JP2005263548A - Heat-resistant expanded graphite sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant expanded graphite sheet which can suppress fluctuation of resistance to oxidative consumption even in a high-temperature region higher than 700°C, has high resistance to oxidative consumption, and can exhibit stable performance. <P>SOLUTION: The heat-resistant expanded graphite sheet contains phosphorus pentoxide, a phosphate, and an organic phosphorus compound, dispersed therein. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat-resistant expanded graphite sheet, and more particularly, to a heat-resistant expanded graphite sheet excellent in oxidation resistance consumption at high temperatures.

Japanese Patent Publication No. 44-23966 Japanese Patent Publication No.54-30678 Japanese Patent No. 3430243

  Expanded graphite sheet is made of natural graphite, quiche graphite, pyrolytic graphite, etc., concentrated sulfuric acid, concentrated nitric acid, concentrated sulfuric acid and potassium chlorate, concentrated sulfuric acid and potassium nitrate, hydrogen peroxide and other strong oxidizing agents, bromine or chloride. An interlayer compound is formed by treatment with a halide such as aluminum, and the graphite particles (acid-treated graphite raw material) on which the interlayer compound is formed are rapidly heated, for example, heated at a high temperature of 950 ° C. or higher for 1 to 10 seconds. The cracked gas is generated, and the graphite layer is expanded by the gas pressure to form expanded graphite particles. The expanded graphite particles are formed by compression molding or roll molding in the presence or absence of a binder ( Patent Document 1). The expanded graphite sheet produced in this way has the heat resistance that graphite itself has, and is flexible, so it has excellent formability such as bending and compression molding. It is used in a wide range of fields such as heat insulating materials and cushion materials.

  As expanded graphite particles forming the expanded graphite sheet, those having a low expansion ratio of about 20 to 70 times and those having a high expansion ratio of about 200 to 300 times are used. In the former case where expanded graphite particles having a low expansion ratio are used, a binder is inevitably used for forming a sheet, so that the purity and physical properties of the expanded graphite sheet are lowered. In contrast, the latter, which uses expanded graphite particles with a high expansion ratio, can be made into a sheet only with expanded graphite particles without using a binder, so the expanded graphite sheet has high purity and various physical properties. It will be excellent.

  The above-described expanded graphite sheet, particularly an expanded graphite sheet produced from expanded graphite particles having a high expansion ratio, is excellent in various physical properties, but its use conditions are in the air, and a high temperature region exceeding 700 ° C. However, there is a problem in heat resistance and, as a result, there is a drawback that the so-called oxidation consumption rate is high, which causes oxidation consumption of graphite.

  In order to eliminate this drawback, there has been proposed an expanded graphite sheet in which expanded graphite particles having a low expansion ratio are used and phosphoric acid or phosphate is contained in the expanded graphite particles to suppress oxidation of graphite (Patent Document). 2)). In this, it is disclosed that by using phosphoric acid or phosphate, it can be made into a sheet without using an adhesive, but even if it can be made into a sheet, basically no adhesive is used, Various properties as an expanded graphite sheet, particularly mechanical properties, sheet uniformity, etc. are not always satisfactory. In addition, although it is disclosed that the oxidation resistance is improved, when it is exposed for a long time, the oxidation consumption is severe, and it is never satisfactory.

  In view of the above-mentioned points, the present applicant has previously proposed a heat-resistant expanded graphite sheet that has improved the heat resistance and oxidation consumption resistance of expanded graphite (Patent Document 3). This is an expanded graphite sheet in which phosphorus pentoxide and phosphate are dispersed and contained in predetermined proportions to improve heat resistance and oxidation consumption resistance. Subsequent experiments have confirmed that the use in the region is not satisfactory from the viewpoint of causing variation in oxidation resistance and maintaining stable performance.

  As a result of diligent research, the present inventors have improved the variation in resistance to oxidation and consumption in a region exceeding 700 ° C. of the heat-resistant expanded graphite sheet described in Patent Document 2 and have maintained stable performance. An expanded graphite sheet in which a predetermined amount of an organophosphorus compound is further added to expanded graphite in which phosphorus oxide and phosphate are dispersed and contained at a predetermined ratio, is resistant to oxidation and wear when used in a high temperature region exceeding 700 ° C. It has been found that the variation in temperature can be suppressed and stable performance can be exhibited.

