JP5373307B2 - Method for producing lightweight polyimide molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-weight polyimide molded body which can be manufactured with a simple process without using a binder and has satisfactory mechanical characteristics in spite of the low density, and to provide a manufacturing method of the light-weight polyimide molded body. <P>SOLUTION: The light-weight polyimide molded body having density of 300 to 1,000 kg/m<SP>3</SP>is provided by pressure-molding and heat-treating a prescribed amount of foamed body chips substantially formed of aromatic polyimide without using the binder. The manufacturing method of the light-weight polyimide molded body comprises: a process of putting a prescribed amount of the foamed body chips substantially formed of aromatic polyimide into a mold and pressure-molding the chips at a temperature of 100&deg;C or lower to provide the pressure-molded body; and a process of putting the pressure-molded body into a mold having a target shape and heating the pressure-molded body at a temperature of 250 to 500&deg;C. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention is a lightweight polyimide molded body having a density of 300 to 1000 kg / m ³ obtained by subjecting a foam chip substantially formed of an aromatic polyimide to pressure molding and heat treatment without using a binder . It relates to a manufacturing method.

  Patent Documents 1 to 3 describe a polyimide foam as a heat-resistant foam and a method for producing the same. In Patent Document 4, a previously foamed polyimide resin mass is pulverized, mixed with a heat-resistant binder, and the mixture is put into a predetermined mold, and then pressed and fired to a predetermined density. A foamed polyimide molded body is disclosed. The binder specifically used here was a solution of polyamic acid which is a polyimide precursor.

U.S. Pat. No. 4,241,193 JP-A-4-21440 JP 2002-12688 A JP 2004-323715 A

In the method of mixing with the heat-resistant binder of Patent Document 4, it is not easy to uniformly mix the foam chip and the binder solution, and it is necessary to remove the solvent of the binder solution, so there is room for improvement in workability. was there.
As a result of various investigations to improve the processing method of a polyimide foam chip obtained by pulverizing a polyimide foam, the present inventors have used a foam chip substantially formed of an aromatic polyimide without using a binder. The present inventors have found that a lightweight polyimide molded body having a density of about 300 to 1000 kg / m ³ can be obtained by pressure molding and heat treatment.

That is, the present invention is related to the following sections.

1 . Placing a predetermined amount of a foam chip formed of aromatic polyimide in a mold and press-molding at a temperature of 100 ° C. or lower without using a binder, A method for producing a lightweight polyimide molded body having a density of 300 to 1000 kg / m ³ , comprising a step of placing the pressure molded body in a mold having a target shape and heat-treating at a temperature of 250 to 500 ° C.

According to the present invention, a lightweight polyimide molded body having a density of 300 to 1000 kg / m ³ can be easily obtained by subjecting a foam chip substantially formed of an aromatic polyimide to pressure molding and heat treatment without using a binder. Can get to. Since no binder is used, the processing and molding process is simple, the density can be easily adjusted, and lightweight polyimide molded articles having various shapes can be suitably obtained. This lightweight polyimide molding has good mechanical properties despite its relatively low density. Further, according to the present invention, the remaining polyimide foam after the product is cut out from the foamed polyimide foam bulk can be effectively used.

  In the present invention, the “lightweight polyimide molded body” is a term used for the purpose of distinguishing from a dense polyimide molded body obtained by, for example, heating and compressing polyimide powder. “Lightweight polyimide molded body” has a higher density due to a smaller proportion of bubble (pore) space than the foam chip of the raw material, but the molded body has a space due to bubbles in the foam chip. The polyimide molded body is lighter than the dense polyimide molded body as described above.

