JP3211704B2 - Aromatic polycarbodiimide and film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to novel aromatic polycarbodiimides. The aromatic polycarbodiimide of the present invention is a film or adhesive having various excellent properties such as high heat resistance,
Give moldings.

[0002] As the aromatic polycarbodiimide, those obtained by polymerizing diphenylmethane diisocyanate (MDI) or tolylene diisocyanate (TDI) as a monomer have been known. Such polycarbodiimides are used as flame-resistant films and heat-resistant adhesives due to their excellent heat resistance.

[0003]

However, the polycarbodiimides obtained from TDI and MDI have poor solubility, and as the molecular weight increases, they gel or precipitate as solids to obtain a sufficiently high molecular weight polymer. I can't. In addition, these polycarbodiimides have heat resistance in that they do not generate volatile gas or decomposed monomers even when exposed to a high temperature of 400 ° C. or higher, but have no self-holding property when heat-treated at 200 ° C. or higher, and become brittle and practical. I can't stand it. In addition, moisture resistance is low at high temperatures and high pressures, and the adhesive strength when heat-pressed to an adherend such as copper foil is not sufficient.

[0004] The present inventors have repeatedly studied various aromatic polymers in order to solve such disadvantages of the conventional polycarbodiimides, and as a result, have found the novel polymers of the present invention. That is, the present invention relates to an aromatic polycarbodiimide having a structural unit represented by the following general formula (I).

[0005]

Embedded image (In the formula, n represents an integer of 2 to 400.)

This polymer has very high heat resistance with excellent solubility, and also has excellent adhesiveness, low temperature processability and moisture resistance.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The polycarbodiimides of the present invention
Using the corresponding diisocyanate of the following formula (II) as a monomer,
It can be obtained by polymerizing this in a known manner in the presence of a phosphorus-based catalyst.

[0008]

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The diisocyanate monomer may be used alone, and other organic diisocyanates, for example, 4,4'-diphenylmethane diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, as long as their properties are not lost. 1-methoxyphenyl-2,4-diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, o -It may be copolymerized with tolylene diisocyanate.

[0010] The reaction temperature during the polymerization is preferably from 40 to 150 ° C, more preferably from 50 to 140 ° C. Reaction temperature 40
If the temperature is lower than ℃, the reaction time becomes too long and is not practical. If the reaction temperature exceeds 150 ° C., it is difficult to select a solvent.

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

The organic solvent used in the synthesis of the polycarbodiimide and for the polycarbodiimide solution may be a conventionally known organic solvent. Specifically, tetrachloroethylene,
Halogenated hydrocarbons such as 1,2-dichloroethane and chloroform; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone;
Examples include cyclic ether solvents 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.

The catalyst used for the carbodiimidization includes:
Any known phosphorus-based catalyst is suitably used.
-Phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-
Phosphorene oxides such as phosphorene-1-oxide, 3-methyl-1-phenylphospholene-1-oxide, and 3-phospholene isomers thereof are exemplified.

The terminal blocking treatment may be carried out by adding a monoisocyanate at any of the last stage, the middle stage, the initial stage or the whole of the polymerization reaction. As such a monoisocyanate, phenyl isocyanate, p-nitrophenyl isocyanate, p- or m-tolyl isocyanate, p-formylphenyl isocyanate and the like can be used. The polycarbodiimide solution thus obtained is excellent in storage stability of the solution.

After completion of the reaction, the reaction solution may be poured into a poor solvent such as methanol, ethanol or hexane to precipitate polycarbodiimide as a precipitate, thereby removing unreacted monomers or catalyst. By performing such an operation, the solution stability of the polycarbodiimide can be improved.

The molecular weight of the polycarbodiimide of the present invention is
1,000 to 200,000 in number average molecular weight, preferably 4,000
~ 100,000. That is, in the formula (I), n is 2 to
It is an integer of 400, preferably 7 to 200. If the molecular weight of the polycarbodiimide is too high, it will easily gel in a few minutes to a few hours even at room temperature,
Not practically preferable. On the other hand, if the molecular weight is too low, the reliability of the film will be poor, which is not preferable.