  The present invention has been made on the basis of the above knowledge, and its object is to suppress variation in oxidation consumption resistance even in a high temperature region exceeding 700 ° C., high oxidation consumption rate, and stable performance. An object of the present invention is to provide a heat-resistant expanded graphite sheet that can exhibit the above.

  The heat-resistant expanded graphite sheet of the first aspect of the present invention contains phosphorus pentoxide, a phosphate, and an organic phosphorus compound in a dispersed manner.

  According to the heat-resistant expanded graphite sheet of the first aspect, heat resistance is imparted to the sheet by containing phosphorus pentoxide, a phosphate, and an organic phosphorus compound coexistingly dispersed in the sheet. Even in the use in a high temperature region exceeding 700 ° C., the oxidation suppressing action of the expanded graphite forming the main body of the sheet is exhibited, and the weight reduction of the sheet due to the oxidation consumption of the expanded graphite can be suppressed as much as possible. . Further, since the sheet has various properties required for this type of expanded graphite sheet, such as flexibility and easy processability, it can be shaped into a shape according to the application.

  The content of phosphorus pentoxide, which is contained in the expanded graphite sheet in a dispersed manner and is necessary for preferably exhibiting the oxidation inhibiting action on the expanded graphite as a main component, is as in the heat-resistant expanded graphite sheet of the second aspect of the present invention. 0.05 to 5% by weight. If the content of phosphorus pentoxide is less than 0.05% by weight, the expanded graphite cannot be sufficiently imparted with heat resistance and oxidation wear resistance, and even if it exceeds 5% by weight, heat resistance and oxidation resistance No further improvement in wearability can be achieved.

Phosphorus pentoxide is produced by a dehydration reaction of phosphoric acid in the process of producing expanded graphite from acid-treated graphite powder. Examples of phosphoric acid used include orthophosphoric acid (H ₃ PO ₄ ) and metaphosphoric acid. (HPO ₃ ), polyphosphoric acid, specifically chain condensed phosphoric acid such as pyrophosphoric acid (H ₄ P ₂ O), tripolyphosphoric acid (H ₅ P ₈ O ₁₀ ), polymetaphosphoric acid, specifically trimetaphosphoric acid, It is selected from cyclic condensed phosphoric acid such as tetrametaphosphoric acid.

  In the expanded graphite sheet, the content of the phosphate contained in the dispersion of the phosphorus pentoxide in a coexisting manner and preferably exhibiting an oxidation inhibiting action on the expanded graphite as a main component is the heat resistance of the third aspect of the present invention. 1 to 16% by weight as in the case of the expandable graphite sheet. If the phosphate content is less than 1% by weight, the sheet cannot be sufficiently imparted with heat resistance and oxidation resistance, and even if the content exceeds 16% by weight, the heat resistance and oxidation resistance can be prevented. No further improvement can be achieved.

  As the phosphate, as in the heat-resistant expanded graphite sheet of the fourth aspect of the present invention, primary lithium phosphate, secondary lithium phosphate, primary calcium phosphate, secondary calcium phosphate, primary aluminum phosphate and Selected from aluminum diphosphate.

  In the expanded graphite sheet, the content of the organic phosphorus compound that is dispersedly contained in the coexistence with the phosphorus pentoxide and phosphate, and is necessary for preferably exerting an oxidation inhibiting action on the expanded graphite as a main component, is the fifth aspect of the present invention. As in the heat-resistant expanded graphite sheet of the embodiment, the content is 0.1 to 10% by weight. When the content of the organophosphorus compound is less than 0.1% by weight, the heat resistance and oxidation inhibiting action imparted by the inclusion of phosphorus pentoxide and phosphate cannot be further improved, and the content exceeds 10% by weight. Even if it contains, the further improvement of the heat resistance provided by inclusion of phosphorus pentoxide and phosphate and an oxidation inhibitory action cannot be expected.

  As the organic phosphorus compound used, as in the heat-resistant expanded graphite sheet of the sixth aspect of the present invention, organic phosphonic acid and its ester, organic phosphinic acid and its ester, phosphoric ester, phosphorous ester and the following Selected from phosphites.

〔上式（１）中、Ｒ^１は、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基を、Ｒ^２及びＲ^３は、水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。〕 As the organic phosphonic acid and its ester, the organic phosphonic acid represented by the following general formula (1) and its ester are preferably used as in the heat-resistant expanded graphite sheet of the seventh aspect of the present invention.

