KR20000011145A - Aromatic polycarbodiimides and films thereof - Google Patents

Abstract

PURPOSE: Aromatic polycarbodiimides having excellent solubility, thermal resistance, adhesion, low-temperature processability and moisture resistance is provided. CONSTITUTION: Aromatic polycarbodiimides comprise constituting units represented by general formula (I):wherein R represents hydrogen or alkyl(C1-C5), and attaches to the meta or para position of hexafluoroisopropyrene; and n represents an integer of 3 to 600.

Description

Aromatic Polycarbodiimide and Films thereof

As a typical aromatic polycarbodiimide, it is known to polymerize this using diphenylmethane diisocyanate (MDI), triylene diisocyanate (TDI), etc. as a monomer. Such polycarbodiimide has been used as a flame resistant film or a heat resistant adhesive due to its excellent heat resistance.

However, such a polycarbodiimide film is insufficient in solubility and gels or precipitates as a solid with increasing molecular weight, so that a sufficient high molecular weight polymer is not obtained. In addition, it has heat resistance in that it does not generate volatile gases or decomposition monomers even when exposed to high temperatures of 400 ° C. or higher. However, when heat-treated at 200 ° C. or higher, it is not self-maintaining and brittle and cannot be practically tolerated. . Moreover, the adhesive force at the time of heat-compression bonding with a to-be-adhered body, such as copper foil, cannot be said to be enough.

The present invention relates to novel aromatic polycarbodiimides. The aromatic polycarbodiimide of the present invention provides a film, an adhesive, and a molded article having various excellent properties such as high heat resistance.

1 is a diagram showing an infrared absorption spectrum of a polymer obtained in Example 1. FIG.

2 is a diagram showing an infrared absorption spectrum of a polymer obtained in Example 3. FIG.

MEANS TO SOLVE THE PROBLEM In order to eliminate the fault of this conventional polycarbodiimide, this inventor etc. studied various aromatic polymers and came to manufacture the novel aromatic polycarbodiimide of this invention. That is, the present invention provides an aromatic polycarbodiimide having a structural unit represented by the formula (I):

In the above formula,

R is hydrogen or an alkyl group (1 to 5 carbon atoms, preferably 1 to 3 carbon atoms) and n represents an integer of 3 to 600.

In the general formula (I), R particularly preferably represents a hydrogen or methyl group, and the bonding position is preferably the m- or p- position of the hexafluoroisopropylidene group.

The present invention also provides an organic solvent solution and a film thereof. In addition, in this specification, a film means the thing of the film-formed form of a polymer, and includes what is called a sheet | seat. The polymer of the present invention is a novel high molecular compound, has very high heat resistance with excellent solubility, and is also excellent in adhesiveness, low temperature processing and moisture resistance.

The polycarbodiimide of the present invention is obtained by using the corresponding diisocyanate represented by the formula (II) as a monomer and polymerizing it by a known method in the presence of a phosphorus based catalyst:

As typical of such diisocyanate, what is represented by general formula (IIa) and 2b is mentioned.

In the above formula,

R is the same as above.

In addition, compounds of formula (IIb) are novel materials. In addition, the compound of the formula (IIa) is a known substance, and the literature on the preparation thereof and the preparation of the polyurethane using the same [Andrianov, at. al., Vysokomol, Soedin., Ser. B. 20 (6), 471, (1978), and the like, but these documents do not describe any preparation of polycarbodiimides from compounds of formula IIa.

Monomer

The diisocyanate compounds of formula (II), the raw material of the polycarbodiimide of the present invention, can be prepared by forming isocyanates by various known methods from the corresponding diamines represented by the formula (III), the precursors of which:

In the above formula,

R is the same as above.

As an isocyanation method of such a diamine compound, the method of making phosgene, diphenyl carbonate, or carbonyl diimidazole be made to act. Alternatively, it is possible to convert the diamine compound into urethane once using a halogenated alkylformate and isocyanate it in the presence of a catalyst such as chlorosilane, catecholborane and the like.

