JPH0665391A - Method of bonding by using prepreg sheet - Google Patents

Abstract

PURPOSE:To improve the melt flow characteristics of polyimide and realize bonding with excellent heat resistance by impregnating a fibrous reinforcing material with a solution prepared by incorporating an imidizing agent into an organic solvent solution of a specified polyamic acid so that the polyamic acid is imidized to give a prepreg sheet, sandwiching the prepreg sheet between adherends, and heating under pressure. CONSTITUTION:A fibrous reinforcing material is impregnated with a solution prepared by incorporating an imidizing agent into an organic solvent solution of a polyamic acid having repeating units of formula I so that the polyamic acid is chemically imidized to give a prepreg sheet having the polyamic acid converted into a polyimide with repeating units substantially of formula II. This prepreg sheet is sandwiched between adherends and heated to a temperature above the glass transition point of the polyimide under pressure. In formula I, R1 is a divalent 2C or higher aliphatic or monocyclic aromatic group; R2 is a tetravalent 2C or higher aliphatic or monocyclic aromatic group; and Y is H, alkyl or aryl. In formula II, R1 and R2 are each as defined in formula I.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding method using a prepreg sheet obtained by a method for producing a prepreg sheet useful as a heat resistant adhesive, a heat resistant composite material and the like.

[0002]

2. Description of the Related Art In the fields of electronics, aerospace equipment, transportation equipment, etc., various industrial materials are required to have high temperature characteristics in order to achieve high performance and light weight. Conventionally, epoxy-based, modified epoxy-based, phenolic-based resins, etc., which have been used as structural adhesives or prepregs for laminated molded bodies, have a remarkable drawback in heat resistance. Epoxy resins and the like have a problem in storage stability and have a drawback that they need to be stored at a low temperature. A polyimide resin is used as a material for improving such a defect. However, when a normal polyimide resin is completely cyclized to be in a polyimide state, its melt fluidity becomes very poor, which makes it difficult to use. On the other hand, although the melt fluidity improves in the state where the solvent or the polyamic acid remains, voids are generated in the molded product or the adhesive layer due to the water generated during the cyclization of the residual solvent or the amic acid group during processing, It is not preferable because it lowers the physical properties. As a polyimide resin having improved melt fluidity, tetracarboxylic dianhydride such as 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and diamine such as 3,3′-diaminobenzophenone are used in an organic solvent. A polyimide resin obtained by heating and imidizing a polyamic acid obtained by the reaction was developed by the National Aeronautics and Space Administration (NASA). (For example, U.S. Pat.
No. 4,094,862. However, the melt fluidity of this polyimide resin is not yet sufficiently satisfactory, and the performance is not sufficient for use in a prepreg.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made from the above point of view, and an object of the present invention is to improve the melt flowability of polyimide and to provide a heat-resistant adhesive. It is to provide a heat-resistant bonding method using a material widely used as.

[0004]

The inventors of the present invention have finally made the present invention as a result of extensive studies to achieve the above object. That is, the present invention uses the formula (1)

[Chemical 3] [In the formula, R ₁ represents an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-bonded group in which aromatic nuclei are interconnected by a bridging member. Represents a divalent group selected from the group consisting of a condensed polycyclic aromatic group and a heterocyclic group,
R ₂ is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-condensed polycyclic group in which aromatic nuclei are interconnected by a bridging member. It represents a tetravalent group selected from the group consisting of aromatic groups and heterocyclic groups, and Y represents a group selected from the group consisting of hydrogen atoms, alkyl groups and aryl groups. ] The fibrous reinforcing material is impregnated with a solution prepared by adding and mixing a dehydration imidizing agent to an organic solvent solution of a polyamic acid having a repeating unit represented by the formula (2).

[Chemical 4] Wherein, R ₁ and R ₂ has the formula (1) is identical to R ₁ and R ₂ in] a prepreg sheet obtained form a polyimide having a repeating unit represented by between adherends The bonding method is characterized by inserting and heating under pressure to a temperature not lower than the glass transition point of polyimide.