[In the above formula (1), R ¹ comprises an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. In the aralkyl group, R ² and R ³ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. An aralkyl group consisting of ]

〔上式（２）中、Ｒ^４は炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基で又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基あり、Ｒ^５及びＲ^６は水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。〕 As the organic phosphinic acid and its ester, the organic phosphinic acid and its ester represented by the following general formula (2) are suitably used as in the heat-resistant expanded graphite sheet of the eighth aspect of the present invention.

[In the above formula (2), R ⁴ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. Aralkyl group is present, and R ⁵ and R ⁶ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. Is an aralkyl group. ]

〔上式（３）中、Ｒ^７、Ｒ^８、Ｒ^９は、水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。ただし、すべて水素原子の場合を除く。〕 As the phosphate ester, a phosphate ester represented by the following general formula (3) is suitably used as in the heat-resistant expanded graphite sheet of the ninth aspect of the present invention.

[In the above formula (3), R ⁷ , R ⁸ and R ⁹ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and a carbon number. It is an aralkyl group consisting of 6 to 18 aryl moieties. However, the case of all hydrogen atoms is excluded. ]

〔式（４）、（５）中、Ｒ^１０、Ｒ^１１、Ｒ^１２は、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基であり、Ｒ^１３、Ｒ^１４は、水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。ただし、Ｒ^１３、Ｒ^１４共に水素原子の場合を除く。〕 As the phosphite, the phosphorous acid triester represented by the following general formula (4) and the phosphorous acid represented by the following general formula (5) as in the heat-resistant expanded graphite sheet of the tenth aspect of the present invention Phosphites selected from acid diesters and phosphite monoesters are preferably used.

[In the formulas (4) and (5), R ¹⁰ , R ¹¹ , R ¹² are an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and a carbon number. An aralkyl group comprising an aryl part having 6 to 18 atoms, wherein R ¹³ and R ¹⁴ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms. And an aralkyl group consisting of an aryl part having 6 to 18 carbon atoms. However, the case where both R ¹³ and R ¹⁴ are hydrogen atoms is excluded. ]

〔上式（６）、（７）中、Ｒ^１５は、水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基であり、Ｒ^１６、Ｒ^１７、Ｒ^１８は、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。〕 As the hypophosphite, as in the heat-resistant expanded graphite sheet of the eleventh aspect of the present invention, a hypophosphite diester (phosphonite) represented by the following general formula (6) or the following general formula (7 The hypophosphorous acid monoester represented by this is preferably used.

[In the above formulas (6) and (7), R ¹⁵ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and 6 to 6 carbon atoms. An aralkyl group composed of 18 aryl moieties, wherein R ¹⁶ , R ¹⁷ and R ¹⁸ are an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms or an alkylene part having 1 to 10 carbon atoms and carbon. It is an aralkyl group consisting of an aryl part of formulas 6-18. ]

  According to the present invention, a predetermined amount of phosphorus pentoxide, a phosphate, and an organic phosphorus compound coexist in the expanded graphite so that the expanded graphite can be used in a wide temperature range from room temperature to over 700 ° C. Thus, it is possible to provide a heat-resistant expanded graphite sheet having heat resistance and a high oxidation consumption rate. Moreover, in a manufacturing method, it can manufacture, without changing each process in the manufacturing method of a normal expanded graphite sheet.

  The best mode of the present invention will be described.

  The manufacturing method in the heat resistant expanded graphite sheet of this invention is demonstrated.

<Method for producing heat-resistant expanded graphite sheet>
While stirring concentrated sulfuric acid having a concentration of 98%, a 60% aqueous solution of hydrogen peroxide as an oxidant is added to make a reaction solution. The reaction solution is cooled and kept at a temperature of 10 ° C., scale-like natural graphite powder having a particle size of 30 to 80 mesh is added, and the reaction is performed for a predetermined time. After the reaction, the acid-treated graphite is separated by suction filtration, and the washing operation of stirring the acid-treated graphite with water for a predetermined time and suction-filtering is repeated twice to sufficiently remove the sulfuric acid content from the acid-treated graphite. Next, the acid-treated graphite from which sulfuric acid has been sufficiently removed is dried in a drying furnace, and this is used as the acid-treated graphite raw material.

  While stirring the acid-treated graphite raw material, a predetermined amount of phosphoric acid, a phosphate and an organic phosphorus compound are added to the acid-treated graphite raw material, and the mixture is uniformly stirred to obtain a mixture. The mixture is heated (expanded) at a temperature of 950 to 1200 ° C. for 1 to 5 seconds to generate decomposition gas, and the graphite layer is expanded by the gas pressure to expand expanded graphite particles (expansion magnification: 200 to 300 times). Form. The expanded graphite particles are compression molded or roll molded to produce a heat-resistant expanded graphite sheet having a desired thickness.

