JP2007327787A - Method of testing metal corrosiveness of insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quantitatively and quickly test metal corrosiveness for a large number of insulating materials, in research for developing a novel insulating material. <P>SOLUTION: The insulating material 1 is immersed into pure water 2 to prepare an extract 1a, and the metal corrosiveness of the insulating material 1 is evaluated based on a metal dissolution rate into the extracts 1a. The metal dissolution rate is evaluated based on a potential difference between a metal electrode 5 comprising evaluation objective metal and a reference electrode 6, by immersing the electrodes 5, 6 into the extract 1a and reference pure water 4. Alternatively, the extract 1a is divided into two, the metal is immersed/dissolved into one thereof, and a metal dissolved amount is quantitatively determined thereafter by adding a color reaction reagent to the both the extracts to comparing coloring thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for evaluating the corrosiveness of an insulating material to a metal, and more particularly to a method for testing the corrosiveness of an insulating material for quickly evaluating the corrosion characteristics of the insulating material with respect to a metal material used together with the insulating material.

  Flame retardant insulating resin materials are widely used as insulating materials for electronic devices. For example, a resin for sealing a transistor, a diode or an integrated circuit, an insulating resin for a printed circuit board, an insulating resin constituting an electronic component such as a connector, or an insulating resin constituting a cable covering material. These resins are added with halogen-based flame retardants containing halogen elements such as Br and Sb to impart flame retardancy, or softeners and stabilizers containing lead to maintain flexibility and stability. Yes.

  However, the use of materials containing such halogen elements, Sb, or lead in electronic devices is being prohibited, for example, in the European RoHS (Prohibition on Use of Specific Hazardous Substances) Directive for the purpose of preventing environmental pollution. For this reason, development of halogen-free, Sb-free, and Pb-free new insulating materials corresponding to the RoHS directive and the like is being promoted for insulating materials such as flame-retardant insulating resins and cable covering materials.

  In the development of such a new insulating material, it is important that the new insulating material is less corrosive to metals. Along with the miniaturization of electronic devices, metal parts used in electronic devices, for example, wiring of integrated circuits and circuit boards, or contact points of lead frames and connectors of integrated circuits, are becoming increasingly finer. When a fine metal portion of such an electronic device comes into contact with an insulating material or various components eluted from the insulating material, a defect due to electrolytic corrosion or migration may occur. Such electrolytic corrosion and migration impair the reliability of electronic equipment. Therefore, the new insulating material is not only used for the flame retardant, softener and stabilizer added to be halogen-free and Pb-free. It is important that the corrosiveness to the metal material is small.

  Insulating material (for example, insulating resin for sealing) containing halogen-based flame retardant containing conventional Br or insulating material (for example, insulating resin for cable coating) containing softening agent containing Pb or stabilizer containing Pb In the following, "corrosion and migration" have been evaluated or tested for "insulating material containing halogen". Based on the evaluation, an insulating material having excellent electric corrosion resistance and excellent flame retardancy, flexibility or stability has been developed and provided practically.

  The evaluation of the electro-corrosion properties of these insulating materials containing halogen, etc. occurs during the test by manufacturing a dummy electronic device using the insulating material to be evaluated and conducting a reliability test of the dummy electronic device. It was done by observing an electrical short circuit. This reliability test is a long-term leaving test of 500 to 1000 hours under various environments such as high temperature and high humidity, high temperature and pressure, and high voltage stress conditions.

  However, in the development of new insulating materials, especially in the screening process for finding promising materials, the reliability of many insulating materials selected as candidates must be evaluated. It is not practical to perform a long-term reliability test on such a large number of insulating materials. In addition, since an expensive reliability test apparatus that maintains a high-temperature and high-humidity environment is required, the development cost increases. Therefore, as a test method that can be evaluated in a short time with a simple apparatus, a method for evaluating corrosive ions eluted from an insulating material has been devised and put into practical use.

  This method evaluates the amount of ions that are generally recognized as corrosive, for example, chlorine ions such as chloride ions and sulfur ions such as sulfate ions, contained in the substance eluted from the insulating material. The metal corrosion characteristics of these chlorine ions and sulfate ions are well known, and the metal corrosion property of the insulating material can be evaluated from the amount of these ions. (For example, refer to Patent Document 1 and Patent Document 2).