In the present invention, polyamic acid is first synthesized. Polyamic acid can be synthesized by a known method. Generally, it is synthesized by reacting a tetracarboxylic dianhydride and a diamine compound in an organic solvent. Specifically, for example, by dissolving or suspending a diamine compound in an organic solvent and gradually adding tetracarboxylic dianhydride under a stream of dry nitrogen, or vice versa, diamine is added to the tetracarboxylic dianhydride solution. It is synthesized by gradually adding the compound.

The tetracarboxylic dianhydride used is preferably, for example, the following. Pyromellitic anhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3', 4'-benzophenone tetracarboxylic dianhydride, 2,2 ', 3,3' -Benzophenone tetracarboxylic dianhydride, 4,4 ', 5
5 ', 6,6'-hexafluorobenzophenone-2,
2 ', 3,3'-tetracarboxylic dianhydride, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,5,6-trifluoro-3,
4-dicarboxyphenyl) methane dianhydride, 1,1-
Bis (3,4-dicarboxyphenyl) ethane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride Anhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,5,5
6-trifluoro-3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (2,5,6-trifluoro-3,4-dicarboxy) Phenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) -phenylphosphonate dianhydride, bis (3,4-dicarboxyphenyl) -phenylphosphine oxide dianhydride, N,
N- (3,4-dicarboxyphenyl) -N-methylamine dianhydride, bis (3,4-dicarboxyphenyl)
-Diethylsilane dianhydride, bis (3,4-dicarboxyphenyl) -tetramethyldisiloxane dianhydride,
3,3 ', 4,4'-Tetracarboxybenzoyloxybenzene dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,
7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride,
1,4,5,8-tetrafluoronaphthalene-2,3
6,7-Tetracarboxylic acid dianhydride, 1,8,9,10
-Phenanthrene tetracarboxylic dianhydride, 3,4
9,10-perylenetetracarboxylic dianhydride, 2,
3,4,5-thiophenetetracarboxylic dianhydride,
2,3,5,6-pyrazinetetracarboxylic dianhydride,
2,3,5,6-pyridinetetracarboxylic dianhydride,
Tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, 3,3 ', 4,4'-azobenzenetetracarboxylic dianhydride, 3,3', 4,4'-azoxybenzenetetracarboxylic Acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, ethylenetetracarboxylic acid dianhydride, butanetetracarboxylic acid dianhydride and the like. Among them, particularly preferable tetracarboxylic acid dianhydride is 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride (hereinafter abbreviated as BTDA). These tetracarboxylic dianhydrides may be used alone or in admixture of two or more.

The following diamine compounds are desirable. o-, m- and p-phenylenediamine, 2,
4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 2,5-diaminoxylene, 1,3-diamino-4-chlorobenzene, 1,4-diamino-2,5
-Dichlorobenzene, 1,4-diamino-2-bromobenzene, 1,3-diamino-4-isopropylbenzene, 2,2-bis (4-aminophenyl) propane,
3,3'- or 4,4'-diaminodiphenylmethane,
3,4'-diaminodiphenylmethane, 2,2'- or 4,4'-diaminostilbene, 4,4'-diamino-
2,2 ', 3,3', 5,5 ', 6,6'-octafluorodiphenylmethane, 3,3'- or 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4' -Diamino-2,2 ', 3
3 ', 5,5', 6,6'-octafluorodiphenyl ether, 3,4'-diaminodiphenylthioether, 3,3'- or 4,4'-diaminodiphenylthioether, 4,4'-diaminodiphenylsulfone,
3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4-aminobenzoic acid 4'-
Aminophenyl ester, 2,2'-, 3,3'- or 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 2,3'-diaminobenzophenone, 4,4'-diaminobenzyl, 4- (4-Aminophenylcarbamoyl) aniline, bis (4-aminophenyl) -phosphine oxide, bis (4-aminophenyl) -methylphosphine oxide, bis (3-aminophenyl) -methylphosphine oxide, bis (4-aminophenyl) ) -Cyclohexylphosphine oxide,
N, N-bis (4-aminophenyl) -N-phenylamine, N, N-bis (4-aminophenyl) -N-methylamine, 2,2 '-, 3,3'- or 4,4' -Diaminoazobenzene, 4,4'-diaminodiphenylurea, 1,8- or 1,5-diaminonaphthalene, 1,5
-Diaminoanthraquinone, diaminofluoranthene,
3,9-diaminochrysene, diaminopyrene, bis (4
-Aminophenyl) -diethylsilane, bis (4-aminophenyl) -dimethylsilane, bis (4-aminophenyl) -tetramethyldisiloxane, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6- Diaminoacridine, 2,4-diamino-S-triazine,
2,7-diamino-dibenzofuran, 2,7-diaminocarbazole, 3,7-diaminophenothiazine, 5,
6-diamino-1,3-dimethyluracil, 2,5-diamino-1,3,4-thiadiazole, dimethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nona Methylenediamine,
Decamethylenediamine, 2,2-dimethylpropylenediamine, 2,5-dimethylhexamethylenediamine,
2,5-dimethylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 3-methoxyhexamethylenediamine,
5-methylnonamethylenediamine, 2,11-diaminododecane, 1,12-diaminooctadecane, 1,2-
Bis (3-aminopropoxy) -ethane and the like. Among them, a particularly preferred diamine compound is 3,3′-diaminobenzophenone (hereinafter abbreviated as 3,3′-DABP). These diamine compounds may be used alone or in 2
Use by mixing more than one species.

