Patent Application
20090292057
This invention relates to a new composition for reactive injection molding and reactive injection molded articles. Particularly, this invention relates to a composition for reactive injection molding which can produce an injection molded article having an excellent mechanical strength and an excellent electric conductivity, and reactive injection molded articles obtained therefrom.
Recently, as automobile exterior components such as bumper part, resin materials have been studied and some components made of resin materials become commercially practical.
As the manufacturing method for such resinous components, the reactive injection molding method (RIM) where a resin raw material undergoes a reaction in a forming die has been particularly utilized. Because, RIM shows a good fabrication property.
With respect to structural components such as the automobile exterior components as mentioned above or aircraft components, it is desired to be of lightweight, high mechanical strength, high elasticity, and good thermal resistance. Further, with respect to the automobile exterior components, it is desired to have an electric conductivity with a thermal resistance so as to be capable of undergoing electrostatic coating process in consort with steel outside panels.
Carbon fiber reinforced plastics in which carbon fibers are blended into a matrix of resin material has been focused as the material satisfying the above mentioned properties.
Further, with respect to the separator for fuel cell, an attempt that the separator was manufactured by a procedure which includes a graphitizing step and a machining step after molding a mixture of thermosetting resin and carbonaceous powder, and an attempt that the separator was manufactured by a compression molding method have been made. Incidentally, in the graphitizing step, the molded article undergoes burning in order to enhance the electric conductivity, and in the machining step, the burnt molded article undergoes cutting, grinding, and the like, in order to give a prescribed shape. The procedure which includes the graphitizing step and the machining step, however, is accompanied by a substantial cost of manufacturing and difficulty in churning out the products. Hence, procedures utilizing injection molding or injection compression molding have been proposed. According to these procedures, it is possible to shorten the molding time substantially. Thus, it is possible to cope with needs for mass production and provide a low-cost fuel cell separator.
Moreover, in recent years, fine carbon fibers such as carbon nano structures, which are represented by the carbon nanotube (hereinafter, referred to also as “CNT”.) have been focused, and an attempt of utilizing the fine carbon fibers as filler of the carbon fiber reinforced plastics made by injection molding has been also studied as described in Patent Literatures 1 and 2, for instance. The related parts of Patent Literatures 1 and 2 are incorporated herein by reference. However, such fine carbon fibers unfortunately show an aggregate state even just after their synthesis. When these aggregates are used as-is, the fine carbon fibers would be poorly dispersed, and thus the product obtained may show a poor performance. In the Patent Literature 2, it is disclosed that the aggregates of fine carbon fibers added into a liquid curing resin composition are disintegrated by kneading with a biaxial extruder so that the aggregates which are downsized to 35 μm or less are dispersed into the matrix. However, in order to make such fine aggregates, it is necessary to apply a substantially strong shearing force, and which would bring a result that the fine carbon fibers, per se, are forced to cut into their shortened forms. Furthermore, although the carbon fibers are downsized in the final product, the carbon fibers are dispersed in the form of aggregates. Thus, it can be hardly considered that the carbon fibers are dispersed uniformly and in a network configuration. Thus, the improvement in properties was still inadequate.
Patent Literature 1: Description of U.S. Pat. No. 5,611,964
Patent Literature 2: Description of U.S. Pat. No. 5,643,502
Therefore, this invention aims to provide a composition for injection molding which includes new carbon fibrous structures which have preferable physical properties as a conductivity giving agent, and which can improve mechanical, thermal and electrical properties of a matrix while maintaining other properties of the matrix, when added to the matrix in a small amount.
As a result of our diligent study for solving the above problems, we, the inventors, have found that, in order to give adequate mechanical, thermal, and electrical properties even in a small adding amount to the matrix, the effective things are to adapt carbon fibers having a diameter as small as possible; to make an sparse structure of the carbon fibers where the fibers are mutually combined tightly so that the fibers do not behave individually and which sustains their sparse state in the resin matrix; and to adapt as the carbon fibers per se ones which are designed to have a minimum amount of defects, and then, we have attained the present invention.
The present invention to solve the above mentioned problems is, therefore, a composition for injection molding which is characterized in that carbon fibrous structures are contained in a liquid curing resin composition, at a rate of 0.1-20% by weight based on the total weight of the composition, wherein the carbon fibrous structure comprises a three dimensional network of carbon fibers each having an outside diameter of 15-100 nm, wherein the carbon fibrous structure further comprises a granular part with which the carbon fibers are tied together in the state that the concerned carbon fibers are externally elongated therefrom, and wherein the granular part is produced in a growth process of the carbon fibers.
The present invention also provides the above mentioned composition for injection molding, wherein the carbon fibrous structures have ID/IG ratio determined by Raman spectroscopy of not more than 0.2.
The present invention also provides the above mentioned composition for injection molding, wherein the carbon fibrous structures are produced using as carbon sources at least two carbon compounds which have mutually different decomposition temperatures.
The present invention further discloses an injection molded article which is molded using the above mentioned composition for injection molding.
According to the present invention, since the carbon fibrous structure is one comprising carbon fibers of a ultrathin diameter which are configured three dimensionally, and are bound tightly together by a granular part produced in a growth process of the carbon fibers so that the concerned carbon fibers are externally elongated from the granular part, the carbon fibrous structures can disperse promptly into the liquid curing resin composition on adding, while they maintain such a bulky structure. Thus, even when they added at a small amount to the matrix, the fine carbon fibers can be distributed uniformly over the matrix. Since the fine carbon fibers are dispersed uniformly throughout the liquid curing resin composition, the composition can undergo injection molding without causing an extreme elevation in viscosity. Further, in the obtained molded article, it is possible to form good electric conductive paths throughout the matrix, and thus it is to improve the electrical conductivity adequately. In addition, with respect to the mechanical and thermal properties, improvements can be expected in analogous fashions, since the fine carbon fibers as fillers are distributed evenly over the matrix. Further, as mentioned above, since an extreme elevation in viscosity is not caused during the injection molding, the composition can apply to the injection molding even when the content of the carbon fibrous structures as filler are enhanced relatively. Therefore, for instance, it is possible to churn out members which require a high conductivity, such as electrode members of various cells can be manufactured
Now, the present invention will be described in detail with reference to some preferable embodiments.
The injection molding composition according to this invention is characterized in that carbon fibrous structures each having a specific structure like a three dimensional network as mentioned later are contained at a rate of 0.1-20.0% by weight based on the total weight of the composition.
Each carbon fibrous structure to be used in the present invention is, as shown in SEM photo of
The reason for restricting the outside diameter of the carbon fibers which constitutes the carbon fibrous structure to a range of 15 nm to 100 nm is because when the outside diameter is less than 15 nm, the cross-sections of the carbon fibers do not have polygonal figures as described later. According to physical properties of the carbon fiber, the smaller the diameter of a fiber, the greater the number of carbon fibers will be for the same weight and/or the longer the length in the axial direction of the carbon fiber. This property would be followed by an enhanced electric conductivity. Thus, carbon fibrous structures having an outside diameter exceeding 100 nm are not preferred for use as modifiers or additives for a matrix such as a resin, etc. Particularly, it is more desirable for the outside diameter of the carbon fibers to be in the range of 20-70 nm. Carbon fibers that have a diameter within the preferable range and whose tubular graphene sheets are layered one by one in the direction that is orthogonal to the fiber axis, i.e., being of a multilayer type, can enjoy a high flexural rigidity and ample elasticity. In other words, such fibers would have a property of being easy to restore their original shape after undergoing any deformation. Therefore, even if the carbon fibrous structures have been compressed prior to being mixed into the matrix material, they tend to take a sparse structure in the matrix.
Incidentally, when annealing at a temperature of not less than 2400° C., the spacing between the layered graphene sheets becomes lesser and the true density of the carbon fiber is increased from 1.89 g/cm3 to 2.1 g/cm3, and the cross sections of the carbon fiber perpendicular to the axis of carbon fiber come to show polygonal figures. As a result, the carbon fibers having such constitution become denser and have fewer defects in both the stacking direction and the surface direction of the graphene sheets that make up the carbon fiber, and thus their flexural rigidity (EI) can be enhanced.
Additionally, it is preferable that the outside diameter of the fine carbon fiber undergoes a change along the axial direction of the fiber. In the case that the outside diameter of the carbon fiber is not constant, but changed along the axial direction of the fiber, it would be expected that some anchor effect may be provided to the carbon fiber in the matrix such as resin, and thus the migration of the carbon fiber in the matrix can be restrained, leading to improved dispersion stability.