  It is known that the above-described method for evaluating eluted ions gives a good evaluation result to a conventional insulating material containing halogen or the like. However, there are new insulating materials such as metal hydroxide flame retardants using metal hydroxides such as aluminum hydroxide or calcium hydroxide, boron flame retardants using boron compounds or filler flame retardants using silica fillers. Newly added insulating materials are promising and are being developed, but their applicability as evaluation methods for these new insulating materials has not been fully elucidated. In other words, the ions eluted from these new insulating materials often contain various ions in addition to the above-described chlorine ions and sulfur ions. For example, in analysis by ion chromatography, acetate ions, formate ions, oxalate ions, or phosphate ions are often detected, and unidentified ion peaks are often observed.

  At present, the metal corrosivity of these ions has not been fully elucidated, and the metal corrosivity of a solution in which these ions are present simultaneously has not been elucidated. For this reason, the conventional evaluation method which evaluates the metal corrosion property of an insulating material from these ion amounts does not necessarily give a valid evaluation result. For example, a new insulating material that causes a large metal corrosion property, for example, migration, even if containing only a small amount of chlorine and sulfur ions having a high metal corrosion property is also known.

  For this reason, a method has been devised for evaluating the metal corrosivity of a solution in which all substances including unknown substances eluted from the insulating material are present simultaneously. (For example, refer to Patent Document 3).

  FIG. 3 is a process diagram of a conventional method for testing the metal corrosion property of an insulating material, and shows the steps of a method for evaluating the metal corrosion property of a solution in which all substances eluted from the insulating material are present simultaneously.

  In this method, referring to FIG. 3A, first, pure water 2 and pulverized insulating material 1 are placed in a container 3 and left under high temperature and high pressure. An extract 1a eluting the above components is prepared.

  Next, referring to FIG. 3B and FIG. 3C, the circuit board 31 on which the wiring pattern in which the two wirings 32 and 33 are arranged close to each other on the main surface is formed in the extract 1a. Immerse. Then, a constant voltage is applied from the power source 34 between the wiring 32 and the wiring 33, and the time change of the current is measured. Since the immersion time is increased and the corrosion of the wirings 32 and 33 proceeds, and the current flowing between the wirings 32 and 33 increases, the amount of corrosion of the wiring can be evaluated. The wirings 32 and 33 are made of a metal material to be evaluated.

  However, with this method, it is difficult to quantitatively evaluate the corrosion characteristics of the wirings 32 and 33, that is, the metal material. This is because the corrosion of the wirings 32 and 33 does not proceed uniformly in the entire wirings 32 and 33 but locally concentrates. As a result, a corrosion product is locally formed in a part of the wirings 32 and 33, and the gap between the wirings 32 and 33 is locally narrowed. A considerable portion of the current flowing between the wirings 32 and 33 is composed of a current flowing through the locally narrowed gap. This is because the degree and number of the narrowing of the gap depends on the accidental factor, and therefore the time change of the current is greatly influenced by the accidental factor, so that it is difficult to quantitatively evaluate the degree of corrosion from now on. .

For this reason, in this method, the same measurement is performed on an insulating material with known metal corrosion characteristics, and the result is compared with the evaluation result of the new insulating material to be evaluated. Is evaluated.
Japanese Patent Laid-Open No. 7-63721 Japanese Patent Laid-Open No. 9-297116 JP-A 63-284828

  As described above, the development of new insulating materials requires the evaluation of the metal corrosion properties of many types of insulating materials. However, a number of dummy materials manufactured by combining the metal materials to be evaluated and the insulating materials to be evaluated are used. The conventional method for reliability testing of electronic devices is not suitable for practical use because of the long test time.

  In addition, the method of quantifying only specific ions from the extract of insulating material and evaluating the metal corrosivity based on the quantified amount may not be able to properly evaluate a new halogen-free or Pb-free insulating material from which various substances are eluted. . In addition, quantifying all the ions in the extract requires a long time and a lot of labor, and the development cost increases.