  The heat-resistant expanded graphite sheet produced by the above manufacturing method includes a predetermined amount of phosphorus pentoxide, phosphate, organic phosphorus compound, and expanded graphite produced by a dehydration reaction of phosphoric acid, and has flexibility. It is.

Phosphorus pentoxide dispersed and contained in the heat-resistant expanded graphite sheet is produced by the dehydration reaction of phosphoric acid in the production process of expanding the acid-treated graphite powder in the above-described production method. As a chain such as orthophosphoric acid (H ₃ PO ₄ ), metaphosphoric acid (HPO ₃ ), polyphosphoric acid, specifically pyrophosphoric acid (H ₄ P ₂ O), tripolyphosphoric acid (H ₅ P ₈ O ₁₀ ), etc. It is selected from condensed phosphoric acid, polymetaphosphoric acid, specifically cyclic condensed phosphoric acid such as trimetaphosphoric acid and tetrametaphosphoric acid, and these phosphoric acids are used in the form of an aqueous solution. The content of phosphorus pentoxide dispersedly contained in the expanded graphite sheet is 0.05 to 5% by weight, preferably 0.1 to 5% by weight, and more preferably 0.5 to 3% by weight.

As phosphates that are dispersed and contained in the heat-resistant expanded graphite sheet in combination with the above phosphorus pentoxide, primary phosphates and secondary phosphates are preferably used, among which alkali metal salts and alkalis. Earth metal salts are preferred, and lithium and calcium are particularly preferred. An aluminum salt can also be used as the metal salt. Specifically, primary lithium phosphate (LiH ₂ PO ₄ ), secondary lithium phosphate (Li ₂ HPO ₄ ), primary calcium phosphate [Ca (H ₂ PO ₄ ) ₂ ], dicalcium phosphate (CaHPO ₄ ) , Primary aluminum phosphate [Al (H ₂ PO ₄ ) ₃ ], secondary aluminum phosphate [Al ₂ (HPO ₄ ) ₃ ], and these phosphates are aqueous solutions, crystalline powders or aqueous and crystalline powders. Used in combination form. The phosphate content is 1 to 16% by weight, preferably 2 to 10% by weight, and more preferably 4 to 8% by weight.

  In the production method described above, the use of an aqueous solution of phosphate is recommended from the viewpoint of dispersibility in acid-treated graphite powder. However, as the amount of phosphate added increases, the amount of aqueous solution increases. In the powder expansion process, problems such as hindering expansion of the acid-treated graphite powder occur. Therefore, as the phosphate, a phosphate aqueous solution, a combined use of a phosphate aqueous solution and a phosphate crystal powder, or a phosphate crystal powder can be used depending on the amount of phosphate. .

  The organic phosphorus compound dispersed and contained in the expanded graphite sheet in coexistence with the above phosphoric acid and phosphate includes organic phosphonic acid and its ester, organic phosphinic acid and its ester, phosphate ester, phosphite ester, Examples thereof include phosphites. And content of an organophosphorus compound is 0.1 to 10 weight%, Preferably it is 0.5 to 8.0 weight%, More preferably, it is 2.0 to 5.0 weight%.

上式（１）中、Ｒ^１は炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基であり、Ｒ^２及びＲ^３は水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。 As organic phosphonic acid and its ester, the organic phosphonic acid represented by the following general formula (1) and its ester are preferably used.

In the above formula (1), R ¹ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group comprising an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. R ² and R ³ are each composed of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. Aralkyl group.

  As the alkyl group, a linear or branched alkyl group having preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group). The aryl group is preferably an aryl group having 6 to 18 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms (for example, a phenyl group or a naphthyl group). , An ethylphenyl group, a tolyl group, a xylyl group, etc.), and as the aralkyl group, the alkylene part is a linear or branched alkylene, preferably having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. And the aryl moiety is preferably aryl having 6 to 18 carbon atoms, more preferably 6 to 10 carbon atoms (for example, benzyl group, naphthylmethyl). Etc.). Specific examples include methylphosphonic acid, ethylphosphonic acid, phenylphosphonic acid, tolylphosphonic acid, benzylphosphonic acid, methyl methylphosphonate, dimethyl methylphosphonate, diphenyl methylphosphonate, diethyl phenylphosphonate and the like.

