U.S. patent application number 10/624387 was filed with the patent office on 2004-05-06 for method and colorant for the coloring of rubber.
Invention is credited to Rajaraman, Hariharan.
Application Number | 20040087712 10/624387 |
Document ID | / |
Family ID | 24003131 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040087712 |
Kind Code |
A1 |
Rajaraman, Hariharan |
May 6, 2004 |
Method and colorant for the coloring of rubber
Abstract
The present invention provides a method for coloring a rubber
substrate with a latex-based colorant comprising the steps of
providing a latex-based colorant that includes an elastomeric
latex-based binder and a pigment system and mixing the latex-based
colorant with the rubber substrate. Optionally, the latex-based
colorant further comprises a surfactant system, a thickener, a
defoamer, and an antioxidant. The present invention further
provides a colored rubber and a latex-based colorant for coloring
rubber.
Inventors: |
Rajaraman, Hariharan;
(Munroe Falls, OH) |
Correspondence
Address: |
MCDONALD HOPKINS CO., LPA
2100 BANK ONE CENTER
600 SUPERIOR AVENUE, E.
CLEVELAND
OH
44114-2653
US
|
Family ID: |
24003131 |
Appl. No.: |
10/624387 |
Filed: |
July 22, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10624387 |
Jul 22, 2003 |
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10195933 |
Jul 17, 2002 |
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10195933 |
Jul 17, 2002 |
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09503696 |
Feb 14, 2000 |
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6500896 |
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Current U.S.
Class: |
524/552 |
Current CPC
Class: |
C08L 21/02 20130101;
C08L 21/02 20130101; C08K 5/0041 20130101; C08K 3/013 20180101;
C08K 3/013 20180101; C08K 5/0041 20130101 |
Class at
Publication: |
524/552 |
International
Class: |
C08J 003/00 |
Claims
What is claimed:
1. A method of coloring a rubber substrate, comprising the steps
of: providing a latex-based colorant comprising 5-50 percent by
weight latex-based binder, 10-70 percent by weight a pigment system
comprising an organic pigment dispersion and opacifer, and 0-85
percent by weight water; and mixing said latex-based colorant with
said rubber substrate.
2. The method of claim 1 wherein said latex-based colorant
comprises 10-20 percent by weight latex-based binder, 30-55 percent
by weight said pigment, and 25-60 percent by weight water.
3. The method of claim 1 further comprising the step of vulcanizing
the rubber during the mixing of said colorant and said rubber
substrate.
4. The method of claim 3 wherein said rubber is vulcanized with a
vulcanization agent, a cure activator, and an accelerator.
5. The method of claim 4 wherein said vulcanization agent is a
water based dispersion of sulfur, said cure activator is a water
based dispersion of zinc oxide, and said accelerator is selected
from the group consisting of thiuram, dithiocarbonate, xanthate,
mercapto thiazole, mercapto sulfonamide, thiourea, and
guanidine.
6. The method of claim 1 wherein said rubber is black.
7. The method of claim 1 wherein said latex binder comprises an
elastomeric latex selected from the group consisting of natural
rubber, synthetic rubber, or a mixture thereof, wherein said
elastomeric latex forms lattices, or colloidal dispersions of
polymeric material, in a water-based system and has a solids
content between 25-75%.
8. The method of claim 7 wherein said synthetic rubber is selected
from the group consisting of styrene butadiene rubber, nitrile
rubber, butyl rubber, polychloroprene rubber, and
ethylene-propylene rubber.
9. The method of claim 1 wherein said water based colorant further
comprises a surfactant system, a defoamer, an antioxidant, and a
thickener.