  Further, a method of extracting a component of an insulating material in pure water, immersing a circuit board on which a nearby wiring to which a voltage is applied is formed therein, and evaluating the corrosiveness of the wiring metal from a change in current over time Then, since an accidental factor contributes to the time change of an electric current, there exists a problem that it is difficult to evaluate the degree of metal corrosion quantitatively. For this reason, the insulation material with known corrosion characteristics is compared and evaluated, but in this case, an insulation material with known corrosion characteristics must be prepared. It is difficult to apply this method to new insulating materials that cannot be prepared.

  The present invention provides a metal corrosion test method for insulating materials, which can evaluate metal corrosion properties quickly and quantitatively with a simple apparatus without using standard insulating materials even for new insulating materials. The purpose is to do.

  In the first configuration of the present invention for solving the above problems, a metal is immersed in an extract obtained by extracting the components of the insulating material in pure water, and the dissolution rate of the metal is measured. And it comprises as a metal-corrosion evaluation method of the insulating material which evaluates the corrosion property with respect to the metal of an insulating material based on the measured melt | dissolution rate.

  In the first configuration of the present invention, the metal to be evaluated is immersed in the extract, and the dissolution rate of the metal is measured. And the corrosivity of an extract is evaluated from the dissolution rate.

  The metal dissolution rate can be measured quantitatively and rapidly. Furthermore, no extract from the reference insulating material is required. Further, the corrosiveness of the metal, for example, the corrosion rate or the possibility and progress of corrosion can be quantitatively estimated from the dissolution rate. Therefore, quantitative metal corrosion of the insulating material can be quickly evaluated without using a reference insulating material.

  In the second configuration of the present invention, the measurement of the dissolution rate of the metal of the first configuration is performed by immersing the metal electrodes made of the metal to be evaluated in the extract and pure water for reference, respectively. Estimated from electrode potential difference. The electrode potential of the metal electrode indicates whether or not the metal can be dissolved in the extract and the dissolution rate. Therefore, the corrosivity of the extract can be quantitatively estimated from the electrode potential. This electrode potential can be measured quickly using a simple measuring instrument such as a potentiometer.

  In the second configuration, the electrode potential of the extract is measured using the reference pure water electrode as a reference electrode. Furthermore, a reference electrode, for example, a Pt electrode or other standard electrode can be immersed in reference pure water and used as a reference electrode.

  In the third configuration of the present invention, the dissolution rate of the metal of the first configuration is measured by dividing the extract into two parts, immersing the metal in one of them, and dissolving the metal components in the extract. The color reaction reagent is added to the extract, and the color of the extract in which the metal is dissolved is measured using the other extract (the extract not immersed in the metal) as a reference.

  In the third configuration, the metal corrosivity of the insulating material can be evaluated only by measuring the elution amount of the component of a known metal. Therefore, it is very simple compared to a method for identifying and quantifying many substances contained in an extract as in the conventional evaluation method. Moreover, the elution amount for each metal component, that is, the elution rate can be measured. For this reason, it is applicable also to selection of a metal material.

  According to the present invention, the metal corrosivity of the insulating material can be evaluated only by measuring the elution rate of the metal into the extract. For this reason, it is possible to quickly perform a quantitative metal corrosion test of an insulating material using a simple apparatus.

  FIG. 1 is a sectional process diagram illustrating a test method according to a first embodiment of the present invention. 1st Embodiment of this invention is related with the test method which measures an electrode potential and evaluates the metal corrosivity of an insulating material.

  With reference to Fig.1 (a), in 1st Embodiment of this invention, the container 3 of the distillation apparatus which put the pure water 2 first is prepared. Next, the insulating material to be evaluated is pulverized, and the pulverized insulating material 1 is immersed in pure water 2 in the container 3. Further, pure water 2 was boiled at 100 ° C. for 10 to 20 hours to produce an extract 1a from which the insulating material 1 was extracted. The distillation apparatus cools and condenses the vapor of the pure water 2 and recirculates it into the pure water 2 again. Furthermore, using a closed distillation apparatus, the pure water 2 can be kept at a high temperature and high pressure of, for example, 120 ° C. to 130 ° C. to speed up the extraction.

