JPH0157715B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides mesophase pitch, mesophase pitch,
In particular, it relates to a method for producing mesophase pitches containing approximately 100% by weight mesophase. Mesophase pitch is known to be suitable for producing carbon fibers having excellent properties that make it suitable for commercial use. Carbon fibers derived from mesophase pitch are known to be lightweight, strong, electrically conductive, and chemically and physically inert. Carbon fibers derived from mesophase pitch are effective as reinforcing materials in composites and find use in aerospace applications and high-end sports equipment. Generally speaking, carbon fibers are primarily made from three types of precursor materials: rayon, acrylonitrile, and pitch. The use of pitch as a precursor material is economically attractive. Cheap carbon fibers made from ordinary pitch have unfavorable molecular alignment and poor mechanical properties compared to others. In contrast, carbon fibers made from mesophase pitch have a very favorable molecular arrangement and exhibit very good mechanical properties compared to others. As used herein, the term "pitch" as used in the art generally refers to a complex mixture of aromatic compounds that are primarily solids at room temperature and have a relatively wide melting or softening temperature range. should be interpreted as representing carbonaceous residues consisting of When cooled from its melt, pitch changes like glass. As used herein, the term "mesophase" should generally be construed as synonymous with liquid crystal, as used in the art. That is, it is a state of matter that lies between a crystalline solid and a normal liquid. usually,
Substances in the mesophase state exhibit both anisotropic and liquid properties. “Mesophase-containing pitch” as long as it is used in the main text
The term refers to pitches in which the mesophase content is less than about 40% by weight and the non-mesophase portion, ie, the isotropic phase, is the continuous phase. As used herein, the term "mesophase pitch" refers to a mesophase containing about 40% by weight or more and which, when dispersed by stirring or similar methods in accordance with the prior art, has a continuous anisotropic property. A pitch that can form a phase. Conventional methods for producing mesophase pitches from precursor pitches include heat treatment to cause thermal polymerization at temperatures above 350°C. The method produces large molecular weight molecules that can form mesophases. Typical conventional practice is carried out using a reactor maintained at about 400° C. for about 20 hours. The properties of the final material can be controlled by reaction temperature, heat treatment time and volatility rate. If a high molecular weight fraction is present, the melting point of the mesophase pitch will be at least 330°C. Higher temperatures are required to transform the mesophase pitch into fibers. This is called "spinning" in the industry. The following patents are representative of the prior art and are incorporated herein by reference: U.S. Pat. No. 4,005,183 (Singer), U.S. Pat. No. 3,919,387 (Singer), U.S. Pat. US Pat. No. 3,976,729 (Lewis et al.), US Pat. No. 3,995,014 (Lewis) and in particular UK Patent No. 2,005,298 (Chwastiak). The amount of mesophase in the pitch can be determined by known methods by polarized light microscopy. The presence of homogeneous, aggregated mesophase zones can be observed with the naked eye by polarized light microscopy and as described above.
It can be measured quantitatively by the method disclosed in the Chwastiak patent. Previously, the criterion of insolubility in certain solvents, such as quinoline and pyridine, was used to evaluate mesophase content. but,
Since there may be some non-intermediate insolubles present in the precursor pitch, it is common practice to remove these insolubles before processing the precursor pitch. According to the prior art, quinoline insoluble % (%Q.
I.) shows the quinoline insoluble content in pitch extracted with quinoline at 75°C. In addition, pyridine insoluble content%
(% PI) indicates the pyridine insoluble content in pitch extracted in boiling pyridine at about 115° C. using a Soxhlet apparatus. The softening point or softening temperature of pitch is related to its molecular weight composition, and the presence of large amounts of high molecular weight components generally tends to increase the softening temperature. It is common practice in the industry to grade precursor pitches to some extent by their softening points. For mesophase pitches, the softening point is used to determine the appropriate spinning temperature. Generally, the spinning temperature is about 40°C or more above the softening temperature. Generally, there are several methods for determining the softening temperature, and the temperatures measured by these different methods differ to some extent from each other. In general, the Mettler softening point measurement method has been widely adopted as the standard for precursor material pitch evaluation. The method can be applied to mesophase pitches. The softening temperature of the mesophase pitch can also be determined by examination with a heated stage microscope. In this method, the mesophase pitch is placed on the heating stage of the microscope.
Heated under polarized light in an inert atmosphere. The temperature of the mesophase pitch is increased at a controlled rate and the temperature at which the mesophase pitch begins to deform is recorded as the softening temperature. As used herein, softening point or softening temperature refers to the temperature measured by the Mettler method for both the precursor pitch and the mesophase pitch. One of the main objects of the present invention is to subject a carbonaceous precursor pitch to a solvent extraction operation without chemical manipulation (i.e. thermal polymerization by heating), so that
The molecular weight distribution of the mesophase pitch is such that at least 75% of the molecules have a molecular weight in the range of 600 to 1300, no more than 10% of the molecules have a molecular weight less than 600, and no more than 15% of the molecules have a molecular weight less than 1300. The objective is to obtain a mesophase pitch which is manufactured to a high molecular weight and contains about 100% by weight of mesophase. Another object of the present invention is to subject a carbonaceous precursor pitch to a solvent extraction operation without chemical manipulation (i.e., thermal polymerization by heating), so that the mesophase pitch has an atomic interlayer spacing (Co/ 2) is approximately 3.60
