NL2011973C2

NL2011973C2 - Paint comprising carbon black.

Info

Publication number: NL2011973C2
Application number: NL2011973A
Authority: NL
Inventors: Arnoldus Henricus Adrianus Verberne; Jan Anne Jonkman; Christopher Michael Twigg
Original assignee: Black Bear Carbon B V
Priority date: 2013-12-17
Filing date: 2013-12-17
Publication date: 2015-06-18
Also published as: WO2015093947A1

Abstract

The present invention relates to a paint comprising carbon black originating from the pyrolysis of scrap rubber originating from truck tyres. The invention furthermore relates to the use of a carbon black powder originating from truck tyres. The use of the present carbon black shows high colour strength and a high degree of jet blackness combined with significantly less yellow undertone, thereby providing a unique "colour space".

Description

Title: Paint comprising carbon black.

The present invention relates to a paint comprising carbon black, especially carbon black originating from the pyrolysis of scrap rubber, i.e. tyres. The invention furthermore relates to the use of a carbon black powder originating from tyres.

In the manufacture of paintings via dispersion of carbon black, ball mill, sand mill or the like has been traditionally used. However, carbon black paints in which carbon black is highly dispersed are hard to obtain by the dispersion treatment alone. Thus, prior to the dispersion treatment, a pre-treatment step is required. The easiest and simplest method that includes a pre-treatment step for manufacturing carbon black paints is, for example, stirring, such as stirring/dispersing of carbon black on a dissolver type of stirrer. Another method for manufacturing a carbon black paint that includes a pre-treatment step, wherein the pre-treatment step is a step of breaking carbon black particles apart with a high shear force, such as a kneading step using a kneader or a pressure kneader or milling step using a triple roll mill or twin roll mill. In the pre-treatment step, it is critical how to break carbon black particles apart easily to attain a paint.

Tyre recycling or rubber recycling is the process of recycling tyres (generally vehicles’ tyres) that are no longer suitable for use on vehicles due to wear or irreparable damage (such as punctures). These tyres are also known as ‘End-of-Life’ (ELT) tyres. These tyres are among the largest and most problematic sources of waste, due to the large volume produced and their durability. Recycling tyres is, however, a difficult and costly process and as a result millions of tyres every year are worn out and accumulated, often in landfill sites. Scrap tyres are bulky and they take up a significant amount of space, even if compacted. Furthermore such used tyres also cause air pollution if burned.

One known way to recycle tyres is by means of pyrolysis. Pyrolysis uses heat in the absence of oxygen to decompose the tyre to yield steel, volatile gases and carbonaceous char. US5037628 discloses a pyrolysis method for reclaiming carbonaceous materials from scrap tyres by pyrolyzing the scrap tyres in a one step pyrolysis process to form a char material. US2002119089 describes a one stage process for pyrolyzing scrap tyres involving the use of a rotating auger. The carbon black product has an average particle size of 0.125 mm making the product only suitable for low grade applications. US 2008286192 describes a batch process for the two-stage pyrolysis of tyres. The char material is not milled but used directly in rubber formulations.

In addition, WO 2013/095145 in the name of the present inventors discloses a process of pyrolyzing scrap tyres to produce a char material that can be milled to produce a carbon black powder that can be used as a filler or reinforcing agent in a rubber composition, an ink, a paint, a bitumen, a thermoplastic composition or a thermoplastic elastomer. However, WO 2013/095145 does not disclose the specific amount of the carbon black powder to be used, let alone the specific properties of the final product containing carbon black powder.

It is therefore an aspect or feature of the present invention to provide a paint that shows high colour strength, especially when compared with the commercially available carbon black powders.

Another aspect or feature of the present invention is to provide a carbon black powder for use as filler in paints, especially automotive paints, having improved properties, such as high degree of jet blackness.

Another aspect or feature of the present invention is to provide a carbon black powder for use as filler in paints, especially automotive paints, having improved properties, such as low yellow undertone.

