U.S. patent application number 11/529719 was filed with the patent office on 2007-03-29 for retroreflective inks.
Invention is credited to Brian Sagar.
Application Number | 20070071954 11/529719 |
Document ID | / |
Family ID | 27451859 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070071954 |
Kind Code |
A1 |
Sagar; Brian |
March 29, 2007 |
Retroreflective inks
Abstract
The combination of ingredients, especially for use in the
formulation of a one or two-pack retroreflective ink, comprising
retroreflective elements, microbeads additional to said
retroreflective elements and/or constituting said retroreflective
elements at least in part, binder chemicals for attaching the
retroreflective elements and microbeads to a substrate to which the
ink is to be applied, and a coupling agent for coupling the
microbeads and cross-linking the binder chemicals, the coupling
agent being unreactive until the printing process is carried
out.
Inventors: |
Sagar; Brian; (Cheadle
Hulme, GB) |
Correspondence
Address: |
BRACEWELL & GIULIANI LLP
P.O. BOX 61389
HOUSTON
TX
77208-1389
US
|
Family ID: |
27451859 |
Appl. No.: |
11/529719 |
Filed: |
September 26, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09889282 |
Sep 21, 2001 |
7175901 |
|
|
PCT/GB00/00062 |
Jan 12, 2000 |
|
|
|
11529719 |
Sep 26, 2006 |
|
|
|
Current U.S.
Class: |
428/195.1 ;
106/31.13; 106/31.6; 106/31.85; 427/487; 427/508; 428/313.3;
428/313.5; 428/313.7; 428/313.9 |
Current CPC
Class: |
Y10T 428/249972
20150401; C03C 2217/465 20130101; C09D 11/03 20130101; D06P 1/44
20130101; Y10T 428/249973 20150401; C09D 11/02 20130101; C03C
2217/48 20130101; G02B 5/128 20130101; Y10T 428/249974 20150401;
D06P 1/0012 20130101; C03C 2217/475 20130101; C03C 2217/485
20130101; C03C 12/02 20130101; D06P 5/2005 20130101; Y10T 428/24802
20150115; D06P 1/0076 20130101; C03C 17/36 20130101; Y10T
428/249971 20150401 |
Class at
Publication: |
428/195.1 ;
428/313.3; 428/313.5; 428/313.7; 428/313.9; 106/031.13; 106/031.6;
106/031.85; 427/487; 427/508 |
International
Class: |
B32B 3/00 20060101
B32B003/00; B32B 3/26 20060101 B32B003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 1999 |
GB |
9900654.6 |
Jan 19, 1999 |
GB |
9901031.6 |
Sep 10, 1999 |
GB |
9921394.4 |
Sep 14, 1999 |
GB |
9921618.6 |
Claims
1-56. (canceled)
57. A combination of ingredients forming a retroreflective ink, the
combination comprising metallised retroreflective elements,
microbeads additional to said retroreflective elements and/or
constituting said retroreflective elements at least in part, binder
chemicals for attaching the retroreflective elements and microbeads
to a substrate to which the ink is to be applied, a coupling agent
for coupling the microbeads and cross-linking the binder chemicals,
and a buffer, the coupling agent being unreactive and uncured until
a curing step is carried out and reactive when the curing step is
carried out during which a temperature of the substrate and ink
applied to the substrate is elevated to between 60 and 200.degree.
C., the coupling agent having a storage life of not less and about
3 months and being unreactive except at elevated temperature of the
curing step, the coupling agent being selected from the group
consisting of an aminoalkyl silanetriol and a blocked
polyisocyanate.
58. The combination of ingredients according to claim 57, wherein
the buffer is a phosphate buffer.
59. The combination of ingredients according to claim 58, wherein
the phosphate buffer is an ammonium phosphate buffer.
60. The combination of ingredients according to claim 58, wherein
the phosphate buffer is a sodium phosphate buffer.
61. The combination of ingredients according to claim 57, wherein
the binder is a polyvinylidene chloride copolymer and the coupling
agent is an aminoalkyl silanetriol.
62. The combination of ingredients according to claim 57, wherein
the binder is an acrylic copolymer and the coupling agent is an
aminoalkyl silanetriol.
63. The combination of ingredients according to claim 57, wherein
the binder is polyurethane and the coupling agent is a blocked
hexamethylene diisocynate trimer.
64. The combination of ingredients according to claim 57, wherein
the binder is a non-flammable plastisol.