上式（２）中、Ｒ^４は、アルキル基、アリール基又はアラルキル基を、Ｒ^５、Ｒ^６は、水素原子、アルキル基、アリール基又はアラルキル基である。アルキル基、アリール基及びアラルキル基については上記と同じである。具体例としては、メチルホスフィン酸、エチルホスフィン酸、ジエチルホスフィン酸、メチルエチルホスフィン酸、フェニルホスフィン酸、メチルフェニルホスフィン酸、ジフェニルホスフィン酸、メチルホスフィン酸エチル、ジメチルホスフィン酸エチル、メチルホスフィン酸フェニル、フェニルホスフィン酸エチル等が挙げられる。 As the organic phosphinic acid and its ester, an organic phosphinic acid represented by the following general formula (2) and its ester are preferably used.

In the above formula (2), R ⁴ is an alkyl group, an aryl group or an aralkyl group, and R ⁵ and R ⁶ are a hydrogen atom, an alkyl group, an aryl group or an aralkyl group. The alkyl group, aryl group and aralkyl group are the same as described above. Specific examples include methylphosphinic acid, ethylphosphinic acid, diethylphosphinic acid, methylethylphosphinic acid, phenylphosphinic acid, methylphenylphosphinic acid, diphenylphosphinic acid, ethyl methylphosphinate, ethyl dimethylphosphinate, phenylmethylphosphinate, And ethyl phenylphosphinate.

上式（３）中、Ｒ^７、Ｒ^８、Ｒ^９は、水素原子、炭素数１〜１０のアルキル基、炭素数６〜１８のアリール基又は炭素数１〜１０のアルキレン部と炭素数６〜１８のアリール部とからなるアラルキル基である。ただし、すべて水素原子の場合を除く。 As the phosphate ester, a phosphate ester represented by the following general formula (3) is preferably used.

In the above formula (3), R ⁷ , R ⁸ and R ⁹ are each a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms or an alkylene part having 1 to 10 carbon atoms and 6 carbon atoms. An aralkyl group consisting of ˜18 aryl moieties. However, the case of all hydrogen atoms is excluded.

  As the alkyl group, a linear or branched alkyl group having preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group). The aryl group is preferably an aryl group having 6 to 18 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms (for example, a phenyl group, a naphthyl group, and ethyl). A phenyl group, a tolyl group, a xylyl group, etc.), and the aralkyl group is an alkylene part that is linear or branched, preferably alkylene having 1 to 10 carbons, more preferably 1 to 6 carbons. The aryl moiety is preferably aryl having 6 to 18 carbon atoms, more preferably 6 to 10 carbon atoms (for example, benzyl group, naphthylmethyl group, etc.). Specific examples include methyl phosphate, butyl phosphate, phenyl phosphate, diethyl phosphate, diphenyl phosphate, dibenzyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, methyl diphenyl phosphate, and the like. Can be mentioned.

上式（４）、（５）中、Ｒ^１０、Ｒ^１１、Ｒ^１２は、アルキル基、アリール基又はアラルキル基であり、Ｒ^１３、Ｒ^１４は、水素原子、アルキル基、アリール基又はアラルキル基である。ただし、Ｒ^１３、Ｒ^１４共に水素原子の場合を除く。アルキル基、アリール基及びアラルキル基は、上記と同様である。具体例としては、亜リン酸トリメチル、亜リン酸トリフェニル、亜リン酸ジエチル、亜リン酸ジフェニル、亜リン酸ブチル、亜リン酸フェニル等が挙げられる。 As the phosphite, a phosphite triester represented by the following general formula (4) and a phosphite diester and phosphite monoester represented by the following general formula (5) are preferably used.

In the above formulas (4) and (5), R ¹⁰ , R ¹¹ and R ¹² are an alkyl group, an aryl group or an aralkyl group, and R ¹³ and R ¹⁴ are a hydrogen atom, an alkyl group, an aryl group or an aralkyl group. It is. However, the case where both R ¹³ and R ¹⁴ are hydrogen atoms is excluded. The alkyl group, aryl group and aralkyl group are the same as described above. Specific examples include trimethyl phosphite, triphenyl phosphite, diethyl phosphite, diphenyl phosphite, butyl phosphite, and phenyl phosphite.