In the polyimide forming the foam chip in the present invention, the tetracarboxylic acid component is an aromatic tetracarboxylic acid, the diamine component is an aromatic diamine, and the glass transition temperature is 250 ° C. or higher, preferably 300 ° C. or higher, more preferably 330. Those formed by substantially aromatic polyimide having a temperature of not lower than ° C., particularly preferably not lower than 350 ° C. are suitable. When a foam chip formed of polyimide having a low glass transition temperature is used, the foam (pore) structure of the foam is easily softened during heat treatment, resulting in uneven deformation. Is not preferable because the density becomes uneven and the shape is distorted.
Accordingly, in the present invention, the polyimide forming the foam chip is substantially composed of aromatic tetracarboxylic acids and aromatic diamine and has the glass transition temperature. Minor components other than aromatic tetracarboxylic acids and aromatic diamines may be used for the purpose of improving plasticity during foam molding, for example. It is important that the glass transition temperature of the resulting polyimide does not fall below the above value. When using the said small amount component, it is about 10 mol% or less each independently in a tetracarboxylic-acid component and a diamine component, Preferably it is 5 mol% or less, More preferably, it is 2 mol% or less.

Examples of the tetracarboxylic acid component include 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,2 ′, 3,3′-biphenyltetracarboxylic acid Biphenyl tetracarboxylic acids such as acids, pyromellitic acids, benzophenone tetracarboxylic acids such as 3,3 ′, 4,4′-benzophenone tetracarboxylic acids, 2,3,6,7-naphthalene tetracarboxylic acids, 1,2, Naphthalene tetracarboxylic acids such as 5,6-naphthalene tetracarboxylic acids, 1,2,4,5-naphthalene tetracarboxylic acids, 1,4,5,8-naphthalene tetracarboxylic acids, bis (3,4-dicarboxyphenyl) ) Bis (dicarboxyphenyl) ethers such as ethers, 2,2-bis (2,5-dicarboxyphenyl) Bis (dicarboxyphenyl) propanes such as propane, bis (dicarboxyphenyl) ethanes such as 1,1-bis (2,3-dicarboxyphenyl) ethane, 1,1-bis (3,4- Aromatic tetracarboxylic acids such as bis (dicarboxyphenyl) sulfones such as dicarboxyphenyl) sulfones can be suitably used alone or in combination. Among these, in particular, biphenyltetracarboxylic acids can easily obtain a foam and have a high glass transition temperature, so that they are used as a main component (50 mol% or more, preferably 80 mol% or more) of a tetracarboxylic acid component. Is preferred.
Here, the tetracarboxylic acids mean tetracarboxylic acids that can form polyimides, such as tetracarboxylic acids, esterified products thereof, and anhydrides thereof, and derivatives thereof.
The minor component used in consideration of moldability and the like includes bis (dicarboxyphenyl) such as 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane. Cyclohexanetetracarboxylic acids such as tetramethyldisiloxanes, cyclopentanetetracarboxylic acids, 1,2,4,5-cyclohexanetetracarboxylic acid, 3-methyl-4-cyclohexene-1,2,4,5-tetracarboxylic acid Aliphatic tetracarboxylic acids such as acids can be mentioned.

Examples of the diamine component include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, aromatic diamine having one benzene nucleus such as 3,5-diaminobenzoic acid, An aromatic diamine having two benzene nuclei such as 4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 1,3-bis (3- Aromatic diamines having three benzene nuclei such as aminophenoxy) benzene and 1,3-bis (4-aminophenoxy) benzene, bis (4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3- Aminophenoxy) phenyl) sulfone, 4,4′-bis (3-aminophenoxy) biphenyl An aromatic diamine having four benzene nuclei such as 4,4′-bis (4-aminophenoxy) biphenyl and 2,2-bis (4- (4-aminophenoxy) phenyl) propane, and a naphthalene ring such as diaminonaphthalene. An aromatic diamine having an aromatic diamine having a heterocyclic ring such as 2,6-diaminopyridine can be used alone or in combination. Among these, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and 2, It is preferable to use at least one aromatic diamine selected from the group consisting of 6-diaminopyridine as the main component (50 mol% or more, preferably 80 mol% or more).
Minor components used in consideration of moldability and the like include diaminosiloxanes such as 1,3-bis (3-aminopropyl) tetramethylsilane, isophoronediamine, norbornenediamine, 1,2-diaminocyclohexane, 1, Examples include alicyclic diamines such as 3-diaminocyclohexane, 1,4-diaminocyclohexane, and bis (4-aminocyclohexyl) methane, and aliphatic diamines such as hexamethylenediamine and diaminododecane.