Then, in the carbon fibrous structure used in the present invention, fine carbon fibers having a predetermined outside diameter and being configured three dimensionally are bound together by a granular part produced in a growth process of the carbon fibers so that the carbon fibers are elongated outwardly from the granular part. Since multiple carbon fibers are not only entangled each other, but tightly bound together at the granular part, the carbon fibers will not disperse as single fibers, but will be dispersed as intact bulky carbon fibrous structures when added to the matrix of elastomer. Since the fine carbon fibers are bound together by a granular part produced in the growth process of the carbon fibers in the carbon fibrous structure to be used in the present invention, the carbon fibrous structure itself can enjoy superior properties such as electric property. For instance, when determining electrical resistance under a certain pressed density, the carbon fibrous structure to be used in the present invention shows an extremely low resistivity, as compared with that of a simple aggregate of the fine carbon fibers and that of the carbon fibrous structures in which the fine carbon fibers are fixed at the contacting points with a carbonaceous material or carbonized substance therefrom after the synthesis of the carbon fibers. Thus, when the carbon fibrous structures added and distributed in a matrix, they can form good conductive paths within the matrix.
Since the granular part is produced in the growth process of the carbon fibers as mentioned above, the carbon-carbon bonds at the granular part are well developed. Further, the granular part appears to include mixed state of sp2- and sp3-bonds, although it is not clear accurately. After the synthesis process (in the “intermediate” or “first intermediate” defined hereinafter), the granular part and the fibrous parts are continuous mutually because of a structure comprising patch-like sheets of carbon atoms laminated together. Further, after the high temperature treatment, at least a part of graphene layers constituting the granular part is continued on graphene layers constituting the fine carbon fibers elongated outwardly from the granular part, as shown in
With respect to the carbon fibers, the condition of being “extended outwardly” from the granular part used herein means principally that the carbon fibers and granular part are linked together by carbon crystalline structural bonds as mentioned above, but does not means that they are apparently combined together by any additional binding agent (involving carbonaceous ones).
As traces of the fact that the granular part is produced in the growth process of the carbon fibers as mentioned above, the granular part has at least one catalyst particle or void therein, the void being formed due to the volatilization and elimination of the catalyst particle during the heating process after the generation process. The void (or catalyst particle) is essentially independent from hollow parts which are formed in individual fine carbon fibers which are extended outwardly from the granular part (although, a few voids which happened to be associated with the hollow part may be observed).
Although the number of the catalyst particles or voids is not particularly limited, it may be about 1-1000 a granular particle, more preferably, about 3-500 a granular particle. When the granular part is formed under the presence of catalyst particles the number of which is within the range mentioned above, the granular part formed can have a desirable size as mentioned later.
The per-unit size of the catalyst particle or void existing in the granular particle may be, for example, 1-100 nm, preferably, 2-40 nm, and more preferably, 3-15 nm.
Furthermore, it is preferable that the diameter of the granular part is larger than the outside diameter of the carbon fibers as shown in
Although the concrete value for the particle diameter of the granular part will be depended on the size of the carbon fibrous structure and the outer diameters of the fine carbon fibers in the carbon fibrous structure, for example, it may be 20-5000 nm, more preferably, 25-2000 nm, and most preferably, 30-500 nm, on average.
Furthermore, the granular part may be roughly globular in shape because the part is produced in the growth process of the carbon fibers as mentioned above. On average, the degree of roundness thereof may lay in the range of from 0.2 to <1, preferably, 0.5 to 0.99, and more preferably, 0.7 to 0.98.
Additionally, the binding of the carbon fibers at the granular part is very tight as compared with, for example, that in the structure in which mutual contacting points among the carbon fibers are fixed with carbonaceous material or carbonized substance therefrom. It is also because the granular part is produced in the growth process of the carbon fibers as mentioned above. Even under such a condition as to bring about breakages in the carbon fibers of the carbon fibrous structure, the granular part (the binding site) is maintained stably. Specifically, for example, when the carbon fibrous structures are dispersed in a liquid medium and then subjected to ultrasonic treatment with a selected wavelength and a constant power under a load condition by which the average length of the carbon fibers is reduced to about half of its initial value as shown in the Examples described later, the changing rate in the mean diameter of the granular parts is not more than 10%, preferably, not more than 5%, thus, the granular parts, i.e., the binding sites of fibers are maintained stably.
In carbon fibrous structures to be used in the present invention, it is preferable that the carbon fibrous structure has an area-based circle-equivalent mean diameter of 50-100 μm, and more preferably, 60-90 μm. The “area-based circle-equivalent mean diameter” used herein is the value which is determined by taking a picture of the outside shapes of the carbon fibrous structures with a suitable electron microscope, etc., tracing the contours of the respective carbon fibrous structures in the obtained picture using a suitable image analysis software, e.g., WinRoof™ (Mitani Corp.), and measuring the area within each individual contour, calculating the circle-equivalent mean diameter of each individual carbon fibrous structure, and then, averaging the calculated data.
Although it is not to be applied in all cases because the circle-equivalent mean diameter may be influenced by the kind of matrix material such as a resin to be complexed, the circle-equivalent mean diameter may become a factor by which the maximum length of a carbon fibrous structure upon combining with a matrix such as a resin is determined. In general, when the circle-equivalent mean diameter is not more than 50 μm, the electrical conductivity of the obtained composite may not be expected to reach a sufficient level, while when it exceeds 100 μm, an undesirable increase in viscosity may be expected to happen upon kneading of the carbon fibrous structures in the matrix. The increase in viscosity may be followed by failure of dispersion of the carbon fibrous structures into the matrix.
As mentioned above, the carbon fibrous structure according to the present invention has the configuration where the fine carbon fibers existing in three dimensional network state are bound together by the granular part (s) so that the carbon fibers are externally elongated from the granular part(s). When two or more granular parts are present in a carbon fibrous structure, wherein each granular part binds the fibers so as to form the three dimensional network, the mean distance between adjacent granular parts may be, for example, 0.5-300 μm, preferably, 0.5-100 μm, and more preferably, 1-50 μm. The distance between adjacent granular parts used herein is determined by measuring distance from the center of a granular part to the center of another granular part which is adjacent the former granular part. When the mean distance between the granular parts is less than 0.5 μm, a configuration where the carbon fibers form an inadequately developed three dimensional network may be obtained. Therefore, it may become difficult to form good electrically conductive paths when the carbon fiber structures each having such an inadequately developed three dimensional network are added and dispersed to a matrix such as a resin. Meanwhile, when the mean distance exceeds 300 μm, an undesirable increase in viscosity may be expected to happen upon adding and dispersing the carbon fibrous structures in the matrix. The increase in viscosity may result in an inferior dispersibility of the carbon fibrous structures to the matrix.
Furthermore, the carbon fibrous structure to be used in the present invention may exhibit a bulky, loose form in which the carbon fibers are sparsely dispersed, because the carbon fibrous structure is comprised of carbon fibers that are configured as a three dimensional network and are bound together by a granular part so that the carbon fibers are elongated outwardly from the granular part as mentioned above. It is desirable that the bulk density thereof is in the range of 0.0001-0.05 g/cm3, more preferably, 0.001-0.02 g/cm3. When the bulk density exceeds 0.05 g/cm3, it would become difficult to improve the physical properties of the matrix such as resin with a small dosage.
Furthermore, a carbon fibrous structure to be used in the present invention can enjoy good electric properties in itself, since the carbon fibers configured as a three dimensional network in the structure are bound together by a granular part produced in the growth process of the carbon fibers as mentioned above. For instance, it is desirable that a carbon fibrous structure to be used in the present invention has a powder electric resistance determined under a certain pressed density, 0.8 g/cm3, of not more than 0.02 Ω·cm, more preferably, 0.001 to 0.010 Ω·cm. If the particle's resistance exceeds 0.02 Ω·cm, it may become difficult to form good electrically conductive paths when the structures are added to a matrix such as a resin.
In order to enhance the strength and electric conductivity of the carbon fibrous structure used in the present invention, it is desirable that the graphene sheets that make up the carbon fibers have a small number of defects, and more specifically, for example, the ID/IG ratio of the carbon fiber determined by Raman spectroscopy is not more than 0.2, more preferably, not more than 0.1. Incidentally, in Raman spectroscopic analysis, with respect to a large single crystal graphite, only the peak (G band) at 1580 cm−1 appears. When the crystals are of finite ultrafine sizes or have any lattice defects, the peak (D band) at 1360 cm−1 can appear. Therefore, when the intensity ratio (R=I1360/I1580=ID/IG) of the D band and the G band is below the selected range as mentioned above, it is possible to say that there is little defect in graphene sheets.
