DD258996A5 - METHOD FOR CHANGING THE SURFACES OF RUSSIA - Google Patents

Abstract

The invention relates to a method for changing the surface characteristics of a furnace carbon black having an effective nitrogen surface area of more than 140 m 2 / g, which is characterized in that the surface of the carbon black is treated with an organic adsorbate having a molecular structure including at least one linear chain has four carbon atoms.

Description

Field of application of the invention

The present invention relates to a method of altering the surface features of furnace carbon black.

Characteristic of the known state of the art

Carbon black is produced by the thermal decomposition of hydrocarbons at very high temperatures. The carbon blacks formed in this manner consist of essentially elemental carbon in the form of agglomerated particles of colloidal dimensions and large effective surface area. All of the carbon blacks have many similar properties, regardless of the manufacturing process or the raw materials used for their production. The distinction between the different types or types of carbon blacks is more degree-wise than type-wise and is based on such features as particle size, effective surface area, chemical composition of the particle surface and extent of particle association with each other.

The carbon black particles are generally porous and have both external and internal active surfaces. Specific effective surfaces, which are generally assessed by adsorption techniques, are commonly used to identify and classify the carbon blacks. Various behavioral features of the product have been attributed to the inner and / or outer operative surfaces of the carbon blacks therein.

Carbon black is a widely used ingredient that can impart conductivity to polymer systems. One such application is antistatic compounds such as e.g. for films, tapes, tubes and molded articles, to minimize static charges and the risk of explosions in environments such as pits, hospitals and other areas where solvent vapors or oxidants can collect. In the wire and cable industry, conductive carbon black compounds are used as a shield for metal conductor strands in high voltage cables

However, when carbon black is mixed into polymer systems, the compound moisture absorption (CMA), the amount of moisture absorbed by the compound, may increase. Increasing the CMA in conductive polymers can contribute to at least two significant problems. First, the moisture absorbed in the compound can be vaporized during the extrusion operations, where the temperatures may exceed 100 ^° C. (373 ^° K.). This evaporation creates "gas bubbles" on the surface of the extrudate, which are a potential source of dielectric deficiency Secondly, the moisture absorbed in the compound can induce dielectric breakdown even by a process called "branching". (The descriptive term "branching" is derived from the shape of the dielectric breakdown path as observed by microscopic examination.

Object of the invention

The aim of the invention is the substantial elimination of the disadvantages mentioned.

Explanation of the essence of the invention

The invention has for its object to provide a method for changing the surface characteristics of carbon black. In particular, it has been found that the increase in CMA due to the incorporation of certain conductive carbon black in polymer materials is mainly due to the microporosity of the carbon black.

According to the invention, a method has now been discovered by which the microporosity of a carbon black can be selectively modified. The carbon black is treated with an organic adsorbate which adsorbs by the carbon black and effectively blocks the micropores in a specific size range but does not adversely affect other properties of the compound. It has been found that by treating a carbon black with an adsorbate having selective molecular dimensions, pores of a selected diameter range can be filled, thereby effectively blocking detrimental moisture absorption. It has been found that the molecules of selected adsorbate are firmly bound to the carbon black and are not released under normal handling, storage and service conditions. Theoretically, it is believed that the overlapping stress fields present in such small pores bind the adsorbate molecules at relatively high energies, thereby making it difficult to displace the molecule from the micropore.

The treatment according to the invention can be effectively applied to any type of carbon black which has a surface microstructure with a significant proportion of micropores in the range of sizes into which water molecules can penetrate. The carbon black may be in pearlated or flaked form. It has thus been found that the treatment leads to favorable results when furnace surface high-efficiency furnace blacks (having an effective nitrogen surface area greater than about 14 μmV [N ₂ SA]) are modified because these carbon blacks appear to have a high surface area Having surface microstructure with a significant proportion of micropores in the specified size range. Good results have been obtained by treating preferred furnace blacks with N ₂ SA ranging from about 200m ² / g to about 260m ² / g. The adsorbate of the present invention may be any organic molecule having a linear chain of at least four carbon atoms, such as alkanes and substituted alkanes (amines, halides, alcohols, and the like), and mixtures thereof. Typical substances are n-octane, n-aminooctane, n-hexanol, n-bromooctane, n-chlorooctane, 4-methylheptane, 2,5-dimethylheptane, 2,3,4-trimethylpentane, 2,2,4-trimethylpentane, hexamethylethane , n-nonane, n-decane, n-dodecane, n-hexadecane, 1,3-dichloropropane and the like. Because of the efficiency and permanence of the treatment during the thermal processing, adsorbates having a linear chain of at least ten carbon atoms are preferred. Particularly preferred are n-alkanes, Ci ₀ -C ₁₆ , have the heat resistance above about 250 ° C (523 ⁰ K).

