KR100505906B1 - Aromatic polycarbodiimide, and films, solutions and adhesive sheets thereof - Google Patents

Abstract

The present invention provides an aromatic polycarbodiimide having a structural unit represented by the formula (I) which has excellent solubility and heat resistance and is also excellent in adhesiveness, low temperature processing and moisture resistance.

Formula I

In the above formula,

R represents hydrogen or an alkyl group,

n represents an integer of 3 to 600.

Description

Aromatic polycarbodiimides, and films, solutions, and adhesive sheets thereof

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.

As a typical aromatic polycarbodiimide, it is known to polymerize this using diphenylmethane diisocyanate (MDI) or tolylene diisocyanate (TDI) 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 a high temperature of 400 ° C. or higher. However, heat treatment at 200 ° C. or higher results in loss of self-maintenance and brittleness. . 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.

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 the 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):

[Formula I]

In the above formula,

R is hydrogen or an alkyl group (1 to 5 carbon atoms, preferably 1 to 3 carbon atoms),

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.

Best Mode for Carrying Out the Invention

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:

[Formula II]

Typical examples of such diisocyanate include those represented by the formulas (IIa) and (IIb).

[Formula IIa]

Formula IIb]

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 a document relating to the preparation method thereof and a method for producing a 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:

[Formula III]

In the above formula,

R is the same as above.

As a method of isocyanate of such a diamine compound, the method of making phosgene, diphenyl carbonate, or carbonyl diimidazole react is mentioned. As another method, it is also possible to convert the diamine compound into a urethane once using a halogenated alkylformate and to isocyanate it in the presence of a catalyst such as chlorosilane, catechol borane and the like.

As another method, as a precursor of diisocyanate, a carboxylic acid represented by the formula (IV) can be used, and a method of isocyanate by Curtius decomposition can be used.

[Formula IV]

In the above formula,

R is the same as above.

In these production methods, the diamine compound is synthesized once 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 catechol borane [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.

[Formula IIIa]

[Formula IIIb]

In addition, phenylchloroformate or p-nitrophenyl chloroformate is suitable to facilitate isocyanation, but p-nitrophenyl chloroformate has high activity and may cause a lot of side reactions. Mate 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 type compounds, such as THF, dioxane, diethyl ether, aromatic hydrocarbon type compounds, such as toluene, xylene, benzene, ketone type compounds, such as acetone and methyl ethyl ketone, and ester type 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 be any solvent that does not inhibit the reaction. For example, 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, distillation can also be performed as needed.

(a) Isocyanation with Chlorosilane

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

As the chlorosilanes, trimethyl chlorosilane, triethyl chlorosilane, trimethoxychlorosilane, dimethyl dichlorosilane, methyl trichlorosilane, 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, aromatic hydrocarbon, and 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 0 ° C. to the boiling point of the solvent used, preferably from room temperature to 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 preferable to gradually raise the temperature and proceed while tracking the reaction with IR or the like.

As a base to trap the hydrogen chloride produced at the time of reaction, the same base 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 catechol borane include chlorocatechol borane, bromocatechol borane and the like, but from the viewpoint of ease of handling and price, chlorocatechol borane is preferable. In addition, the usage-amount is the same as that of the said chlorosilane. Since catechol boranes have higher activity against pyrolysis of urethanes than chlorosilanes, urethanes other than phenylurethanes can also be used.

It is preferable that a reaction solvent can melt | dissolve or suspend urethane, and the same solvent as isocyanation using the said chlorosilane can be used. 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 preferable 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-tolylene diisocyanate, 2,4-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, 3,3'-dimethoxy-4,4 Copolymerized with '-diphenylmethane diisocyanate, 4.4'-diphenyl ether diisocyanate, 3.3'-dimethyl-4,4'-diphenyl ether diisocyanate, o-tolylene diisocyanate and the like.

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 in the synthesis of polycarbodiimide and in the polycarbodiimide solution may be a conventionally known one in such a reaction. Specifically, halogenated hydrocarbons such as tetrachloroethylene, 1,2-dichloroethane, chloroform, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclic ethers such as tetrahydrofuran and dioxane And aromatic hydrocarbon solvents such as toluene, xylene, and benzene. These may be used alone or in combination of two or more thereof. In addition, some or all of them may be substituted with other solvents during the reaction.