  Next, referring to FIG. 1B, the metal electrode 5 and the Pt electrode 7 made of metal to be evaluated are immersed in the extract 1a. Furthermore, the reference pure water 4 is prepared, and the metal electrode (reference electrode 6) made of a metal to be evaluated and the Pt electrode 7 are immersed in the reference pure water 4. Then, the Pt electrode 7 immersed in the extract 1a and the Pt electrode 7 immersed in the reference pure water 4 are electrically connected, and the potential difference between the metal electrode 5 and the reference electrode 6 is determined by a potentiometer 8. Measured with

  This potential difference between the metal electrode 5 and the reference electrode 6 corresponds to the difference in activity between the extract 1a and the reference pure water 4 for the metal to be evaluated. Since the corrosiveness of the metal to the pure water for reference is well known, the metal corrosiveness of the extract 1a can be quantitatively evaluated based on this potential difference.

  The Pt electrode 7 functions as a reference electrode and holds the potential difference between the extract 1a and the reference pure water 4 at a value determined electrochemically. If necessary, this potential difference can be measured in advance, and the measured value of the potentiometer can be corrected using this value. Alternatively, the extract 1a and the reference pure water 4 may be brought into electrical contact without using the Pt electrode 7.

  Further, the reference electrode 6 can be a reference electrode, for example, a Pt electrode. At this time, the reference electrode 6 functions as a reference electrode for the extract 1a. Further, the electrode potential of the metal electrode 5 can be measured using the Pt electrode 7 in the extract 1a as a reference electrode without using the pure water 4 for reference. At this time, the electrode potential can be measured more precisely by using a standard electrode instead of the Pt electrode 7.

  Further, instead of the potentiometer 8, the corrosion voltage and the corrosion current may be measured using a polarization measuring device, and the metal corrosivity may be evaluated based on these. By using the polarization measurement method, the influence of the electrode shape and the like can be reduced.

  FIG. 2 is a sectional process diagram illustrating a test method according to the second embodiment of the present invention. The second embodiment of the present invention relates to a test method for evaluating the metal corrosivity of an insulating material by measuring the amount of metal dissolved in an extract by colorimetric analysis.

  Referring to FIG. 2 (a), in the first embodiment of the present invention, first, an insulating material 1 to be evaluated is pulverized in a vessel 3 of a distillation apparatus containing pure water 2 and boiled under high temperature and high pressure. Then, an extract 1 a in which the components of the insulating material 1 are dissolved in the pure water 2 is prepared. This step is the same as the extract preparation step of the first embodiment described above.

  Next, referring to FIG. 2 (b), the extract 1a is divided into two and stored in the container 10a and the container 10b, respectively. And the metal piece 11 which consists of the metal which should be evaluated in the extract 1a accommodated in the container 10a is immersed for a half day-1 day, for example. If necessary, the container 10a is maintained at the environmental temperature or high temperature of the electronic device in which the metal is used. By this immersion, the components of the metal piece 11 are dissolved in the extract 1a in the container 10a.

  Next, a color reaction reagent that performs a color reaction on the metal ions of the components to be evaluated of the metal piece 11 is added to the container 10a and the container 10b. This color reaction reagent is, for example, PAR (4- (2-Pyridylazo) resorcinol), cuprizone or bicinchoninin for the component Cu ion to be evaluated, piperidyl or 1.10 phenanthroline for the component Fe ion to be evaluated. However, dimethylglyoxime is used for the component Ni ions to be evaluated. Moreover, it is preferable to select the component to be evaluated of the metal piece 11 that has the highest possibility of corrosion among the components contained in the metal and is contained in a large amount. For example, Cu ions can be selected for applications using Cu or Cu alloy for wiring, and Fe ions or Ni ions can be selected for applications using 42 alloy for lead frames.

  Next, referring to FIG. 2 (c), the extract 1a in the container 10a and the extract 10b in the container 10b are accommodated in the sample cell 9a and the reference cell 9b of the spectrophotometer, respectively, and in the sample cell 9a. The absorbance of the extract 1a is measured with reference to the light absorption of the extract 1b in the reference cell 9b. From the measurement result of the absorbance, the metal component dissolved in the extract 1a in the sample cell 9a is quantified. Based on the quantified dissolution amount, the dissolution rate of the metal component in the extract 1a, that is, the corrosion rate was calculated, and this dissolution rate was used as an evaluation standard for the metal corrosivity of the insulating material 1.

  In the second embodiment, the actual dissolution amount is measured. This test by coloration of the dissolved amount (colorimetric test) is a stable quantitative measurement as compared with the measurement of the electrode potential. Further, pure water as a comparative control as in the first embodiment is also unnecessary, and there are few chances for errors. For this reason, in 2nd Embodiment, metal corrosive evaluation can be performed stably.