The manner in which the adsorbate is added to the carbon black is not critical. Practically, the treatment consists simply of mixing the chosen amount of adsorbate with the carbon black in a corresponding vessel and then moving the carbon black to ensure impregnation of the carbon black surface with the adsorbate. Excess or unadsorbed adsorbate can be removed by drying the treated carbon black at moderate temperatures, which are generally in the range of about 100 to 200 ⁰ C (373 ° K bis473). The treatment of the carbon black can also be conveniently carried out in various process steps during the production or application of the carbon black. For example, a suitable adsorbate may be injected into the process stream of a carbon black reaction vessel prior to collection of the carbon black, or the adsorbate may also be introduced during a mixing operation when a carbon black is blended with a polymer.

The optimum amount of adsorbate to be used depends on the carbon black to be treated, its effective surface area and the percentage at which this effective surface area of micropores in the size range effectively blocked by the adsorbates of the invention is present. In the treatment of conductive carbon black, good results have been obtained using about 0.5 to about 5 mass% adsorbate, with about 1.0 to about 2.0 percent adsorbate being particularly preferred.

embodiment

The following examples serve to further illustrate the invention. The examples are intended to be illustrative only and not limiting the scope of the invention.

test methods

A quantity of soot was weighed into a beaker and a measured weight percent of adsorbate was then added to the carbon black. The beaker was capped and the contents thoroughly mixed by rolling the beaker for about one to five minutes (60 to 300 seconds). After removal of the lid, the beaker and its contents were then placed in an oven to dry.

To evaluate the performance characteristics of the carbon blacks in terms of imparting properties such as moisture absorption and resistivity to the compound, the carbon blacks were mixed with a suitable resin. For explanation, an ethylene / ethyl acrylate (EEA) was used as the resin in the following examples. The compound to be tested was prepared by incorporating the required amount of carbon black in the resin, on a Ma .-% basis. The carbon blacks were compounded in the specified ischers fill volumes in the EEA using a Brabender-M, running at 60 U / mi η with oil to run at 110 ⁰ C (383 ⁰ K) nine minutes (540 seconds) long. The resulting compound was rolled on a two-roll cold roll and formed into films for subsequent testing.

For the determination of the CMA, films of the various ethylene / ethyl acrylate (EEA) compounds were comminuted or cut into pellets to obtain correspondingly granulated samples. A 3-gram sample of the granulated compound was weighed into a glass crucible of known mass and at ¹ 60 ⁰ C ± 3 ° (333 ⁰ K), and ^1/3 atmosphere (3.4 + 10 ⁴ Pa) two hours (7200 seconds) dried long to remove the moisture from the compound. After cooling in a desiccator, the weight was determined to a tenth of a milligram. The compound was then held in a room temperature appropriate condition (70 ± 2 ° F [294 ° K]) and 79 percent relative humidity (RH) for 48 hours (1.728 x 10 ⁵ seconds). The compound was then weighed after 30 minutes (1800 seconds) and periodically at 24 hour intervals (8.64 × 10 ⁴ seconds) until a constant weight (0.03 percent increase in CMA) was achieved. Equilibrium moisture absorbance was calculated as wt% of the compound using the following equation:

in which mean:

C + S = final mass of container + sample C + DS = mass of container + dry sample TC = tared mass Glass crucible B = change in the mass of the empty container

By resistivity of a material is meant the ratio of the voltage gradient parallel to the current in the material and the current density. The resistivity is measured in ohm-centimeters; it is the reciprocal value of the volume conductivity. To determine the resistivity of carbon black-containing plastic compounds, samples were prepared by cutting 80 mil standard tensile panels from the rolled sheets and cutting 2 "χ 6" (5.1 x 15.2 cm) electrical specimens from the tensile panels. Each test piece was provided with a silver paint (conductive silver coating in ethyl alcohol) to produce a V2Z0II (1.27 cm) wide silver electrode at each end. The specimens were placed in a sample holder (between 8 χ 6 [20.3 χ 15.2] cm glass plates arranged crosswise with each other so that the edge of the top plate is level with the edge of the specimen), and the electrodes were connected to a Leeds and Northrup meter (# 5035) consisting of a Wheatstone bridge and a galvanometer. The voltage applied to the test specimens was approximately 4.5 volts. The DC resistances in the length of the sample were measured and converted to ohm-cm resistivity using the following formula:

. *. ,,, ·, ·, ·, ,, ^, ν 2 χ T χ (2,54) χ R Specific resistance (ohm-cm) = -

in which mean:

T = thickness of the sample (inch)

R = resistance (ohms)

2.54 = conversion constant (in. -> cm)

5 = distance constant (inches) - measure of the distance between the two ¹ /2-inch silver electrodes painted on each end of the specimen.