Furthermore, it is desirable that the carbon fibrous structure to be used in the present invention has a combustion initiation temperature in air of not less than 750° C., preferably, 800° C.-900° C. Such a high thermal stability would be brought about by the above mentioned facts that it has little defects and that the carbon fibers have a predetermined outside diameter.
A carbon fibrous structure having the above described, desirable configuration may be prepared as follows, although it is not limited thereto.
Basically, an organic compound such as a hydrocarbon is chemical thermally decomposed through the CVD process in the presence of ultrafine particles of a transition metal as a catalyst in order to obtain a fibrous structure (hereinafter referred to as an “intermediate”), and then the intermediate thus obtained undergoes a high temperature heating treatment.
As a raw material organic compound, hydrocarbons such as benzene, toluene, xylene; carbon monoxide (CO); and alcohols such as ethanol may be used. It is preferable, but not limited, to use as carbon sources at least two carbon compounds which have different decomposition temperatures. Incidentally, the words “at least two carbon compounds” used herein not only include two or more kinds of raw materials, but also include one kind of raw material that can undergo a reaction, such as hydrodealkylation of toluene or xylene, during the course of synthesis of the fibrous structure such that in the subsequent thermal decomposition procedure it can function as at least two kinds of carbon compounds having different decomposition temperatures.
When as the carbon sources at least two kinds of carbon compounds are provided in the thermal decomposition reaction system, the decomposition temperatures of individual carbon compounds may be varied not only by the kinds of the carbon compounds, but also by the gas partial pressures of individual carbon compounds, or molar ratio between the compounds. Therefore, as the carbon compounds, a relatively large number of combinations can be used by adjusting the composition ratio of two or more carbon compounds in the raw gas.
For example, the carbon fibrous structure to be used in the present invention can be prepared by using two or more carbon compounds in combination, while adjusting the gas partial pressures of the carbon compounds so that each compound performs mutually different decomposition temperature within a selected thermal decomposition reaction temperature range, and/or adjusting the residence time for the carbon compounds in the selected temperature region, wherein the carbon compounds to be selected are selected from the group consisting of alkanes or cycloalkanes such as methane, ethane, propanes, butanes, pentanes, hexanes, heptane, cyclopropane, cycrohexane, particularly, alkanes having 1-7 carbon atoms; alkenes or cycloolefin such as ethylene, propylene, butylenes, pentenes, heptenes, cyclopentene, particularly, alkenes having 1-7 carbon atoms; alkynes such as acetylene, propyne, particularly, alkynes having 1-7 carbon atoms; aromatic or heteroaromatic hydrorocarbons such as benzene, toluene, styrene, xylene, naphthalene, methyl naphtalene, indene, phenanthrene, particularly, aromatic or heteroaromatic hydrorocarbons having 6-18 carbon atoms; alcohols such as methanol, ethanol, particularly, alcohols having 1-7 carbon atoms; and other carbon compounds involving such as carbon monoxide, ketones, ethers. Further, to optimize the mixing ratio can contribute to the efficiency of the preparation.
When a combination of methane and benzene is utilized among such combinations of two or more carbon compounds, it is desirable that the molar ratio of methane/benzene is >1-600, preferably, 1.1-200, and more preferably 3-100. The ratio is for the gas composition ratio at the inlet of the reaction furnace. For instance, when as one of carbon sources toluene is used, in consideration of the matter that 100% of the toluene decomposes into methane and benzene in proportions of 1:1 in the reaction furnace, only a deficiency of methane may be supplied separately. For example, in the case of adjusting the methane/benzene molar ratio to 3, 2 mol methane may be added to 1 mol toluene. As the methane to be added to the toluene, it is possible to use the methane which is contained as an unreacted form in the exhaust gas discharged from the reaction furnace, as well as a fresh methane specially supplied.
Using the composition ratio within such a range, it is possible to obtain the carbon fibrous structure in which both the carbon fiber parts and granular parts are efficiently developed.
Inert gases such as argon, helium, xenon; and hydrogen may be used as an atmosphere gas.
A mixture of transition metal such as iron, cobalt, molybdenum, or transition metal compounds such as ferrocene, metal acetate; and sulfur or a sulfur compound such as thiophene, ferric sulfide; may be used as a catalyst.
The intermediate may be synthesized using a CVD process with hydrocarbon or etc., which has been conventionally used in the art. The steps may comprise gasifying a mixture of hydrocarbon and a catalyst as a raw material, supplying the gasified mixture into a reaction furnace along with a carrier gas such as hydrogen gas, etc., and undergoing thermal decomposition at a temperature in the range of 800° C.-1300° C. By following such synthesis procedures, the product obtained is an aggregate, which is of several to several tens of centimeters in size and which is composed of plural carbon fibrous structures (intermediates), each of which has a three dimensional configuration where fibers having 15-100 nm in outside diameter are bound together by a granular part that has grown around the catalyst particle as the nucleus.
The thermal decomposition reaction of the hydrocarbon raw material mainly occurs on the surface of the catalyst particles or on growing surface of granular parts that have grown around the catalyst particles as the nucleus, and the fibrous growth of carbon may be achieved when the recrystallization of the carbons generated by the decomposition progresses in a constant direction. When obtaining carbon fibrous structures according to the present invention, however, the balance between the thermal decomposition rate and the carbon fiber growth rate is intentionally varied. Namely, for instance, as mentioned above, to use as carbon sources at least two kinds of carbon compounds having different decomposition temperatures may allow the carbonaceous material to grow three dimensionally around the granular part as a centre, rather than in one dimensional direction. The three dimensional growth of the carbon fibers depends not only on the balance between the thermal decomposition rate and the growing rate, but also on the selectivity of the crystal face of the catalyst particle, residence time in the reaction furnace, temperature distribution in the furnace, etc. The balance between the decomposition rate and the growing rate is affected not only by the kinds of carbon sources mentioned above, but also by reaction temperatures, and gas temperatures, etc. Generally, when the growing rate is faster than the decomposition rate, the carbon material tends to grow into fibers, whereas when the thermal decomposition rate is faster than the growing rate, the carbon material tends to grow in peripheral directions of the catalyst particle. Accordingly, by changing the balance between the thermal decomposition rate and the growing rate intentionally, it is possible to control the growth of carbon material to occur in multi-direction rather than in single direction, and to produce three dimensional structures that are related to the present invention. In order to form the above mentioned three-dimensional configuration, where the fibers are bound together by a granular part, with ease, it is desirable to optimize the compositions such as the catalyst used, the residence time in the reaction furnace, the reaction temperature and the gas temperature.
With respect to the method for preparing the carbon fibrous structure to be used in the present invention with efficiency, as another approach to the aforementioned one that two or more carbon compounds which have mutually different decomposition temperature are used in an appropriate mixing ratio, there is an approach that the raw material gas supplied into the reaction furnace from a supply port is forced to form a turbulent flow in proximity to the supply port. The “turbulent flow” used herein means a furiously irregular flow, such as flow with vortexes.
In the reaction furnace, immediately after the raw material gas is supplied into the reaction furnace from the supply port, metal catalyst fine particles are produced by the decomposition of the transition metal compound as the catalyst involved in the raw material gas. The production of the fine particles is carried out through the following steps. Namely, at first, the transition metal compound is decomposed to make metal atoms, then, plural number of, for example, about one hundred of metal atoms come into collisions with each other to create a cluster. At the created cluster state, it can not function as a catalyst for the fine carbon fiber. Then, the clusters further are aggregated by collisions with each other to grow into a metal crystalline particle of about 3-10 nm in size, and which particle comes into use as the metal catalyst fine particle for producing the fine carbon fiber.
During the catalyst formation process as mentioned above, if the vortex flows belonging to the furiously turbulent flow are present, it is possible that the collisions of metal atoms or collisions of clusters become more vigorously as compared with the collisions only due to the Brownian movement of atoms or collisions, and thus the collision frequency per unit time is enhanced so that the metal catalyst fine particles are produced within a shorter time and with higher efficiency.
Further, since concentration, temperature, etc. are homogenized by the force of vortex flow, the obtained metal catalyst fine particles become uniform in size. Additionally, during the process of producing metal catalyst fine particles, a metal catalyst particles' aggregate in which numerous metal crystalline particles was aggregated by vigorous collisions with the force of vortex flows can be also formed. Since the metal catalyst particles are rapidly produced as mentioned above, the decomposition of carbon compound can be accelerated so that an ample amount of carbonaceous material can be provided. Whereby, the fine carbon fibers grow up in a radial pattern by taking individual metal catalyst particles in the aggregate as nuclei. When the thermal decomposition rate of a part of carbon compounds is faster than the growing rate of the carbon material as previously described, the carbon material may also grow in the circumferential direction so as to form the granular part around the aggregate, and thus the carbon fiber structure of the desired three dimensional configuration may be obtained with efficiency. Incidentally, it may be also considered that there is a possibility that some of the metal catalyst fine particles in the aggregate are ones that have a lower activity than the other particles or ones that are deactivated on the reaction. If non-fibrous or very short fibrous carbon material layers grown by such catalyst fine particles before or after the catalyst fine particles aggregate are present at the circumferential area of the aggregate, the granular part of the carbon fiber structure to be used in the present invention may be formed.