After precipitation as a precipitate, washing and drying are performed by a predetermined operation, and the polycarbodiimide is dissolved in an organic solvent again to obtain a polycarbodiimide solution. Further, the by-products contained in the polymer solution may be adsorbed on a suitable adsorbent or the like and purified. As the adsorbent, for example, alumina gel, silica gel, activated carbon, zeolite, activated magnesium oxide, activated bauxite, flour earth, activated clay, molecular sieve carbon, or the like can be used alone or in combination.

The polycarbodiimide resin composition of the present invention may contain a fine inorganic filler as long as its processability and heat resistance are not impaired. Various additives such as a smoothing agent, a leveling agent, and a defoaming agent for improving surface smoothness may be added as necessary.

(Production of Film and Adhesive Sheet) In order to produce the polycarbodiimide film (or sheet) of the present invention, a polycarbodiimide varnish is formed by a known method (casting, spin coating, roll coating, etc.). be able to. This film is
Usually, drying may be performed at a temperature necessary for removing the solvent, for example, drying at 30 to 300 ° C. To dry so that the curing reaction of the polycarbodiimide resin does not proceed so much, it is desirable to dry at 50 to 250 ° C. If the drying temperature is too low, the reliability of the film becomes poor, which is not preferable. On the other hand, if the drying temperature is higher than the above range, the crosslinking of the polycarbodiimide resin proceeds, and when the film is stretched, breakage or poor stretching tends to occur, which is not preferable.

The thickness of a sheet that can be formed into a film or an adhesive sheet is generally from 1 to 200 μm, but is not limited thereto and can be appropriately selected according to the purpose. Also, the shape and size of the sheet can be appropriately selected according to the adherend such as a lead frame and a semiconductor chip.

When an adhesive sheet is manufactured, for example, aluminum, copper, silver, gold, nickel, chromium, lead, and the like are used in order to impart conductivity, improve heat conductivity, adjust elastic modulus, and particularly increase elastic modulus. Metals such as tin, zinc, palladium and solder, or alloys, ceramics such as alumina, silica, magnesia and silicon nitride, and various other inorganic powders composed of carbon and the like may be blended, if necessary, in one or more kinds. .

Further, these films may be formed on a support to form an adhesive sheet. In order to manufacture the adhesive sheet having such a configuration, a varnish may be coated on the support, or a film may be formed in advance and the film may be laminated by pressing or the like.

Examples of the support used here include a metal foil and an insulating film. As the metal foil, any of aluminum, copper, silver, gold, nickel, indium, chromium, lead, tin, zinc, palladium and the like may be used, and these may be used alone or as an alloy. As the insulating film, any film having heat resistance and chemical resistance, such as polyimide, polyester, and polyethylene terephthalate, may be used.

Further, the metal foil and the insulating film may be used alone, or a two-layer base material such as a metal foil / insulating film obtained by laminating two or more layers thereof may be used. Examples of such a two-layer substrate include a copper / polyimide two-layer substrate.

[0025] The sheet adhesive of the present invention is thermally cured by heat treatment to exhibit a strong adhesive force, and becomes a cured product having low moisture absorption. In order to perform the heat treatment, for example, an appropriate method such as a heater, ultrasonic waves, or ultraviolet rays may be used. Therefore, the adhesive sheet of the present invention is preferable for the bonding treatment of various materials, and in particular, is required to have a highly reliable fixing treatment, and is therefore required to have low moisture absorption. It is preferable for fixing parts. The adhesive sheet of the present invention is excellent in that it has low moisture absorption, is flexible and easy to handle, has good adhesiveness to semiconductor elements, and has good storage stability. The resin composition of the present invention is used as a varnish, and the varnish is applied to one surface of the metal foil, and the dried metal foil with an adhesive layer is particularly useful for manufacturing a multilayer circuit board and the like.

