JP5190955B2 - POLYMER, PROCESS FOR PRODUCING THE SAME AND CARBON FILM OBTAINED FROM THE POLYMER - Google Patents

Description

  The present invention relates to a polymer, a production method thereof, and a carbon film obtained from the polymer.

  Polyimide (PI) films represented by polyoxadiazole (POD) and Kapton are known to give carbon films with extremely high crystallinity even though carbonization proceeds in a solid phase (for example, Non-Patent Document 1). In recent years, highly crystalline carbon films obtained from PI films have been used as heat dissipation materials for small electronic devices, taking advantage of the high thermal diffusivity in the film plane. Factors that cause these polymer films to exhibit unique carbonization behavior include the high flatness and selective orientation of molecules and the ease of desorption of elements other than carbon during the carbonization process. (Non-patent document 2). Benzimidazobenzophenanthroline ladder polymer (BBL polymer) is a ladder-like polymer obtained by polycondensation of naphthalenetetracarboxylic acid (NTCA) and benzenetetraamine (BTA). Since BBL polymer has higher molecular flatness and higher heat resistance than POD and PI, it gives a higher crystalline carbon film with higher yield (Non-patent Document 3). The carbonization yield of POD and PI films (ratio of the mass of the resulting highly crystalline carbon film to the mass of the polymer film) is about 50%, whereas that of BBL polymer is 64% is there.

  Therefore, development of a technique for producing a highly crystalline carbon film that can achieve a higher yield is demanded.

Synth. Met., 509 (1987) Chem. Phys. Carbon, 26, 245 (1999) Proceedings of the 34th Annual Meeting of the Carbon Materials Society of Japan, 314-315 (2007)

  In view of the above technical flow, an object of the present invention is to provide a technique for producing a highly crystalline carbon film from an organic polymer at a higher yield.

As a result of intensive studies to solve the above problems, the present inventors have surprisingly obtained the knowledge that the carbonization yield greatly exceeds 64% when a carbon film is produced from the following polymer. Based on this finding, the present inventors have made further studies and finally completed the present invention.
The reason why a carbon film having a carbonization yield greatly exceeding 64% can be produced from the polymer has not been elucidated, but is considered as follows. For example, since the BBL polymer is a completely flat molecule, the steric hindrance when the molecule grows by polycondensation is large, and it is difficult to increase the molecular weight. Therefore, the proportion of molecular chain ends is increased, and this portion is easily decomposed / desorbed during carbonization, so that a high carbonization yield comparable to the carbon content in the polymer cannot be achieved. However, since a single bond is introduced into the molecular chain of the polymer, the molecular chain can be rotated. As a result, the steric hindrance during polycondensation can be reduced, and the molecular weight can be increased. .

（２）

That is, this invention consists of the following invention.
(1) A polymer comprising a repeating unit represented by the following general formula (1) or (2) and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
(1)

(2)

(2) A method for producing a polymer comprising a repeating unit represented by the general formula (1) described in the above (1), wherein binaphthyltetracarboxylic acid and biphenyltetraamine are reacted.
(3) A method for producing a polymer comprising a repeating unit represented by the general formula (2) described in the above (1), wherein binaphthyltetracarboxylic acid and benzenetetraamine are reacted.
(4) For carbon film production, comprising a repeating unit represented by the general formula (1) or (2) described in (1) above, and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ Polymer.
(5) It is obtained by firing a polymer comprising a repeating unit represented by the general formula (1) or (2) described in (1) above and having an intrinsic viscosity of 0.5 to 3.5 dlg ^−1. Characteristic carbon film.

Hereinafter, the present invention will be described in detail.
The polymer of the present invention includes a polymer comprising a repeating unit represented by the following general formula (1) and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
As the polymer, a polymer having an intrinsic viscosity of 1.0 to 3.5 dlg ⁻¹ is more preferable. The intrinsic viscosity (η) of a polymer is a physical property value that serves as an index of molecular weight, and η increases as the molecular weight increases. A method for measuring the intrinsic viscosity is already known. In the present invention, the polymer was dissolved in methanesulfonic acid, adjusted to a concentration of 0.15 gdl ^−1, and measured in an atmosphere at 30 ° C.

