JP2010065183A - Manufacturing method for syntactic foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a syntactic foam being advantageous for attaining reduction of manufacturing cost. <P>SOLUTION: The syntactic foam is obtained by placing a mold 20 for storing a micro-balloon M impregnated with a thermosetting resin in a heating oven and heating/curing the thermosetting resin impregnated in the micro-balloon M in the mold 20 by controlling an atmosphere temperature of the oven. At this time, while reaction for curing the thermosetting resin is continued in the mold 20, the same liquid thermosetting resin R as the one impregnated in the micro-balloon M is poured in the mold 20. Thereby, the thermosetting resin R at a peripheral portion lacked by the fact that the thermosetting resin R at a central portion is cured/contracted and the volume is reduced in the mold 20 can be compensated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a syntactic foam.

Conventionally, a syntactic foam made of a composite material of a microballoon (a fine hollow sphere) and a thermosetting resin has been provided (see Patent Documents 1 and 2).
Conventionally, the manufacturing method of syntactic foam is performed as follows.
That is, first, a microballoon is filled in a mold, a liquid thermosetting resin having thermosetting properties is injected into the mold, the microballoon is impregnated, the mold is placed in an oven, and the atmosphere of the oven By controlling the temperature, the thermosetting resin impregnated in the microballoons in the mold is cured by heating, thereby obtaining a syntactic foam.
Since the syntactic foam is used as a buoyancy material in the sea, particularly a deep sea probe used at a large depth, it is required to have a high crushing strength.
JP-A-5-64818 JP-A-8-319368

By the way, in the conventional manufacturing method described above, when the thermosetting resin impregnated in the microballoon in the mold is heat-cured, the temperature of the thermosetting resin located at the center of the mold (referred to as the center temperature), There is a difference between the temperature of the thermosetting resin located in the peripheral portion away from the center of the mold (referred to as the peripheral temperature).
That is, when the thermosetting resin is cured by heating, the thermosetting resin undergoes self-heating due to a crosslinking reaction. Heat generation from such a thermosetting resin is called curing heat generation.
Therefore, in the process of heat-curing the thermosetting resin, the central temperature of the thermosetting resin tends to be higher than the peripheral temperature due to the action of the above-described curing heat generation.
Furthermore, since the microballoon has a low thermal conductivity because it has a hollow structure, the thermosetting resin located in the center of the mold of the thermosetting resin stores more heat, and the center temperature of the thermosetting resin The tendency to be higher than the temperature becomes more prominent.
As a result, in the process of thermosetting the thermosetting resin, the central temperature of the thermosetting resin reaches a high temperature exothermic peak within a short time and then gradually decreases.
Therefore, the thermosetting resin located at the center portion of the mold is cured and contracted earlier in time than the thermosetting resin located at the peripheral portion.
Thus, the thermosetting resin in the central portion of the mold is cured and contracted in a short time before the peripheral portion, and the volume is reduced. As the volume of the thermosetting resin in the central portion decreases, the liquid thermosetting resin that is not yet cured and flows in the peripheral portion flows toward the central portion. As a result, the thermosetting resin in the peripheral portion becomes insufficient, and the thermosetting resin is cured in this state.
Accordingly, the peripheral portion constitutes the surface of the syntactic foam, and therefore, the surface portion is not only disadvantageous for improving the crushing strength because the thermosetting resin is insufficient or missing. There is a disadvantage that the water absorption rate deteriorates due to water entering the cavity (defect) portion of the thermosetting resin.
Therefore, among the syntactic foam taken out from the mold 20, the peripheral portion is cut off as an end material, and only the central portion is cut out and used. Therefore, there is a disadvantage in reducing the production cost due to material loss. is there.
This invention is made | formed in view of such a situation, The objective is to provide the manufacturing method of a syntactic foam advantageous in aiming at reduction of manufacturing cost.

  To achieve the above object, the present invention includes a first step of filling a microballoon in a mold, and injecting a liquid thermosetting resin having thermosetting properties into the mold to impregnate the microballoons. In the second step, the mold is placed in an oven and the atmosphere temperature in the oven is controlled to heat and cure the thermosetting resin impregnated in the microballoon in the mold to obtain a syntactic foam. A syntactic foam manufacturing method including a third step, wherein the third step continues a reaction in which the thermosetting resin injected in the second step is cured in the mold. And a resin injection step of injecting the same liquid thermosetting resin as the liquid thermosetting resin injected in the second step into the mold. To.