Apparent stack height (Lc) below angstrom
is made to have an X-ray structure larger than about 20 angstroms, and to obtain a mesophase pitch containing about 100% by weight mesophase. The solvent used in the process of the invention to achieve the above object is a 1:2 mixture of petroleum ether and toluene. Pitch fibers can be formed from the mesophase pitch obtained by the present invention by spinning without any chemical manipulation. Preferably, spinning from the mesophase pitch is carried out at a temperature of about 370°C or less. Since the mesophase pitch is stable at such high temperatures, spinning using the conventional method can be performed at temperatures below approximately 370°C.
Time does not cause chemical changes in pitch. Therefore, pitch fibers can be formed from carbonaceous pitch via the present invention without any chemical manipulation. In conventional thermal mesophase formation methods, a pitch of carbonaceous precursor material is heated to cause polymerization. The resulting mesophase pitch is characterized by a molecular weight distribution with two large peaks. The low molecular weight peak corresponds to the precursor pitch component, and the high molecular weight peak corresponds to molecules produced by thermal polymerization. In contrast, the mesophase pitch obtained according to the present invention generally has a molecular weight distribution with a single large peak located midway between the two peaks that would appear if thermal polymerization were carried out. It has Other objects and advantages of the invention will be realized and attained in part as set forth in the following specification, and in part as pointed out in the claims herein without specific reference. It is clear that it is the same as In practicing the invention, certain embodiments were chosen for discussion in the tables and herein. Examples and reference examples are provided below to facilitate understanding of the invention. Numerous embodiments can readily be developed with the aid of the guiding principles and teachings therein. The examples provided herein are intended to be illustrative of the invention and are not in any way limiting of the manner in which the invention may be practiced. Parts and percentages listed herein are by weight, unless otherwise specified. In general, carbonaceous precursor pitches suitable for carrying out the present invention are prepared by conventional thermal processes, such as those described in the aforementioned Singer patent 4005183, in which the mesophase is extensively dispersed. The precursor material pitch must be such that it can form a pitch that occupies a large area.
The suitability of any carbonaceous pitch can be determined by a direct method according to the teachings herein. Of course, there is an interplay between the carbonaceous precursor pitch and the appropriate and preferred physical manipulations for producing the mesophase pitch. The teachings herein provide guidance in the selection and optimization of physical operations for specific carbonaceous pitches. Example 1 (Reference Example) Commercially available petroleum pitch was used in a solvent extraction method. The softening temperature of the oil pitch is approximately
At 130°C, the pyridine insoluble content was 0% and no intermediate phase was contained. 10g of that pitch is mixed with 200ml of toluene at room temperature for about 1
Stir for an hour and filtrate under reduced pressure. The dry insoluble matter or yield was about 8% by weight.
The obtained product had a softening point of about 319°C, a pyridine insoluble content of 47%, and a mesophase of about 40% by weight. Example 2 (Reference Example) Example 1 was repeated using boiling toluene. The yield was 6% by weight and its mesophase content was approximately 100%. Example 3 (Example) Different from Example 1, a commercially available oil pit was selected. The softening temperature of the pitch is approximately 123℃,
The pyridine-insoluble content was almost 0% and no intermediate phase was contained. Example 1 was repeated, replacing the solvent with a 1:2 mixture of petroleum ether and toluene. Approximately 14% by weight
A product was obtained, which had a softening temperature of 239°C, a pyridine insoluble content of about 3%, and a mesophase content of about 100% by weight. Example 4 (Reference Example) Example 3 was repeated, replacing the solvent with a 1:1 mixture of petroleum ether and toluene. Approximately 32% of what was obtained
It contained approximately 50% by weight mesophase. Example 5 (Reference Example) The mesophase pitch of Example 3 was spun into fibers at 290°C on a single fiber spinning machine. The diameter of the fiber is about 20 microns, and it is heated at a rate of about 2°C per minute in air.
It was heated to 375°C for thermosetting. The thermoset fibers were examined using a polarizing microscope and confirmed to contain approximately 100% anisotropy. The thermoset fibers were carbonized at temperatures up to 1700°C in an inert atmosphere according to conventional methods. Tests conducted on the carbonized fibers showed a modulus of 172 gigapascals (approximately 25 x ¹⁰⁶ psi) and a tensile strength of 1.72 gigapascals (250,000 psi). Methods for producing carbonized fibers from mesophase pitch are well known in the industry, with specific reference to the aforementioned Singer Patent No. 4,005,183 and Chwastiak Patent No. 2,005,298. Example 6 (Reference example) We selected the third type of petroleum pittuce available as a commercial product. The softening temperature of the petroleum pitcher is approximately 130
It was warm at ℃. In accordance with a preferred embodiment, the pitch is first distilled and its new softening temperature is about 201
℃, the pyridine insoluble content is about 3%, and the mesophase is 3%.