Alternatively, as a precursor of the diisocyanate, a carboxylic acid represented by the formula (IV) may be used, and a method of isocyanate by Curtis decomposition may be used:

In the above formula,

R is the same as above.

Among these production methods, the diamine compound is first synthesized into urethane using halogenated alkylformate or halogenated arylformate and isocyanated using chlorosilane as a catalyst [G Greber, et. al., Angew, Chem. Int. Ed., Vol. 17, No. 12, 941 (1968)], or a method of isocyanate using catecholborane [V.L.K. Valli, et. al., J. 0rg. Chem., Vol. 60, 257 (1995) are preferred in terms of yield and safety, and are described in detail below.

Urethane synthetic

First, urethane is synthesized by reacting a corresponding diamine compound of formula III with methylchloroformate, ethylchloroformate, phenylchloroformate, p-nitrochloroformate and the like. As a diamine compound which can be used as a raw material, Specifically, 2, 2-bis (4-aminophenyl) hexafluoro propane represented by general formula (IIIa), or 2, 2-bis (3-amino-4- methylphenyl represented by general formula (IIIb). Hexafluoropropane and the like.

In addition, phenylchloroformate or p-nitrophenylchloroformate is suitable for smoothly proceeding isocyanation, but p-nitrophenylchloroformate has high activity and may cause a lot of side reactions. Formate is most preferred. The amount of these chloroformates used is preferably 1.5 to 4.0 mole times, preferably 1.6 to 3.8 mole times, and optimally 1.8 to 3.6 mole times the number of moles of diamine.

The solvent used for these reactions may dissolve diamine. For example, ether compounds, such as THF, dioxane, and diethyl ether, aromatic hydrocarbon compounds, such as toluene, xylene, and benzene, ketone compounds, such as acetone and methyl ethyl ketone, ester compounds, such as ethyl acetate, etc. are mentioned. Can be. These solvents may be used alone or in combination of two or more thereof.

The reaction temperature is -40 to 100 ° C, preferably -20 to 80 ° C, most preferably 0 to 60 ° C. If it is less than -40 degreeC, reaction will hardly progress, and there exists a possibility that side reactions, such as condensation, may occur at high temperature 100 degreeC or more.

The base for trapping the hydrogen chloride produced by the reaction may be dissolved in the solvent used but may not inhibit the reaction. Examples thereof include triethylamine, sodium hydroxide, pyridine, diazabicycloundecene (DBU), and the like. Can be mentioned. The amount of the base used is 1.5 to 4.0 times the molar number of the diamine used, preferably 1.8 to 3.5 times.

In order to refine | purify the obtained urethane, it is possible to use conventionally well-known methods, such as recrystallization and a column. Moreover, you may distill as needed.

(a) Isocyanation with Chlorosilane

In order to isocyanate the urethane with chlorosilane, pyrolysis is carried out using 1.5 to 4.6 times of molar amount of urethane, preferably 1.6 to 4.0 times, most preferably 1.8 to 3.5 times of chlorosilane as a catalyst. .

As the chlorosilanes, trimethylchlorosilane, triethylchlorosilane, trimethoxychlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane and the like are used. Among them, however, trimethylchlorosilane is suitable in view of ease of handling and price.

It is preferable that the solvent used can melt | dissolve or suspend urethane, and the said ether type compound, an aromatic hydrocarbon, and a halogenated hydrocarbon are mentioned as an example. These solvents may be used alone or in combination. In some cases, it is also possible to change the reaction temperature by substituting part or all of the solvent with another solvent during the reaction.

The reaction temperature is from boiling point to the boiling point of the solvent used, preferably from room temperature to the boiling point. When reaction temperature is too low, reaction may not progress at all. On the contrary, when the reaction temperature is excessively raised or heated for too long, the product may be decomposed. Therefore, it is advisable to gradually raise the temperature and proceed while tracking the reaction with IR or the like.

As a base which traps hydrogen chloride produced at the time of reaction, the same thing as what was used for the said urethane manufacture is used, and its usage is also the same.