  According to the present invention, since the thermosetting resin in the mold is cured and contracted to reduce the volume, the lack of the thermosetting resin is compensated for by the shortage of the thermosetting resin in the surface portion of the syntactic foam. In this case, it is possible to prevent defects, and therefore, it is not necessary to cut off the peripheral portion as an end material from the syntactic foam formed by the mold, which is advantageous in reducing the manufacturing cost.

Next, a method for producing a syntactic foam according to an embodiment of the present invention will be described with reference to the drawings.
In this specification, a composite material of a microballoon (a fine hollow sphere) and a thermosetting resin is referred to as a syntactic foam. In other words, a composite material using a microballoon as a filler and a thermosetting resin as a matrix is referred to as a syntactic foam.
First, a microballoon is prepared.
In this embodiment, a microballoon using glass is used as the microballoon.
The average particle size of the microballoon is 10 μm or more and 500 μm or less.
Here, if the average particle size of the microballoons is less than 10 μm, the microballoons become too dense, and there is a disadvantage that it is difficult to impregnate the liquid thermosetting resin. When the thickness exceeds 500 μm, there is a problem that the filling rate of the microballoon is lowered and the formed syntactic foam has a high density (high specific gravity).
The material for forming the microballoon is not limited to glass, and various conventionally known inorganic substances (inorganic materials) or organic substances (organic materials) can be used.
Examples of the inorganic substance include borosilicate glass, silica, carbon, and ceramic.
Examples of the organic material include various thermoplastic resins and various thermosetting resins.

Next, the mold 20 shown in FIG. 1 is prepared.
The mold 20 is for forming a syntactic foam.
In the present embodiment, the mold 20 includes a mold body 22, a lower lid body 24, and an upper lid body 26.
In the present embodiment, the mold body 22 has a cylindrical wall shape with a uniform cross-sectional shape.
In the present embodiment, the lower lid body 24 has a disk shape that closes the lower opening of the mold body 22.
The lower lid body 24 is formed with a first hole portion 28 penetrating in the thickness direction.
The upper lid body 26 has a small-diameter portion 2602 having an outer diameter large enough to be inserted while being in contact with the upper inner periphery of the mold body 22, and has a larger outer diameter coaxially with the small-diameter portion 2602 than the small-diameter portion 2602. A large-diameter portion 2604 that closes the upper opening of the main body 22.
The upper lid body 26 is formed with a second hole 30 that penetrates in the thickness direction.
That is, in the present embodiment, the syntactic foam formed by the mold 20 has a flat columnar shape having a height and a diameter larger than the height. Specifically, the height of the syntactic foam is 190 mm and the diameter is 340 mm.
The diameter of the syntactic foam is determined by the diameter of the mold body 22, and the height of the syntactic foam is determined by the distance between the upper surface of the lower lid body 24 and the lower surface of the small diameter portion 2602 of the upper lid body 26.
Of course, the outer diameter shape of the syntactic foam is not limited to a flat cylindrical shape, and various conventionally known shapes such as a rectangular parallelepiped shape, a cubic shape, and a spherical shape can be adopted as the outer diameter shape of the syntactic foam. .
The syntactic foam obtained by the production method of the present invention has a volume of 15 liters or more and the thinnest part has a thickness of 150 mm or more. Buoyancy sufficient for use can be obtained, which is advantageous in terms of manufacturing cost.
When the volume of the syntactic foam is 15 liters or more and the thickness of the thinnest part is not more than 150 mm, the syntactic foams are joined with an adhesive or metal fittings to obtain the required buoyancy. Therefore, there is a disadvantage in reducing the manufacturing cost.

The syntactic foam is formed as follows.
First, the lower lid body 24 is attached to the mold body 22, the first hole 28 of the lower lid body 24 is sealed with the closing member 32, and the microballoon M is placed in the mold 20 with the upper lid body 26 removed. Fill.
Next, the upper opening of the mold body 22 is closed with the upper lid body 26.
The above process corresponds to the first process in the claims.
After the first step, the mold 20 is placed in an oven, and a negative pressure is applied to the second hole 30 of the upper lid body 26 in a state where the atmosphere temperature of the oven is about 40 to 80 degrees. You may perform the drying process which removes the moisture of the microballoon M with which 20 was filled, and dries. When the microballoon M is dried by such a drying process, it is advantageous in stably curing the thermosetting resin.