The stretched film of the polycarbodiimide of the present invention may have various shapes such as a sheet shape and a tube shape. For example, what is formed into a film is obtained by stretching the film obtained by the above method under predetermined conditions in one direction (main axis direction) by 1.2 to 10 times, preferably 2 to 6 times. . Further, if desired,
The film can be stretched 1 to 5 times, preferably 1.1 to 1.6 times in the direction perpendicular to the stretching direction (main axis direction). The above stretching may be performed in any direction. By stretching in the direction perpendicular to the main axis direction in this manner, the stretched film has improved impact resistance and alleviates the property of being easily torn in one direction. When the stretching ratio in the direction orthogonal to the stretching direction (main axis direction) exceeds 5 times, the heat shrinkage in the direction orthogonal to the main axis direction becomes too large, and the finish after the heat shrinking treatment does not have wavy. Uniformity is not preferred.

The stretching temperature is set to a value in the range of 40 to 40 so that the curing reaction of the polycarbodiimide resin does not proceed so much and the drying is carried out.
Preferably, the temperature is 200 ° C. If the stretching temperature is lower than 40 ° C., a sufficient stretching ratio cannot be obtained, and the film is easily broken. On the other hand, when the temperature exceeds 200 ° C., the curing reaction of the polycarbodiimide resin partially proceeds, so that the heat recovery performance tends to decrease.

The stretching method is not particularly limited, and any known methods such as a roll stretching method, a long gap stretching method, a tenter stretching method and a tubular stretching method may be employed.

(Applications) The stretched polycarbodiimide film thus produced is used as a heat-resistant coating material for various articles. In order to coat an article using a stretched film, for example, after covering an adherend (article) to be protected using a heat-shrinkable film made of a molding material containing a polycarbodiimide resin as a main component, followed by heat treatment The film is cured. By this heat treatment, the curing reaction of the polycarbodiimide proceeds, the polycarbodiimide resin flows into the uneven portion on the surface of the adherend, and an anchor (anchoring) effect is generated, and the cumulative multiple bond between the polar group on the surface of the adherend and the polycarbodiimide resin is generated. Action such as a chemical reaction with
Chemical and physical bonding is achieved.

The above-mentioned adherend is not particularly limited, and examples thereof include glass, metal, resin, ceramic sheets and plates, and annular materials. Specific products include electric wires such as power cables, glass bottles, and electronic components.

(Monomer) The isocyanate compound represented by the above formula (II), which is an isocyanate monomer of the polycarbodiimide of the present invention, is a novel aromatic diisocyanate, and its production method will be described. In order to produce this diisocyanate compound, the amino precursor of the diisocyanate compound can be produced by isocyanation by a method known per se. As such a precursor, a known diamine compound represented by the following formula (III) can be used.

[0032]

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As a method for converting such a diamine compound into isocyanate, there is a method in which phosgene, diphenyl carbonate, or carbonyldiimidazole is allowed to act. Alternatively, urethane may be temporarily formed from a diamine compound by using a halogenated alkylformate, and this may be isocyanated in the presence of a catalyst such as chlorosilane or catecholborane. Further, in another method, a method in which a carboxylic acid represented by the following formula (IV) is used as a diisocyanate precursor and is converted to isocyanate by Curtius decomposition may be used. In addition, it is preferable to use a diamine from the viewpoint of easy availability of raw materials.

[0034]

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Among these production methods, a method is described in which a diamine compound is once converted to urethane using an alkyl halide or aryl halide and then isocyanated using chlorosilane as a catalyst.
(G.Greber.et.al., Angew.Chem.Int.Ed., Vo.l7, No.12,94
1 (1968)) or a method of isocyanation using catechol borane (VLKValli.et.al., J. Org.Chem.,
Vol. 60, 257 (1995)) is preferred in terms of yield and safety, and this method will be described in detail.

(Urethane Synthesis) First, urethane is synthesized by reacting a corresponding diamine compound with methyl chloroformate, ethyl chloroformate, phenyl chloroformate, p-nitrophenyl chloroformate, or the like.
Of these, phenylchloroformate or p-nitrophenylchloroformate is preferred in order to make the next isocyanation proceed smoothly, but p-nitrophenylchloroformate has high activity and may cause side reactions. Phenyl chloroformate is most preferred because

The solvent used in these reactions may be any solvent that can dissolve the diamine. Examples thereof include 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; and ester compounds such as ethyl acetate. These solvents may be used alone or as a mixture of two or more.