上記重合体としては、固有粘度が１．０〜２．７ｄｌｇ^-1である重合体がより好ましい。 The polymer of the present invention includes a polymer comprising a repeating unit represented by the following general formula (2) and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
(2)

As the polymer, a polymer having an intrinsic viscosity of 1.0 to 2.7 dlg ⁻¹ is more preferable.

Hereafter, the manufacturing method of the polymer of this invention is demonstrated.
The polymer consisting of the repeating unit represented by the above general formula 1 of the present invention includes a binaphthyltetracarboxylic acid or a binaphthyltetracarboxylic acid derivative such as acid chloride, acid anhydride, ester or amide thereof and biphenyltetraamine or a salt thereof. Can be obtained by reaction. Examples of the binaphthyltetracarboxylic acid include 4,4′-binaphthyl-1, l ′, 8,8′-tetracarboxylic acid, and examples of the biphenyltetraamine include 3,3 ′, 4,4′-biphenyltetraamine. It can be illustrated. Examples of the salt of biphenyltetraamine include tetrahydrochloride of 3,3 ′, 4,4′-biphenyltetraamine.
The binaphthyltetracarboxylic acid or a carboxylic acid derivative thereof and biphenyltetraamine or a salt thereof are added to a reaction vessel containing a solvent, and stirred at 100 to 250 ° C. for 3 to 48 hours. A polymer composed of the repeating units represented can be obtained. The solvent is not particularly limited as long as it has an action as a catalyst that dissolves the starting material and the polymer to be produced and promotes polymerization. Specifically, polyphosphoric acid,
Examples thereof include methanesulfonic acid in which polyphosphate ester, diphenylcresyl phosphate and the like, diphosphorus pentoxide and the like are dissolved.

The polymer comprising the repeating unit represented by the above general formula 2 of the present invention includes a binaphthyltetracarboxylic acid or binaphthyltetracarboxylic acid derivative such as acid chloride, acid anhydride, ester or amide thereof and benzenetetraamine or salt thereof. Can be obtained by reaction. Examples of benzenetetraamine include 1,2,4,5-benzenetetraamine. Examples of the salt of benzenetetraamine include tetrahydrochloride of 1,2,4,5-benzenetetraamine. Specific examples of the binaphthyltetracarboxylic acid or its carboxylic acid derivative are as described above.
The reaction conditions for obtaining a polymer comprising a repeating unit represented by the above general formula 2 from the binaphthyltetracarboxylic acid or a carboxylic acid derivative thereof and benzenetetraamine or a salt thereof are the repeating units represented by the above general formula 1. This overlaps with the conditions for obtaining a polymer comprising:

The polymer comprising the repeating unit represented by the above general formula 3 of the present invention includes naphthalene tetracarboxylic acid or a naphthalene tetracarboxylic acid derivative such as acid chloride, acid anhydride, ester or amide thereof and biphenyltetraamine or a salt thereof. Can be obtained by reaction. Examples of naphthalenetetracarboxylic acid include 1,4,5,8-naphthalenetetracarboxylic acid, and specific examples of biphenyltetraamine or a salt thereof are as described above.
The reaction conditions for obtaining a polymer comprising the repeating unit represented by the above general formula 3 from the naphthalenetetracarboxylic acid or its carboxylic acid derivative and biphenyltetraamine or a salt thereof are the repeating represented by the above general formula 1. This overlaps with the conditions for obtaining a polymer comprising units.

4,4'-binaphthyl-1, l ', 8,8'-tetracarboxylic acid is synthesized from 4-chloro-1,8-naphthalic anhydride by three steps of esterification, coupling and hydrolysis be able to. Or you may purchase a commercial item.
1,4,5,8-naphthalenetetracarboxylic acid can be synthesized from pyrene by two steps of oxidation with potassium permanganate and oxidation with sodium hypochlorite solution. Or you may purchase a commercial item.

1,2,4,5-Benzenetetraamine can be synthesized from m-chlorobenzene by three steps of nitration, amination and reduction of the nitro group, and can be isolated and used as the tetrahydrochloride. Or you may purchase a commercial item.
3,3 ′, 4,4′-phenyltetraamine can be synthesized from o (ortho) -nitroaniline by three steps of iodination, cross-coupling, and reduction of amino group. Or you may purchase a commercial item.