Next, the closing member 32 is removed from the first hole portion 28, an uncured liquid thermosetting resin R is injected from the first hole portion 28 at a predetermined pressure, and a negative pressure is applied to the second hole portion 30.
In this embodiment, an epoxy thermosetting resin is used as the thermosetting resin. As the thermosetting resin, phenol resin, polyurethane, thermosetting polyimide, melamine resin, urea resin (urea resin), unsaturated polyester, and the like are used. Various conventionally known thermosetting resins such as resins can be used.
Thereby, the liquid thermosetting resin R is impregnated into the microballoon M filled in the mold body 22.
Eventually, when the uncured liquid thermosetting resin R overflows from the second hole 30, the injection of the thermosetting resin R from the first hole 28 is stopped.
As shown in FIG. 2, the first hole 28 is closed by the closing member 32, and the resin tank 34 is connected to the second hole 30.
The resin tank 34 communicates with the inside of the mold 20 through the first hole 28.
Further, the resin tank 34 stores a predetermined amount of liquid uncured thermosetting resin R and is supplied with air from the compressor 36. Therefore, the liquid thermosetting resin in the resin tank 34 is supplied. R is pressurized by air pressure, and in the present embodiment, the air pressure is 0.5 to 5 kg / cm.
The above process corresponds to the second process in the claims.

  Next, the mold 20 containing the microballoon M impregnated with the liquid thermosetting resin R is placed in a heating oven, and the atmosphere temperature of the oven is controlled to impregnate the microballoon M in the mold 20. The thermosetting resin thus obtained is heated and cured to obtain a syntactic foam. This step corresponds to the third step in the claims.

The third step will be described.
FIGS. 3A to 3C are schematic views for explaining the state of curing of the thermosetting resin in the third step.
FIG. 3A shows a state where the mold 20 is placed in an oven.
When the atmospheric temperature of the oven rises in this state, the liquid thermosetting resin R impregnated in the microballoon M in the mold 20 starts to undergo a cross-linking reaction between molecules and gradually hardens.
At this time, curing heat is generated by cross-linking of the molecules of the thermosetting resin R, and the central temperature of the thermosetting resin R becomes higher than the peripheral temperature by the action of the curing heat generation.
Furthermore, since the microballoon M has a hollow structure and has low thermal conductivity, the thermosetting resin R1 located in the center portion of the mold 20 in the thermosetting resin R stores heat, and the center of the thermosetting resin R is stored. The part temperature becomes higher than the peripheral part temperature.
Therefore, the thermosetting resin R positioned at the center portion of the mold 20 is cured and contracted earlier in time than the thermosetting resin R positioned at the peripheral portion, and the volume is reduced.
As the volume of the thermosetting resin R in the central portion is reduced, as shown in FIG. 3 (B), the liquid thermosetting resin R that has not yet been cured located in the peripheral portion is in the central portion. It flows toward. As a result, the peripheral portion of the thermosetting resin R is insufficient.

Therefore, in the present embodiment, as shown in FIG. 3C, while the reaction of curing the thermosetting resin R injected in the second process in the mold 20 continues, in the second process. A resin injection step of injecting the same liquid thermosetting resin R as the injected liquid thermosetting resin R into the mold 20 is performed.
Injection of the liquid thermosetting resin R into the mold 20 is performed by injecting the liquid thermosetting resin R pressurized in the resin tank 34 into the mold 20 through the first hole 28. That is done.
That is, as indicated by an arrow in FIG. 3C, the liquid thermosetting resin R injected into the mold 20 flows toward the thermosetting resin R in the peripheral portion whose volume is reduced.
The volume of the liquid thermosetting resin R injected by this resin injection process corresponds to the volume that decreases as the thermosetting resin R cures in the mold 20.
By such a resin injection process, the thermosetting resin is cured in a state in which the state where the thermosetting resin R in the peripheral portion is insufficient is eliminated.
After the thermosetting resin is cured, if the temperature in the mold 20 drops to about room temperature, the mold 20 is taken out from the oven, the lower lid body 24 and the upper lid body 26 are removed from the mold body 22, and the molded syntactic Take out the form.
Thereby, the third step is completed.
In the present embodiment, VaRTM molding (Vacuum Assisted Resin Transfer Molding) that applies a negative pressure to the mold 20 when the thermosetting resin R is injected into the mold 20 is employed. It goes without saying that RTM molding (Resin Transfer Molding) that does not apply a negative pressure into the mold 20 when the conductive resin R is injected may be adopted.