Further, N, N'-dialkyl or diaryl-substituted diamine compounds such as N, N'-diethylethylenediamine, N, N'-diethyl-1,3-diamino are used within a range that does not significantly affect the physical properties of the polyimide resin. Propane, N, N'-dimethyl-1,6-diaminohexane, N, N'-diphenyl-1,4-phenylenediamine and the like can be used in combination. The organic solvent used is N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N-acetyl-2-pyrrolidone, sulfolane, dimethyl sulfoxide, diethylene glycol dimethyl ether and the like.
These solvents are used alone or as a mixture. The resulting polyamic acid solution contains the usual 2 to 50% resin content, or the viscosity of the solution is in the range of 10 to 50,000 centivoice as the viscosity measured by Brookfield viscometer. It is preferable because it is easy to handle and it is easy to impregnate the reinforcing material.

The polyamic acid has an intrinsic viscosity of 0.2 to
It is preferable to be in the range of 2.0 dl / g from the viewpoint of mechanical strength, melt fluidity, heat resistance and the like of the obtained resin. The intrinsic viscosity is calculated by the following formula. η inh = (1 / C) · ln (η / η _O ) (In the above formula, ln = natural logarithm η = viscosity of a solution of 0.5 g of polyamic acid dissolved in 100 ml of N, N-dimethylacetamide (35 ° C.) η _O = viscosity of N, N-dimethylacetamide (35 ° C.) C = polymer solution concentration expressed in g of polyamic acid per 100 ml of solvent.)

Next, a dehydration imidizing agent is added to and mixed with the obtained organic solvent solution of polyamic acid. As the dehydrating imidizing agent, acetic anhydride, propionic anhydride, isobutyric anhydride, acetic anhydride may be used alone or as a mixture. The addition of the dehydrating imidizing agent is preferably performed at -10 ° C to 150 ° C. The dehydrating imidizing agent may be added directly to the polyamic acid or diluted with a polyamic acid-soluble solvent and added. The amount of the dehydration imidizing agent to be added is 0.8 to 4 equivalents, particularly preferably 1 to 2 equivalents, relative to the carboxy groups present in the polyamic acid. It is also possible to add an imidization catalyst at the same time, and examples of the catalyst include tertiary amines such as trimethylamine, triethylamine, tributylamine, pyridine, α-picoline, β-picoline, γ-picoline and lutidine. To be
When a catalyst is used, it is used in an amount of 0.05 to 1.5 equivalents, preferably 0.1 to 1 equivalents, based on the carboxy groups present in the polyamic acid. When the dehydration imidizing agent is added and mixed, imidization starts, and finally the solution precipitates in the form of gel or powder and cannot be impregnated into the reinforcing material. It is preferable to use

Next, the fiber reinforcing material is impregnated with a polyamic acid solution to which a dehydration imidizing agent has been added. Typical examples of the fibrous reinforcing material include glass fiber, carbon fiber, aromatic polyamide fiber, aromatic polyamide non-woven fabric, and boron fiber, and these are used alone or in combination. Further, if necessary, other reinforcing materials such as silicon carbide fiber, mica, calcium silicate, silica and alumina may be used in combination with the above fiber. The simplest impregnation method is to immerse the fibrous reinforcing material in a polyamic acid solution to which a dehydration imidizing agent has been added. Of course, it may be impregnated by another method.