It was in weight%. The pitch was then extracted with a solvent as in Example 1, yielding about 36% by weight. The pyridine insoluble content was 41%, and the intermediate phase was about 90% by weight. The softening point of the mesophase pitch was about 343°C. Example 7 (reference example) The only difference is that the solvent extraction is performed using boiling toluene.
Example 6 was repeated. Approximately 30% by weight of the product was obtained,
Its softening temperature was approximately 360°C. The yield had a pyridine insoluble content of about 69% and contained about 100% mesophase by weight. Example 8 (Reference Example) Example 7 was repeated with the only difference that the solvent extraction was carried out with benzene at about 80°C. The yield is about 30% by weight, its pyridine-insoluble content is about 55%, and about 100% by weight.
% mesophase by weight. Its softening temperature is approximately
It was 360℃. Example 9 (Reference Example) An air-blown petroleum pit having a softening temperature of about 152° C. was subjected to solvent extraction using toluene at room temperature to obtain a product of about 34% by weight. The yield contained no mesophase. Similar results were obtained for pitch obtained from high-temperature decomposition tar. Both types of pitches were not able to produce extensive mesophases even when heat treated according to conventional methods. This fact indicates that this type of pitch is unsuitable for use in the present invention. Example 10 (Reference Example) In order to remove components with extremely low molecular weight, the petroleum pit of Example 6 was heated at about 390° C. for about 1 hour while expelling volatile matter with an inert gas. About 21% by weight was distilled off, the softening temperature of the residual pitch was about 162°C, the pyridine insoluble content was 0%, and no intermediate phase was contained. Thoroughly crush 120g of pith and 2400ml of toluene.
Solvent extraction was performed by stirring at room temperature. The yield after vacuum filtration through a sintered glass filter was about 19% by weight. The softening temperature of the obtained material was approximately 320°C, the pyridine insoluble content was approximately 39%, and approximately
It contained 80% by weight mesophase. Example 11 (reference example) The only change is that the solvent extraction is performed at about 110℃,
Example 10 was repeated. The obtained product was about 7% by weight, the softening temperature of the obtained product was about 370°C, and the pyridine insoluble content was about 64%.
It contained approximately 100% by weight mesophase. Example 12 (Reference Example) 50 g of the pulverized distilled pitcher from Example 6 was refluxed with 1000 ml of boiling benzene for about 2 hours and subjected to solvent extraction. The hot solution was passed through a sintered glass filter and the yield was approximately 30% by weight. The obtained product has a softening temperature of about 360°C and a pyridine insoluble content of about 55%.
It contained approximately 100% by weight mesophase. Example 13 (Reference Example) Example 6 was repeated without prior distillation.
No insoluble matter was obtained. Example 14 (Reference Example) The petroleum pitch of Example 3 was solvent extracted with petroleum ether. The yield was approximately 77% by weight and contained no mesophase. Further solvent extraction with toluene was carried out according to Example 3, yielding about 1% by weight of a product containing about 100% by weight of the mesophase. Example 15 (Reference Example) Coal tar pitch with a softening temperature of about 125°C and a mesophase of about 0% was extracted with a solvent. 60 g of pitch and 1200 ml of toluene were stirred at room temperature for about 2 hours. The yield was approximately 47% by weight. The softening point of the obtained product is approximately 318℃, and the pyridine-insoluble content is approximately
53% and contained approximately 60% by weight of mesophase. Example 16 (Reference example) 29.5g of coal tar pitch from Example 15 was added to toluene.
It was refluxed at 500 ml and about 110°C for about 2 hours. A yield of 40% by weight was obtained containing about 85% by weight of mesophase. Example 17 (Reference Example) A test was conducted to confirm the mesophase content as a correlation factor in the composition of the soluble and insoluble components of pitch extracted with a solvent. For naphthalene pitches solvent extracted with toluene at room temperature, in the range of about 10 to about 100% by weight of the mesophase, which corresponds to a range of about 35 to 82% of the insoluble content.
It was confirmed that there was a sufficient linear relationship between the weight of the intermediate phase and the weight of the insoluble matter. This relationship was essentially the same when formulation tests were conducted using the soluble and insoluble fractions from the naphthalene pitch and the corresponding portions from Example 3. Samples in which a given amount of insoluble from the naphthalene pitch was replaced with the same weight of insoluble from Example 3 resulted in the same mesophase content. This is an unexpected result in view of the different chemical compositions of the precursor pitches. Example 18 (Reference example) A test was conducted to confirm the effect of repeated solvent extraction. It has been found that exhaustive solvent extraction with toluene at room temperature results in reduced yields and virtually no weighable amounts of mesophase. Therefore, this is a supplementary guide for implementing the invention. Example 19 (Reference Example) Tests were conducted to confirm both the molecular weight distribution and X-ray diffraction characteristics of the various products obtained from the examples. Using gel permeation chromatography, number average molecular weight (n), weight average molecular weight (w) and Z
- The average molecular weight (z) value was confirmed. Also, a quantitative molecular weight molecule was confirmed. In addition, X-ray diffraction measurements were performed to confirm the values of atomic layer spacing (Co/2) and apparent stacking height (Lc). The results of these tests for various mesophase pitches are shown in Table 1. Lewis et al. Patent No. 3976729 and
Molecular distribution data were obtained according to Chwastiak UK Patent No. 2005298. The solvent used in the gel permeation chromatography procedure was quinoline.