(b) Isocyanation with Halogenated Catecholborane

In the isocyanation of urethane, the method which used the halogenated catechol borane as a catalyst instead of the said chlorosilane can be applied. Examples of the halogenated catecholborane include chlorocatecholborane and bromocatecholborane, but chlorocatecholborane is preferred from the viewpoint of ease of handling and price. In addition, the usage-amount is the same as that of the said chlorosilane. Since catecholboranes have higher activity against pyrolysis of urethanes than chlorosilanes, urethanes other than phenylurethanes can also be used.

The reaction solvent may be any one capable of dissolving or suspending urethane, and may be the same as isocyanate using the chlorosilane. These solvents may be used alone or in combination of two or more thereof. In some cases, it is also possible to change the reaction temperature by substituting part or all of the solvent with another solvent during the reaction.

The reaction temperature is generally -50 to 80 ° C, preferably -20 to 60 ° C, more preferably 0 to 40 ° C, depending on the urethane used. When reaction temperature is too low, reaction may not progress at all. On the contrary, if the reaction temperature is excessively raised or heated for too long, the product may decompose. Therefore, it is advisable to gradually raise the temperature and proceed while tracking the reaction with IR or the like. In order to trap the hydrogen chloride produced at the time of reaction, a base is used similarly to the above.

After the reaction, the diisocyanate monomer obtained can be purified by removing the solvent and performing a flash column or recrystallization or distillation under reduced pressure.

Preparation of Polycarbodiimide

In order to prepare polycarbodiimide using the diisocyanate, other organic diisocyanates such as 4,4 are used within the range of not using the diisocyanate monomer alone or impairing its properties, that is, 50 mol% or less. '-Diphenylmethane diisocyanate, 2,6-torylene diisocyanate, 2,4-torylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, 3,3'-dimethoxy-4,4'- You may copolymerize with diphenylmethane diisocyanate, 4.4'- diphenyl ether diisocyanate, 3.3'- dimethyl- 4,4'- diphenyl ether diisocyanate, o- toylene diisocyanate.

40-150 degreeC is preferable and 50-140 degreeC of polymerization temperature is more preferable. When reaction temperature is lower than 40 degreeC, reaction time becomes too long and it is not practical. Moreover, when it exceeds 150 degreeC, selection of the solvent which can be used at reaction temperature is difficult.

The concentration of diisocyanate in the polycarbodiimide synthesis is 2 to 50% by weight (hereinafter referred to as%), preferably 5 to 45%, most preferably 15 to 40%. If the concentration is lower than 2%, carbodiimidization may not proceed. If it exceeds 60%, the reaction may be difficult to control.

The organic solvent used at the time of synthesis | combination of a polycarbodiimide and in a polycarbodiimide solution may be a conventionally well-known thing in such reaction. Specifically, halogenated hydrocarbons such as tetrachloroethylene, 1,2-dichloroethane and chloroform, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, cyclic ethers such as tetrahydrofuran and dioxane And aromatic hydrocarbon solvents such as toluene, xylene, and benzene. These may be used independently, or may mix and use 2 or more types. In addition, one part or all part may be substituted by the other solvent in the middle of reaction.

As a catalyst used for carbodiimidation, any well-known phosphorus catalyst is used suitably, For example, 1-phenyl- 2-phosphole 1-oxide and 3-methyl- 2-force Force such as pollen-1-oxide, 1-ethyl-2-phosphole-1-1-oxide, 3-methyl-1-phenyl-2-phosphole-1-1-oxide, or these 3-phosphole isomers And phospho oxides.

In addition, you may perform terminal blocking treatment by adding a monoisocyanate in all the terminal, middle, and initial stages of a polymerization reaction, or the whole. As such monoisocyanate, any of aromatic monosocyanates of phenyl isocyanate, p-nitrophenyl isocyanate, p- or m-tolyl isocyanate, p-formylphenyl isocyanate and p-isopropylphenyl isocyanate can be used. The polycarbodiimide solution thus obtained is excellent in the storage stability of the solution.

After completion of the reaction, the reaction solution may be added to a poor solvent such as methanol, ethanol, isopropylene alcohol, or hexane to precipitate polycarbodiimide as a precipitate to remove unreacted monomers and catalysts. . By performing such an operation, the solution stability of the polycarbodiimide can be improved.