上式（６）、（７）中、Ｒ^１５は、水素原子、アルキル基、アリール基又はアラルキル基であり、Ｒ^１６、Ｒ^１７、Ｒ^１８は、アルキル基、アリール基又はアラルキル基である。アルキル基、アリール基及びアラルキル基は、上記と同様である。具体例としては、ジメチルホスホナイト、ジフェニルホスホナイト、ジベンジルホスホナイト、ジエチルフェニルホスホナイト、ジメチルフェニルホスホナイト、次亜リン酸メチル、次亜リン酸エチル、次亜リン酸フェニル等が挙げられる。 As the hypophosphite, a hypophosphite diester (phosphonite) represented by the following general formula (6) and a hypophosphite monoester represented by the following general formula (7) are preferably used.

In the above formulas (6) and (7), R ¹⁵ is a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, and R ¹⁶ , R ¹⁷ and R ¹⁸ are an alkyl group, an aryl group or an aralkyl group. The alkyl group, aryl group and aralkyl group are the same as described above. Specific examples include dimethyl phosphonite, diphenyl phosphonite, dibenzyl phosphonite, diethyl phenyl phosphonite, dimethyl phenyl phosphonite, methyl hypophosphite, ethyl hypophosphite, phenyl hypophosphite and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

Examples 1-7
While stirring 300 parts by weight of concentrated sulfuric acid having a concentration of 98%, 5 parts by weight of a 60% aqueous solution of hydrogen peroxide was added as an oxidizing agent, and this was used as a reaction solution. The reaction solution was cooled and maintained at a temperature of 10 ° C., 100 parts by weight of flaky natural graphite powder having a particle size of 30 to 80 mesh was added, and the reaction was performed for 30 minutes. After the reaction, the acid-treated graphite is separated by suction filtration, and the washing process of stirring the acid-treated graphite with 300 parts by weight of water for 10 minutes and suction filtration is repeated twice to sufficiently remove the sulfuric acid content from the acid-treated graphite. did. Next, the acid-treated graphite from which sulfuric acid was sufficiently removed was dried in a drying furnace maintained at a temperature of 110 ° C. for 3 hours, and this was used as the acid-treated graphite raw material.

  While stirring 100 parts by weight of the acid-treated graphite raw material, 1.2 parts by weight of an orthophosphoric acid aqueous solution having a concentration of 84% as phosphoric acid and 50% by weight of a primary aluminum phosphate aqueous solution as a phosphate are added to the acid-treated graphite raw material. 2. An organic phosphorus compound selected from 4.2 parts by weight of an organic phosphorus compound selected from phenylphosphonic acid, diethyl phenylphosphonate, diphenylphosphinic acid, phenylphosphinic acid, diphenyl phosphate, triphenyl phosphite, and dimethylphosphonite 1 weight part was mix | blended and it stirred and mixed uniformly and produced the mixture. These mixtures were heat-treated at a temperature of 1000 ° C. for 5 seconds to generate decomposition gas, and the graphite layer was expanded by the gas pressure to obtain expanded graphite particles having an expansion ratio of 240 times. The expanded graphite particles were passed through a rolling roll and subjected to roll forming to produce an expanded graphite sheet having a thickness of 0.38 mm. The component compositions of the expanded graphite sheet thus produced are shown in Tables 1 and 2.

Examples 8-14
An acid-treated graphite material (powder) was produced in the same manner as in the above example. While stirring 100 parts by weight of the acid-treated graphite raw material, 1.2 parts by weight of an orthophosphoric acid aqueous solution having a concentration of 84% as phosphoric acid and 50% by weight of a primary aluminum phosphate aqueous solution as a phosphate are added to the acid-treated graphite raw material. 4.2 parts by weight and 2.1 parts by weight of primary aluminum phosphate crystal powder as an organic phosphorus compound, phenylphosphonic acid, diethyl phenylphosphonate, diphenylphosphinic acid, phenylphosphinic acid, diphenyl phosphate, triphenyl phosphite Then, 2.1 parts by weight of an organic phosphorus compound selected from dimethylphosphonite was blended, and the mixture was stirred and mixed uniformly to prepare a mixture. These mixtures were heat-treated at a temperature of 1000 ° C. for 5 seconds to generate decomposition gas, and the graphite layer was expanded by the gas pressure to obtain expanded graphite particles having an expansion ratio of 240 times. The expanded graphite particles were passed through a rolling roll and subjected to roll forming to produce an expanded graphite sheet having a thickness of 0.38 mm. The component compositions of the expanded graphite sheet thus prepared are shown in Tables 3 and 4.