Another object of the present invention is to provide carbon black powder for use as a filler in paints, especially automotive paints, wherein no undispersed particles or other physical disturbances visible to the naked eye are present when a drop of paint was poured on a sheet of transparent plastic, allowed to run and held up to a halogen light (often referred to as a “pour-down test” in the paint industry).

The present invention thus relates to a paint, comprising a basecoat and usual additives, such as carbon black powder, wherein the amount of said carbon black powder originating from pyrolysed tyres is in the range of 0.001 wt.% to 12 wt.%, on basis of the total weight of said paint, wherein said carbon black powder comprises a) 60-98 wt. % of carbon black, b) less than 2.0 wt. % of volatiles and c) 0-30 wt. % of silica, based on the total weight of said carbon black powder, and said paint having a value for dL* (lightness scale) in a range of less than -2,70, a value for da* (red/green scale) in a range of more than 0,90, and a db* (yellow/blue scale) in a range of less than 1,00, all data measured at an angle of reflection of 25o, 45o and 75o , in a white reference basecoat paint using an amount of carbon black powder of 0.1 wt.%, on basis of the total weight of said paint, following the method described herein.

The present inventors found that such paint shows an unexpected benefit regarding high colour strength, a high degree of jet blackness combined with significantly less yellow undertone. The present inventors assume that the carbon black powder as mentioned above provides a unique “colour space” and thereby provides solutions to on-going automotive customer requests to improve the level of jet blackness and reduced levels of undertone deviations.

In a preferred embodiment of the present invention the percentage reflectance, measured over a wavelength range of 400 - 700 nm, of said paint is lower than 3.

According to another embodiment of the present invention the percentage reflectance, measured over a wavelength range of 400 - 700 nm, of said paint is in a range of 3 - 1,5, wherein said reflectance measured at a wavelength around 420-480 nm is higher than said reflectance measured at a wavelength around 620-680 nm. 4. It is also preferred that the value of (dL* - db*) > 1.7, especially (dL* - db*) > 1.9. In the eyes of the customer looking for a dark paint it is wanted to have a high recorded dL* value in combination with a low db* value. Therefore the difference between these two values is highly significant - the bigger the difference the better.

The present paint further comprises zinc oxide in an amount of 1-5 wt. %, based on the total weight of said carbon black powder, and/or zinc sulphide in an amount of 1-5 wt. %, based on the total weight of said carbon black powder, preferably wherein the ratio between said zinc oxide and said zinc sulphide is between 1:10 to 10:1, preferably between 1:2 and 2:1.

The carbon black powder used in the paint according to the present invention has a particle size distribution of preferably D99 less than 30 pm and D50 less than 6 pm, D99 less than 20 pm and D50 less than 4 μηι, more preferably D99 less than 9 μη and D50 less than 3 μη, even more preferably more preferably D99 less than 4 pm and D50 less than 0.3 pm.

The present carbon black powder has preferably an average primary particle size in a range of 25 to 40 nanometres, preferably an average particle size distribution in a range of 10 to 70 nanometres, preferably STSA surface area (statistical thickness surface area) in a range of 60 - 80 m2/g, preferably BET nitrogen surface area in a range of 75 - 95 m2/g, and preferably OAN (oil absorption number) in a range of 68 - 88 m3/kg. BET surface areas can be measured according to ASTM D-6556-2010. The primary particle size can be measured according to ASTM D-6556-2010. Oil absorption is measured according to ASTM D-2414-2012. The particle size distribution can also be determined using dry or wet laser diffraction on an instrument such as a Malvern Mastersizer S Ver 2.19.

In a preferred embodiment the paint according to present further comprises 0.1-10 wt. % binding agent, based on the total weight of said carbon black powder, wherein said binding agent is starch, preferably pre-gelatinized starch.