  A polyimide foam can be suitably manufactured by a conventionally well-known method. For example, a tetracarboxylic dianhydride and the lower alcohol are reacted in a lower alcohol solvent to form a tetracarboxylic ester solution, and a diamine is added and mixed to obtain a polyimide precursor solution composition. The alcohol solvent of the solution composition is removed by evaporation at a low temperature to obtain a powdered polyimide precursor composition. This powder polyimide precursor composition can be suitably obtained by pre-molding as necessary to form a green body, and then heating and foaming by microwave heating or the like. Moreover, after adding a lower alcohol again to the said polyimide precursor composition of a powder to make a polyimide precursor composition of a solution thru | or a suspension, it can obtain suitably by heating by microwave heating etc. and making it foam.

  The polyimide precursor solution composition is prepared by mixing the tetracarboxylic acid component and the diamine component at a composition ratio such that the equimolar amounts of the tetracarboxylic acid component and the diamine component. In order to make the foam uniform, for example, diaminodisiloxane is added to the diamine. It is suitably used as a minor component of the component. As the lower alcohol of the solvent, methanol, ethanol, propanol or the like is used, and it may be mixed with other solvents. When a diamine is added to and mixed with the tetracarboxylic acid ester solution to obtain a polyimide precursor solution composition, the concentration of each component is preferably below the solubility limit of diamine, and the amount of non-volatile components is 3 in the total amount. It becomes about 50 mass%. This polyimide precursor solution composition includes 1,2-dimethylimidazole, benzimidazole, isoquinoline, substituted pyridine and other imidation catalysts, surfactants, or other known additives such as inorganic fillers. -Inorganic or organic pigments may be added.

  The polyimide precursor solution composition is evaporated to dryness and pulverized using an evaporator in the laboratory and a spray dryer in the industry. The temperature at this time is preferably 100 ° C. or less, particularly preferably 80 ° C. or less. When evaporating to dryness at a high temperature, the foamability of the polyimide precursor composition is extremely lowered. Evaporation to dryness may be performed under normal pressure, under pressure, or under reduced pressure.

  The green body is prepared by, for example, a method in which a powdered polyimide precursor composition is compression-molded at room temperature, a method in which it is cast and solidified as a slurry solution, and a microwave inactive to Teflon (registered trademark). It can be performed by a method of filling the container. If a green body having a substantially uniform state can be obtained, uniformization during foaming can be achieved.

Foaming of the polyimide precursor composition can be suitably performed by heating by microwave heating. At this time, the operation is generally performed at 2.45 GHz. This is based on Japanese domestic law (Radio Law). It is preferable to use the microwave output per weight of the powder as a guide. This should be defined by experimentation. For example, when microwaves of about 100 g / 1 kW are irradiated for about 1 minute, foaming starts, and foaming converges in 2 to 3 minutes.
Since the foamed foam is very brittle, it is preferable to immediately heat it using an oven or the like. Heating is preferably performed by gradually increasing the temperature from about 200 ° C. (as a guideline, a temperature increase rate of about 100 ° C./10 minutes). Finally, it is heated for 5 to 60 minutes, preferably about 10 minutes at a temperature of polyimide glass transition temperature + α (about 10 to 100 ° C.).
By the above manufacturing method, a polyimide foam having a density of ³ to 20 kg / m ³ and having a uniform foam structure and having elasticity and excellent restoring force can be suitably obtained.