The concrete means for creating the turbulence to the raw material gas flow near the supply port for the raw material gas is not particularly limited. For example, it is adaptable to provide some type of collision member at a position where the raw material gas flow introduced from the supply port can be interfered by the collision section. The shape of the collision section is not particularly limited, as far as an adequate turbulent flow can be formed in the reaction furnace by the vortex flow which is created at the collision section as the starting point. For example, embodiments where various shapes of baffles, paddles, tapered tubes, umbrella shaped elements, etc., are used singly or in varying combinations and located at one or more positions may be adaptable.
The intermediate, obtained by heating the mixture of the catalyst and hydrocarbon at a constant temperature in the range of 800° C.-1300° C., has a structure that resembles sheets of carbon atoms laminated together, (and being still in a half-raw, or incomplete condition). When analyzed with Raman spectroscopy, the D band of the intermediate is very large and many defects are observed. Further, the obtained intermediate is associated with unreacted raw materials, nonfibrous carbon, tar moiety, and catalyst metal.
Therefore, the intermediate is subjected to a high temperature heat treatment at 2400-3000° C. using a proper method in order to remove such residues from the intermediate and to produce the intended carbon fibrous structure with few defects.
For instance, the intermediate may be heated at 800-1200° C. to remove the unreacted raw material and volatile flux such as the tar moiety, and thereafter annealed at a high temperature of 2400-3000° C. to produce the intended structure and, concurrently, to vaporize the catalyst metal, which is included in the fibers, to remove it from the fibers. In this process, it is possible to add a small amount of a reducing gas and carbon monoxide into the inert gas atmosphere to protect the carbon structures.
By annealing the intermediate at a temperature of 2400-3000° C., the patch-like sheets of carbon atoms are rearranged to associate mutually and then form multiple graphene sheet-like layers.
After or before such a high temperature heat treatment, the aggregates may be subjected to crushing in order to obtain carbon fibrous structures, each having an area-based circle-equivalent mean diameter of several centimeters. Then, the obtained carbon fibrous structures may be subjected to pulverization in order to obtain the carbon fibrous structures having an area-based circle-equivalent mean diameter of 50-100 μm. It is also possible to perform the pulverization directly without crushing. On the other hand, the initial aggregates involving plural carbon fibrous structures to be used in the present invention may also be granulated for adjusting shape, size, or bulk density to one's suitable for using a particular application. More preferably, in order to utilize effectively the above structure formed from the reaction, the annealing would be performed in a state such that the bulk density is low (the state that the fibers are extended as much as they can and the voidage is sufficiently large). Such a state may contribute to improved electric conductivity of a resin matrix.
The carbon fibrous structures used in the present invention may have the following properties:
A) a low bulk density;
B) a good dispersibility in a matrix such as resin;
C) a high electrical conductivity;
D) a high heat conductivity;
E) a good slidability;
F) a good chemical stability;
G) a high thermal stability; and etc.
The injection molding composition according to this invention is prepared by adding the carbon fibrous structures as mentioned above into a liquid curing resin composition. With respect to the liquid curing resin composition used in the present invention, there is no particular limitation and various known liquid curing resin compositions may be usable. Incidentally, the “liquid curing resin composition” described herein denotes one which shows liquid state within working temperature range, and which able to form three dimensional polymeric matrix by curing reaction. It can include not only matrix former(s) such as reactive monomer, oligomer, cross-linkable polymer, or mixtures thereof, but also component(s) which can contribute to the reaction, such as polymerization initiator, catalyst, curing agent, activating agent, etc. Further, if necessary, it may include other components such as solvent, viscosity controlling agent, various stabilizers, etc., as known in the art.
As the liquid curing resin composition, it may be either one-part type or two-part type. When it is two-part type, the carbon fibrous structures may be added to either the principal ingredient side or the curing ingredient side.
As the curing resin, concretely, for instance, thermosetting resins such as urethane resin, epoxy resin, norbornene resin, phthalic resin, phenolic resin, furan resin, xylene-formaldehyde resin, urea resin, unsaturated polyester resin, melamine resin, aniline resin, modified acrylic resin, silicone type resin, etc., are enumerated, but it is not limited thereto.
Among them, urethane resin, norbornene resin, epoxy resin, phenolic resin, etc., are particularly preferable, although the kind may be varied depending upon the usage of the obtained molded article and so on.
Incidentally, although some thermosetting resins show solid state at ordinary temperature, these are also usable as far as they can show liquid state at a working temperature. Further, not only the thermosetting resins, but also various known photosetting resins, various known electron-beam curing resin compositions, etc., are also usable.
Furthermore, into the liquid curing resin composition, any thermoplastic resin or thermoplastic elastomer such as acrylic resin, polyolefin resin, polystyrene resin, polyamide resin, polyimide resin, polyacrylonitrile resin, polyvinyl chloride resin, saturated polyester resin, ionomer resin, etc., may be incorporated in conjunction with the curing resin.
As the epoxy resin, there is not particular limitation, and, for instance, bisphenol-A type epoxy resin, bisphenol-F type epoxy resin, bisphenol-S type epoxy resin, amino glycidyl type epoxy resin, amino phenol type epoxy resin, novolac type epoxy resin, naphthalene type epoxy resin, alicyclic type epoxy resin, etc., are usable. As the curing agent, for instance, aromatic amines; aliphatic amines; modified amines which are obtained by reacting these active hydrogen containing amines with a compound such as epoxy compound, acrylonitrile, phenol and formaldehyde, thiourea, etc.; tertiary amines which have no active hydrogen; carboxylic anhydrides; polycarboxylic acid hydrazides; polyphenol compound such as novolac resins; polymercaptans such as ester of thioglycolic acid and polyol; Lewis acid's complexes such as boron trifluoride ethyl amine complex; aromatic sulfonium salts are enumerated. It is possible to combine a known appropriate curing aid with the curing agent in order to enhance the curing activity. For instance, a case that a urea derivative such as 3-phenyl-1,1-dimethyl urea, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), 3-(3-chloro-4-methylphenyl)-1,1-dimethyl urea, or 2,4-bis (3,3-dimethyl ureid) toluene, as the curing agent is combined with dicyandiamide; a case of a tertiary amine as curing agent is combined with carboxylic anhydride or novolac resin, are enumerated.
As known in the art, the urethane resin contains an isocyanate and a polyol ingredient. As the isocyanate, all isocyanates which are used in the generic polyurethane resin are usable. Namely, aromatic isocyanates; aliphatic isocyanates; alicyclic isocyanates; dimer or trimer of these isocyanates; or prepolymers in which one of these isocyanates is previously reacted with one of polyols, are enumerated. For instance, ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexane-1,3- or 1,4-diisocyanate, and isophorone diisocyanate, are enumerated. Typical aromatic polyisocyanates includes phenylene diisocyanates, toluene diisocyanates, and 4,4′-diphenyl methane diisocyanate. Particularly, 2,4- and 2,6-toluene diisocyanates are usable singly or in combination thereof as commercially available mixture. In addition, mixtures known as a trade name of “crude MDI” which include about 60% 4,4′-diphenylene diisocyanate in combination with higher polyisocyanate(s) of other analogical isomer(s) are also usable. Further, prepolymers of these polyisocyanates which comprise a mixture of polyisocyanate and polyether or polyester polyol parts of which are previously reacted mutually are also usable. Among them, aromatic isocyanates are preferable because the aromatic isocyanates are more reactive than the aliphatic or alicyclic isocyanates. Even in the case of using the aliphatic or alicyclic isocyanate having such a relatively low reactivity, however, it is still possible to make the composition more effective if a tin type catalyst is used in combination. Because, tin catalyst, particularly, mercapto group thereof acts so as to repress the activity of isocyanate, and when contacting with amine steam the isocyanate becomes active Meanwhile, as the polyol, all polyols which are used in the generic polyurethane resin are usable. Namely, for instance, polyether polyols, polyester polyols, polyacrylic polyols, polycarbonate polyols, epoxy modified polyols, urethane modified polyols, etc., are enumerated. Although the usage amount of isocyanate to such a polyol can not be generally limited because it may be varied depending upon the kind and amount of polyol to be used and the kind of isocyanate, it would be suitable to set the equivalent ratio of NCO/OH to be 1/9-2/1, particularly, 1/3-1.5/1, more particularly 1/2-1.2/1. Further, in the urethane resin composition, a catalyst for urethane, a chain elongating agent, etc., may be included. As the chain elongating agent, for instance, aromatic diamine chain elongating agents such as diethyl toluene diamine, t-butyl toluene diamine, etc., are enumerated. As the catalyst for urethane, known amine catalysts and known tin catalysts such as triethylene diamine, dibutyl tin dilaurate, etc., are included. An appropriate amount of the catalyst may be 0.025-0.3 part, more preferably 0.05-0.2 part based on 100 parts by weight of polyols in the composition.
