JP2001270955A - Foamed polyimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide useful as a heat resistant cushioning material for aerospace applications and for materials for electronic parts. SOLUTION: The polyimide foam has fine voids in its structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to space and aircraft equipment,
The present invention relates to a polyimide foam useful as a heat-resistant buffer in a substrate for electronic components.

[0002]

2. Description of the Related Art The following method is known as a method for producing a polyimide foam having excellent heat resistance and mechanical properties. (1) The elasticity of a foam is improved by using two kinds of diamines containing not only an aromatic diamine but also an aliphatic amine and a foaming agent (JP-A-61-195126). (2) A thermoplastic polyimide foam produced using an aromatic ether diamine as a diamine
-2555841) and the like.

[0003]

However, the molecular structure of the wholly aromatic polyimide is rigid and difficult to mold, and the foaming agent remains so that the physical properties of the obtained polyimide foam deteriorate at high temperatures. There was a problem. An object of the present invention is to provide a polyimide foam which can be used to produce a polyimide foam without lowering heat resistance and mechanical properties, and which is produced using the polyamic acid and has the above properties. I do.

[0004]

That is, the present invention is a polyimide foam characterized by having fine voids in the structure, wherein the voids have an average pore diameter of 0.0001 mm to 1 mm.
Is a foamed polyimide.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, as a method for producing a polyamic acid which is a precursor of polyimide, an aromatic dianhydride and an aromatic diamine are reacted in the presence of a solvent to obtain a polyamic acid in a solution state. By heating the obtained polyamic acid, a polyimide foam having a large expansion ratio can be obtained without lowering heat resistance and mechanical properties.

[0006] In order to obtain a polyimide foam having fine voids as in the present invention, it is most important to heat the polyamic acid obtained by the above means. , The temperature is preferably 150 to 400 ° C, more preferably 0.5 to 200 to 300 ° C.
Heating for 4 hours is preferred. By these heating methods, the polyamic acid is rapidly heated, and it is found that the residual solvent and the generated condensed water are volatilized to foam uniformly, and it is possible to obtain a polyimide foam particularly usable as a heat-resistant buffer. Was.

The polyimide foam of the present invention preferably has voids in the form of cells having an average pore diameter of 0.0001 mm to 1 mm, more preferably 0.0001 to 0.1 mm, and still more preferably 0.0001 to 0.01 mm. It is. Further, the porosity expressed as the total volume of the cavities is preferably 5% to 50%, more preferably 10% to 35%, based on the entire polyimide foam. Here, the porosity can be obtained from the following equation.

Porosity: V _AIR / V = (Dd _PI ) / (d
_AIR -d _PI) V: volume of the product, d: density of the product, V _AIR: void volume, d _PI: Density of polyimide, d _AIR: density of the air.

The polyimide foam of the present invention is preferably used as a heat-resistant cushioning material. In this case, it can be used as a sheet having a thickness of 0.01 mm to 100 mm. Further, the thickness of the sheet is L (mm),
When the average particle size of the voids contained in the polyimide is R (mm), it is preferably 1 × 10 ⁻⁵ ≦ R / L ≦ 1 × 10 ⁻¹ , and 1 × 10 ⁻⁵ ≦ R / L ≦ 1 It is more preferably × 10 ^{−2, and} further preferably satisfies the range of 1 × 10 ⁻⁵ ≦ R / L ≦ 1 × 10 ⁻³ . Here, the method for measuring the average particle size of the voids was determined by observing the sheet cross section by SEM or the like.

In the present invention, preferred acid dianhydrides include pyromellitic dianhydride (PMDA: hereinafter, abbreviations are shown in parentheses), 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) ), 3, 3 ', 4,
4′-biphenyltetracarboxylic acid, 3,3 ′, 4
4′-diphenylethertetracarboxylic acid, 3,
3 ', 4,4'-diphenylhexafluoropropanetetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic acid, pyromellitic acid , Butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, and the like, but are not limited thereto.

Preferred diamines are 1,3-
Bis- (3-aminophenoxy) benzene (APB),
3,3'-diaminodiphenylsulfone (3,3-D
DS), bisaminopropyltetramethyldisiloxane (SiDA), paraphenylene diamine, metaphenylene diamine, methyl paraphenylene diamine, methyl metaphenylene diamine, dimethyl paraphenylene diamine, dimethyl metaphenylene diamine, trimethyl paraphenylene diamine, trimethyl metaphenylene Diamine, tetramethyl paraphenylenediamine, tetramethyl metaphenylenediamine, trifluoromethyl paraphenylenediamine, trifluoromethyl metaphenylenediamine, bis (trifluoromethyl) paraphenylenediamine, bis (trifluoromethyl) metaphenylenediamine, methoxypara Phenylenediamine, methoxymetaphenylenediamine, trifluoromethoxyparaphenylenediamine Trifluoromethoxymetaphenylenediamine, fluoroparaphenylenediamine, fluorometaphenylenediamine, chloroparaphenylenediamine, chlorometaphenylenediamine, bromoparaphenylenediamine, bromometaphenylenediamine, carboxyparaphenylenediamine, carboxymetaphenylenediamine, methoxycarbonylpara Examples thereof include phenylenediamine, methoxycarbonyl metaphenylenediamine, diaminodiphenylmethane, bis (aminomethylphenyl) methane, bis (aminotrifluoromethylphenyl) methane, and bis (aminoethylphenyl) methane.