According to a preferred embodiment the present carbon black originates from two stages pyrolysed scrap rubber, comprising the following steps: a) a first pyrolysis stage of scrap rubber to obtain an intermediate char material, and b) a second pyrolysis stage of said intermediate char material to obtain said carbon black, wherein at least one of the stages a) or b) is carried out in a rotary kiln, wherein in step a) the percentage of volatiles originally present in said scrap rubber is reduced to an amount of about 5-10 wt.%, based on the total weight of the intermediate char material, and wherein the intermediate char material is introduced in the second pyrolysis stage b) in which the percentage volatiles is further reduced to a percentage of less than 2.0 wt. %, based on the total weight of the char material, wherein the pyrolysis conditions in terms of the required total energy per square meter of feedstock surface area are from 20 to 30 kW/m2 of feedstock (tyre) surface area. Such a method has been disclosed in WO 2013/095145 and is incorporated herein by reference in total.

The present invention further relates to the use of a carbon black powder originating from tyres, said carbon black powder comprising a) 60-98 wt. % of carbon black, b) less than 2.0 wt. % of volatiles and c) 0-30 wt. % of silica, based on the total weight of said carbon black powder, in a paint in an amount of 0.001 wt.% to 12 wt.%, on basis of the total weight of said paint, for reducing the level of undertone deviation.

The present invention further relates to the use of a carbon black powder in a paint for improving the colour strength and the degree of jet blackness.

The present invention further relates to the use of a carbon black powder in a paint for improving the degree of jet blackness.

According to another embodiment the present invention relates to the use of a carbon black powder in a paint according wherein said paint is an automotive paint, especially wherein said amount of carbon black is in a range of 1,5 wt.% to 5 wt.%, on basis of the total weight of said paint.

For example WO 2013/095145 teaches, in the first pyrolysis stage, the percentage of volatiles present in said scrap rubber is reduced to an amount of about 5-10 wt.% based on the total weight of the intermediate char material, and wherein the intermediate char material is introduced in the second pyrolysis stage b) in which the percentage volatiles is further reduced to a percentage of less than 2.5 wt.%, preferably less than 2.0 wt. %, based on the total weight of the char material.

In addition WO 2013/095145 teaches that the temperature during the first pyrolysis stage a) is preferably 500-800 °C, more preferably 600-700 °C and even more preferably 630-670 °C, wherein the temperature during the second pyrolysis stage b) is preferably between 550-800 °C, more preferably 650-750 °C and even more preferably 680-720 °C.

Furthermore WO 2013/095145 teaches that the residence time of each the first pyrolysis stage a) and the second pyrolysis stage b) are independently between 20-50 minutes, preferably 25-45 minutes and more preferably 30-40 minutes. WO 2013/095145 teaches that in the second pyrolysis stage a) the percentage volatiles is reduced to less than 1.0 wt.% based on the total weight of the char material, especially the milling of step ii) is carried out by jet milling using compressed air or steam. WO 2013/095145 teaches that the pelletizing of step iii) is carried out by mixing a binding agent with the carbon black powder obtained in step ii) and pelletizing the mixture thus obtained to obtain a pelletized carbon black powder, wherein the binding agent is pre-gelatinized starch.

The term ‘carbon black’ as used here relates to a black finely divided form of amorphous carbon. In other words, a virtually pure elemental carbon in the form of colloidal particles. Carbon black is, for example, produced by incomplete combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. Its physical appearance is that of a black, finely divided pellet or powder. Its use in tires, rubber and plastic products, printing inks and coatings is related to properties of specific surface area, particle size and structure, conductivity and colour. It is to be noted that the definition of carbon black as used herein does not include soot (finely divided carbon deposited from flames during the incomplete combustion of organic substances such as coal) or black carbon (pure carbon in several linked forms obtained through the incomplete combustion of carbon-containing materials). Soot and black carbon are the two most common, generic terms applied to various unwanted carbonaceous by-products resulting from the incomplete combustion of carbon-containing materials, such as oil, fuel oils or gasoline, coal, paper, rubber, plastics and waste material. Soot and black carbon also contain large quantities of dichloromethane and toluene extractable materials, and can exhibit an ash content of 50% or more.