Next, in the norbornene type liquid curing resin component, a metathesis catalyst and an activating agent are normally included in addition to norbornene type monomer.
As the norbornene type monomer, any monomers having norbornane ring(s) are usable. As concrete examples, for example, norbornane; bicyclic compound such as norbonadiene etc.; tricyclic compounds such as dicyclopenta diene (cyclopentadiene dimer), dihydro dicyclopenta diene, etc.; tetracyclic compounds such as tetracyclo dodecene, etc.; pentacyclic compounds such as cyclopentadiene trimer, etc.; heptacyclic compounds such as cyclopentadiene tetramer, etc.; substituted compounds of these di- to hepta-cyclic compounds such as alkyl-substituted compound, for instance, methyl-, ethyl-, propyl-, and butyl-substituted compounds, alkenyl-substituted compound, for instance, vinyl-substituted compound, alkylidene-substituted compounds, for instance, ethylidene-substituted compound, aryl-substituted compounds, for instance, phenyl-, tolyl-, naphtyl-substituted compounds, etc.; and substituted compounds of these di- to hepta-cyclic compounds having polar group(s) such as ester group, ether group, cyano group, halogen atom, etc.; are enumerated. Among them, polycyclic norbonene type monomers having more than three rings are preferable, because of their easy available and their excellent reactivitiy. Particularly, tricyclic, tetracyclic, and pentacyclic norbonene type monomers are preferable. These norbonene type monomers may be used singularly, or in any combinations of two or more of them. In addition, monomers such as cyclobutene, cyclopentene, cyclopentadiene, cyclooctene, cyclododecene, etc., which can be ring-opening copolymerized with the norbonene type monomer, are usable as comonomers. As the metathesis catalyst, any known compound capable of causing catalysis for ring-opening polymerization of the norbonene type monomer in the RIM procedure can be used without any particular limitation. For instance, tungsten hexachloride, and organic ammonium molybdates such as tridecyl ammonium molybdate, tri (tridecyl) ammonium molybtate, etc., which are known as metathesis catalyst for the norbonene type monomer in bulk polymerization, can be used without any particular limitation. Among them, organic ammonium molybdates are more desirable.
The injection molding composition according to the present invention includes an effective amount of the aforementioned carbon fibrous structures in conjunction with the above mentioned liquid curing resin composition.
Although the amount may be varied depending upon the usage of the injection molding composition, the kinds of the polymer which constitute the matrix, etc., it may be about 0.1-20% based on the total weight of the composition (incidentally, when the composition contains some volatile ingredient(s) such as solvent, etc., the total weight of the composition as mentioned above should be considered as the total weight of the vehicle solid content excluding such volatile ingredient(s)).
When it is less than 0.1%, there is fear that improvements of electrical conductivity, mechanical strength, heat stability, etc., in an obtained molded article can not be amply attained.
On the other hand, when it exceeds 20%, there is fear that the injection molding can be hardly practiced because of the increased viscosity.
In addition, in an embodiment of providing a conductivity capable of performing the electrostatic coating, or an embodiment of providing an antistatic property, it is preferable that the amount of the carbon fibrous structures is set to be about 0.5-5%, for example. On the other hand, in embodiments of attaching importance to the electrical conductivity rather than the mechanical strength, for instance, in an embodiment of being used as electrode material, it is possible to set it to be a relatively high content, so as to be 5-20%, for instance.
With respect to the injection molding composition according to the present invention, fine carbon fibers of the carbon fibrous structures can distribute themselves uniformly throughout the matrix even when the carbon fibrous structures are added at a relative small amount. Thus, the injection molding composition which has an excellent electrical conductivity can be prepared as mentioned above.
The injection molding composition of this invention may contain various known additives such as bulking agents, reinforcing agents, various stabilizers, antioxidants, ultraviolet rays absorbents, flame retardants, lubricants, plasticizers, solvents, etc., within the range where the primary objective of the present invention is not obstructed.
Especially, when it is desired to manufacture an electrical conductivity resin molded article in the present invention, any other conductive fillers such as metallic powder, carbon powder, etc., may be added to the composition.
Incidentally, in the case that the injection molding composition according to the present invention contains the other conductive filler such as metal powder, carbon powder, etc., in addition to the above mentioned carbon fibrous structures, the high conductivity which has been never attained in the art unless quite large amount of the conductive filler is added to the composition can be attained when a relatively small amount of the carbon fibrous structures are added to the composition instead of the addition of a relatively large amount of the conductive filler. Thus, the problems due to the increment of the additive amount of the conductive filler such as degression of cured film strength, easy exfoliating tendency, etc., can be solved, and simultaneously, an advantage in costs owing to the reduction in the using amount of expensive metal can be obtained.
Although the accurate functions and mechanisms for exhibiting such a high conductivity is not yet elucidated, it can be presumed that the relatively small carbon fibrous structures would be in contact with the relatively large conductive filler such as metal or carbon powder in the resin matrix, and which contributes to the high conductivity.
In details, it can be presumed that the high conductivity would be obtained by formation of electrical chains which are constituted by allowing the carbon fibrous structures to enter into and place in gaps caused when the conductive filler comes into contact mutually.
As the metal powder, for instance, metals such as silver, platinum, palladium, copper, nickel, etc., can be used singly or in various mixtures thereof, although it is not particularly limited thereto.
The particle shape of the metal powder is not particularly limited as far as the powder in the shape can be used for the conductive filler, such as flake, spherical, dendritic, acinous, indefinite, etc.
Although the particle size of the metal powder is not particularly limited, for instance, it is desirable to be in the range of 0.5-15 μm.
When mean particle size is less than 0.5 μm, the surface area of the metal powder becomes larger, and therefore, the metal powder becomes easy to be oxidized, and the desired adequate conductivity is no longer obtained.
Contrary, when mean particle size is more than 15 μm, there is a fear that numeral gaps are formed when the particles come into contact mutually, and the desired adequate conductivity is no longer obtained.
As the carbon powder which constitutes the conductive filler, it is desirable to use carbon black in general, although it is not particularly limited thereto.
As the carbon black, although any known carbon black obtained by various methods can be used, for instance, furnace black, channel black, thermal black, Ketjen black, etc., are enumerated as preferable examples. In addition, gas black, oil black, acetylene black, etc., which are classified by the difference of raw material, are also enumerated as preferable examples. Among them, acetylene black and Ketjen black are particularly preferable.
In the case that the conductive filler such as the metal powder and carbon powder is added to the thermosetting resin composition, for instance, with respect to the filler being of the metal powder, it is preferable that the additive amount of the filler is in the range of 100-500 parts by weight per 100 parts by weight of the thermosetting resin composition. When it is less than 100 parts by weight, there is a fear that a sufficient conductivity may not be obtained because the contacting points between the metal particles will become lesser. On the other hand, when it is more than 500 parts by weight, there is a fear that the tendency of bearing some malfunction, such as easy exfoliation of the conductive path made by this conductive resin composition, is increased, because the relative content of the resin component in the composition decreases.
With respect to the filler being of the carbon black, it is preferable that the additive amount of the carbon black is in the range of 5-50 parts by weight per 100 parts by weight of the thermosetting resin composition. When it is less than 5 parts by weight, there is a fear that a sufficient conductivity may not be obtained. On the other hand, when it is more than 50 parts by weight, there is a fear that a sufficient conductivity may not be obtained, because both of the relative content of the resin component and that of the carbon fibrous structures in the composition decrease, or a fear that the tendency of bearing some malfunction, such as easy exfoliation of the conductive path made by this conductive resin composition, is increased.
Incidentally, when the conductive filler is added to the injection molding composition, the reasonable additive amount of the carbon nanostructures is in the range of 0.1-30 parts by weight per 100 parts by weight of the thermoplastic elastomer.