The resistance of the specimen was measured in an oven maintained at 90 ^° C. (363 ^° K.). The resistance was initially after three minutes (180 seconds) measured at 90 ⁰ C (363 ° K), and subsequent readings were (1800 seconds) (120 seconds) made at intervals of 2 minutes in the next 30 minutes. After 30 minutes (100 seconds), readings were taken every five minutes (300 seconds) until the specimen had spent a total of 60 minutes (3600 seconds) in the 9O ⁰ C (363 ° K) oven. The value for the resistance of the specimen at 90 ° C (363 K ⁰⁾ was plotted on a graph as the point at which the readings were constant.

The effective nitrogen surface area (N ₂ SA) of the carbon black samples was determined in accordance with ASTM Test Method D 3037-76, Method C, and is expressed in square meters per gram (m ² / g).

The following tables contain representative results obtained using a selection of carbon blacks and absorbents.

Tables I and II show results with two different carbon black samples and using different amounts of two adsorbates.

The data presented in Table III show that treatment with homologs of n-alkanes provides comparable favorable results. The extension of the chain length of the adsorbate has the advantage that higher atmospheric boiling points and higher temperature resistance against decomposition are made possible.

Tables IV illustrate the effects of treatment using various isomers of octane. The adsorbate molecules all have the same molecular formula, but show increasing degrees of branching running from top to bottom in the table. Although treatment with all adsorbates gave good results, linear molecules were the most effective.

Table V contains treatment results using various adsorbates, including substituted and unsubstituted alkanes. The amines and alcohols appear to have a slight affinity for water, which is absent in the halogenated and unsubstituted alkanes.

Table VI contains the results from the treatment of carbon blacks having different effective surfaces. The example using a low effective surface carbon black (about 50 m ² / g) showed no effect in a subsequent treatment according to the invention.

Table VI contains results for which carbon blacks having different effective surface areas were treated with varying amounts of N-decane adsorbate.

Table I

Compound: carbon black * (36% filler) in EEA

adsorbate

treatment conditions

Specific resistance 25 ° C 90 ° C

CONTROL 3% n-octane CONTROL 1.5% n-octane

150T / 60 min

150T / 60 min

3.12 2.76 2.75 2.59

13.5 10.8 11.5 10.3

The carbon black was VULCAN XC-72 (ASTM-N-472), a conductive carbon black available from Cabot Corporation having an effective nitrogen surface area of about 215 to 260m ² / g.

Table II

Compound: carbon black * (36% filler) in EEA

adsorbate

Behandlungsbe CM/ conditions (Ma 150T / 60 min 2.45 150 T / 60 min 0.92 150 T / 60 min 0.43 150T / 60min 2.49 150 T / 60 min 1.08 150 T / 60 min 0.55

Specific resistance 25X 90 ^c

CONTROL

3% n-octane

4.5% n-octane

COULD TROLLS

3% n-octane

4.5% n-octane

The carbon black used had an effective nitrogen surface area of about 610 m ² / g.

1.9 2.2 2.1 1.9 1.6 2.1

5.1 5.1 6.0 5.6 3.9 6.0

Table III

Compound: carbon black *

adsorbate

(36% filler) in EEA

treatment conditions

Specific resistance

25T 9OT

CONTROL 1 ¹ /2% n-octane 1 ¹ /2% n-decane 1 ¹ /2% n-dodecane 1 V2% n-hexadecane

200 T / 12 h 200 T / 12 h 200 T / 12 h 200 T / 12 h

0.56 0.22 0.23 0.24 0.24

10.4

9.1

8.7

10.1

10.3

Table IV

Compound: carbon black * (36% filler) in EEA

adsorbate

treatment CM/ conditions (Ma 200 T / 12 h 0.66 200 T / 12 h 0.20 200 T / 12 h 0.28 200 T / 12 h 0.28 200 T / 12 h 0.35 200 T / 12 h 0.38 200 T / 12 h 0.44

CONTROL 1.5% n-octane 1.5% 4-methylheptane 1.5% 2,5-dimethylheptane 1.5% 2,3,4 trimethylpentane 1,5% 2,2,4 trimethylpentane 1,5% hexamethylethane

The carbon black used was VULCAN XC-72 (ASTM-N-472), a conductive carbon black to be obtained from Cabot Corporation having an effective nitrogen surface area of about 215 to 260 m ² g.