As the foam chip used in the present invention, a chip obtained by crushing and sizing the polyimide foam using, for example, a crushing and sizing device can be preferably used. The density of the foam chip is preferably ³ to 20 kg / m ³ , particularly 5 to 20 kg / m ³ . The shape of the foam chip is not particularly limited, but a preferable shape is a shape close to a sphere that can be fed when put into a predetermined mold. The maximum diameter of the foam chip is preferably 50 mm or less, and more preferably, the chip having the maximum diameter of 10 to 50 mm occupies 80% by volume or more with respect to the total volume. When the maximum diameter of the foam chip exceeds 50 mm, it is difficult to obtain a lightweight polyimide molded body having a uniform density, which is not preferable. It is also possible to use a chip with a minimum diameter of 5 mm or less, and there is no particular problem with the characteristics of the resulting lightweight polyimide molded body, but to crush the maximum diameter from a polyimide foam to 5 mm or less. Since it takes a considerable amount of time, it becomes inefficient.

  The lightweight polyimide molded body of the present invention can be obtained by subjecting a predetermined amount of the foam chip to pressure molding and heat treatment without using a binder. In the present invention, the pressure molding and heat treatment steps may be performed in a single step, but a predetermined amount of the foam chip is placed in a mold and pressure molded at a temperature of 100 ° C. or lower to form a pressure molded body. A multi-stage method including a step of obtaining a pressure polyimide molded body in a mold having a desired shape and a heat treatment at a temperature of 250 to 500 ° C. It is preferable because it can be manufactured stably.

Hereinafter, the multistage manufacturing method will be described.
First, a predetermined amount of a foam chip is put into a mold and press-molded. The input amount is an amount calculated from the volume of the final lightweight polyimide molded body and the target density. This is pressure-molded by, for example, a press machine to obtain a pressure-molded body (green body) in which the foam chip is compressed. The density of the pressure-molded body must take into account the return of dimensions due to the springback that occurs after pressure molding. Therefore, at the time of pressure molding, it is 102 to 120%, preferably 105%, of the (target) density of the pressure-molded body. It is preferable to adjust the molding pressure, the mold dimensions, and the amount of foam chips introduced so that the density is ˜110%. By this springback, it becomes easy to eliminate the voids and obtain a more uniformly pressed body. Moreover, it is preferable that the shape and dimensions of the chip are as described above in order to obtain a pressure-molded body having a uniform density in the pressure-molding step.
The (target) density of the pressure-molded body is preferably set to a density of 85 to 115%, more preferably 90 to 100%, with respect to the (target) density of the lightweight polyimide molded body as the product.
In this step, there is no particular need for heating, and it is sufficient that the pressure-molded body is pressure-molded to such an extent that it can be integrated so that it can be easily taken out of the mold. That is, the pressurization temperature is 100 ° C. or less, preferably −10 to 100 ° C., more preferably 0 to 50 ° C., and still more preferably room temperature (about 15 to 30 ° C.). Is preferred.
In addition, since the polyimide foam is easily deformed, any special pressure can be used as long as it can apply a pressure that can be sufficiently compressed (usually 200 to 5000 kg / cm ² , preferably 500 to 2000 kg / cm ² ). Conditions are not required. Although the pressurization time is not particularly limited, a short time of about 1 second to 10 minutes is preferable, and it is preferable to repeat the pressurization for a short time a plurality of times.

  The mold used for the pressure molding is not particularly limited as long as a predetermined amount of the foam chip can be pressure molded. The shape is preferably a shape according to the shape of the final product (in the case of manufacturing a single product by combining a plurality of pressure-formed bodies, each partial shape). For example, if a plate-shaped product is to be manufactured, it can be suitably carried out by combining a mold that compresses a box-shaped container with an inner lid (punch) and a uniaxial hydraulic molding machine.