The injection molding composition according to the present invention can be prepared by adding and mixing the carbon fibrous structures into the liquid thermosetting resin composition while stirring them by some appropriate stirring machine so as to form a premix. As the stirring machine to be used herein, any machine may be utilizable as far as it can perform stirring under a condition that the materials to be mixed are not exposed to an excessive shearing stress. For instance, various stirring machine which is provided with uniaxial or multiaxial rotator(s) such as screw or propeller, paddle, ribbon, etc., may be usable.
While stirring the liquid thermosetting resin composition with such a stirring machine, and maintaining the temperature of the liquid thermosetting resin not so as to cause the viscosity of the composition a sudden rising, the carbon fibrous structures are gradually added and mixed to the composition with a continuous procedure or divisional procedures. In such a procedure, it is preferable to maintain the temperature of the liquid thermosetting resin composition to be in the range of 10-70° C., preferably, 30-70° C., and more preferably, 50-70° C., although the condition is varied depending upon the kind of the liquid thermosetting resin composition. When it becomes a temperature of more than 70° C., as a general rule, the reaction of the liquid thermosetting resin composition will progress, and there is a great possibility that the fact will bring a sudden rising in the viscosity of the composition, and will affect adversely the preserving stability of the carbon fibrous structures containing thermosetting resin composition. Further, since it also affects the workability during the usage and the physical properties of the composition, it will be preferable to maintain the temperature to be not more than 70° C.
On the other hand, when the temperature of the resin composition becomes less than 10° C., the rising in the resin viscosity will be also caused due to decrease in the temperature, and there is a great possibility that the fact will bring a failure in the expected mixing or stirring.
Further, it is preferable that the liquid curing resin composition shows a viscosity in the range of about 0.01-80 Pa·s at this temperature range of 10-70° C. When the viscosity is less than 0.01 Pa·s, the dispersion of the carbon fibrous structure will become worse even when the rotation rate in stirring or extrusion is accelerated. This is because the carbon fibrous structures can be dispersed by the flow of resin having a certain extent of viscosity.
On the other hand, when the viscosity exceeds 80 Pa·s, there is a fear that the stress applied to the carbon nanostructures on the extrusion will become high, and this fact will cause a temperature rising in the thermosetting resin composition. As the result, a sudden rising in the viscosity of the composition will happen, and the preserving stability of the carbon fibrous structures containing thermosetting resin composition will be affected adversely.
Incidentally, in the case that the liquid curing resin composition contains the conductive filler as mentioned above, or other bulking agent, it is preferable that addition and dispersion of such conductive filler or other bulking agent into the liquid curing resin composition are performed in advance of the addition and stirring of the carbon fibrous structures into the liquid curing resin composition. Because, it is difficult to disperse such conductive filler or other bulking agent under a stirring condition of a relatively weak shearing stress as mentioned above.
Next, the premix liquid thermosetting resin composition thus prepared is introduced to a known appropriate injection molding device, while the temperature of the premix liquid thermosetting resin composition is similarly maintained to 10-70° C., and undergoes injection molding or injection compression molding where the temperature of molding die is maintained at a temperature of curing the thermosetting resin composition in order to produce a molded article of a prescribed shape. In the case of using the injection compression molding, for instance, a fashion where the resin composition is injected and filled into a molding die in its opening state and thereafter the die is closed so as to compress the content, a fashion where the resin composition is injected and filled into a molding die in its closed but zero clamping pressure's state so as to open the molding die with the inner pressure caused by the injected resin composition and thereafter the die is closed so as to compress the content, etc., may be adaptable. The molding condition at the injection molding or the injection compression molding may be selected appropriately depending upon the viscosity of the melted state of the liquid thermosetting resin, kinds and amounts of the curing agent, lubricant, etc., and the size of molded article to be produced.
Incidentally, in the case of two component type reactive injection molding, the molded article will be prepared by storing two monomer solutions into a first and a second vessels respectively, mixing them at a mixing rate of 1:1 within a reactive injection molding device, and then injecting the mixture into a molding die to allow the mixture to react with each other and to harden in the die.
Injection molded article made of the injection molding composition according to the present invention can possess, typically, a surface resistivity of not more than 1013 Ω/cm2, particularly, of 104-1012 Ω/cm2, although this property of the molded articles are, however, not limited thereto.
Although the uses of the injection molded article according to the present invention are not particularly limited and may belong in a wide and various fields, for instance, structural components such as the automobile exterior panel, aircraft components, etc; separator for fuel cell; electrode for electric double layer capacitor, material for electromagnetic wave absorber, etc., are enumerated.
Hereinafter, this invention will be illustrated in detail by practical examples. However, it is to be understood that the invention is not limited to the described examples.
Incidentally, the respective physical properties described in later are measured by the following protocols.
First, a photograph of pulverized product was taken with SEM. On the taken SEM photo, only carbon fibrous structures with a clear contour were taken as objects to be measured, and broken ones with unclear contours were omitted. Using all carbon fibrous structures that can be taken as objects in one single field of view (approximately, 60-80 pieces), about 200 pieces in total were measured with three fields of views. Contours of the individual carbon fibrous structures were traced using the image analysis software, WinRoof™ (trade name, marketed by Mitani Corp.), and area within each individual contour was measured, circle-equivalent mean diameter of each individual carbon fibrous structure was calculated, and then, the calculated data were averaged to determine the area based circle-equivalent mean diameter.
1 g of powder was placed into a 70 mm caliber transparent cylinder equipped with a distribution plate, then air supply at 0.1 Mpa of pressure, and 1.3 liter in capacity was applied from the lower side of the distribution plate in order to blow off the powder and thereafter allowed the powder to settle naturally. After the fifth air blowing, the height of the settled powder layer was measured. Any 6 points were adopted as the measuring points, and the average of the 6 points was calculated in order to determine the bulk density.
The Raman spectroscopic analysis was performed with the equipment LabRam 800 manufactured by HORIBA JOBIN YVON, S.A.S., and using 514 nm the argon laser.
Combustion behavior was determined using TG-DTA manufactured by MAC SCIENCE CO. LTD., at air flow rate of 0.1 liter/minute and heating rate of 10° C./minute. When burning, TG indicates a quantity reduction and DTA indicates an exothermic peak. Thus, the top position of the exothermic peak was defined as the combustion initiation temperature.
Using the powder X ray diffraction equipment (JDX3532, manufactured by JEOL Ltd.), carbon fibrous structures after annealing processing were examined. Kα ray which was generated with Cu tube at 40 kV, 30 mA was used, and the measurement of the spacing was performed in accordance with the method defined by The Japan Society for the Promotion of Science (JSPS), described in “Latest Experimental Technique For Carbon Materials (Analysis Part)”, Edited by Carbon Society of Japan, 2001), and as the internal standard silicon powder was used.
1 g of CNT powder was scaled, and then press-loaded into a resinous die (inner dimensions: 40 L, 10 W, 80H (mm)), and the displacement and load were read out. A constant current was applied to the powder by the four-terminal method, and in this condition the voltage was measured. After measuring the voltage until the density come to 0.9 g/cm3, the applied pressure was released and the density after decompression was measured. Measurements taken when the powder was compressed to 0.5, 0.8 or 0.9 g/cm3 were adopted as the particle's resistance.
First, a photograph of the carbon fibrous structures was taken with SEM in an analogous fashion as in the measurement of area based circle-equivalent mean diameter. On the taken SEM photo, only carbon fibrous structures with a clear contour were taken as objects to be measured, and broken ones with unclear contours were omitted. Using all carbon fibrous structures that can be taken as objects in one single field of view (approximately, 60-80 pieces), about 200 pieces in total were measured with three fields of views.
On the carbon fibrous structures to be measured, assuming each individual granular part which is the binding point of carbon fibers to be a particle, contours of the individual granular parts were traced using the image analysis software, WinRoof™ (trade name, marketed by Mitani Corp.), and area within each individual contour was measured, circle-equivalent mean diameter of each individual granular part was calculated, and then, the calculated data were averaged to determine the area based circle-equivalent mean diameter. Roundness (R) was determined by inputting value of the area (A) within each individual contour computed by the above and a measured value of each individual contour's length (L) to the following equation to calculate the roundness of each individual granular part, and then, averaging the calculated data.
R=A*4π/L2 [Numerical Formula 1]
Further, the outer diameter of the fine carbon fibers in the individual carbon fibrous structures to be measured were determined, and then, from the outer diameter determined and the circle-equivalent mean diameter of the granular part calculated as above, the ratio of circle-equivalent mean diameter to the outer diameter of the fine carbon fiber was calculated for each individual carbon fibrous structure, and then the data obtained are averaged.