In the present invention, first, the impregnated polyamic acid is chemically dehydrated and imidized. The imidization is preferable in view of the physical properties of the prepreg sheet obtained by suppressing the thermal imidization reaction as much as possible. Therefore, the imidization temperature is 10 to 200.
It is desirable to carry out in the range of ° C. Most of the imidized prepreg sheet is further dried by heating to remove volatile components such as a solvent, an unreacted imidizing agent, a reaction product of the imidizing agent, and an imidizing catalyst. The volatile matter in the prepreg sheet causes blisters in the subsequent bonding operation, and therefore it is preferable to remove it as much as possible, and the volatile matter is preferably 10% by weight or less of the entire prepreg sheet. Further, there is no problem even if the polyimide has an uncyclized amic acid group remaining in a range that does not significantly affect the physical properties, or has a thermally imidized portion that is not due to chemical imidization. Further, the resin content is preferably 20 to 80% by weight based on the whole prepreg sheet.

The polyimide-impregnated prepreg sheet produced by the chemical imidization operation of the present invention has a melting point of polyimide contained in comparison with a prepreg sheet obtained by impregnating a conventional polyamic acid solution into a fibrous reinforcing material and then heating and imidizing the same. Since it has excellent fluidity, it is suitable as an adhesive. The bonding is performed by inserting the prepreg sheet between the adherends and heating it under pressure. Bonding pressure is 0~ 500kg / cm ^2, in particular in the range of 0.1 to 20 kg / cm ² is desirable. The bonding temperature is not lower than the glass transition point of the polyimide contained in the prepreg sheet, preferably 240 to 3
60 ° C. The heating and pressurizing method may be a known method such as a heat press, a heat roll, induction heating with a high frequency wave, a double belt press, or an autoclave. The adhesive body obtained by the above operation exhibits excellent adhesive strength even at high temperatures.

[0014]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples. Example-1 (a) Polymerization N, N-dimethylacetamide was added to a 500 ml four-necked flask.
300ml, 3,3'-DABP 31.85g (0.15mol) was added, and BTDA powder with stirring at 15 ° C under a dry nitrogen stream.
48.33 g (0.15 mol) was added slowly. The viscosity of the solution increases with the addition. After the addition was completed, stirring was continued for a further 4 hours to complete the reaction. The obtained polyamic acid was light brown and transparent and had an intrinsic viscosity of 0.73 dl / g (0.5 g / 100 ml N, N-dimethylacetamide solvent, 35 ° C.). (b) Preparation of prepreg sheet To the polyamic acid solution obtained in (a), an imidizing agent consisting of 45.94 g of acetic anhydride, 8.4 g of pyridine and 40 g of N, N-dimethylacetamide was added dropwise at room temperature in a dry nitrogen stream while stirring. And mixed until well homogenous. A glass fiber cloth (WF-230 manufactured by Nitto Boseki) was immersed in the obtained solution. Remove the prepreg sheet impregnated with polyamic acid and polyimide.
100 ℃ for 1 hour, 150 ℃ for 30 minutes, 180 ℃ for 30 minutes, 200 ℃
And dried for 1 hour to obtain a polyimide-impregnated prepreg sheet. The resin content in the prepreg sheet was 40%. (c) Adhesion test Two cold-rolled steel sheets (JIS-G3141, SPCC-SD size 1.6 × 25 × 100m) prepared from the prepreg sheet obtained in (b) were used.
m) and bonded with a hot press at 340 ° C. and 5 kg / cm ² . The tensile shear bond strength was 265 kg / cm ² at room temperature.
(The measuring method is based on JIS K-6848 and K-6850.)