10. The method of claim 11 wherein said surfactant system is
selected from the group consisting of non-ionic, anionic, and
cationic surfactants, and mixtures thereof; said defoamer comprises
a mixture of hydrophobic solids and polysiloxanes; said antioxidant
is selected from the group consisting of is N-N'
Di(2-octyl)-p-phenylene diamine, diphenyl-p-phenylendedeiamine- ,
octylated diphenulamine; dioctylated diphenylamine, styrenated
phenol, hindered phenol, and mixtures thereof; and said thickener
is selected from the group consisting of a gum, starch, cellulose
polymer, mineral, alginate, and mixtures thereof.
11. The method of claim 1 wherein said pigment system comprises
titanium oxide and an organic pigment dispersion.
12. The method of claim 11 wherein said pigment system comprises
titanium dioxide and a water dispersion of an organic pigment
between a 3:1 and 2:1 ratio, respectively.
13. The method of claim 1 wherein said rubber substrate is selected
from the group consisting of crumb rubber, natural rubber, styrene
butadiene rubber, nitrile rubber, butyl rubber, polychloroprene
rubber, and ethylene-propylene rubber.
14. The method of claim 1 wherein said rubber substrate is crumb
rubber.
15. A latex-based colorant for coloring a rubber substrate
comprising a latex binder and a pigment system.
16. The latex-based colorant of claim 15 wherein said latex binder
comprises an elastomeric latex selected from the group consisting
of natural rubber, synthetic rubber, or a mixture thereof, wherein
said elastomeric latex forms lattices, or colloidal dispersions of
polymeric material, in a water-based system and has a solids
content between 25-75%.
17. The latex-based colorant of claim 16 wherein said synthetic
rubber is selected from the group consisting of styrene butadiene
rubber, nitrile rubber, butyl rubber, polychloroprene rubber, and
ethylene-propylene rubber.
18. The latex-based colorant of claim 16 wherein said water-based
colorant further comprises a surfactant system, a defoamer, an
antioxidant, and a thickener.
19. The latex-based colorant of claim 18 wherein said surfactant
system surfactant system is selected from the group consisting of
non-ionic, anionic, and cationic surfactants, and mixtures thereof;
said defoamer is a mixture of hydrophobic solids and polysiloxanes;
said antioxidant is selected from the group consisting of is N-N'
Di(2-octyl)-p-phenylene, diamine, diphenyl-p-phenylendedeamine,
octylated diphenulamine, dioctylated diphenylamine, styrenated
phenol, hindered phenol, and mixtures thereof; and said thickener
is selected from the group consisting of a gum, starch, cellulose
polymer, mineral, alginate, and mixtures thereof.
20. The latex-based colorant of claim 16 wherein said pigment
comprises titanium oxide and an organic pigment dispersion.
21 Colored rubber comprising a rubber substrate and a colored latex
coating in contact with said rubber substrate.
22. The colored rubber of claim 21 wherein said colored latex
coating comprises a pigment system and latex binder.
23. The colored rubber of claim 22 wherein said pigment system
comprises an opacifer and an organic pigment dispersion.
24. The colored rubber of claim 21 wherein said rubber substrate is
selected from the group consisting of natural rubber, crumb rubber,
styrene butadiene rubber, nitrile rubber, butyl rubber,
polychloroprene rubber, and ethylene-propylene rubber.
25. The colored rubber of claim 21 wherein said rubber substrate is
crumb rubber.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method used in the coloring of
rubber. This invention further relates to a colorant used to color
rubber and colorized rubber.
BACKGROUND OF THE INVENTION
[0002] Crumb rubber, commonly manufactured from recycled tires, is
used in road paving, horse tracks, floor mats, bedding for farm
animals, shingles for roofing and sports turf surfaces (such as
football fields, tracks, etc.) to add resilience to the surfaces
and to absorb impact better than asphalt or turf. Crumb rubber is
also gaining popularity as playground cover for areas where
children climb or face dangers from falling. Its superior ability
to cushion impacts makes it a very desirable ground surface for
high-impact activities.