65. The combination of claim 64, wherein the non-flammable
plastisol is polyvinylidene chloride.
66. The combination of claim 64, wherein the non-flammable
plastisol is polyvinyl chloride.
67. The combination of ingredients according to claim 57,
additionally including a humectant.
68. The combination of ingredients according to claim 67, wherein
the humectant is urea.
69. The combination of ingredients according to claim 67, wherein
the humectant is a combination of urea and 2,3 propane diol.
70. The combination of claim 57, wherein the combination comprises
a one pack retroreflective ink.
71. The combination of claim 57, wherein at least some of the
microbeads are without the retroreflective elements.
72. The combination of claim 57, wherein a polyvinylidene chloride
copolymer is the binder chemical and a mixture of an aminoalkyl
silanetriol and a blocked hexamethylene diisocyanate trimer is the
coupling agent.
73. The combination of claim 57, further comprising one or more
components selected from the group consisting of: pigment,
dispersant, defoamer, thickening agent, cross-linking agent,
softening agent, carbon black, UV absorbing material, anti-scuffing
agent, a silicone or fluoropolymer, light spill-suppressing agent,
anti-static agent, water repellent agent, a silicone, and a
fluoropolymer.
74. The combination of claim 57, wherein the volume ratio of the
binder to the microbeads is equal to or less than 50%.
75. The combination of claim 57, wherein essentially all of the
microbeads are unmetallised and the retroreflective elements
include reflective flake particles.
76. The combination of claim 57, wherein the binder forms at least
part of a liquid carrier medium for the retroreflective elements or
microbeads.
77. The combination of claim 57, wherein the binder chemicals,
retroreflective elements and microbeads are comprised of a one-pack
retroreflective ink or a two-pack retroreflective ink having the
coupling agent as the second pack.
78. The combination of claim 77, wherein the two-pack ink includes
a reactive polyisocyanate or an alkoxysilyl alkyl derivative.
79. The combination of claim 57, wherein the microbeads are
metallised with an aluminum coating that is superposed on a
stannous chloride pre-treatment.
80. The combination of claim 79, wherein the metallised microbeads
are treated with a solution of a silicate, followed by treatment
with a silane.
81. The combination of claim 80, wherein the microbeads have at
least one of the following characteristics selected from the group
consisting of: a refractive index in the range of about 1.8 to 2.2,
a median size of the microbeads in the range of about 10 to 100
microns and the microbeads are composed of titanium glass or barium
glass.
82. The combination of claim 79, wherein the metallised microbeads
are treated with an amino silane.
83. A composition that a is one-pack or a two-pack retroreflective
ink which is comprised of the combination claimed in claim 57.
84. The composition of claim 83, wherein the ink has a viscosity of
between 10 and 30 Pascal seconds at room temperature.
85. The composition of claim 83, wherein the retroreflective ink is
water-based.
86. The composition of claim 85 that is suitably formulated for
screen printing.
87. The composition of claim 83, wherein the ink has a viscosity
that is less than or equal to about 40 Pascal seconds at room
temperature.
88. The composition of claim 57, wherein the coupling agent has a
storage life of not less than about 3 months and is unreactive
except at elevated temperature of between 130 and 180.degree. C. at
which the one-pack retroreflective ink printed on the substrate is
cured.
89. A method for making a one-pack retroreflective ink comprising
the steps of: (a) making metallised microbeads; and (b) suspending
the microbeads in a liquid carrier medium, the liquid carrier
medium being comprised of binder chemicals for attaching the
microbeads to a substrate to which the ink is to be applied, a
coupling agent which couples the microbeads and cross-links the
binder chemicals, and a buffer, the one-pack retroreflective ink
having a storage life of not less than about 3 months and the
coupling agent being unreactive and uncured until a curing step is
carried out and reactive when the curing step is carried out during
which a temperature of the substrate and ink applied to the
substrate is elevated to between 60 and 200.degree. C., the
coupling agent having a storage life of not less than about 3
months and being unreactive except at elevated temperature of the
curing step, the coupling agent being selected from the group
consisting of an aminoalkyl silanetriol and a blocked
polyisocyanate.
90. The method of claim 89, wherein step (a) includes applying an
aluminium coating to the microbeads.
91. The method of claim 90, wherein step (a) includes pre-treating
the microbeads with stannous chloride prior to application of the
aluminium coating.
92. The method of claim 89, wherein step (a) includes treating the
microbeads with a silane or an amino silane prior to inclusion in
the ink.