By ‘carbon black powder’ is meant a powdery form of carbon black. In other words, fine particulates of carbon black. Carbon black powder in the composition according to the invention obtained by milling of a char material, the carbon black powder comprising, for example, carbon black, residue material, silica, volatiles and water.

With ‘scrap rubber derived carbon black powder’ is meant a carbon black powder derived from a scrap rubber, preferably a carbon black powder that is obtained from the pyrolysis of a scrap rubber. A ‘rotary kiln’ is a cylindrical vessel, inclined slightly to the horizontal, which is rotated about its axis. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end, and may undergo a certain amount of stirring and mixing. Hot gases pass along the kiln. The gases may pass along the kiln in the same direction as the process material (concurrent), but preferably pass along the kiln in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated inside the kiln, e.g. by a flame.

With ‘volatile’ is meant any element or compound that is removed in a gaseous state during the pyrolysis of scrap rubber. In other words, an element or compound that is readily evaporated. Typically the volatiles released during pyrolysis can be classified as non-condensable and condensable.

With ‘particle size distribution of D99’ or ‘particle size distribution of D50’ is meant the 99th and 50th percentile of the particle size distribution, respectively, as measured by volume. The D99 describes a sample of particles whereby 99 vol. % of the particles have a size smaller than the stated particle size distribution. With a D99 < x micrometre is meant that 99 vol.% of the particles has a size of less than x micrometre. The D50 describes a sample of particles whereby 50 vol. % of the particles have a size smaller than the stated particle size distribution. With a D50 < x micrometre is meant that 50 vol. % of the particles has a size of less than x micrometre.

The particle size distribution can be determined according to the method disclosed in: ASTM D3849 - 2011.

The invention will be further elucidated by means of several embodiments. % (color) Strength WSUM. This shows the methodology for calculating color strength as shown above for the three commercially available carbon blacks, i.e. Raven 410 (lamp black), from Birla Carbon, Special Black 100 (oxidized ‘furnace black’), from De Gussa, and FW 200 Black (post-oxidized ‘gas black’), from De Gussa, and the present JetBlack-100.

This strength method is sometimes listed as integrated strength. The strength WSUM respresents the ration of sums of (K/S) data multiplied by the sum of weighted observer/illumination at all wavelengths for the sample in the relation to the standard. It will be expressed in percent.

The result is illuminant/observer depending. F.e. If a red color is evaluated for strength difference this method will show for D65 illumination a smaller color strength difference than for a illuminant A. The calculation for WSUM color strenght based on reflectance is:

R is the reflectance at the wavelength of maximum absorption in a decimal way (20%R = 0.02R). The calculation for WSUM strength based on Transmission is: R = loe10( 1/ T)

Interpretation

Percent color strength < 100 = sample is more strong in color than the standard Percent color strength > 100 = sample is weaker in color than the standard Percent color strength = 100 = sample and standarrd have the same color strength

Fig. 1 shows spectral data of Test Toner, wavelength values measured in nanometers, measured on an X-Rite Spectrophotometer at an angle of 45°.

Fig. 2 shows spectral data curve of Test Toner, based on data provided in Fig. 1.

Fig. 3 shows color results determined in white automotive reference basecoat paint. Fig. 4 shows dL* comparisons (lightness).

Fig. 5 shows da* comparisons (+red / -green).

Fig. 6 shows db* comparisons (+yellow / -blue).

Fig. 7 shows dL* - db* comparisons using average values of all three angles. Examples

The present carbon black pigment produced from end-of-life tyres, also called JetBlack-100 hereafter, was compared against the following three specialty grades of carbon blacks commonly used for pigmenting automotive paints by an international paint manufacturer:

Raven 410 (lamp black), from Birla Carbon;

Special Black 100 (oxidized ‘furnace black’), from De Gussa; FW 200 Black (post-oxidized ‘gas black’), from De Gussa.