Comparative Example-1 3,3'-DABP and BTDA under the same conditions as in Example-1.
Was reacted to obtain a polyamic acid solution having an intrinsic viscosity of 0.75 dl / g (0.5 g / 100 ml N, N-dimethylacetamide solvent, 35 ° C.). This solution was diluted with N, N-dimethylacetamide so that the resin content was 8% by weight, and then a glass fiber cloth was immersed. The glass fiber cloth was soaked and then air dried. Do this operation 3
This was repeated to obtain a polyamic acid-containing prepreg sheet. The resulting prepreg sheet was heated and dried at 100 ° C. for 1 hour, 150 ° C. for 1 hour, 180 ° C. for 1 hour, and 220 ° C. for 3 hours for imidization and removal of volatile components to obtain a polyimide resin-containing prepreg sheet. . (a) Adhesion test Using the obtained prepreg sheet, adhesion was performed under the same conditions as in Example-1 (d). The tensile shear bond strength of the obtained adhesive body was 101 kg / cm ² at room temperature, which was less than half that of Example-1 (c).

Examples 2 to 6 Polymerization was carried out in the same manner as in Example-1 (a) using various diamines and tetracarboxylic dianhydride, and further Example-1 (b).
A polyimide-impregnated prepreg sheet was obtained in the same manner as in.
An adhesion test was conducted using the obtained prepreg sheet and
A result of 1 was obtained.

[Table 1]

Example-7 (a) Polymerization In the same reactor as in Example-1, 300 ml of N-methyl-2-pyrrolidone, 32.22 g (0.1 mol) of BTDA and 10.91 g (0.05 mol) of pyromellitic dianhydride were placed. , 3,4'-diaminobenzophenone 31.85 g (0.15 mol) with stirring at 15 ° C
Was gradually added. After the addition was completed, stirring was continued for another 4 hours to complete the reaction. The obtained polyamic acid solution was light yellow and transparent and had an intrinsic viscosity of 0.88 dl / g (0.5 g / 100 ml N, N-dimethylacetamide solvent, 35 ° C.). (b) Production of prepreg sheet To the obtained polyamic acid solution, 46 g of acetic anhydride, 7.5 g of triethylamine and 40 g of N-methyl-2-pyrrolidone were added and mixed. The obtained solution was applied to a carbon fiber cloth (Torayca cloth # 6343 manufactured by Toray Industries, Inc.) and impregnated by pressing with a rubber roll. The obtained polyamic acid- and polyimide-impregnated prepreg sheet was dried at 100 ° C. for 1 hour, 150 ° C. for 30 minutes, 180 ° C. for 30 minutes, and 230 ° C. for 1 hour to obtain a polyimide-impregnated prepreg sheet. The fiber content was 58% vol. (c) Adhesion test The obtained prepreg sheet was formed into two cold-rolled steel sheets (JI
S-G3141 and SPCC-SD size 0.5 × 25 × 150 mm), and bonded with a hot press at 340 ° C. and 5 kg / cm ² . 18
The 0 ° peel strength was 13 kg / 25 mm at room temperature. (The measurement method is based on JIS K-6848 and K-6854.)

[0018]

Since the present invention is constructed as described above,
According to the present invention, it is possible to provide an adhesive method having excellent heat resistance using a prepreg sheet obtained by a method for producing a novel prepreg sheet that exhibits particularly excellent strength even at high temperatures.

Claims (3)

[Claims] 1. Formula (1): [In the formula, R ₁ represents an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-bonded group in which aromatic nuclei are interconnected by a bridging member. Represents a divalent group selected from the group consisting of a condensed polycyclic aromatic group and a heterocyclic group,
R ₂ is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or a non-condensed polycyclic group in which aromatic nuclei are interconnected by a bridging member. It represents a tetravalent group selected from the group consisting of aromatic groups and heterocyclic groups, and Y represents a group selected from the group consisting of hydrogen atoms, alkyl groups and aryl groups. ] The fibrous reinforcing material is impregnated with a solution prepared by adding and mixing a dehydration imidizing agent to an organic solvent solution of a polyamic acid having a repeating unit represented by the formula (2). [Chemical 2] Wherein, R ₁ and R ₂ has the formula (1) is identical to R ₁ and R ₂ in] inserting a prepreg sheet obtained without a polyimide having a repeating unit represented by between adherends Then, it is heated to a temperature not lower than the glass transition point of the polyimide under pressure, which is a bonding method. 2. The polyamic acid is obtained by reacting 3,3′-diaminobenzophenone and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride in an organic solvent. Adhesion method described. 3. The bonding method according to claim 1, wherein the dehydration imidizing agent is at least one selected from acetic anhydride, propionic anhydride, isobutyric anhydride and butyric anhydride.