In order to prepare a solution of polycarbodiimide, the polymer is precipitated as a precipitate, and then the precipitate is recovered by a predetermined operation, washed and dried, and dissolved in an organic solvent again.

Moreover, you may refine | purify by adsorbing the adduct contained in a polymer solution etc. by an adsorbent. As the adsorbent, for example, alumina gel, silica gel, activated carbon, zeolite, activated magnesium oxide, activated bauxite, clay, activated clay, molecular sieve carbon and the like can be used alone or in combination.

The molecular weight of the polycarbodiimide of this invention is a number average molecular weight 1,000-200,000, Preferably it is 2,000-10,000. That is, in the formula (I), n is an integer of 3 to 600, preferably an integer of 6 to 300. If the molecular weight of polycarbodiimide is too high than this, since it gelatinizes easily even if it stays at normal temperature in several minutes-several hours, it is not practically preferable. Moreover, when molecular weight is too low, since the reliability with respect to the film is insufficient, it is unpreferable.

Preparation of Films and Adhesive Sheets

The polycarbodiimide film (or sheet) of the present invention is obtained by forming a polycarbodiimide and a varnish into an appropriate thickness using a known method (casting, spin coating, roll coating, etc.). This film may be dried at the temperature normally required for removing the solvent, and can be dried at, for example, 30 to 300 ° C. In particular, in order to dry without hardening reaction too much, 50-250 degreeC is preferable. If the drying temperature is lower than 30 ° C, the solvent remains in the film, and the reliability of the film is insufficient, which is not preferable. Moreover, when drying temperature is higher than 300 degreeC, crosslinking of a polycarbodiimide resin may advance and it may become practically inadequate from a viewpoint of strength, etc., and is unpreferable.

A fine inorganic filler may be mix | blended with the polycarbodiimide resin composition of this invention in the range which does not impair the workability and heat resistance. Moreover, in order to obtain surface smoothness, you may add various additives, such as a leveling agent, a leveling agent, and a defoaming agent, as needed.

The molded article shape | molded the polymer of this invention in the film form can be used as a heat resistant adhesive sheet. As sheet thickness which can be shape | molded by a film or an adhesive sheet, although it is 1-2000 micrometers in general, it is not limited to this and can select suitably according to the objective. The shape and size of the sheet can also be appropriately selected depending on the adherend such as a lead frame or a semiconductor chip.

In the case of manufacturing the adhesive sheet, for example, aluminum, copper, silver, gold, nickel, chromium, lead, tin, zinc, palladium, in order to provide conductivity, improve heat transfer properties, control elastic modulus, and particularly high elastic modulus. You may mix | blend 1 type, or 2 or more types of various inorganic powders which consist of metals, such as a solder, or ceramics, such as an alloy, alumina, silica, magnesia, and silicon nitride, other carbon, etc. as needed.

Moreover, these films may be formed on a support body and may be a multilayer adhesive sheet. In order to manufacture the adhesive sheet of such a structure, a varnish may be apply | coated on a support body, a film may be formed previously, and this may be manufactured by laminating by press etc.

As a support body used here, metal foil, an insulating film, etc. are mentioned. As metal foil, any of aluminum, copper, silver, gold, nickel, indium, chromium, lead, tin, zinc, palladium, etc. can be used, You may use these independently or as an alloy. Moreover, as an insulating film, you may use any film as long as it is a film which has heat resistance and chemical-resistance, such as a polyimide, polyester, and a polyethylene terephthalate.

The metal foil and the insulating film may be used alone or as two-layer base materials such as a metal foil / insulating film in which two or more layers are laminated, for example. As such a two-layer base material, a copper / polyimide two-layer base material etc. are mentioned, for example.