The QC results of test toner are as follows:

Test ASTM Specification Result

Method

Viscosity D856 60 - 65 KU @ 25 °C 65.1 KU

Specific Gravity D1475 0960 — 0980 0972

Non Volatile Content (NVC) D1644 35 wt.% min @ 130 °C 34.66 wt.%

Fineness of Grind D1210 < 4 microns < 4 microns

Clean Test (pour-down) n/a No pigment kick-out* No pigment kick-out*

Test toners using JetBlack-100 and the three reference carbon blacks were made up in a balanced resin blend of polyester, melamine and cellulose acetate butyrate (CAB). The solids content of the toners was nominally 35 wt.%. The carbon black pigment content was 4 wt.% (based on wet paint). The test toner samples were analyzed for color strength using an X-Rite Spectrophotometer. Comparative results are given below. Color Strength values were normalized according to those of the JetBlack-100 test toner and were calculated by the software of the Spectrophotometer according to a specific method.

Therefore color strength values higher than 100 indicate relatively weak color strengths. In other words JetBlack-100 according to the invention presents the highest magnitude of color strength when compared to the three reference pigments. The Raven Black 410 presents the weakest color strength.

Pigment Paste dL da db Colour Strength, %

JetBlack-100 0.00 0.00 0.00 100.00

Carbon Black FW200 -1.08 0.08 -1.45 110.74

Carbon Black FW100 -3.22 0.22 0.36 134.32

Raven Black 410 -5.74 0.35 1.10 167.01

The four test toners were used to tint a white reference basecoat paint using an addition of 0.1 wt.%. The four tinted white samples were then analyzed for comparative dL* (lightness scale), da* (red/green scale) and db* (yellow/blue scale) values using an X-Rite Spectrophotometer. Measurements were taken at three angles of reflection (25°, 45° and 75°).

Fig. 1 shows spectral data of Test Toner, wavelength values measured in nanometers, measured on an X-Rite Spectrophotometer at an angle of 45°. Fig.2 shows spectral data curve of Test Toner, based on data provided in Fig. 1, and this Figure 2 demonstrates that the percentage reflectance, measured over a wavelength range of 400 - 700 nm, is lower than 3. Fig.3 shows color results determined in white automotive reference basecoat paint, which data have been shown graphically in Fig 4, i.e. dL* comparisons (lightness), in Fig 5, i.e. da* comparisons (+red / -green)and in Fig. 6, i.e. db* comparisons (+yellow / -blue). These Figures 4-6 clearly demonstrate that the performance of JetBlack-100 is better than the three commercially available carbon blacks. Fig. 7 shows dL* - db* comparisons using average values of all three angles and these data show that only JetBlack-100 fulfills the requirement of (dL* - db*) > 1.7.

On basis of the test results one can conclude that JetBlack-100 was considered closest to De Gussa’s FW 200 specialty carbon black but importantly with higher color strength and a higher degree of jet blackness combined with significantly less yellow undertone. The use of JetBlack-100 according to the present invention provides a unique “color space” and thereby has provides solutions to ongoing automotive customer requests to improve the level of jet blackness and reduced levels of undertone deviations.

Reference numbers in drawings

White 1

Green 2

Blue 3

Yellow 4

Red 5

Black 6

Claims

A paint comprising a base layer and conventional additives such as carbon black powder, wherein the amount of said carbon black powder from pyrolyzed tires is in the range of 0.001% to 12% by weight based on the total weight of said paint, wherein carbon black powder comprises a) 60 to 98% by weight of carbon black, b) less than 2.0% by weight of volatile components and c) 0 to 30% by weight of silica based on the total weight of said carbon black powder and said paint having a value for dL * (lightness scale) in a range of less than -2.70, has a value for da * (red / green scale) in a range of more than 0.90, and a db * (yellow / blue scale) ) in a range of less than 1.00, has all the data measured with an angle of reflection of 25 °, 45 ° and 75 °, in a white reference base coat paint with an amount of soot powder of 0.1 wt%, based on the total weight of said paint, according to the method described herein.