A carbon film can be obtained using the polymer of the general formula (1) or (2) thus obtained as a raw material. That is, this invention is invention of the polymer for carbon film manufacture characterized by being represented by the said General formula (1) or (2).

When producing a carbon film, the polymer of the above general formula (1) or (2) or a plurality of the above polymers can be mixed and then baked to obtain a carbon film.

  In the present invention, it is desirable to form the polymer or polymer mixture into a film in advance, and it is desirable to fire the film. The means for forming the polymer or polymer mixture into a film is not particularly limited.

The means for firing the polymer film will be described in more detail. The polymer film is preferably baked in an inert atmosphere. Here, the inert atmosphere means an atmosphere in which there is no oxidizing active gas such as oxygen, and for example, an atmosphere of argon, helium, nitrogen, or the like is preferable. An argon atmosphere is particularly preferable.
The firing temperature is preferably 1200 to 2800 ° C., and the firing time is preferably about 1 to 8 hours.

When baking the polymer film, it is preferable to perform carbonization treatment while applying tension or applying pressure perpendicular to the film surface, thereby suppressing shrinkage that occurs during carbonization and orienting the precursor during carbonization. Because it is easy to do, a strong carbide is made.
When the polymer film is baked, the polymer molecules spontaneously form a highly oriented structure in the film molding process, so that a highly crystalline carbon film can be produced without applying stress.

The carbon film thus produced has a high density and is a highly crystalline carbon film. The density of the complete carbon crystal can be determined from the crystal structure, and the value is known to be 2.26 g cm ⁻³ . The closer to this value, the higher the crystallinity. The density of the carbon film obtained from the existing BBL polymer (Comparative Example 1) is 2.19 g cm ⁻³ . A carbon film having a density comparable to that of the polymer composed of the repeating unit represented by the general formula (2) could be obtained. Wide-angle X-ray diffraction is generally used as a means of evaluating crystallinity, but when applied to a carbon film with very high crystallinity such as the one obtained this time, a very large error in determining the crystal size and interplanar spacing. May occur. On the other hand, density measurement can be performed with very high accuracy, and this is also advantageous. Another feature of the carbon film of the present invention is that the c-axis of the carbon crystal is highly oriented in the normal direction of the film. The carbon film obtained by the present invention has a feature that the degree of orientation is higher than the conventional one.

  The carbon film of the present invention can be applied to known applications such as heat dissipation materials for small electronic devices, negative electrode materials for lithium secondary batteries, conductive assistants for battery materials, X-ray monochromators, and brush materials for motors.

According to the present invention, a highly crystalline carbon film can be produced from an organic polymer at a higher yield. In particular, a carbon film having a crystallinity as high as that of a BBL polymer-derived carbon film could be produced with a higher yield from a polymer that was easier to polymerize. The carbon film is a dense and smooth carbon film having a high density and no deformation, and can be applied to many applications.
Further, according to the present invention, it is possible to provide a polymer having a higher intrinsic viscosity, that is, a polymer having a higher molecular weight.

EXAMPLES Hereinafter, although an Example etc. demonstrate this invention, this invention is not limited to these Examples at all.
Examples 1-3 Preparation of Polymer 100 g of polyphosphoric acid (PPA) (concentration of orthophosphoric acid 115%) was placed in a 200 ml four-necked flask equipped with a mechanical stirrer, argon gas inlet tube, exhaust tube and thermometer. Then, argon gas was bubbled to remove dissolved oxygen, and 12 mmol of tetraamine shown in Table 1 below was added and dissolved. Next, 12 mmol of tetracarboxylic acid described in Table 1 below was added, and the mixture was stirred at 200 ° C. for 24 hours to obtain a PPA solution of a polymer.
The PPA solution of the polymer is poured into a large amount of water to solidify the polymer, and then separated. The obtained polymer is washed successively with water and methanol (MeOH), and then dried under reduced pressure at room temperature. I got a molecule. In order to remove PPA remaining in the crude polymer, the crude polymer is dissolved in methanesulfonic acid (MSA), and this solution is poured into a large amount of water to coagulate the polymer, and water, dimethylacetamide (DMAc) Then, the mixture was washed successively with MeOH and dried under reduced pressure at 240 ° C. for 24 hours to obtain a purified polymer.
The intrinsic viscosity (η) of the polymer was measured for an MSA solution having a concentration of 0.15 gdl ⁻¹ at 30 ° C. using an Ostwald viscometer (manufactured by Shibata Kagaku Co., Ltd.).
The results are shown in Table 1.
Moreover, the elemental analysis value of the polymer was measured. The instrument used for the measurement was EA1110 manufactured by CE Instruments.
The results are shown in Table 2.