[0003] The use of crumb rubber has been limited due to the lack of
aesthetic appeal in that most tires are black. Some methods of
coloring crumb rubber have been developed, such as wetting and
drying material or painting over the black, but these methods are
not efficient, practical or durable. Painting over the rubber
consumes a large amount of paint and commonly results in a
non-durable product as the paint is rubbed off when in consistent
contact with another object. Spraying the crumb rubber and allowing
it to air dry also creates a wide variety of problems. The spray
method produces a product with poor color uniformity and incomplete
coverage. Sprayed on paints tend to demonstrate poor adhesion of
the colorants to the rubber. In addition, the spray method wastes
an excessive amount of paint and create problems with waste
disposal when a solvent-based paint is used. Traditional methods
also lack the ability to achieve vibrant colors due to the carbon
black that is present in the rubber. The carbon black darkens or
dirties the colorant thereby producing a color that lacks vibrancy.
It would be desirable to have a method of coloring rubber which
will produce a durable, vibrant product.
SUMMARY OF THE INVENTION
[0004] The present, invention provides a method for coloring a
rubber substrate with a latex-based colorant comprising the steps
of providing a latex-based colorant that includes an elastomeric
latex-based binder and a pigment system and mixing the latex-based
colorant with the rubber substrate. Optionally, the latex-based
colorant further comprises a surfactant system, a thickener, a
defoamer, and an antioxidant. The present invention further
provides a colored rubber and a latex-based colorant for coloring
rubber.
DETAILED DESCRIPTION OF THE INVENTION
[0005] The present invention pertains to a colored rubber
substrate, a method of coloring a rubber substrate, and a
latex-based colorant for such a coloring method. The steps involved
in the method include, providing the colorant, and applying the
colorant to the rubber substrate. The method may further comprise
the step of vulcanizing the rubber.
[0006] The latex-based colorant comprises a latex-based binder and
a pigment system. The latex-based colorant preferably comprises
5-50 percent by weight elastomeric latex-based binder, 10-70
percent by weight the pigment system and 0-85 percent by weight
water. It is more preferred for the latex-based colorant to
comprise 10-20 percent by weight elastomeric latex-based binder,
30-55 percent by weight the pigment system, and 25-60 percent by
weight water. The latex-based binder comprises an elastomeric
latex, either natural or synthetic, that forms lattices, or
colloidal dispersions of polymeric material, in a water-based
system. When lattices are applied on a substrate, a uniform coating
of the rubber results after the water evaporates. The elastomeric
latex preferably has a solids content in the range of 25-75
percent, and it is more preferred to have an elastomeric latex with
a solids content in the range of 45-65 percent. Examples of
synthetic elastomeric latex are styrene butadiene rubber, nitrile
rubber, butyl rubber, polychloroprene rubber, and
ethylene-propylene rubber. It is preferred to use an elastomeric
latex comprising a mixture of natural rubber and styrene butadiene
rubber.
[0007] In addition, the latex-based colorant includes a pigment
system. The pigment system comprises an opacifer and an organic
pigment dispersion, preferably between a 3:1 and 2:1 ratio,
respectively. Examples of suitable opacifers are zinc oxide, zinc
sulfate, and barium sulfate. The preferred opacifer has a
refractive index greater than 2. Such an opacifer would include
titanium oxide, and more preferably a rutile grade of titanium
dioxide. The opacifer provides the opacity to cover up the carbon
black on the rubber and the color is achieved by using a suitable
organic pigment dispersion. Use of a latex-based colorant permits
application of a wide variety of colors to the rubber substrate.
Examples of suitable organic pigment dispersions are phthalocyanine
blues and greens, DNA orange, Diarylide yellows, Naphthol red,
Lithol Rubine red, Toluidine red, Red Lake C, Carbazole violet,
Barium Lithol red, Rhodamine Red, Methyl violet, and Quinacridone
Magenta. Organic pigment dispersions that are water-based are
preferred because they are compatible with the elastomeric
latex-based binders.