93. The method of claim 89, wherein step (a) includes
hemispherically metallising the microbeads in a vacuum metallising
process in which the microbeads are held on a film with an adhesive
coating for transport through the metallising process, the adhesive
coating is comprised of styrene-butadiene type adhesive.
94. The method according to claim 93, wherein step (a) includes
passing the film through an aqueous solution of citric acid after
metallisation.
95. The method of claim 93, wherein step (a) includes
ultrasonically treating the film to assist in release of the
microbeads from the adhesive.
96. The method of claim 91, wherein step (a) includes treating the
microbeads with a dilute aqueous solution of stannous chloride.
97. The method of claim 96, wherein step (a) includes treating the
microbeads prior to inclusion in the ink with a silicate.
98. The method of claim 97, wherein step (a) includes treating the
microbeads with an amino silane after the silicate treatment.
99. The method of claim 98, wherein the microbeads have at least
one of the following characteristics selected from the group
consisting of: a refractive index in the range of about 1.8 to 22.,
a median size of the microbeads in the range of about 10 to 100
microns and the microbeads are composed of titanium glass or barium
glass.
100. The method of claim 89, wherein step (b) includes preparing
the liquid carrier medium from the binder chemicals and the
coupling agent before suspending the microbeads in the liquid
carrier medium.
101. The method of claim 100, wherein the liquid carrier medium of
step (b) includes additives selected from the group consisting of:
pigment, dispersant, defoamer, thickening agent, cross-linking
agent, softening agent, carbon black, UV absorbing material,
anti-scuffing agent, silicone, fluoropolymer, light
spill-suppressing agent, anti-static agent and water repellent
agent.
102. The method of claim 101, wherein step (b) includes adding a
thickener to the liquid carrier medium before or after the addition
of the binder chemicals and coupling agent.
103. A composition of an ink produced by the method of claim
89.
104. A composition of a substrate coated or printed with a
composition of claim 103.
105. The composition of claim 104, wherein the substrate is a
screen for displaying projected images or a studio background for
chroma-keying applications.
106. The composition of claim 104, wherein the substrate is a
flexible tape.
107. The method of providing a substrate having a retroreflective
coating, comprising the steps of: applying to the substrate an ink
as claimed in claim 103, wherein the ink is formulated as a
one-pack retroreflective ink and the coupling agent is activated
after the ink is printed or coated on to the substrate.
108. The method of claim 107, wherein the coupling agent is
activated by curing the ink coating at elevated temperature.
109. The method of claim 107, wherein the coupling agent is
activated by UV light or other high energy radiation during or
after the printing process.
110. The composition of claim 103, wherein the ink is a
retroreflective one-pack ink having a storage life of not less than
about 3 months.
111. The composition of claim 110, wherein the retroreflective
one-pack ink has a viscosity of between about 10 and 30 Pascal
seconds after storage of not less than about 3 months.
112. The composition of claim 110, wherein the retroreflective
one-pack ink applied to the substrate and cured has a laundering
durability such that the retroreflectivity is not reduced by more
than about 40% when the substrate is in the form of a cotton, nylon
or polyester fabric and laundered for 5 cycles in accordance with
ISO 6330, method 5A.
113. The method of claim 89, wherein the coupling agent has a
storage life of not less than about 3 months and is unreactive
except at elevated temperature of between 130 and 180.degree. C. at
which the one-pack retroreflective ink printed on the substrate is
cured.
114. The method of claim 89, wherein the liquid carrier medium of
step (b) includes a phosphate buffer.
115. The method of claim 114, wherein the phosphate buffer is an
ammonium phosphate buffer.
116. The method of claim 114, wherein the phosphate buffer is a
sodium phosphate buffer.
117. The method of claim 89, wherein the liquid carrier medium of
step (b) additionally includes a humectant.
118. The method of claim 117, wherein the humectant is urea.
119. The method of claim 117, wherein the humectant is a
combination of urea and 2,3 propane diol.
120. The method of claim 89, wherein the binder of the liquid
carrier medium is a non-flammable plastisol.
121. The method of claim 120, wherein the non-flammable plastisol
is polyvinylidene chloride.
122. The method of claim 120, wherein the non-flammable plastisol
is polyvinyl chloride.