First, a photograph of the carbon fibrous structures was taken with SEM in an analogous fashion as in the measurement of area based circle-equivalent mean diameter. On the taken SEM photo, only carbon fibrous structures with a clear contour were taken as objects to be measured, and broken ones with unclear contours were omitted. Using all carbon fibrous structures that can be taken as objects in one single field of view (approximately, 60-80 pieces), about 200 pieces in total were measured with three fields of views.
On the carbon fibrous structures to be measured, all places where the granular parts were mutually linked with a fine carbon fiber were found out. Then, at the respective places, the distance between the adjacent granular parts which were mutually linked with the fine carbon fiber (the length of the fine carbon fiber including the center of a granular part at one end to the center of another granular part at another end) was measured, and then the data obtained were averaged.
To 100 ml of toluene in a lidded vial, the carbon fiber structures were added at a rate of 30 μg/ml in order to prepare the dispersion liquid sample of the carbon fibrous structure.
To the dispersion liquid sample of the carbon fibrous structure thus prepared, Ultrasound was applied using a ultrasonic cleaner (manufactured by SND Co., Ltd., Trade Name: USK-3) of which generated frequency was 38 kHz and power was 150 w, and the change of the carbon fibrous structure in the dispersion liquid was observed in the course of time aging.
First, 30 minutes after the application of ultrasound was started, a 2 ml constant volume aliquot of the dispersion sample was pipetted, and the photo of the carbon fibrous structures in the aliquot was taken with SEM. On the obtained SEM photo, 200 pieces of fine carbon fibers in the carbon fibrous structures (fine carbon fibers at least one end of which is linked to the granular part) were selected randomly, then the length of the each individual selected fine carbon fibers was measured, and mean length D50 was calculated. The mean length calculated is taken as the initial average fiber length.
Meanwhile, on the obtained SEM photo, 200 pieces of granular parts which each were the binding point of carbon fibers in the carbon fibrous structures were selected randomly. Assuming each individual selected granular part to be a particle, contours of the individual granular parts were traced using the image analysis software, WinRoof™ (trade name, marketed by Mitani Corp.), and area within each individual contour was measured, circle-equivalent mean diameter of each individual granular part was calculated, and then, D50 mean value thereof is calculated. The D50 mean value calculated was taken as the initial average diameter of the granular parts.
Thereafter, according to the same procedure, a 2 ml constant volume aliquot of the dispersion sample was pipetted every constant periods, and the photo of the carbon fibrous structures in the each individual aliquot was taken with SEM, and the mean length D50 of the fine carbon fibers in the carbon fibrous structure and the mean diameter D50 of the granular part in the carbon fibrous structure were calculated individually.
At the time when the mean length D50 of the fine carbon fibers comes to be about half the initial average fiber length (in the following Examples, 500 minutes after the application of ultrasound is stated.), the mean diameter D50 of the granular part was compared with the initial average diameter of the granular parts in order to obtain the rate of variability (%) thereof.
In an obtained sheet sample, using 4-pin probe type low resistivity meter (LORESTA-GP, manufactured by Mitsubishi Chemical), the resistance (Ω) at nine points of coated film surface was measured. Then, the measured values are converted into volume resistivity (Ω·cm) by the resistivity meter, and an average was calculated.
By the CVD process, carbon fibrous structures were synthesized from toluene as the raw material.
The synthesis was carried out in the presence of a mixture of ferrocene and thiophene as the catalyst, and under the reducing atmosphere of hydrogen gas. Toluene and the catalyst were heated to 380° C. along with the hydrogen gas, and then they were supplied to the generation furnace, and underwent thermal decomposition at 1250° C. in order to obtain the carbon fibrous structures (first intermediate).
The generation furnace used for the carbon fibrous structures (first intermediate) is illustrated schematically in
The synthesized first intermediate was baked at 900° C. in nitrogen gas in order to remove hydrocarbons such as tar and to obtain a second intermediate. The R value of the second intermediate measured by the Raman spectroscopic analysis was found to be 0.98. Sample for electron microscopes was prepared by dispersing the first intermediate into toluene.
Further, the second intermediate underwent a high temperature heat treatment at 2600° C. The obtained aggregates of the carbon fibrous structures underwent pulverization using an air flow pulverizer in order to produce the carbon fibrous structures to be used in the present invention.
A sample for electron microscopes was prepared by dispersing ultrasonically the obtained carbon fibrous structures into toluene.
Further, X-ray diffraction analysis and Raman spectroscopic analysis were performed on the carbon fibrous structure before and after the high temperature heat treatment in order to examine changes in these analyses. The results are shown in
Additionally, it was found that the carbon fibrous structures had an area based circle-equivalent mean diameter of 72.8 μm, bulk density of 0.0032 g/cm3/Raman ID/IG ratio of 0.090, TG combustion temperature of 786° C., spacing of 3.383 Å, particle's resistance of 0.0083 Ω·cm, and density after decompression of 0.25 g/cm3.
The mean diameter of the granular parts in the carbon fibrous structures was determined as 443 nm (SD 207 nm), that is 7.38 times larger than the outer diameter of the carbon fibers in the carbon fibrous structure. The mean roundness of the granular parts was 0.67 (SD 0.14).
Further, when the destruction test for carbon fibrous structure was performed according to the above mentioned procedure, the initial average fiber length (D50) determined 30 minutes after the application of ultrasound was started was found to be 12.8 μm, while the mean length D50 determined 500 minutes after the application of ultrasound was started was found to be 6.7 μm, which value was about half the initial value. This result showed that many breakages were given in the fine carbon fibers of the carbon fibrous structure. Whereas the variability (decreasing) rate for the diameter of granular part was only 4.8%, when the mean diameter (D50) of the granular part determined 500 minutes after the application of ultrasound was started was compared with the initial average diameter (D50) of the granular parts determined 30 minutes after the application of ultrasound was started. Considering measurement error, etc., it was found that the granular parts themselves were hardly destroyed even under the load condition that many breakages were given in the fine carbon fibers, and the granular parts still function as the binding site for the fibers mutually.
Table 2 provides a summary of the various physical properties as determined in Synthetic Example 1.
By the CVD process, carbon fibrous structures were synthesized using apart of the exhaust gas from the generation furnace as a recycling gas in order to use as the carbon source the carbon compounds such as methane, etc., included in the recycling gas, as well as a fresh toluene.
The synthesis was carried out in the presence of a mixture of ferrocene and thiophene as the catalyst, and under the reducing atmosphere of hydrogen gas. Toluene and the catalyst as a fresh raw material were heated to 380° C. along with the hydrogen gas in a preheat furnace, while a part of the exhaust gas taken out from the lower end of the generation furnace was used as a recycling gas. After it was adjusted to 380° C., it was mixed with the fresh raw material gas on the way of the supplying line for the fresh raw material to the generation furnace. The mixed gas was then supplied to the generation furnace.
The composition ratio in the recycling gas used were found to be CH4 7.5%, C6H6 0.3%, C2H2 0.7%, C2H6 0.1%, CO 0.3%, N2 3.5%, and H2 87.6% by the volume based molar ratio. The mixing flow rate was adjusted so that the mixing molar ratio of methane and benzene in the raw material gas to be supplied to the generation furnace, CH4/C6H6 was set to 3.44 (wherein, it was considered that the toluene in the fresh raw material gas had been decomposed at 100% to CH4:C6H6=1:1 by the heating in the preheat furnace.
In the final raw material gas, C2H2, C2H6, and CO which were involved in the recycling gas to be mixed were naturally included. However, since these ingredients were very small amount, they may substantially be ignored as the carbon source.
Then they were underwent thermal decomposition at 1250° C. in order to obtain the carbon fibrous structures (first intermediate) in an analogous fashion as Synthetic Example 1.
The constitution of the generation furnace used for the carbon fibrous structures (first intermediate) was the same as that shown in
The synthesized first intermediate was baked at 900° C. in argon gas in order to remove hydrocarbons such as tar and to obtain a second intermediate. The R value of the second intermediate measured by the Raman spectroscopic analysis was found to be 0.83. Sample for electron microscopes was prepared by dispersing the first intermediate into toluene. SEM photo and TEM photo obtained for the sample are in much the same with those of Synthetic Example 1 shown in
Further, the second intermediate underwent a high temperature heat treatment at 2600° C. in argon gas. The obtained aggregates of the carbon fibrous structures underwent pulverization using an air flow pulverizer in order to produce the carbon fibrous structures to be used in the present invention.