[0008] Optionally, the colorant further comprises a defoamer, a
surfactant system, a thickener, and an antioxidant. Any
conventional defoamer that minimizes the formation of foam and
bubbles during the manufacture of water-based dispersions may be
employed. It is preferred to use a mixture of hydrophobic solids
and polysiloxanes in polyglycol as the defoamer. One suitable
example is BYK022, manufactured by BYK-Chemie USA.
[0009] The surfactant system is preferably a blend of non-ionic and
ionic surfactants. Examples of non-ionic surfactants are
condensation products of fatty alcohols with ethylene oxide,
polyethylene glycol esters or chain fatty acids, or sobitan esters.
Ionic surfactants can be either anionic or certain cationic
compounds. Suitable anionic surfactants are, for example, sodium
alkyl sulfate, sodium salt of polymeric polycarboxylic acid, sodium
polymethacrylate, and sodium alkyl sulfate. Suitable cationic
surfactants are, for example, salts of primary, secondary, or
tertiary amines and quartenary salts such as cetylpyridinium
bromide, hexa-decyl-ethyl morpholinium chloride and diethyl
didodecyl ammonium chloride. The preferred surfactant system is a
blend of sodium salt of polymeric polycarboxylic acid and a
non-ionic surfactant based on modified alkylaryl polyther,
preferably with an 80:20 blend, respectively.
[0010] The thickener is desired to provide an increased shelf-life
and to impart a viscosity between 75 and 95 KU for the latex-based
colorant. A thickener with a viscosity between 75 and 100 KU, as
measured by a Stormer Viscometer, is preferred, and more preferably
is between 80 and 90 KU. Suitable thickeners are gums, starches,
cellulose polymers, minerals, or alginates. The preferred thickener
is a hydrated aluminum magnesium silicate, commonly designated as
Attagel, commercially available from Engelhard Corporation, or
Min-U-Get, commercially available from Floridin Industries.
[0011] An antioxidant is optionally added to protect the latex film
from degradation due to heat and ultraviolet light. Suitable
antioxidants are, for example, N-N' Di(2-octyl)-p-phenylene
diamine, diphenyl-p-phenylendediamine, octylated diphenulamine,
dioctylated diphenylamine, styrenated phenol, or hindered phenol.
The preferred antioxidant is a water based dispersion of octylated
diphenylamine, commonly designated under the trade names Agerite
Stalite and C-560 dispersion, commercially available from R.T.
Vanderbilt Company.
[0012] The latex-based colorant is prepared by placing the
components into a mixer, preferably a Cowles type mixer, and
thoroughly mixing. The mixing wets the pigments with the
surfactants and ensures that all the ingredients are uniformly
incorporated.
[0013] The latex-based colorant is applied to a rubber substrate to
be colored, such as, for example, crumb rubber, natural rubber,
ethylene-propylene rubber, butyl rubber, nitrile rubber,
styrene-butadiene rubber, or polychloroprene rubber for example.
The colorant and the rubber to be colored are thoroughly mixed in,
for example, a paint shaker, drum tumbler, ribbon or paddle type
blender, or a double cone blender. Good results have been obtained
by mixing with a standard a paint shaker for at least 1.5
minutes.
[0014] Optionally, the rubber is vulcanized during the mixing
process to reduce tackiness, increase tensile strength, decrease
solubility in solvents, increase elasticity, and decrease
temperature sensitivity. To accomplish the vulcanization of the
rubber, a vulcanizing agent, a cure activator, and accelerator are
added before mixing. The vulcanizing agent is typically a colloidal
sulfur, preferably as a water based dispersion. The cure activator,
which increases the rate of vulcanization and improves tensile
strength, is typically a zinc oxide, preferably as a water based
dispersion. Examples of the accelerator are thiuram,
dithiocarbonate, xanthate, mercapto thiazole, mercapto sulfonamide,
thiourea, and guanidine. Dithiocarbonate in a water based
dispersion is the preferred accelerator. The following are examples
employing this method of coloring crumb rubber.