123. A combination of ingredients forming a retroreflective ink,
the combination comprising retroreflective elements, microbeads
additional to said retroreflective elements and/or constituting
said retroreflective elements at least in part, binder chemicals
for attaching the retroreflective elements and microbeads to a
substrate to which the ink is to be applied, and a coupling agent
for coupling the microbeads and cross-linking the binder chemicals,
the coupling agent being unreactive and uncured until a curing step
is carried out and reactive when the curing step is carried out
during which a temperature of the substrate and ink applied to the
substrate is elevated to between 60 and 200.degree. C., the
coupling agent having a storage life of not less than about 3
months and being unreactive except at elevated temperature of the
curing step, the coupling agent being selected from a group
consisting of an aminoalkyl silanetriol and a combination of
aminoalkyl silanetriol and blocked polyisocyanate and wherein the
ink retains a viscosity of between 10 and 30 Pascal seconds for not
less than 3 months.
124. A method for making a one-pack retroreflective ink comprising
the steps of: (a) making metallised microbeads; and (b) suspending
the microbeads in a liquid carrier medium, the liquid carrier
medium being comprised of binder chemicals for attaching the
microbeads to a substrate to which the ink is to be applied and a
coupling agent which couples the microbeads and cross-links the
binder chemicals, the one-pack retroreflective ink having a storage
life of not less than about 3 months and the coupling agent being
unreactive and uncured until a curing step is carried out and
reactive when the curing step is carried out during which a
temperature of the substrate and ink applied to the substrate is
elevated to between 60 and 200.degree. C., the coupling agent
having a storage life of not less than about 3 months and being
unreactive except at elevated temperature of the curing step, the
coupling agent being selected from a group consisting of an
aminoalkyl silanetriol and a combination of aminoalkyl silanetriol
and block polyisocyanate; and wherein the ink retains a viscosity
of between 10 and 30 Pascal seconds for not less than 3 months.
Description
[0001] Retroreflective coating compositions have been the subject
of numerous patents, for example U.S. Pat. No. 2,963,378, Palmquist
et al, U.S. Pat. Nos. 3,099,637, 3,228,897 and 3,420,597,
Nellessen, U.S. Pat. No. 3,535,019, Longlet et al and U.S. Pat.
Nos. 4,103,060 and 4,263,345, Bingham et al. A retroreflective ink
has been commercially available for a number of years, marketed by
the 3M company, this product being available in dark grey and sold
as a three pack system, comprising a binder dispersion system, a
pack of hemispherically coated glass microspheres or beads and a
coupling agent, which are mixed just prior to use.
[0002] One pack inks were proposed in WO 94/06869, M N Ellis and in
EP 0 729 592, Reflective Technology Industries Limited and U.S.
Pat. No. 5,650,213, Reflective Technology Inc., which also disclose
the incorporation of pigment. U.S. Pat. No. 5,650,213 specified a
range of pigment particle size which is what is, in fact, the usual
range commercially available, and ranges of binder/bead and
binder/(bead and pigment) volume ratios which are seemingly the
ranges of choice to produce an ink which is printable by
conventional screen printing techniques.
[0003] Problems associated with the performance of reflective
coatings, especially in the convenient, one-pack form that does not
require mixing just prior to printing, involve shelf life,
washfastness and abrasion resistance. These key areas are
interrelated--the binder system must be such as will not allow the
beads to settle even over extended storage periods, and it must
also not couple to the beads during that storage, yet it must, on
printing, adhere the beads to the substrate in a reasonably
washfast and abrasion resistant manner while permitting the beads
to be exposed appropriately to retroreflect light.
[0004] The severity of these problems may explain the sale by 3M of
the three pack system and the fact that the inks produced according
to U.S. Pat. No. 5,650,213 are formulated solely for the production
of printed fabric by the patentee Reflective Technology Inc. and
not for sale to printers.
[0005] The present invention addresses these--and other--problems
and provides long shelf life one pack retroreflective ink systems
with good washfastness and abrasion resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic flow diagram of one specific
embodiment of a method of forming a retroreflective ink in
accordance with the present invention.
[0007] FIG. 2 is a block diagram of another specific embodiment of
the method of forming a retroreflective ink in accordance with the
present invention.
[0008] According to one aspect of the present invention there is
provided the combination of ingredients, especially for use in the
formulation of a one or two-pack retroreflective ink, comprising
retroreflective elements, microbeads additional to said
retroreflective elements and/or constituting said retroreflective
elements at least in part, binder chemicals for attaching the
retroreflective elements and microbeads to a substrate to which the
ink is to be applied, and a coupling agent for coupling the
microbeads and cross-linking the binder chemicals, the coupling
agent being unreactive until the printing process is carried
out.