The solvent used for obtaining the polyamic acid of the present invention is preferably dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NM
P), a polar solvent mainly containing N, N-dimethylformamide, dimethyl sulfoxide, hexamethyl phosphorotriamide and the like, a solvent mainly containing γ-butyrolactone and the like are preferably used.

The polyamic acid solution obtained by combining the aromatic carboxylic dianhydride and the aromatic diamine is processed into a film or a sheet by a usual film forming method as described below, and is processed into at least 150 ° C, preferably 2
By rapidly heating to 00 ° C. or higher, the condensed water generated by the imidization reaction is rapidly volatilized to obtain a foamed polyimide molded article. The rapid heating is performed while increasing the temperature stepwise or continuously. However, in any case, a rapid temperature change is required.

Next, the method of using the composition of the present invention will be described. First, the composition of the present invention is coated on a suitable support. Examples of the material of the support include, but are not limited to, metal, glass, and ceramics. Further, the foamed polyimide of the present invention can be obtained by casting the polyamic acid solution not only on the substrate but also on a mold formed in a predetermined shape and heat-treating.

As a coating method, means such as spin coating using a spinner, spray coating using a spray coater, dipping, printing, roll coating and the like are possible. The coating thickness can be adjusted by the coating means, the solid content concentration of the composition, and the viscosity, but the coating is usually performed in a range of 0.01 to 100 mm.

As a heating means, an oven, a hot plate, an infrared ray or the like is used, and the heating is preferably performed at a temperature in the range of 150 to 400 ° C., more preferably in the range of 200 to 300 ° C. The heating time is preferably 0.5 to 4 hours.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Example 1 1,3-bis- (3-aminophenoxy) benzene (A
48 mol of PB), 48 mol of 3,3'-diaminodiphenylsulfone (abbreviated as DDS), 4 mol of bisaminopropyltetramethyldisiloxane (abbreviated as SiDA), and pyromellitic dianhydride as an acid dianhydride 100 mol (abbreviated as PMDA) was added to 300 ml of a dimethylacetamide solution, and the mixture was stirred at 50 ° C. for 4 hours to prepare a polyamic acid. The viscosity of the obtained polyamic acid solution was 7,480 mPa · s. The obtained polyamic acid solution was applied on an aluminum foil to a thickness of 1 mm,
The mixture was rapidly heated in an oven at 00 ° C for 1 hour. Table 1 shows the thickness, average pore size, porosity, and tensile strength at 150 ° C. of the polyimide foam thus obtained.

[0019]

[Table 1]

Example 2 96 mols of DDS, 4 mols of SiDA and 100 mols of BTDA as an acid dianhydride were added to 300 ml of an NMP solution for 6 hours.
Polymerization was carried out at 0 ° C. for 4 hours. The viscosity of the obtained polyamic acid solution was 9,800 mPa · s. The obtained solution was treated under the same conditions as in Example 1 to prepare a polyimide foam. Table 1 shows the physical property results thus obtained.

Example 3 In the same composition as in Example 1, 2% of a nonionic surfactant was added.
Was added to prepare a polyamic acid solution. It was applied on an aluminum foil to a thickness of 1 mm and rapidly heated in an oven at 200 ° C. for 1 hour. The tensile strength at 150 ° C. was 20 MPa. The properties obtained are shown in Table 1.

Comparative Example 1 95.5 mol of PMDA, 96 mol of 4,4'-diaminodiphenyl ether (hereinafter abbreviated as DAE), SiD
A4mol was polymerized at 300C for 5 hours under 300ml of NMP solution. The viscosity of the obtained polyamic acid solution was 1220 mPa · s. The obtained solution was heated in a screw tube in a 200 ° C. oven for 2 hours in a solution state. No foaming phenomenon occurred with this combination of monomers.

Comparative Example 2 PMDA 46 mol, BTDA 50 mol, DAE96
and 4 mol of SiDA were polymerized at 300C for 5 hours under 300 ml of NMP solution. The viscosity of the obtained polyamic acid solution was 1350 mPa · s. The obtained solution was heated in a screw tube in a 200 ° C. oven for 2 hours in a solution state. No foaming phenomenon occurred with this combination of monomers.

[0024]

According to the present invention, rapid heating using a polyamic acid, which is a precursor of the polyimide produced in the present invention, allows foaming due to evaporation of condensed water and residual solvent generated during heating without using a foaming agent. As a result, a polyimide useful as a heat-resistant buffer material having no strength reduction even at high temperatures was obtained.

Claims (6)

[Claims] 1. A polyimide foam having fine voids in its structure. 2. The void has an average pore diameter of 0.0001 mm to 1 mm.
2. The polyimide foam according to claim 1, wherein the foam is in the form of cells. 3. The polyimide foam according to claim 1, wherein the porosity, which is the total volume of the voids, is 5% to 50% of the whole foam. 4. The polyimide foam according to claim 1, which is in the form of a sheet having a thickness of 0.01 mm to 100 mm. 5. The thickness is L (mm), and the average pore diameter of the void is R.
(Mm), 1 × 10 ⁻⁵ ≦ R / L ≦ 1 × 10 ⁻¹
The polyimide foam according to claim 4, wherein 6. The polyimide foam according to claim 1, which is used as a heat-resistant cushioning material.