5: Use of hardening material

The curable material package is placed in a thermostatic chamber. The thermostatic chamber is heated to heat the freeze-dried curable material contained in the curable material package. The temperature of the curable material is monitored while the curable material is heated. For example, a temperature sensor (e.g., a thermocouple) is attached to a predetermined position of the curable material package that can measure the temperature of the vacuum-packed curable material in the vacuum container (packaging container), and the thermostatic chamber is gradually heated while monitoring the temperature of the curable material using the temperature sensor. The vacuum-packed curable material is heated to a temperature in the vacuum container (packaging container) that exceeds the dew point in the removal environment (atmospheric pressure) by heating. The vacuum-packed curable material is then thawed by secondary heating to around 30°C in the vacuum container (packaging container). The curable material package is removed from the thermostatic chamber. The freeze-dried curable material is removed from the vacuum container (packaging container) of the curable material package. The freeze-dried curable material is transferred directly to a baking process, where it is baked to perform hardening and bonding operations.

At this time, the hardening material is in a dry state and is at a temperature higher than the dew point, so condensation does not occur. As a result, adverse effects on hardening and adhesion, such as elution of the hardener and polymerization reactions associated with moisture in the liquid phase, are resolved. This makes it possible to completely and easily avoid poor hardening, polymerization, and adhesion caused by moisture, even when performed by inexperienced workers.

2. Comparative test

The curing material used was 3M's AF555M bisphenol A type (containing chlorine) epoxy adhesive. The CFRP material used was Toray Industries' T800S/3900-2B 8-ply unidirectional material. The vacuum freeze dryer used was Tokyo Rikakikai's EYELA FDU-1200 freeze dryer. The analytical measuring instrument used was Shimadzu's Autograph AG-X universal testing machine. The test method used was the DCB (Double Cantilever Beam) test method described in JIS K7086 "Test method for interlaminar fracture toughness of carbon fiber reinforced plastics."

As an example, the curing material "AF555M Bisphenol A type (containing chlorine) epoxy adhesive manufactured by 3M" was frozen at about -20°C, vacuum freeze-dried, and thawed according to the method for handling the curing material according to this embodiment (steps S1 to S5 in FIG. 1). The moisture content of the curing material after thawing was measured with a Karl Fischer moisture meter and was about 0.1%. The curing material thawed after vacuum freeze-drying was sandwiched between two CFRP materials, baked and hardened to bond the two CFRP materials together, thereby producing the adhesive structure according to the example (drying process performed using the freeze-drying method).

As a comparative example, the same curing material "3M AF555M Bisphenol A type (containing chlorine) epoxy adhesive" was frozen at approximately -20°C and thawed. When thawed, the curing material absorbs moisture from the air. The moisture content of the thawed curing material was measured with a Karl Fischer moisture meter to be approximately 1%. The frozen and thawed curing material was sandwiched between two CFRP materials, baked and hardened to bond the two CFRP materials together, thereby producing an adhesive structure according to the comparative example (normal construction).

In the measurement, it is desirable to prepare three or more samples of the test piece and use the average value of the samples as the measured value, taking into consideration the inevitable variation in the measurement. Therefore, a total of six test pieces, including three test pieces of the adhesive structure according to the embodiment and three test pieces of the adhesive structure according to the comparative example, were manufactured, and the average value of each of the three test pieces was used as the measured value for comparison. The manufacturing conditions of the test pieces of the adhesive structure according to the embodiment and the adhesive structure according to the comparative example are the same except for the handling method of the cured material according to this embodiment. A total of six test pieces were tested under the same conditions specified by JIS K7086. The modified compliance calibration method recommended by JIS K7086 was used to calculate the fracture toughness value G _IC . Table 1 shows the fracture toughness values (kJ/m ² ).

As shown in the top three rows of Table 1, the fracture toughness values G _IC of the three test pieces of the bonded structure according to the comparative example were 0.679 (kJ/m ² ), 0.773 (kJ/m ² ), and 0.599 (kJ/m ² ). The fracture toughness values G _IC of the three test pieces of the bonded structure according to the example were 1.087 (kJ/m ² ), 0.941 (kJ/m ² ), and 0.974 (kJ/m ² ). As shown in the bottom row of Table 1, the average value of the fracture toughness values G _IC of the three test pieces of the bonded structure according to the comparative example was 0.684 (kJ/m ² ), and the average value of the fracture toughness values G _IC of the three test pieces of the bonded structure according to the example was 1.001 (kJ/m ² ). The freeze-dried hardened material (Example) had a fracture toughness value after hardening that was approximately 1.46 times higher (46% improvement) than the hardened material hardened without going through the freeze-drying process (Comparative Example). From the above, it can be seen that the mechanical properties were improved by using the freeze-dried hardened material.

II. Second embodiment

In the first embodiment, the hardening material is placed in a vacuum container (a container capable of storing the hardening material in a vacuum frozen state), and the hardening material placed in the vacuum container is vacuum freeze-dried to produce a hardening material package (a package in which the vacuum freeze-dried hardening material is sealed in a vacuum container). This hardening material package may be transported to a point where the hardening material is used. When the hardening material is used, the hardening material sealed in the hardening material package is thawed. In contrast, in the second embodiment, the frozen hardening material is vacuum freeze-dried and thawed when used. In a use case, the frozen hardening material is transported to a point where the hardening material is used, and the hardening material is vacuum freeze-dried and thawed at the point where the hardening material is used. Therefore, in the second embodiment, it is not necessary to produce a hardening material package. In the following description, the points already described will be omitted, and the differences will be mainly described. In the second embodiment, the vacuum freeze dryer corresponds to the vacuum container (a container capable of storing the hardening material in a vacuum frozen state).