  The color measurement of the second embodiment was performed by measuring the absorbance with a spectrophotometer. This color measurement can also be performed by other known colorimetric analysis, for example, a visual colorimetric test.

  Table 1 shows the test results according to the first and second embodiments, and shows the results of the metal corrosion test of the insulating material. The potential difference in Table 1 represents the electrode potential difference measured in the first embodiment, and the absorbance in Table 1 represents the absorbance measured in the second embodiment.

表１を参照して、絶縁材料として、水酸化金属難燃剤を含有するエポキシ樹脂Ａ、勇気燐難燃剤を含有するエポキシ樹脂Ｂ、鉛フリーのケーブル被覆材Ｃ及び鉛安定剤を含有するケーブル被覆材を評価した。なお、評価される金属として銅配線材料を選択した。また、比較例として従来広く使用されているＢｒ系難燃剤を含有するエポキシ樹脂を比較例として評価した。さらに、抽出液との比較のために、純水に対する金属腐食性試験の結果を示した。

Referring to Table 1, as insulation materials, epoxy resin A containing metal hydroxide flame retardant, epoxy resin B containing courageous phosphorus flame retardant, lead-free cable coating material C, and cable coating containing lead stabilizer The material was evaluated. A copper wiring material was selected as the metal to be evaluated. Moreover, the epoxy resin containing the Br type flame retardant widely used conventionally as a comparative example was evaluated as a comparative example. Furthermore, the result of the metal corrosion test with respect to pure water was shown for comparison with the extract.

  In the order of the insulating materials, epoxy resin A to epoxy resin E, the potential difference increases and the absorbance decreases on the contrary. This indicates that the activity in the extract 1a is high in this order and the metal is easily dissolved, and that there are many metal components dissolved in the extract in this order. That is, in this order, the metal corrosivity with respect to Cu of an insulating material is large. Since the activity or amount of dissolution calculated from the potential difference and absorbance quantitatively represents the difficulty of metal dissolution, the potential difference or absorbance quantitatively indicates the metal corrosivity of the extract, that is, the insulating material. It can be an indicator.

  The cable coating material D has a potential difference of 140 mV and an absorbance of 0.10, which is very close to the potential difference of 150 mV and the absorbance of 0.08 of the epoxy resin E of the comparative example. This indicates that the cable covering material D has a copper corrosivity close to (or slightly larger than) the epoxy resin E of the comparative example. Pure water has a potential difference of 240 mV and an absorbance of 0.01 or less, indicating that it is extremely corrosive. The potential difference between the metal electrode and pure water was measured with reference to the potential of the standard electrode.

  On the other hand, the epoxy resin B and the cable covering material C have a potential difference of 70 mV and 50 mV, and absorbances of 0.38 and 0.40, respectively, indicating that the Cu corrosivity is larger than that of the epoxy resin E of the comparative example. Further, the epoxy resin A has a potential difference of 37 mV and an absorbance of 1.56, which is the most corrosive. In addition, the ratio of the absorbance of the cable coating material D to the epoxy resin A normalized by the absorbance 0.08 of the epoxy resin E of the comparative example is 1.25, 4.75, 5, 0, 19, 5 in this order. is there.

  In Table 1, the result of measuring Cu ions contained in the extract 1a by the ICP-MS method (high frequency inductively coupled plasma mass spectrometry) is displayed as the Cu elution amount. The Cu elution amount measured by the ICP-MS method is in good agreement with the measurement result of absorbance when compared with the elution amount normalized by the epoxy resin E of the comparative example. This confirms that the absorbance measured in the second embodiment quantitatively represents the elution amount of Cu, that is, the corrosion rate of Cu.

  Further, Table 1 shows the results of a 500-hour reliability test of the dummy electronic device under a temperature of 85 ° C. and a humidity of 85% RH. In this test, only the epoxy resin A evaluated as having the highest corrosivity due to the potential difference and the absorbance was determined to be defective (NG). This conclusion shows that the metal corrosivity test of the present invention correctly evaluates the reliability of electronic equipment, and more accurately predicts the reliability.