EXAMPLE 1
[0015] Blue colored crumb rubber was produced by mixing 200 grams
of crumb rubber and 4 grams of latex-based colorant and 0.15 grams
of vulanizing agent in a paint shaker for 2 minutes. The
latex-based colorant had the following formulation and was made by
mixing on a Cowles type mixer at a blade tip speed of 150 feet per
minute for 10 minutes.
[0016] Latex-Based Colorant:
1 MATERIAL Percentage by Weight Water 40.20% BYK022 polysiloxane
defoamer 0.40% Triton CF 10 alkyl aryl ether surfactant 0.40% Tamol
731A anionic dispersant 2.00% Tioxide TR-92 rutile titanium dioxide
(opacifer) 30.00% Alper DB15C-888 Phthalo Blue dispersion 10.00%
(organic pigment dispersion) Dynatex GTZ natural rubber latex 62%
solid 7.50% DL 313 NA modified SBR latex 48% solid 7.50% Min-U-Gel
400 thickener 2.00%
[0017] Vulcanizing Agents:
2 MATERIAL Percentage by Weight Water 62.50% 50% sulfur dispersion
6.25% 60% zinc dispersion 18.75% Butyl Zimate Slurry 6.25% C-560
dispersion 6.25%
[0018] The resulting product was aged at room temperature for a
period of between 7 and 14 days, and was examined for color,
colorfastness in water, and colorfastness to mild friction and
contact. The crumb rubber was observed to have a bright blue color
and no carbon black showed through the blue. Colorfastness in water
is tested by immersing the crumb rubber in water at room
temperature for a period of 21 days and then the water is
subsequently checked for discoloration due to bleeding of pigment
from the crumb rubber. Colorfastness to mild friction is tested by
rubbing the crumb rubber with the tester's hands and the hands are
subsequently checked for discoloration due to bleeding of pigment
from the crumb rubber. The adhesion of colorants to the crumb
rubber was very good as no significant bleeding of the pigment
occurred.
EXAMPLE 2
[0019] A green latex-based colorant was made, as in Example 1, by
replacing the Phthalo blue dispersion in the latex-based colorant
with a Phthalo Green dispersion DG007-448, from Alper dispersions.
A green colored crumb rubber was produced by mixing 200 grams of
crumb rubber, 4 grams of green latex-based colorant and 0.15 grams
of vulcanizing agents, as in Example 1, in a paint shaker for two
minutes. The crumb rubber thus produced was bright green in color
and had the required colorfast properties.
EXAMPLE 3
[0020] A violet latex-based colorant was produced, as in Example 1
using the following formulation:
[0021] Latex-Based Colorant:
3 MATERIAL Percentage by Weight Water 35.20% BYK022 polysiloxane
defoamer 0.40% Triton CF 10 alkyl aryl ether surfactant 0.40% Tamol
731A anionic dispersant 2.00% Tioxide TR-92 rutile titanium dioxide
30.00% Creanova Carbazole violet dispersion 877-8895 15.00% Dynatex
GTZ natural rubber latex 62% solid 7.50% DL 313 NA modified SBR
latex 48% solid 7.50% Min-U-Gel 400 thickener 2.00%
[0022] Two hundred grams of crumb rubber was mixed with 6 grams of
the latex-based colorant and 0.15 grams of the vulcanizing agents,
as in Example 1. The colorized crumb rubber produced was a bright
violet with good colorfast properties.
[0023] Using similar methods to those employed in examples 1-3,
crumb rubber can be colored to obtain different hues such as
yellow, orange, red, and an infinite number of other shades by
using suitable organic pigment dispersions, or mixtures thereof, to
obtain the desired hues.
[0024] Although illustrative embodiments of the present invention
have been described herein, it is to be understood that the
invention is not limited to those precise embodiments, and that
various other changes and modifications may be effected therein by
one skilled in the art without departing from the scope or spirit
of the present invention.
* * * * *