The paint of claim 1, wherein the percentage of reflection, measured over a wavelength range of 400 to 700 nm, of said paint is less than 3.

The paint of claim 2, wherein the percentage of reflection, measured over a wavelength range of 400 to 700 nm, of said paint is in a range of 3 to 1.5, wherein said reflection measured at a wavelength around 420 to 480 nm is higher then said reflection measured at a wavelength around 620 to 680 nm.

Paint according to one or more of the preceding claims 1 to 3, wherein (dL * - db *) > 1.7, in particular (dL * - db *) > 1.9.

A paint according to any one of claims 1 to 3, further comprising zinc oxide in an amount of 1 to 5% by weight, based on the total weight of said carbon black powder, and / or zinc sulfide in an amount of 1-5% by weight. % based on the total weight of said carbon black powder, preferably wherein the ratio between said zinc oxide and said zinc sulfide is between 1:10 to 10: 1, preferably between 1: 2 and 2: 1.

A paint according to any one of the preceding claims, wherein said soot powder has a particle size distribution of preferably D99 less than 30 μηι and D50 less than 6 μηι, D99 less than 20 μηι and D50 less than 4 μηι, more preferably D99 less than 9 μηι and D50 less than 3 μηι, and even more preferably D99 less than 4 μηι and D50 less than 0.3 μηι.

A paint according to any one of the preceding claims, wherein said carbon black powder has an average primary particle size in a range of 25 to 40 nm, preferably an average particle size distribution in a range of 10 to 70 nm, preferably STSA surface area (statistical thickness surface area) in a range of 60 to 80 m2 / g, preferably BET nitrogen surface area in a range of 75 to 95 m2 / g, and preferably has OAN (oil absorption number) in a range of 68 to 88 m2 / kg .

A paint according to any one of the preceding claims, further comprising 0.1 to 10% by weight binder based on the total weight of said carbon black powder, wherein said binder is starch, preferably pre-gelatinized starch.

A paint according to any one of the preceding claims, wherein said carbon black comes from a two-phase waste rubber pyrolysis, comprising the following steps: a) a first waste rubber pyrolysis phase to obtain a carbonized intermediate material, and b) a second pyrolysis phase of said waste rubber charred intermediate material for obtaining said carbon black, wherein at least one of phases a) or b) is carried out in a rotary kiln, wherein in step a) the percentage of volatile constituents from said waste rubber is reduced to an amount of around 5 to 10 wt. % based on the total weight of the carbonized intermediate material, and wherein the carbonized intermediate material is introduced into the second pyrolysis phase b) wherein the percentage of volatile components is further reduced to a percentage of less than 2.0% by weight based on the total weight of the carbonized material, wherein the pyrolysis conditions with respect to the required tot ale energy per square meter of raw material surface area of 20 to 30 kW / m2 of raw material (tire) surface area.

Use of a carbon black powder from tires, said carbon black powder comprising a) 60 to 98% by weight of carbon black, b) less than 2.0% by weight of volatile constituents and c) 0 to 30% by weight of silica based on the total weight of said carbon black powder, in a paint in an amount of 0.001% to 12% by weight, based on the total weight of said paint, to reduce the level of under-deviation.

Use of a carbon black powder in a paint according to claim 10 for improving the color strength and the degree of jet blackness.

Use of a carbon black powder in a paint according to one or more of claims 10 to 11 for improving the degree of jet blackness.

Use of soot powder in a paint according to one or more of claims 10 to 12, wherein said paint is a car paint, in particular wherein said amount of soot is in a range of 1.5% to 5% by weight on based on the total weight of said paint.