The invention described in the following supplementary notes is disclosed in the present specification.
(Appendix 1) A step of immersing an insulating material in pure water to produce an extract in which the components of the insulating material are extracted in the pure water;
Immersing a metal in the extract and measuring the dissolution rate of the metal,
A method for testing a metal corrosion property of an insulating material, wherein the corrosion property of the insulating material with respect to the metal is evaluated based on the dissolution rate.
(Additional remark 2) The measurement of the said dissolution rate measures the said dissolution rate based on the electrode potential difference between the metal electrodes which consist of the said metal respectively immersed in the said extract and the pure water for reference. The metal corrosivity test method for the insulating material according to appendix 1.
(Additional remark 3) It replaces with the said metal electrode immersed in the said pure water for reference, The reference electrode immersed in the said pure water for reference is used, The metal corrosivity of the insulating material of Additional remark 2 characterized by the above-mentioned Test method.
(Additional remark 4) The measurement of the electrode potential difference between the said metal electrodes is made by electrically connecting the said extract and the said pure water for a reference, The metal corrosivity of the insulating material of Additional remark 2 or 3 characterized by the above-mentioned Test method.
(Supplementary Note 5) The electrical connection between the extract and the pure water for reference is made by connecting a reference electrode immersed in the extract and the pure water for reference with wiring. The metal corrosivity test method for the insulating material according to appendix 4.
(Additional remark 6) The process which divides the said extract into 2 parts, immerses the said metal in one, and dissolves the component of the said metal in the said extract,
Next, the coloring reaction reagent of the component is added to one and the other of the extracted liquid divided into two, and the corrosion rate is measured by comparing the coloration of one of the extracted liquid and the other of the extracted liquid. The method for testing a metal corrosion property of an insulating material according to appendix 1, which is characterized by the above.
(Additional remark 7) The said coloring comparison is made by a colorimetric test, The metal-corrosion test method of the insulating material of Additional remark 6 characterized by the above-mentioned.
(Additional remark 8) The said coloring comparison is made by the comparison of a light absorbency, The metal-corrosion test method of the insulating material of Additional remark 6 characterized by the above-mentioned.
(Additional remark 9) Preparation of the said extract is carried out by immersing the said insulating material in the said pure water for extraction of high temperature or high temperature, and high pressure of the insulating material in any one of Additional remark 1-8 characterized by the above-mentioned. Metal corrosion test method.

  In the development of a new insulating material that needs to quickly evaluate a large number of insulating materials, the present invention is applied to screening, in particular, to evaluate the metal corrosivity of the new insulating material simply, quickly and quantitatively. Can be applied.

Sectional process drawing explaining the test method of 1st Embodiment of this invention Sectional process drawing explaining the test method of 2nd Embodiment of this invention Process diagram of conventional methods for testing metal corrosion of insulating materials

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation material 1a Extract 2 Pure water 3, 10a, 10b Container 4 Reference pure water 5 Metal electrode 6 Reference electrode 7 Pt electrode (reference electrode)
8 Potentiometer 9a Data cell 9b Reference cell 11 Metal piece

Claims (5)

Immersing the insulating material in pure water to produce an extract in which the components of the insulating material are extracted in the pure water;
Immersing a metal in the extract and measuring the dissolution rate of the metal,
A method for testing a metal corrosion property of an insulating material, wherein the corrosion property of the insulating material with respect to the metal is evaluated based on the dissolution rate. 2. The dissolution rate is measured by measuring the dissolution rate based on an electrode potential difference between the metal electrodes made of the metal soaked in the extract and pure water for reference, respectively. Metal corrosion test method for insulating materials. 3. The metal corrosivity test method for an insulating material according to claim 2, wherein a reference electrode immersed in the reference pure water is used instead of the metal electrode immersed in the reference pure water. Immersing the extract in 2 minutes, immersing the metal in one, and dissolving the metal components in the extract;
Next, the coloring reaction reagent of the component is added to one and the other of the extracted liquid divided into two, and the corrosion rate is measured by comparing the coloration of one of the extracted liquid and the other of the extracted liquid. The method for testing a metal corrosion property of an insulating material according to claim 1. The metal extract of the insulating material according to any one of claims 1 to 4, wherein the extract is prepared by immersing the insulating material in pure water for extraction at high temperature or high temperature and pressure. Method.

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