See Figure 1. Step S1 (preparing the hardened material) and step S2 (freezing the hardened material) are the same as the process in the first embodiment.

Step S3: Vacuum freeze-drying (freeze-drying) of the hardened material

The hardened material is removed from the freezer. A temperature sensor (e.g., a thermocouple) is attached to a predetermined position of the frozen hardened material. The frozen hardened material with the temperature sensor attached is placed in a vacuum freeze dryer. The vacuum freeze dryer is depressurized by a vacuum pump. Then, in the vacuum freeze dryer, the ice contained in the frozen hardened material sublimes into water vapor, and the moisture contained in the hardened material is removed. The vacuum freeze dryer has a cold trap (also called a cooling trap). The cold trap may be part of a freezer. The cold trap removes the water vapor in the vacuum freeze dryer. The vacuum freeze dryer is gradually heated while monitoring the temperature of the hardened material using a temperature sensor. After confirming that the temperature of the hardened material exceeds the dew point (dew point in the removal environment (atmospheric pressure)), secondary heating (secondary drying) is performed to about 30°C (a temperature that does not affect the hardened material). The secondary heating evaporates the water (water bonded between molecules) remaining in the hardened material, and the moisture contained in the hardened material is further removed. This allows the hardened material to be vacuum lyophilized (freeze-dried).

Step S4: Remove

Remove the freeze-dried hardened material from the freeze dryer.

Step S5: Use of hardening material

The vacuum freeze-dried hardened material is then transferred directly to the baking process, where it is baked to harden and adhere.

III. Conclusion

According to the first and second embodiments, the hardening material is vacuum freeze-dried, so that the moisture content of the hardening material is extremely low. Therefore, when the vacuum freeze-dried hardening material is thawed, the hardening material does not condense, and no frost or water droplets are formed. As a result, the hardening material, which has hygroscopicity, does not contain, adhere to, or absorb moisture, so that the hardening material does not dissolve in water. Therefore, the equivalence ratio of the materials contained in the hardening material maintains a consistent value. In other words, the hardening material is not easily altered. As a result, polymerization is not easily impaired, and hardening and adhesion are not easily impaired. In addition, in the vacuum freeze-drying process, the hardening material is placed in a vacuum freeze-drier from a freezer and the temperature of the hardening material is monitored, so that even an inexperienced worker can easily achieve a dry state comparable to that of a skilled worker. By vacuum freeze-drying the hardening material, condensation is eliminated, and even a small amount of moisture that was originally contained in the hardening material can be dehydrated. Since the hardening material is dehydrated by vacuum freeze-drying after the fact in this way, expensive drying and dehydration processes are not required even in the manufacturing process of the hardening material (before freezing). This allows the use of an inexpensive synthesis process that produces water during a chemical reaction, thereby reducing the manufacturing cost of the hardened material. This embodiment can be used in any field that uses hardened materials that require refrigeration or freezing. For example, this embodiment can be used in technical fields such as manufacturing, maintenance, repair, and overhaul that use FRP prepregs and adhesives.

Although the embodiments and variations of the present technology have been described above, the present technology is not limited to the above-described embodiments, and various modifications can of course be made without departing from the spirit of the present technology.

10: Hardening material package 11: Vacuum freeze-dried hardening material 12: Vacuum container S1: Preparation of hardening material S2: Freezing of hardening material S3: Vacuum freeze-drying of hardening material S4: Removal S5: Use of hardening material

Claims (8)

a cured material having hygroscopic properties , which contains a water-soluble curing agent and is made of an adhesive or resin before curing that is cured by the water-soluble curing agent, or a cured material having hygroscopic properties , which contains an adhesive or resin before curing that undergoes a polymerization reaction with moisture, is placed in a vacuum container and subjected to vacuum freeze-drying;
The method of claim 1, further comprising: bringing the curable material to a temperature in the vacuum vessel above a dew point in the removal environment, and then removing the curable material from the vacuum vessel and curing the material. 2. A method for handling the hardening material according to claim 1, comprising the steps of:
The method for handling a curable material, wherein the step of bringing the curable material to a temperature exceeding a dew point in the vacuum container comprises heating the curable material while monitoring a temperature of the curable material. A method for handling the hardening material according to claim 1 or 2, comprising the steps of:
The method for handling a curable material includes heating the curable material in the vacuum container to a temperature exceeding a dew point, and then secondarily heating the curable material to about 30° C. in the vacuum container, and then removing the curable material from the vacuum container and curing the material. 4. A method for handling the hardening material according to claim 3, comprising the steps of:
The second-heated hardening material is removed from the vacuum vessel and baked to harden it. A method for handling a hardening material according to any one of claims 1 to 4, comprising the steps of:
The curable material is an epoxy adhesive, an epoxy resin, a benzoxy adhesive, a benzoxy resin, a cyanoacrylate resin, or a cyanoacrylate adhesive. 6. A method for handling a hardening material according to claim 5, comprising the steps of:
The epoxy adhesive is a bisphenol A type adhesive. A method for handling a cured material. A freeze-dried cured material that contains a water-soluble curing agent, is made of an adhesive or resin before curing that is cured by the water-soluble curing agent, and has hygroscopic properties; or A freeze-dried cured material that contains an adhesive or resin before curing that undergoes a polymerization reaction with moisture, and has hygroscopic properties ;
A vacuum container capable of storing the hardened material in a vacuum frozen state;
The freeze-dried hardened material is sealed in the vacuum container, forming a hardened material package. 8. The hardenable material package of claim 7,
The freeze-dried hardening material is a bisphenol A type adhesive. Hardening material package.

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