The reaction temperature is between -40 and 100 ° C, preferably between -20 and 80 ° C, most preferably between 0 and 60 ° C. −
When the temperature is lower than 40 ° C, the reaction hardly proceeds, while
If it exceeds, side reactions such as condensation may occur.

The base for trapping hydrogen chloride generated by the reaction may be any base as long as it dissolves in the solvent used and does not inhibit the reaction. For example, triethylamine, sodium hydroxide, pyridine, diazabicycloundecene (DB)
U) and the like. The amount of the base used is preferably 1.5 to 4.0 times the number of moles of the diamine used, and is preferably 1.8 to 4.0 times.
3.5 times is more preferable.

In order to purify the obtained urethane, a conventionally known method such as recrystallization or column can be used.
Further, distillation may be performed as necessary.

(A) Isocyanation using chlorosilane To isocyanate the urethane using chlorosilane, the molar amount of urethane is 1.5 to 4.6 times, preferably 1.6 to 4.0 times, Most preferably, thermal decomposition is carried out using 1.8 to 3.5 times chlorosilane as a catalyst. Examples of such chlorosilanes include trimethylchlorosilane, triethylchlorosilane, trimethoxychlorosilane, tetrachlorosilane and the like, and trimethylchlorosilane is preferred from the viewpoint of easy handling and price.

The solvent used may be any one capable of dissolving or suspending urethane. In addition to the above ether compounds and aromatic hydrocarbons, halogenated hydrocarbons such as dichloromethane, chloroform, dichloroethane and tetrachloroethylene; acetone, methyl ethyl ketone And ketone compounds such as cyclohexane; and ester compounds such as ethyl acetate.

These solvents may be used alone or in combination of two or more. In some cases, the reaction temperature may be changed by substituting a part or all of the reaction during the reaction.

The reaction temperature is from 0 ° C. to the boiling point of the solvent used, preferably from room temperature to the boiling point. If the reaction temperature is too low, the reaction may not proceed at all. Conversely, if the reaction temperature is set too high or heated too long, the product may decompose. Therefore, it is preferable to gradually raise the temperature while tracing the reaction by IR or the like and proceed with the reaction.

A base such as triethylamine may be similarly used for trapping hydrogen chloride generated during the reaction.

(B) Isocyanation Using Halogenated Catechol Borane For the isocyanation of urethane, a method using halogenated catechol borane as a catalyst instead of the chlorosilane may be employed. Examples of the halogenated catechol borane include chlorocatechol borane, bromocatechol borane, and the like, and chlorocatechol borane is preferable from the viewpoint of price and handling. In addition, since catecholboranes have higher activity for thermal decomposition of urethane than chlorosilanes, urethanes other than phenyl urethane can be used as urethanes.

As the solvent used for such a reaction, the same solvent as used in the isocyanation using chlorosilane may be used.

When phenyl urethane is used, the reaction temperature is generally -50 to 80 ° C, preferably 20 to 60 ° C.
The temperature is more preferably 0 to 40 ° C, and may be changed depending on the type of urethane to be used. If the reaction temperature is out of these ranges or is excessively heated, the reaction may not proceed as described above or the product may be decomposed, so the temperature is gradually increased while tracing the reaction by IR or the like. It is better to proceed with the reaction.

The same base as described above may be used as a base for trapping hydrogen chloride generated during the reaction.

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

The urethanization, isocyanation, and carbodiimidization of the diamine may be carried out in a stepwise manner by performing isolation and purification in each step, and may be carried out in a stepwise manner. It may be performed as a series of reactions.

[0052]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the characteristic of the obtained polycarbodiimide was measured as follows.

IR was measured using FT / IR-230 manufactured by JEOL.

The thermosetting temperature was measured using a DSC-200 (manufactured by Seiko Denshi Kogyo Co., Ltd.), and the exothermic peak of trimerization was defined as the thermosetting temperature.

Glass transition point (Tg) The temperature was increased from room temperature to 400 ° C. at a rate of 10 ° C./min using SEIKO SSC / 560M (manufactured by Seiko Denshi Kogyo) and measured.