The sheet-like adhesive of the present invention is thermally cured by heat treatment to express a firm adhesive force and to become a low hygroscopic cured product. In order to perform the heat treatment, a suitable method such as a heater, an ultrasonic wave, a high frequency wave, or an ultraviolet ray may be used, for example. Therefore, the adhesive sheet of this invention is suitable for the adhesion | attachment process of various materials, and especially the highly reliable fixing process is requested | required, for this reason, electrical and electronics represented by a semiconductor chip, a lead frame, etc. which require low hygroscopicity, etc. It is suitable for the fixing process of parts. The adhesive sheet of the present invention is excellent in view of low hygroscopicity, abundance of flexibility and ease of handling, good adhesion to semiconductor elements, and good storage stability.

In addition, the urethanation, isocyanation, and carbodiimide-ization of said diamine may be isolated and refine | purified in each process, and may be advanced in stages, and these processes are continued as a series of reactions in one reactor, Also good.

In the following, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, the characteristic of the obtained polycarbodiimide was measured as follows.

Molecular Weight

Using HLC8020 (manufactured by Tosoh), THF is measured as a developing solvent and calculated in terms of polystyrene standard.

IR

It is measured using FT / IR-230 (manufactured by Nippon Denshi).

Thermosetting temperature

The exothermic peak of trimerization is made into thermosetting temperature by measuring using DSC-200 (manufactured by Seiko-Denshi Co., Ltd.).

Glass transition point (Tg)

It measures by heating up to 400 degreeC at room temperature from 10 degreeC / min using TMA / SS100 (manufactured by Seiko-Denshi Co., Ltd.).

Pyrolysis Initiation Temperature (Td)

It measured using TG / DTA300 (manufactured by Seiko-Denshi Co., Ltd.).

Example 1

To a three-necked flask (300 mL) is introduced 5.0 g (15.0 mmol) of 2,2-bis (4-aminophenyl) hexafluoropropane, 120 mL of dichloromethane and 3.0 g (30.0 mmol) of triethylamine. The flask is ice cooled and 4.7 g (30.0 mmol) of phenylchloroformate are added under nitrogen gas. After stirring for 15 minutes, the reaction system is returned to room temperature and stirred overnight.

At room temperature, 3.0 g (30.0 mmol) of triethylamine, followed by 3.3 g (30.0 mmol) of trimethylchlorosilane, are stirred for 45 minutes. 100 mL of toluene was added and stirred for 5.5 hours while slowly raising the reaction temperature to 80 ° C. In the meantime, most of dichloromethane is distilled off. The triethylamine hydrochloride produced according to the reaction was filtered off, and then 540 mg (2.8 mmol) of a carbodiimide catalyzed catalyst (3-methyl-1-phenyl-2-phosphole-1-oxide) was added to the mixture at 80 ° C. Stir for time. After confirming carbodiimidation by IR (FIG. 1), the polymer solution was added to 3 L of hexane, and the precipitated solid was collected and dried at 30 ° C. under reduced pressure for 12 hours, yielding 89% of a polymer having Mn = 2,400. Obtained as

This polymer was redissolved in cyclohexanone, cast with 35 micrometers copper foil, and dried at 200 degreeC for 20 minutes, and the adhesive sheet was created. The copper foil of the sheet was etched with an aqueous solution of iron chloride to obtain a film having a thickness of 20 µm, a thermal curing temperature of 400 ° C or higher, Tg = 220 ° C, and Td = 490 ° C. The film also appears to have flexibility even when dried at 200 ° C. for 60 minutes.

Example 2

The copper / polycarbodiimide adhesive sheet obtained in Example 1 is affixed to a 42 alloy plate, and it presses for 1 second at 350 degreeC and the pressure of 50 kg / cm <2>, and attaches it to one. The adhesive force was measured, indicating an adhesive force of 1200 g / cm. After 168 hours of incorporation in a constant temperature and humidity chamber at 80 ° C./90% RH, the adhesive strength was 1000 g / cm.

Example 3

To a three-necked flask (300 mL), 5.0 g (13.7 mmol) of 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 100 mL of toluene and 2.8 g (27.5 mmol) of triethylamine are introduced. The flask is ice cooled and 4.3 g (27.5 mmol) of phenylchloroformate are added under nitrogen gas. After stirring for 30 minutes, the reaction system is returned to room temperature and stirred for one day.