[0009] A one-pack ink produced using the above combination of
ingredients may have a storage life of not less than 3 months,
preferably not less than 6 months and more preferably not less than
12 months when stored under ambient conditions (i.e. a temperature
of about 20.degree. C.). Also such inks, when stored for prolonged
periods of 3 months or more under ambient conditions, show no
significant change in rheology while retaining adequate
retroreflectivity properties and durability to laundering. Thus, a
retroreflective one-pack ink in accordance with the invention may
retain a viscosity of between 10 and 30 pascal after storage for
not less than 3 months, preferably not less than 6 months and more
preferably not less than 12 months, and may also exhibit laundering
durability such that retroreflectivity is not reduced by more than
40% (preferably by not more than 30% and more preferably by not
more than 20%) when applied to a substrate in the form of a cotton,
nylon or polyester and laundered for 5 cycles in accordance with
ISO 6330, method 5A.
[0010] The coupling agent is usually one which is substantially
unreactive at ambient temperature, namely 20.degree. C. Typically
the coupling agent is unreactive except at elevated temperature at
which the printed substrate is cured, e.g. a temperature within the
range of 60 to 200.degree. C., e.g. 130 to 180.degree. C.
[0011] The coupling agent may be rendered active by elevated
temperature; however, we do not exclude the possibility that the
coupling agent may be rendered active by other means such as
exposure to UV light or other high energy radiation.
[0012] Typically the binder is polymeric and the coupling agent
serves to couple the beads to the polymeric binder.
[0013] Viewed from another aspect, the invention resides in a
one-pack or a two-pack retroreflective ink comprising microbeads in
a liquid carrier medium including binder chemicals for attaching
the microbeads to a substrate to which the ink is to be applied,
the microbeads being incorporated in the carrier medium, and a
coupling agent which couples the microbeads and cross-links the
binder chemicals, characterised in that the coupling agent is not
activated until the ink is printed.
[0014] The two-pack system comprises a separate pack for the
coupling agent.
[0015] The ink may comprise retroreflective and/or
non-retroreflective microbeads. Typically the proportion of
microbeads which do not have a retroreflective coating constitute
no more than 50% by volume of the total microbead content but may
be up to 100% when reflective flakes are used in conjunction with
microbeads to provide retroreflectivity.
[0016] The binder and coupling agent may be selected from, but is
not limited to, the following combinations: [0017] polyvinylidene
chloride copolymer as binder and (3-aminopropyl) silanetriol and/or
blocked 1, 6 hexamethylene diisocyanate trimer as coupling agent;
an acrylic copolymer as binder and (3-aminopropyl) silanetriol
and/or blocked 1, 6 hexamethylene diisocyanate trimer as coupling
agent; and polyurethane as binder and blocked 1, 6 hexamethylene
diisocyanate trimer as coupling agent.
[0018] The microbeads may have an aluminium coating, and may be
pre-treated with a silicate before inclusion in the ink. They may
for instance be pretreated with sodium silicate. They may be
treated with a silane, especially a silane having a reactive group
such as an amino group, which treatment may be after a silicate
treatment and before inclusion in the ink. A suitable amino silane
is bis-[gamma-(trimethoxysilyl) propyl] amine.
[0019] The ink may comprise pigment, and may, especially when
comprising pigment, comprise non-retroreflective, which usually
means un-metallised, microbeads. The pigment content is typically
up to 5% by weight of the ink.
[0020] The microbeads may be pretreated before metallisation with
stannous chloride.
[0021] The ink may be formulated--as to, e.g. viscosity, particle
size--suitably for screen printing. The microbeads may have a
median size in the range of 10 to 100 microns, e.g. 25 to 70
microns. Typically in the case of inks using metallised
retroreflective microbeads, the median size is about 40 microns
whereas in the case of inks using non-retroreflective microbeads in
conjunction with other reflective elements such as reflective flake
particles, the microbeads typically have a median size of about 60
microns.
[0022] The microbeads, whether retroreflective or not, are
preferably composed of high refractive index glass, such as a
titanium/barium based glass with a refractive index in the range of
1.8 to 2.2, e.g. about 1.9.