Comparative Example 1
Using the compounds shown in Table 1 as the tetraamine and tetracarboxylic acid as starting materials, the other procedures were carried out in the same manner as in Examples 1 to 3 to obtain purified polymers.
The intrinsic viscosity (η) of the polymer was measured in the same manner as in Examples 1 to 3.
The results are shown in Table 1.

表２

Table 1

Table 2

  The polymerization behavior of the polymer is summarized in Table 1. For all the polymers, the polymerization yield was almost quantitative. Further, the intrinsic viscosity (η) of the polymers of Examples 1 to 3 is large, and in particular, η of Examples 1 and 2 is significantly larger than that of the polymer of Comparative Example 1, and the starting material used in the present invention is used. Is effective for increasing the molecular weight.

Examples 4-6
(Production of polymer film)
A viscous solution obtained by dissolving 0.3 g of the polymer prepared in Examples 1 to 3 in 7 ml of MSA was developed on a glass flat dish having an inner diameter of 70 mm. This petri dish was kept horizontal in a 500 ml flat bottom separable flask placed in a mantle heater. After the pressure inside the separable flask was reduced with a rotary pump, the solvent was removed stepwise to 200 ° C. to prepare a polymer film.
The polymer film could be easily peeled from the glass petri dish. In order to remove methanesulfonic acid remaining in the film, it was immersed in a methanol solution of triethylamine for 12 hours at room temperature, then washed with methanol, and then dried under reduced pressure. The resulting film thickness was approximately 50 microns. All the films were flexible and could be cut into a desired shape.
(Production of carbon film)
The polymer film was carbonized by the following two-stage heat treatment.
The polymer film cut into a predetermined shape was sandwiched between graphite plates and placed in an electric furnace (self-made) using silicon carbide as a heater. While nitrogen gas into the electric furnace was circulated at a flow rate of 250mlmin ^-1, heated at a rate of 2 ° C. min ^-1, and a heat treatment and held 1 hour at 1500 ° C., to obtain a carbon film.
The carbon film was sandwiched between graphite plates and placed in an electric furnace (manufactured by Shinsei Electric Furnace) using graphite as a heater. While argon gas in an electric furnace was circulated at a flow rate of 2000mlmin ^-1, heated at a rate of 5 ° C. min ^-1, and a heat treatment and held 1 hour at 2800 ° C., to obtain a carbon film.
The density of the polymer film and the carbon film was measured at 25 ° C. using a flotation method. As the density solution, a mixed solution of n-heptane, carbon tetrachloride, 1,2 ethylene dibromide and 1,1,2,2 tetratetrabromide ethane was used. For the measurement, a 10 ml Geryac type specific gravity bottle (manufactured by Sansho) was used.
The results are shown in Table 3.

Comparative Example 2
Using the polymer obtained in Comparative Example 1, the same operation as in Examples 4 to 6 was performed to obtain a carbon film.
The density of the said polymer film and the carbon film was operated like Example 4-6, and the density was measured.
The results are shown in Table 3.