2.8 g (27.5 mmol) of triethylamine, followed by 3.0 g (27.5 mmol) of trimethylchlorosilane at room temperature are added to the flask and stirred for 1 hour. Stirred for 5 hours while slowly raising the reaction temperature to 80 ℃. Subsequently, 500 mg (2.6 mmol) of a carbodiimide catalyst (3-methyl-1-phenyl-2-phosphole-1-1-oxide) were added and stirred at 80 ° C. for 2 hours. After confirming carbodiimidation by IR (FIG. 2), the resulting triethylamine hydrochloride is removed by filtration. Subsequently, the polymer solution was poured into 4 L of hexane, and the precipitated solid was collected and dried at 30 ° C. for 12 hours under reduced pressure to give a polymer of Mn = 4,600 in a yield of 70%.

This polymer is redissolved in toluene, cast with 35 µm copper foil, dried at 200 ° C. for 20 minutes to form an adhesive sheet. The copper foil of the sheet was etched with an aqueous solution of iron chloride to obtain a film having a thickness of 17 µm, a thermal curing temperature of 400 ° C or higher, Tg = 160 ° C, and Td = 460 ° C. The film also appears to have flexibility even when dried at 200 ° C. for 60 minutes.

Example 4

The copper / polycarbodiimide adhesive sheet obtained in Example 3 is affixed on a 42 alloy plate, and it presses at 350 degreeC and the pressure of 50 kg / cm <2> for 1 second, and sticks it together. Adhesion was measured to show an adhesion of 980 g / cm. The adhesion after 168 hours of application at 80 ° C./90% RH in a thermo-hygrostat is 860 g / cm.

Comparative Example 1

The polymerization was carried out in the same manner as in Example 1 and Example 3 except that TDI was used as the monomer. That is, in an eggplant flask (100 mL), 5.0 g (29 mmol) of TDI, 25 mL of THF and a carbodiimidation catalyst (3-methyl-1-phenyl-2-phosphole-1-1-oxide) 43.0 mg (0.22 mmol) is introduced. Stirring at 60 ° C. for 15 hours yields a polycarbodiimide solution with Mn = 6,700. The varnish is cast on a glass plate and dried at 90 ° C. for 30 minutes to form a film. The heat curing temperature of the film is discolored when the heat treatment is performed at 350 ° C. for 1 hour at 200 ° C., and the flexibility is lost and self-maintainability is lost.

Comparative Example 2

The varnish created in the comparative example 1 was apply | coated on 35 micrometer copper foil, and it dried at 90 degreeC for 30 minutes, and created the adhesive sheet. Using this, the adhesive force was measured in the same manner as in Example 2, but initially exhibited an adhesive force of 600 g / cm, but was peeled off after 168 hours in a constant temperature and humidity chamber at 80 ° C / 90% RH.

The resin composition of this invention is easy to melt | dissolve in a general organic solvent, and shaping | molding process is easy. Moreover, a glass transition point is low and low temperature workability improves. Moreover, adhesiveness is good with adherends, such as a semiconductor element, it is low hygroscopicity, is excellent in storage stability, and long-term storage at normal temperature is possible. Moreover, also when it heat-processes at 200 degreeC or more, it is excellent also in heat resistance, such as having flexibility. In addition, in the case of the polymer in which the polymer chain is bonded at the m- position, the glass transition point is lower and the low temperature workability is improved.

Claims (5)

Aromatic polycarbodiimide which has a structural unit represented by general formula (I). Formula I In the above formula, R is hydrogen or an alkyl group, n represents an integer of 3 to 600. The aromatic polycarbodiimide of Claim 1 which has a structural unit represented by general formula (Ia) or general formula (Ib). Formula Ia Formula Ib In the above formula, n represents an integer of 3 to 600. A polycarbodiimide solution comprising the aromatic polycarbodiimide of claim 1 dissolved in an organic solvent. A polycarbodiimide film comprising the aromatic polycarbodiimide of claim 1. The polycarbodiimide adhesive sheet containing the aromatic polycarbodiimide of Claim 1.