Specific cons 9OT was standing 9.6 25 T 9.1 2.9 11.5 2.8 10.1 3.1 10.5 3.3 8.5 3.2 25.5 2.7 5.4

Table V

Compound: carbon black * (36% filler) in EEA

adsorbate

treatment CMA Specific cons 9O ⁰ C conditions (Wt .-%) was standing 12.2 25 ⁰ C 10.3 0.65 2.8 17.4 150 T / 50 min 0.29 2.6 14.0 150T / 50 min 0.34 3.6 31.9 150 T / 12 h 0.44 3.0 17.1 0.77 4.5 18.1 110 ° C / 60min. 0.36 3.7 19.5 110 T / 60 min 0.32 3.7 14.6 110T / 60 min 0.38 3.9 9.3 110T / 60min 0.33 3.3 110 T / 60 min 0.30 2.8

CONTROL 1% η-octane 3% n-aminooctane 2% n-hexanol CONTROL 2% n-octane 2% n-decane 2% n-bromooctane '2% n-chlorooctane 1.5% 1,3-dichloropropane * In the Carbon black used is VULCAN XC-72 (ASTM-N-472), a conductive carbon black to be supplied by Cabot Corporation

an effective nitrogen surface area of about 215 to 260 m ² / g.

Table VI

Compound: soot (36% filler) in EEA

adsorbate N ₂ SA filler treatment CMA Specific resistance 9OT (Wt .-%) (m ² / g). (Wt .-%) conditions (Wt .-%) 25 T 74 KONTROLLEA 50 36 150 T / 60 min 0.38 4.1 76 1.5% Norpar12 ¹ 36 150 T / 60 min 0.38 4.2 21 KONTROLLEB 138 36 150T / 60 min 0.44 3.5 21 1.5% Norpar12 36 150 T / 60 min 0.27 3.9 11 KONTROLLEC 224 36 150T / 60 min 0.78 2.6 9 1.5% Norpar12 36 150 T / 60 min 0.46 2.6 8th 1.5% Norpar12 ² 36 N / A 0.52 2.2 146 KONTROLLED 635 14 150T / 60 min 1.03 45 192 4.5% n-nonane 14 150 T / 60 min 0.22 56 26 KONTROLLEE 810 14 150 T / 60 min 0.45 9 27 3% n-decane 14 150 T / 60 min 0.26 11 19 KONTROLLEF 1727 12 150 T / 60 min 0.33 16 18 3% Norpar12 12 150 T / 60 min 0.11 15

(1) Norpar 12 is a mixture of n-alkanes having an average of 12 carbon atoms (commercially available from Exxon Company, USA).

(2) In this example, the adsorbate was added during the carbon black-EEA mixing process.

Table VII filler) in EEA filler treatment CMA specific Compound: soot (36%) N ₂ SA amount conditions Wt .-% resistance adsorbate (Wt .-%) 9OT (m ² / g) 36 150T / 60min 0.49 34.2 (Wt .-%) 142 36 150 T / 60 min 0.37 34.7 CHECK 1 36 150 T / 60 min 0.78 16.7 0.75% n-decane 235 36 150 ° C / 60min 0.39 13.0 CHECK 2 14 150 ° C / 60min 0.45 26.0 1.5% n-decane 1052 14 150 T / 60 min 0.26 26.5 CHECK 3 14 150 T / 60 min 0.63 19.2 3% n-decane 1322 14 150 T / 60 min 12:38 20.6 CONTROL 4 3% n-decane

Claims (10)

A method of modifying the surface features of a furnace carbon black having an effective nitrogen surface area above about 140m ² / g, characterized in that the surface of the carbon black is treated with an organic adsorbate having a molecular structure including a linear chain having at least four carbon atoms , 2. The method of claim 1, characterized in that the carbon black has an effective nitrogen surface area between about 200 and about 260m ² / g. A method according to claim 1, characterized in that the carbon black is treated with an organic adsorbate selected from the group consisting of n-alkanes, n-alkanamines, n-alkane halides, n-alkane alcohols and the like. A method according to claim 3, characterized in that the organic adsorbate is selected from the group consisting of n-alkanes having 10 to 16 carbon atoms and mixtures thereof. The method of claim 4, characterized in that the carbon black having between about 200 and about 26OmVg effective nitrogen surface area is treated with adsorbate in a filler amount between about 1 and about 2Ma%. A modified carbon black characterized in that it is obtained by treating a furnace carbon black having an effective nitrogen surface area above about 140m ² / g with an organic adsorbate having a linear chain of at least four carbon atoms. > 7. carbon black according to claim 6, characterized in that the organic adsorbate from the n-alkanes, n-alkanamines, n-alkane halides, n-alkanol and the like comprehensive group is selected. 8. carbon black according to claim 6, characterized in that the organic adsorbate is selected from the n-alkanes having 10 to 16 carbon atoms and mixtures thereof comprising group. 9. Carbon black according to claim 6, characterized in that it is obtained by the treatment of a carbon black with an effective nitrogen surface of about 200 to about 26OmVg. A carbon black according to claim 8, characterized in that it comprises, by the treatment of a furnace carbon black having an effective nitrogen surface area between about 200 and about 26 μmVg, an adsorbate at a filler level of between about 1 and about 2% by mass is won.