When the polymer film defined by the present invention was carbonized, a dense and smooth carbon film without deformation was obtained for any film. These points are conclusions based on observation results by an electron microscope in addition to small changes in the macroscopic shape (shapes seen with the naked eye), and conclusions from the measurement results of the density of the carbon film. .
The carbonization yield of the polymer (BBL polymer) in Comparative Example 1 at a carbonization temperature of 2800 ° C. was 63.9%, which corresponds to the remaining 88.9% of the carbon atoms in the polymer. . On the other hand, the carbonization yield and the carbon atom residual ratio of the polymer in Example 1 were 76.7 and 95.2%, respectively. The carbonization yield and carbon atom survival rate of the polymer in Example 2 are 69.2 and 93.7%, respectively, and the carbonization yield and carbon atom survival rate of the polymer in Example 3 are as follows. Were 76.7 and 91.0%, respectively. For the polymer synthesized this time as defined by the present invention, the introduction of a single bond into the molecular chain does not lead to a decrease in thermal stability, but rather increases the carbon content, thereby increasing the carbonization yield and the residual ratio of carbon atoms. You can see that it increases.
The density of the carbon film is one of the physical property values that change sensitively depending on the difference in crystallinity, and is easy to measure, so that it can be used as an index representing the crystallinity. The density of the carbon film derived from the polymer of Comparative Example 1 having high crystallinity and high selective orientation of crystals was 2.19 gcm ⁻³ . On the other hand, the density of the carbon film derived from the polymer of Example 2 was able to obtain a carbon film having a density of 2.18 gcm ⁻³ comparable to the density of the carbon film derived from the polymer of Comparative Example 1.
As described above, a carbon film having high crystallinity comparable to that of a BBL polymer-derived carbon film could be produced from a polymer that can be easily polymerized with a higher yield.

上記表中、炭素化収率及び炭素原子残存率は下式に基づき算出した。
炭素化収率=（（炭素フィルムの質量）/（高分子フィルムの質量））ｘ１００
炭素原子残存率=（(炭素化収率)/（高分子の炭素含有率））ｘ１００ Table 3

In the above table, the carbonization yield and carbon atom residual ratio were calculated based on the following formulas.
Carbonization yield = ((mass of carbon film) / (mass of polymer film)) × 100
Carbon atom residual rate = ((carbonization yield) / (carbon content of polymer)) × 100

（官能基１）

（官能基２）

（官能基３）

（官能基４）

（式中、Ａｒ^１は官能基１又は官能基２を示し、Ａｒ^２は官能基３又は官能基４を示し、ｎは重合度を示す自然数である。ただし、Ａｒ^１が官能基２のときはＡｒ^２は官能基４ではない。）
（２）上記一般式で表される重合体からなることを特徴とする炭素フィルム製造用重合体。 The present invention can also be described as follows.
(1) A polymer represented by the following general formula and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
(General formula)

(Functional group 1)

(Functional group 2)

(Functional group 3)

(Functional group 4)

(In the formula, Ar ¹ represents functional group 1 or 2, Ar ² represents functional group 3 or 4, and n is a natural number indicating the degree of polymerization. Provided that Ar ¹ is functional group 2. Ar ² is not functional group 4.)
(2) A polymer for producing a carbon film, comprising a polymer represented by the above general formula.

（４）上記（３）記載の重合体からなることを特徴とする炭素フィルム製造用重合体。
（５）上記（１）又は（３）記載の重合体を不活性ガス雰囲気下にて焼成することを特徴とする炭素フィルムの製造方法。 (3) It is made of any polymer represented by the following general formulas (4), (5) and (6), and has an intrinsic viscosity of 0.5 to 3.5 dlg ^−1. Coalescence. However, in the formula, n is a natural number.

(4) A polymer for producing a carbon film, comprising the polymer described in (3) above.
(5) A method for producing a carbon film, comprising firing the polymer described in (1) or (3) in an inert gas atmosphere.

Claims (5)

A polymer comprising a repeating unit represented by the following general formula (1) or (2) and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
(1)

(2)

Binaphthyltetracarboxylic acid and biphenyltetraamine are reacted, A method for producing a polymer comprising a repeating unit represented by formula (1) according to claim 1. Binaphthyltetracarboxylic acid and benzenetetraamine are reacted, A method for producing a polymer comprising a repeating unit represented by the general formula (2) according to claim 1. A polymer for producing a carbon film, comprising a repeating unit represented by the following general formula (1) or (2) and having an intrinsic viscosity of 0.5 to 3.5 dlg ⁻¹ .
(1)

(2)

Carbon obtained by firing a polymer comprising a repeating unit represented by the general formula (1) or (2) according to claim 1 and having an intrinsic viscosity of 0.5 to 3.5 dlg ^-1 the film.