A sample for electron microscopes was prepared by dispersing ultrasonically the obtained carbon fibrous structures into toluene. SEM photo and TEM photos obtained for the sample are in much the same with those of Synthetic Example 1 shown in
Separately, the obtained carbon fibrous structures were mounted on a sample holder for electron microscope, and observed for the particle distribution. The obtained results are shown in Table 3.
Further, X-ray diffraction analysis and Raman spectroscopic analysis were performed on the carbon fibrous structure before and after the high temperature heat treatment in order to examine changes in these analyses. The results are in much the same with those of Synthetic Example 1 shown in
Additionally, it was found that the carbon fibrous structures had an area based circle-equivalent mean diameter of 75.8 μm, bulk density of 0.004 g/cm3/Raman ID/IG ratio of 0.086, TG combustion temperature of 807° C., spacing of 3.386 Å, particle's resistance of 0.0077 ω·cm, and density after decompression of 0.26 g/cm3.
The mean diameter of the granular parts in the carbon fibrous structures was determined as 349.5 nm (SD 180.1 nm), that is 5.8 times larger than the outer diameter of the carbon fibers in the carbon fibrous structure. The mean roundness of the granular parts was 0.69 (SD 0.15).
Further, when the destruction test for carbon fibrous structure was performed according to the above mentioned procedure, the initial average fiber length (D50) determined 30 minutes after the application of ultrasound was started was found to be 12.4 μm, while the mean length D50 determined 500 minutes after the application of ultrasound was started was found to be 6.3 μm, which value was about half the initial value. This result showed that many breakages were given in the fine carbon fibers of the carbon fibrous structure. Whereas the variability (decreasing) rate for the diameter of granular part was only 4.2%, when the mean diameter (D50) of the granular part determined 500 minutes after the application of ultrasound was started was compared with the initial average diameter (D50) of the granular parts determined 30 minutes after the application of ultrasound was started. Considering measurement error, etc., it was found that the granular parts themselves were hardly destroyed even under the load condition that many breakages were given in the fine carbon, and the granular parts still function as the binding site for the fibers mutually.
Table 4 provides a summary of the various physical properties as determined in Synthetic Example 2.
0.2-10 parts by weight of the carbon fibrous structures obtained in Synthetic Example 1 or 2 were added to a monomer mixture consisting of 95 parts by weight of purified dicycrlopentadiene (purity: 99.7%) and 5 parts by weight of purified ethylidene norbornene, and further tungsten hexachloride was added to the resultant mixture so as to obtain a tungsten content of 0.01 M/L, and then, the resultant mixture was mixed uniformly in order to prepare a monomer solution A which included the carbon fibrous structures and catalyst component.
0.2-10 parts by weight of the carbon fibrous structures obtained in Synthetic Example 1 or 2 were added to a monomer mixture consisting of 95 parts by weight of purified dicycrlopentadiene and 5 parts by weight of purified ethylidene norbornene, and then 3 parts of ethylene-propylene-ethylidene norbornene copolymerized rubber of which ethylene content was 70 mol % was dissolved into the resultant mixture. Further, an polymerization activating agent mixture which had been previously prepared by adding trioctyl aluminum, dioctyl aluminum iodide, and diglyme in the proportion of 85 mol, 15 mol, and 100 mol, respectively, was added to the above obtained solution so as to obtain an aluminum content of 0.03M/L, and then, the resultant mixture was mixed uniformly in order to prepare a monomer solution B which included the carbon fibrous structures and the activating agent components.
The monomer solutions were stored into a first and second vessels respectively, then they were mixed together at a mixing rate of 1:1 within an injection molding device, and then the mixture was injected into a molding die to allow the mixture to react with each other and to harden in the die. Thereby, plate sample pieces each having 50 mm in length, 30 mm in width and 3 mm in thickness were manufactured. Incidentally, as the molding conditions, the temperatures both of the solution A and the solution B as the raw materials were set to 30° C., and the temperature of the molding die was set to 90° C.
The conductivities of the obtained plate sample pieces were determined in accordance with the above mentioned procedure. The obtained results are shown in Tables 5 and 6.
Using the same raw material solutions as in Examples 1-10 except that the addition of carbon fibrous structures was omitted, the plate sample pieces were manufactured and underwent the determination, in accordance with the same procedure and manners as in Examples 1-10. The results obtained were shown in Tables 5 and 6.
2 parts by weight of a resol type phenolic resin (residual carbon content: 46%, nonvolatile content: 76%, manufactured by Sumitomo Duress Co., Ltd. and under commercialized under the product code of “PR-51708”) were added to 100 parts by weight of the carbon fibrous structures obtained in Synthetic Example 1 or 2, and they were mixed using a Henschel mixer (manufactured by Mitsui Mitsuike Chemical Plants Co. Ltd.) at 30° C. under 1000 rpm for 5 minutes. Thereafter, the obtained mixture were placed into a compression molding die and underwent thermal treatment under compression condition at 150° C. for 30 minutes in order to obtain preforms.
To a monomer mixture consisting of 95 parts by weight of purified dicycrlopentadiene (purity: 99.7%) and 5 parts by weight of purified ethylidene norbornene, tungsten hexachloride was added to the resultant mixture so as to obtain a tungsten content of 0.01 M/L, and then, the resultant mixture was mixed uniformly in order to prepare a monomer solution A which included the catalyst component.
To a solution which was prepared by dissolving 3 parts of ethylene-propylene-ethylidene norbornene copolymerized rubber, of which ethylene content was 70 mol %, into a monomer mixture consisting of 95 parts by weight of purified dicycrlopentadiene and 5 parts by weight of purified ethylidene norbornene, an polymerization activating agent mixture which had been previously prepared by adding trioctyl aluminum, dioctyl aluminum iodide, and diglyme in the proportion of 85 mol, 15 mol, and 100 mol, respectively, was added so as to obtain an aluminum content of 0.03 M/L, and then, the resultant mixture was mixed uniformly in order to prepare a monomer solution B which included the activating agent components.
A prescribed amount of the preforms were set into a molding die, and then the die was closed. On the other hand, the monomer solutions were stored into a first and second vessels respectively, then they were mixed together at a mixing rate of 1:1 within an injection molding device, and then the mixture was injected into the molding die to allow the mixture to react with each other and to harden in the die. Thereby, plate sample pieces each having 50 mm in length, 30 mm in width and 3 mm in thickness were manufactured. Incidentally, as the molding conditions, the temperatures both of the solution A and the solution B as the raw materials were set to 30° C., and the temperature of the molding die was set to 90° C.
Using 4-pin probe type low resistivity meter (LORESTA-GP, manufactured by Mitsubishi Chemical), the resistance (Ω) at nine points of the surface of the obtained plate sample piece was measured. Then, the measured values are converted into volume resistivity (Ω·cm) by the resistivity meter, and an average was calculated.
Using the same raw material solutions as in Examples 11-20 except that the addition of carbon fibrous structures was omitted, the plate sample pieces were manufactured and underwent the determination, in accordance with the same procedure and manners as in Examples 11-20.
Surface resistivity of Examples 11-20 and Control 2 were shown in Tables 7, volume resistivity of Examples 11-20 and Control 2 were shown in Tables 8.
Thermosetting resin composition which were previously prepared by blending 90 parts by weight of a bisphenol-A type epoxy resin (ADEKA RESIN™ EP4100E, epoxy equivalent:190, manufactured by Asahi Denka Co., Ltd.) and 7.2 parts by weight of a dicyandiamide (ADEKA HARDENER™ EH3636-AS, manufactured by Asahi Denka Co., Ltd.) was installed into a mixing chamber. While stirring it with a stirring machine at a rotation rate of 40 rpm, 0.5-10 parts by weight of the carbon fibrous structures obtained in Synthetic Example 1 or 2 were successively added to the thermosetting resin composition. Thereafter, while controlling the temperature of each resin composition in the chamber was regulated at a prescribed temperature in the range of 10-70° C. as shown in Table 1, premixing of the resin composition and the carbon fibrous structures were performed for 10 minutes. Then, the obtained premix liquid thermosetting resin composition were put into a general purpose reactive injection molding machine, and underwent molding at the die temperature of 150° C. Thereby, plate sample pieces each having 50 mm in length, 30 mm in width and 3 mm in thickness were manufactured.
According to the above described procedures, determination of the conductivity was performed to the obtained plate sample pieces. The results obtained were shown in Tables 9 and 10.
Using the same raw material solutions as in Examples 21-30 except that the addition of carbon fibrous structures was omitted, the plate sample pieces were manufactured and underwent the determination, in accordance with the same procedure and manners as in Examples 21-30. The results obtained were shown in Tables 9 and 10.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-305071 | Oct 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/320731 | 10/18/2006 | WO | 00 | 4/18/2008 |