As a catalyst used for carbodiimidation, any well-known phosphorus catalyst is used suitably, For example, 1-phenyl- 2-phosphorene- 1-oxide, 3-methyl- 2- Phosphorene-1-oxide, 1-ethyl-2-phosphorene-1-oxide, 3-methyl-1-phenyl-2-phosphorene-1-oxide, or 3-phosphorene isomers thereof Phosphorene oxide.

In addition, the terminal blocking process can be performed by adding 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, isopropyl alcohol, hexane, and the like 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.

In addition, by-products contained in the polymer solution can be adsorbed on an adsorbent or the like to be purified. 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 can be dried at the temperature normally required for removal of a solvent, for example, can be dried at 30-300 degreeC. 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.

You may mix | blend a fine inorganic filler with the polycarbodiimide resin composition of this invention in the range which does not impair workability and heat resistance. In addition, various additives such as a leveling agent, a leveling agent, and an antifoaming agent may be added as necessary in order to obtain surface smoothness.

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, According to the objective, it can select suitably. 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. And various inorganic powders made of a metal such as solder or an alloy, ceramic such as alumina, silica, magnesia, silicon nitride, other carbon, and the like can be blended one or two or more as necessary.

In addition, these films can be formed on the support and formed into a multilayer adhesive sheet. In order to manufacture the adhesive sheet of such a structure, a varnish can be apply | coated on a support body, or a film can be previously formed and it can be manufactured by lamination | molding 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, and these can be used individually or as an alloy. As the insulating film, any film can be used as long as it is a film having polyimide, polyester, polyethylene terephthalate, that is, heat resistance or chemical resistance.

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 heat cured by heat treatment to develop a firm adhesive force, and at the same time becomes 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 carbodiimidation of the diamine can be carried out in stages by performing isolation and purification in each step, or they can be carried out as a series of reactions by continuing these steps in one reactor. May

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 is 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 from room temperature to 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

Into a three neck 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, and then 3.3 g (30.0 mmol) of trimethylchlorosilane are placed in a flask and stirred for 45 minutes. 100 mL of toluene was added and stirred for 5.5 hours while gradually 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 carbodiimide catalyzed catalyst (3-methyl-1-phenyl-2-phosphorene-1-oxide) was added thereto, and the mixture was heated at 80 ° C. for 3 hours. Stir. 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 is redissolved in cyclohexanone, cast into 35 micrometers copper foil, and dried at 200 degreeC for 20 minutes, and an adhesive sheet is manufactured. 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 if 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 a pressure of 50 kg / cm <2> at 350 degreeC, and attaches it to one. As a result of measuring the adhesive force, the adhesive force of 1200 g / cm is shown. The adhesion after 1000 hours in a constant temperature and humidity chamber of 80 ℃ / 90% RH is 1000g / ㎝.

Example 3

Into a three-neck 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 were 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, then 3.0 g (27.5 mmol) of trimethylchlorosilane are added to the flask at room temperature and stirred for 1 hour. Stirred for 5 hours while slowly raising the reaction temperature to 80 ℃. Subsequently, 500 mg (2.6 mmol) of carbodiimide catalyst (3-methyl-1-phenyl-2-phosphorene-1-oxide) were added, and it stirred at 80 degreeC 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 into a 35 μm copper foil, and dried at 200 ° C. for 20 minutes to prepare 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 if 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 with the pressure of 50 kg / cm <2> for 1 second, and attaches it to one. As a result of measuring the adhesive force, it showed an adhesive force of 980 g / cm. The adhesion after 168 hours in 80 ° C / 90% RH constant temperature and humidity chamber is 860g / cm.

Comparative Example 1

The polymerization was carried out in the same order as in Examples 1 and 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 43.0 mg of a carbodiimidation catalyst (3-methyl-1-phenyl-2-phosphorene-1-oxide) ( 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 produce a film. The film has a heat curing temperature of 350 ° C. and undergoes heat treatment at 200 ° C. for 1 hour to discolor, lose flexibility, and lose self-maintainability.

Comparative Example 2

The varnish prepared in Comparative Example 1 was applied onto a 35 μm copper foil, and dried at 90 ° C. for 30 minutes to prepare an adhesive sheet. As a result of measuring the adhesive force using this in the same manner as in Example 2, the initial stage showed 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 processability is improved.

Claims (5)

Aromatic polycarbodiimide, characterized by having the structural unit of 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 having a structural unit of formula (Ia) or 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 according to claim 1 dissolved in an organic solvent. Polycarbodiimide film comprising the aromatic polycarbodiimide according to claim 1. Polycarbodiimide adhesive sheet containing the aromatic polycarbodiimide according to claim 1.