Subsequently, in order to heat-process, a press-molded body is moved to another metal mold | die normally equipped with a heating apparatus. In this mold, the pressure-molded body is heated to a target shape (target density) of the product and kept in the target shape. At this time, if the density of the press-molded body is smaller than the target density of the product, it is compressed into a mold and becomes high density. On the other hand, when the density of the press-molded body is larger than the target density of the product, the press-molded body expands due to heating, resulting in a low density. The heat treatment is preferably performed in the temperature range of 250 to 500 ° C. for about 0.1 to 10 hours. Note that springback may occur even after the heat treatment. In that case, it is preferable to determine the mold shape in consideration of the amount of springback required empirically. The lower limit of the temperature range of the heat treatment is preferably 300 ° C, more preferably 330 ° C, still more preferably 350 ° C, and particularly preferably 380 ° C. The upper limit of the temperature range of the heat treatment is preferably 450 ° C. The temperature at which heat treatment is performed is based on the glass transition temperature of the polyimide forming the foam chip. That is, it is −20 ° C. to + 100 ° C., preferably −10 ° C. to + 50 ° C., more preferably 0 to 50 ° C. with respect to the glass transition temperature of the polyimide forming the foam chip. When the glass transition temperature is not observed in the polyimide, it is preferable to carry out in a temperature range of 400 to 500 ° C.
When the temperature of the heat treatment is too low, the mechanical strength of the lightweight polyimide molded body is lowered, which is not preferable. In addition, if heat treatment is performed at a temperature higher than 500 ° C., the carbonization of polyimide starts, which is not preferable.

  The glass transition temperature of the polyimide forming the foam chip can be measured from the dynamic viscoelasticity of the foamed material using a dynamic viscoelasticity measuring device.

  The mold used in the heat treatment has the shape of a lightweight polyimide molded body whose product is a product. Accordingly, a metal that is not easily deformed is preferably used. When obtaining a plate-like lightweight polyimide molded body, a combination of metal spacers having a predetermined thickness between two metal plates can be suitably used. And if it can perform the pressurization function for adjusting a shape and heat processing, there will be no limitation in particular, It can use suitably combining a hot press apparatus with a metal plate and a spacer.

The lightweight polyimide molded body of the present invention is suitably obtained by increasing the density to 15 to 330 times, preferably about 20 to 200 times the density of the foam chip to be used. The density of lightweight polyimide molded product of the present invention, 300~1000kg / m ^3, preferably 400~1000kg / m ^3, more preferably 500~900kg / m ^3, more preferably lightweight those 550~850kg / m ³ Nevertheless, it is suitable because it has excellent mechanical strength.
The shape of the lightweight polyimide molded body of the present invention may be any of a sheet shape, a plate shape, a half-pipe shape, a column shape, a cube shape, a box shape, etc., but a plate shape is particularly suitable for ease of molding. It is. Since these lightweight polyimide moldings have excellent properties such as heat resistance and mechanical properties, they can be suitably used as a heat insulating material or a cushioning material used at high temperatures.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to a following example.

The measurement methods used in the following examples are as follows.
(Density measurement)
Measured according to ASTM D 3574 TEST A.
(Measurement of tensile strength)
Based on ASTM D 3574 TEST E, it was measured using Tensilon UTM-100 (manufactured by Orientec Co., Ltd.).

Reference Example 1 Preparation of Polyimide Foam In a 1 m ³ jacketed reactor equipped with a stirrer, 55.519 kg of 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride and 15.201 kg of 3, After charging 3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 139.7 kg of methanol and replacing the inside of the reaction tank with nitrogen, the jacket was heated by circulating 90 ° C. warm water, After the temperature reached 90 ° C., the mixture was refluxed for 90 minutes to carry out an esterification reaction. Then, after cooling a reaction liquid to 30 degrees C or less, 25.052 kg p-phenylenediamine and 0.628 kg 1,3-bis (3-aminopropyl) tetramethyldisiloxane were added to the reaction liquid. Further, 2.892 kg of 1,2-dimethylimidazole was added and stirred to make the reaction solution uniform. Next, using a spray dryer, the reaction solution was dried while adjusting the spray amount so that the drying temperature was 50 ° C. or less, thereby obtaining a dry powder of a foamed polyimide precursor. Next, 2 kg of this dried polyimide precursor powder was filled in a 300 mmφ × 200 mmt mold and pressed with a press to compress the green body. The obtained green body had a size of 300 mmφ × 15 mmt. This green body is put in a microwave irradiation apparatus, and irradiated with microwaves at an output of 5 kw for 10 minutes to obtain a foamed polyimide precursor foam, which is put into an oven heated to 120 ° C. and heated to 375 ° C. for 10 After raising the temperature at a rate of temperature increase of ° C./min, the temperature was maintained at 375 ° C. for 5 minutes and then cooled to room temperature to obtain a foamed polyimide. The obtained foamed polyimide was dense and uniform foaming, and the density was 7.5 kg / m ³ .