【table】

Table 2 For comparison, mesophase pitches prepared by conventional conventional thermal methods from the precursor pitches used in each of the above examples are shown in Table 2. As is clear from a comparison of Tables 1 and 2, even if the same precursor pitch is used, the second
The mesophase pitch shown in the table shows a completely different molecular weight distribution from the mesophase pitch shown in Table 1 which is not subjected to thermal polymerization.

[Table] For reference, Table 3 shows the X-ray data of the precursor material pitch before various operations were performed.

[Table] Precursor material pitch as shown in Table 3
Comparing the values of Co/2 and Lc with those of the mesophase pitches in Table 1 shows that the mesophase pitches in Table 1 essentially form molecular alignments by solvent extraction of the precursor pitches. It can be seen that this shows that it becomes like this, that is, it shows that it comes to form an intermediate phase. In particular, solvent extraction without any heat converts a relatively disordered precursor pitch into an essentially ordered mesophase pitch. It is interesting to compare the solubility parameter ∂ of various solvents with respect to the mesophase content in the pitch after treatment. Table 4 shows that compatible and non-compatible solvents are within the same range.

Table: Example 20 (Reference Example) The mesophase pitch of Example 3 was melted at about 300° C. and stirred for about 30 minutes in an inert atmosphere to remove the solvent. The product was spun into single fibers at a temperature of approximately 300°C. The diameter of the as-spun fiber is 15
It was micron and 25 micron. The 25 micron fibers were ground and examined by X-ray. That Co/
2 was measured to be 3.54 angstroms, and Lc was measured to be 34 angstroms. X-ray data for the mesophase pitch before spinning showed Co/2 of 3.58 angstroms and Lc of about 25 angstroms. The molecular orientation that accounts for the majority of the as-spun fibers was determined to be approximately 30°C. For comparison, the Singer patent no.
The Co/2 of the as-spun fiber produced by the conventional method as disclosed in No. 4032430 is 3.45 to 3.55.
angstrom, Lc was 30-50 angstroms, and the preferential molecular orientation was 25-30°. In addition, 15 micron fibers are heated at 2°C per minute in air.
The material was heated to approximately 375°C at a speed of 375°C for thermosetting. The thermoset fiber was examined and the anisotropic state therein was approximately 100%. The thermoset fibers were carbonized at temperatures up to 1700° C. in an inert atmosphere according to conventional methods. The modulus of the carbonized fiber is approximately 193
gigapascal (28×10 ⁶ psi), and the tensile strength was 1.88 gigapascal (273000 psi).

Claims (1)

[Scope of Claims] 1. A method for producing a mesophase pitch containing about 100% by weight of a mesophase, which is a carbonaceous residue consisting of a complex mixture of mainly aromatic organic components, and which has been subjected to conventional thermal treatment. Select a precursor pitch that can form a pitch in which the mesophase occupies a wide area according to the method, and at least 75% of the molecules have a molecular weight in the range of 600 to 1300, and no more than 10% of the molecules are smaller than 600. extracting the precursor pitch with a solvent consisting of a 1:2 mixture of petroleum ether and toluene until an insoluble fraction is obtained having a molecular weight and a molecular weight distribution in which not more than 15% of the molecules have a molecular weight greater than 1300; A method characterized in that no heating is carried out, thereby obtaining said insoluble portion, ie said mesophase pitch.