As described above, according to the present embodiment, in the third step, the second step is performed while the reaction of curing the thermosetting resin R injected in the second step in the mold 20 continues. A resin injection step of injecting the same liquid thermosetting resin R as the liquid thermosetting resin R injected in step 1 into the mold 20 is included.
Therefore, since the thermosetting resin R in the center portion cures and shrinks in the mold 20 and the volume is reduced, the insufficient thermosetting resin R in the peripheral portion can be compensated. Needless to say, deficiency and deficiency of the curable resin can be prevented and it is advantageous for improving the crushing strength, and water absorption into the cavity (defect) portion of the thermosetting resin R deteriorates. Can solve the problem. Thereby, in the case of the buoyancy material used on the seabed, the durability performance during repeated use can be improved.
As a result, in the syntactic foam taken out from the mold 20, the peripheral portion is not cut off as an end material, and only the central portion is not cut out and used, so that no material loss occurs, so that the manufacturing cost can be reduced. Is advantageous.

(Example)
Next, examples of the syntactic foam will be described.
FIG. 4 is an explanatory view showing the water absorption test results of Examples and Comparative Examples.
The thermosetting resins used in the syntactic foams of the examples and comparative examples are all amine-cured epoxy resins mainly composed of alicyclic epoxy, and the blending ratios are the same in the examples and comparative examples.
The microballoons used in the syntactic foams of the examples and comparative examples are both made of glass material, and the trade name Glass Bubbles of Sumitomo 3M Limited was used.
The dimensions of the syntactic foams of the examples and comparative examples are 190 mm in height and 340 mm in diameter.
In this test, in accordance with ASTM standard ASTM D2735-78, which is an industry standard of the American Society for Testing Materials, after 1000 cycles of pressurization at 116 MPa, a water absorption test was performed.
In FIG. 4, the solid line extending vertically indicates the range of variation in the measured value of water absorption, and the bar graph indicates the average value of the measured values.
In the comparative example, the average value of water absorption was about 6%, whereas in the example, the average value of water absorption was about 2.8%, and the syntactic foam obtained by the manufacturing method of the present embodiment. It can be seen that the water absorption is significantly improved as compared with the comparative example.

In this embodiment, a syntactic foam using a microballoon as a filler and a thermosetting resin as a matrix has been described. However, the present invention uses various fibers as a filler and uses a thermosetting resin as a matrix. It can also be applied to FRP (Fiber-Reinforced Plastic).
In addition, while the resin injection step of the present invention, that is, while the reaction of curing the thermosetting resin injected into the mold continues, the same liquid thermosetting property as the already injected liquid thermosetting resin. The step of injecting the resin into the mold, in other words, the step of injecting the thermosetting resin corresponding to the volume that is reduced when the thermosetting resin in the mold shrinks by curing is a resin transfer molding using a thermosetting resin. Of course, the present invention can be applied to general molding (RTM transfer (Resin Transfer Molding)), that is, general RTM molding without using a filler.

It is explanatory drawing of the mold. FIG. 3 is an explanatory diagram in which a mold 20 is filled with a microballoon M. (A) thru | or (C) is a schematic diagram explaining the state of hardening of the thermosetting resin in a 3rd process. It is explanatory drawing which shows the test result of the water absorption rate of an Example and a comparative example.

Explanation of symbols

  M: Microballoon, R: Thermosetting resin, 20: Mold.

Claims (6)

A first step of filling the mold with a microballoon;
A second step of injecting a liquid thermosetting resin having thermosetting into the mold and impregnating the microballoon;
A third step of obtaining a syntactic foam by placing the mold in an oven and controlling the atmosphere temperature of the oven to heat and cure the thermosetting resin impregnated in the microballoon in the mold; A method for producing a syntactic foam comprising:
In the third step, the liquid thermosetting resin injected in the second step while the reaction of curing the thermosetting resin injected in the second step in the mold continues. A resin injection step of injecting the same liquid thermosetting resin into the mold,
A method for producing a syntactic foam, characterized in that The liquid thermosetting resin is reduced in volume by curing,
The volume of the liquid thermosetting resin injected by the resin injection step corresponds to a volume that decreases as the thermosetting resin is cured in the mold.
The method for producing a syntactic foam according to claim 1. The syntactic foam obtained in the third step has a volume of 15 liters or more, and the thickness of the thinnest part is 150 mm or more.
The method for producing a syntactic foam according to claim 1. The liquid thermosetting resin is an epoxy thermosetting resin,
The method for producing a syntactic foam according to claim 1. The average particle diameter of the microballoon filled in the mold in the first step is 10 μm or more and 500 μm or less.
The method for producing a syntactic foam according to claim 1. The material forming the microballoon filled in the mold in the first step is glass.
The method for producing a syntactic foam according to claim 1.

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