Thermal decomposition onset temperature (Td) Measured using TG / DTA300 (manufactured by Seiko) and measured at 5%
The weight loss temperature was defined as Td.

Adhesive Strength A 180-degree peel strength was measured using Shimadzu Autograph AGS-100D. Example 1 1,1-bis [2′-methyl-4 ′-(p-aminophenoxy) -5′-t was placed in a 50 mL eggplant flask.
ert-butylphenyl] butane 2.0 g (3.5 mmol), dichloromethane 20 mL and triethylamine 0.72 g
(7.1 mmol) was charged. The flask was ice-cooled and 1.1 g (7.1 mmol) of phenyl chloroformate was charged. After stirring for several minutes, the mixture was stirred at room temperature overnight. At room temperature, 0.65 g (6.4 mmol) of triethylamine and then 0.69 g (6.4 mmol) of trimethylchlorosilane were put into a flask, stirred for 5 minutes, and then stirred at 50 ° C. for 30 minutes.

Then, a carbodiimidation catalyst (3-methyl-2-phospholene-1-oxide) was added to 20 mL of toluene.
61 mg (0.32 mmol) was dissolved, and this was charged into a flask and stirred at 60 ° C. for 1.5 hours. Then 100 ° C
The mixture was stirred for 5.5 hours while elevating the temperature. During this time, dichloromethane was distilled off. After confirming carbodiimidation by IR (FIG. 1), triethylamine hydrochloride was removed by filtration to obtain a polymer having Mn = 6,000 (yield: 70%).

This polymer was coated on a glass plate,
After drying at 0 ° C. for 10 minutes, a film was obtained. This film is flexible, has a thermosetting temperature of 375 ° C., and Tg = 17.
2 ° C., Td = 351 ° C. In addition, 60 at 200 ° C
It was flexible even after drying for minutes.

Example 2 The varnish obtained in Example 1 was cast on a copper foil (thickness: 35 μm),
After drying for a minute, an adhesive sheet having a film thickness of 20 μm was prepared. This is stuck on a 42 alloy plate, 350 ° C, 50k
The sheets were pressed together for 1 second at a pressure of g / cm ² and bonded. When the adhesive strength was measured, the adhesive strength was 980 g / cm. The adhesive strength was 810 g / cm after being put into a thermo-hygrostat at 80 ° C./90% RH for 168 hours.

[Comparative Example 1] In Example 1, TDI was used as an isocyanate monomer, and the same treatment was carried out to carry out polymerization to produce a polycarbodiimide having a molecular weight of 9,600. The obtained varnish was applied on a glass plate and dried at 90 ° C. for 30 minutes to prepare a film having a Tg of 78 ° C.
The thermosetting temperature of this film is 350 ° C.
When heat treatment was performed for a long time, the color changed, the flexibility was lost, and the self-holding property was lost.

Comparative Example 2 Using the varnish prepared in Comparative Example 1, the same treatment as in Example 2 was performed to produce an adhesive sheet. When the adhesive strength was measured, it showed an adhesive strength of 600 g / cm. When this was put into a thermo-hygrostat at 80 ° C./90% RH for 168 hours, it was peeled off.

[0063]

The polymer of the present invention is easily soluble in general organic solvents and is easy to mold. Further, since the glass transition point is around 200 ° C., the low-temperature workability is high. Furthermore, it has good adhesiveness to adherends such as semiconductor elements, low hygroscopicity, excellent storage stability, and long-term storage at room temperature.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takahiro Fukuoka 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nippon Denko Corporation (56) References JP-A-9-194556 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) C08G 18/02 C08J 5/18 C08L 79/04

Claims (4)

(57) [Claims] 1. An aromatic polycarbodiimide having a structural unit represented by the following general formula (I). Embedded image (In the formula, n represents an integer of 2 to 400.) 2. A polycarbodiimide solution obtained by dissolving the aromatic polycarbodiimide according to claim 1 in an organic solvent. 3. A polycarbodiimide film comprising the aromatic polycarbodiimide of claim 1. 4. The polycarbodiimide film according to claim 3, which is stretched in at least one direction.