[Example 1]
The polyimide foam obtained in Reference Example 1 was put into a crushing apparatus (a crushing and granulating machine Fiore, manufactured by Kotokakusho Co., Ltd.) and crushed. A schematic diagram of the pulverization and sizing machine is shown in FIG. 345 g of a chip having a particle diameter of 30 mm or less that has passed through a screen with a hole diameter of 30 mm is placed in a 315 × 315 × 80 mm stainless steel mold, and a pressure of 710 kg using a press device (single screw hydraulic molding machine, manufactured by Toho Machinery Co., Ltd.) The plate-shaped press-molded body was obtained by cold molding at room temperature for 10 seconds at / cm ² . A schematic cross-sectional view of this process is shown in FIG. The size of this press-molded body was 315 × 315 × 7.5 mmt, and the density was 460 kg / m ³ . The pressure-formed body is sandwiched between two 330 × 330 × 10 mm stainless steel flat plates with a spacer of 8 mm thickness, and squares are fixed with bolts as shown in FIG. Was heated at 400 ° C. for 3 hours in a calcination furnace DF-200HS (manufactured by Futaba Kagaku Co., Ltd.) to obtain a lightweight polyimide molded body having dimensions of 315 × 315 × 8.1 mmt. This lightweight polyimide molded body had a density of 430 kg / m ³ and a tensile strength of 4.9 MPa.

[Example 2]
A lightweight polyimide molded body having dimensions of 315 × 315 × 8.1 mmt in the same manner as in Example 1 except that the amount of the foam chip was changed to 482 g and the pressure at the time of producing the pressure molded body was changed to 992 kg / cm ^2. Got. This lightweight polyimide molded body had a density of 600 kg / m ³ and a tensile strength of 6.2 MPa.

Example 3
A lightweight polyimide molded body having dimensions of 315 × 315 × 8.1 mmt was obtained in the same manner as in Example 1 except that the amount of the foam chip was 642 g and the molding pressure was 1480 kg / cm ² . This lightweight polyimide molded body had a density of 800 kg / m ³ and a tensile strength of 8.3 MPa.

[Comparative Example 1]
A plate-like foam having a thickness of 96 mm was cut out from the polyimide foam obtained in Reference Example 1, and this was sandwiched with a spacer between two flat plates made of stainless steel, and a hot press device (single-screw hydraulic molding machine, Toho Machinery Co., Ltd.) The pressure was increased to 2 mm, and heat treatment was performed at 400 ° C. for 30 minutes. The obtained molded body had a density of 432 kg / m ³ and a tensile strength of 4.0 MPa.

[Comparative Example 2]
In the same manner as in Comparative Example 2, molded bodies having different densities were obtained. The obtained molded body had a density of 603 kg / m ³ and a tensile strength of 5.5 MPa.

It is the schematic for demonstrating the crushing apparatus for crushing a polyimide foam. It is the schematic for demonstrating the process for obtaining a press-molding body. It is the schematic for demonstrating the process of obtaining a lightweight polyimide molded object from a press-molded object.

Claims (1)

Placing a predetermined amount of a foam chip formed of aromatic polyimide in a mold and press-molding at a temperature of 100 ° C. or lower without using a binder, A method for producing a lightweight polyimide molded body having a density of 300 to 1000 kg / m ³ , comprising a step of placing the pressure molded body in a mold having a target shape and heat-treating at a temperature of 250 to 500 ° C.

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