Examples 15-21
An acid-treated graphite raw material (powder) was produced in the same manner as in the above example. While stirring 100 parts by weight of acid-treated graphite raw material, 3.8 parts by weight of an orthophosphoric acid aqueous solution having a concentration of 84% as phosphoric acid and 50% concentration of a primary aluminum phosphate aqueous solution as a phosphate are added to the acid-treated graphite raw material. 9.2 parts by weight and 4.6 parts by weight of primary aluminum phosphate crystal powder as an organic phosphorus compound, phenylphosphonic acid, diethyl phenylphosphonate, diphenylphosphinic acid, phenylphosphinic acid, diphenyl phosphate, triphenyl phosphite Then, 2.3 parts by weight of an organic phosphorus compound selected from dimethylphosphonite was blended, and the mixture was uniformly stirred and mixed to prepare a mixture. These mixtures were heat-treated at a temperature of 1000 ° C. for 5 seconds to generate decomposition gas, and the graphite layer was expanded by the gas pressure to obtain expanded graphite particles having an expansion ratio of 240 times. The expanded graphite particles were passed through a rolling roll and subjected to roll forming to produce an expanded graphite sheet having a thickness of 0.38 mm. The component compositions of the expanded graphite sheet thus produced are shown in Tables 5 and 6.

Comparative Examples 1-3
An acid-treated graphite raw material was produced in the same manner as in the above example. While stirring 100 parts by weight of the acid-treated graphite raw material, the acid-treated graphite raw material is mixed with an orthophosphoric acid aqueous solution having a concentration of 84% at a ratio of 1.2 to 3.4 parts by weight, and uniformly stirred to improve wettability. A mixture having was prepared. Thereafter, expanded graphite particles having an expansion ratio of 250 times were produced in the same manner as in the above example, and an expanded graphite sheet having a thickness of 0.38 mm was produced in the same manner as in the above example. In this comparative example, orthophosphoric acid blended with the acid-treated graphite raw material generates a dehydration reaction in the expansion treatment step to produce phosphorus pentoxide. Table 7 shows the component compositions of the expanded graphite sheets of Comparative Examples 1 to 3.

Comparative Examples 4-6
An acid-treated graphite raw material was produced in the same manner as in the above example. While stirring 100 parts by weight of the acid-treated graphite raw material, the acid-treated graphite raw material has a concentration of 50% primary aluminum phosphate aqueous solution (4) 8.4 parts by weight, (5) 17.4 parts by weight, (6) A solution obtained by diluting 38 parts by weight of methanol with 30 parts by weight of methanol was blended in a spray form, and stirred uniformly to prepare a mixture having wettability. Thereafter, expanded graphite particles having an expansion ratio of 250 times were produced in the same manner as in the above example, and an expanded graphite sheet having a thickness of 0.38 mm was produced in the same manner as in the above example. The component composition of the expanded graphite sheet thus prepared is shown in Table 8.

Comparative Examples 7-9
An acid-treated graphite raw material was produced in the same manner as in the above example. While stirring 100 parts by weight of the acid-treated graphite raw material, (7) 1.2 parts by weight of an orthophosphoric acid aqueous solution having a concentration of 84% and 4.2 parts by weight of a primary aluminum phosphate aqueous solution having a concentration of 50% are added to the acid-treated graphite raw material. (8) 1.2 parts by weight of an aqueous orthophosphoric acid solution having a concentration of 84% and 8.4 parts by weight of an aqueous solution of primary aluminum phosphate having a concentration of 50%, (9) 3.5 parts by weight of an aqueous solution of orthophosphoric acid having a concentration of 84% A 50% aqueous solution of primary aluminum phosphate was blended at a ratio of 8.6 parts by weight, and the mixture was uniformly stirred to prepare a wettable mixture. Thereafter, expanded graphite particles having an expansion ratio of 250 times were produced in the same manner as in the above example, and an expanded graphite sheet having a thickness of 0.38 mm was produced in the same manner as in the above example. In this comparative example, orthophosphoric acid blended with the acid-treated graphite raw material generates a dehydration reaction in the expansion treatment step to produce phosphorus pentoxide. The component composition of the expanded graphite sheet thus prepared is shown in Table 9.

For the expanded graphite sheets obtained in Examples 1 to 21 and Comparative Examples 1 to 9 described above, the oxidation consumption rate was tested. The test method indicated the weight loss rate (%) of the expanded graphite sheet after leaving the expanded graphite sheet in air kept at a temperature of 720 ° C. for 3 hours. In addition, the expanded graphite sheets obtained in Examples 1 to 21 and Comparative Examples 1 to 9 were tested for flexibility. The test method is shown by the number of times until the expanded graphite sheet having a width of 10 mm and a length of 100 mm is alternately bent at an angle of 90 degrees and the sheet is cut using the test apparatus shown in FIG. In FIG. 1, 1 is an expanded graphite sheet, 2 is a weight of 50 g, and 3 is a bending range. These test results are shown in Tables 1-9.

  As is clear from the above test results, the heat-resistant expanded graphite sheet consisting of the examples is obtained by dispersing phosphorus pentoxide, a phosphate, and an organic phosphorus compound in the sheet, and thereby expanding the expanded graphite sheet of the comparative example. In comparison, the heat resistance is improved and the effect of high oxidation consumption rate is exhibited even at a temperature exceeding 700 ° C., and various properties such as flexibility inherently possessed are not impaired. It has the same properties.

It is drawing which shows an example of the testing apparatus which evaluates the flexibility of an expanded graphite sheet.

Claims (11)

  A heat-resistant expanded graphite sheet containing phosphorus pentoxide, a phosphate, and an organic phosphorus compound in a dispersed manner.   The heat-resistant expanded graphite sheet according to claim 1, wherein phosphorus pentoxide is dispersed in an amount of 0.05 to 5% by weight.   The heat-resistant expanded graphite sheet according to claim 1 or 2, wherein the phosphate is dispersed and contained in an amount of 1 to 16% by weight.   4. The method according to claim 1, wherein the phosphate is selected from primary lithium phosphate, secondary lithium phosphate, primary calcium phosphate, secondary calcium phosphate, primary aluminum phosphate, and secondary aluminum phosphate. The heat-resistant expanded graphite sheet described.   The heat-resistant expanded graphite sheet according to any one of claims 1 to 4, wherein the organic phosphorus compound is dispersed and contained in an amount of 0.1 to 10% by weight.   6. The organic phosphorus compound according to any one of claims 1 to 5, wherein the organic phosphorus compound is selected from organic phosphonic acids and esters thereof, organic phosphinic acids and esters thereof, phosphate esters, phosphite esters and hypophosphite esters. Heat-resistant expanded graphite sheet. The heat-resistant expanded graphite sheet according to claim 6, wherein the organic phosphonic acid and its ester are represented by the following general formula (1).

[In the formula (1), R ¹ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group comprising an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. R ² and R ³ are each composed of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. Aralkyl group. ] The heat-resistant expanded graphite sheet according to claim 6, wherein the organic phosphinic acid and its ester are represented by the following general formula (2).

[In formula (2), R ⁴ is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group comprising an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. R ⁵ and R ⁶ are each composed of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms or an alkylene part having 1 to 10 carbon atoms and an aryl part having 6 to 18 carbon atoms. Aralkyl group. ] The heat-resistant expanded graphite sheet according to claim 6, wherein the phosphate ester is represented by the following general formula (3).

Wherein ^{(3), R 7, R} 8, R 9 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkylene unit and a carbon number of 1 to 10 aryl group or a carbon of 6 to 18 carbon atoms 6 An aralkyl group consisting of ˜18 aryl moieties. However, the case of all hydrogen atoms is excluded. ] The heat resistance according to claim 6, wherein the phosphite is selected from a phosphite triester represented by the following general formula (4) and a phosphite diester and a phosphite monoester represented by the following general formula (5). Expandable graphite sheet.

[In the formulas (4) and (5), R ¹⁰ , R ¹¹ , R ¹² are an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and a carbon number. An aralkyl group comprising an aryl part having 6 to 18 atoms, wherein R ¹³ and R ¹⁴ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms. And an aralkyl group consisting of an aryl part having 6 to 18 carbon atoms. However, the case where both R ¹³ and R ¹⁴ are hydrogen atoms is excluded. ] The heat resistance according to claim 6, wherein the hypophosphite is a hypophosphite diester (phosphonite) represented by the following general formula (6) or a hypophosphite monoester represented by the following general formula (7). Expandable graphite sheet.

[In the formulas (6) and (7), R ¹⁵ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and 6 to 18 carbon atoms. R ¹⁶ , R ¹⁷ , and R ¹⁸ are each an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an alkylene part having 1 to 10 carbon atoms and a carbon number. It is an aralkyl group consisting of 6 to 18 aryl moieties. ]

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