[0023] The ink may comprise a humectant, which may comprise urea
and/or 2,3 propane diol, and may be water-based. It may comprise a
buffer, to ensure an appropriate pH, such buffer, for example,
comprising an ammonium phosphate buffer or a sodium phosphate
buffer. A dispersant may also be included, as may a defoamer, a
thickening agent, a cross-linking agent and a softening agent.
[0024] Other constituents that may be present in the ink may be
selected from the group comprising carbon black; UV absorbing
material; anti-scuffing agent, optionally a silicone or
fluoropolymer; light spill-suppressing agent; anti-static agent and
water repellant agent, optionally a silicone or fluoropolymer.
[0025] Non-water based inks may also be comprised within the
invention. In this case, the need to protect the aluminium coating
against attack in water-based media may be less important.
[0026] Surprisingly, having regard to the teaching of U.S. Pat. No.
5,650,213, substantially better quality inks--in terms of
reflectivity, washfastness, abrasion resistance and shelf life--are
produced with binder to bead volume ratios equal to or less than
50%. Essentially, more beads can be attached using less obscuring
binder, more firmly and more permanently than when the prior art
binder to bead ratios are used.
[0027] For a screen printing ink, the viscosity is desirably equal
to or less than 40 pascals, preferably between 10 and 30 pascals,
at room temperature.
[0028] The invention also comprises a method for making a one-pack
retroreflective ink comprising the steps of: [0029] making
microbeads; [0030] suspending the microbeads in a liquid carrier
medium; [0031] the liquid carrier medium comprising binder
chemicals for attaching the microbeads to a substrate to which the
ink is to be applied and a coupling agent which couples the
microbeads and cross-links the binder chemicals, the coupling agent
being unreactive except at elevated temperature (e.g. within the
range from 60 to 200.degree. C. and usually from 130 to 180.degree.
C.) at which the printed substrate is cured.
[0032] The method may involve the application of an aluminium
coating to glass microbeads. The microbeads may be pretreated with
stannous chloride prior to application of the aluminium coating,
and may be treated with a dilute solution of stannous chloride.
[0033] The microbeads maybe hemispherically metallised in a vacuum
metallising process in which they are held on a film with an
adhesive coating for transport through the metallising process, the
adhesive coating comprising a styrene/butadiene type or other
adhesive, which loses its tack when wet. The film may comprise a
polyester or polyolefin film. Following metallisation, the film may
be passed through an aqueous solution of citric acid or other
aqueous solution with a pK.sub.a value of around 2, and may be
treated ultrasonically to assist in release of the microbeads from
the adhesive surface. In contradistinction to other methods for
attachment of beads for metallisation, this method is easier at
least inasmuch as the citric acid bath can be re-used over and over
without replenishment.
[0034] The microbeads may be treated prior to inclusion in the ink
with a silicate, which may be a dilute aqueous solution of sodium
silicate. The beads may also (with or without such sodium silicate
treatment) be treated with a silane such as an amino silane prior
to inclusion in the ink, and such silane treatment may follow the
silicate treatment. A particularly beneficial amino silane is
bis-[gamma-(trimethoxysilyl) propyl] amine. These treatments,
severally and collectively, appear to enhance the permanence of the
attachment of the aluminium coating to the microbeads and of the
microbeads to the substrate on printing.
[0035] An aminoalkyl silanetriol and/or a blocked polyisocyanate
may be added to the liquid carrier medium as coupling agent.
[0036] In the event, see below, that a two-pack, rather than a
one-pack system is required, an alkoxysilyl alkyl derivative such
as an amino silane--which could be the same amino silane used to
treat the microbeads--and/or a polyisocyanate (typically where the
microbeads are amine treated) may also be added to the liquid
carrier medium as coupling agent.
[0037] In the preparation of the ink, a liquid carrier medium may
be prepared comprising binder chemicals and coupling agent, the
microbeads being added to the medium. A pigment may be added to the
medium containing the microbeads.
[0038] Further additive or additives to be incorporated in the
liquid carrier medium, may be selected from the group
comprising:
[0039] pigment; humectant, optionally urea and/or 2,3 propane diol;
buffer, optionally based on ammonium or sodium phosphates;
dispersant; defoamer; thickening agent; cross-linking agent;
softening agent; carbon black; UV absorbing material; anti-scuffing
agent, optionally a silicone or fluoropolymer; light
spill-suppressing agent; anti-static agent and water repellant
agent, optionally a silicone or fluoropolymer.
[0040] Where a thickener is included, it may be added to the medium
in two steps, namely before and after the addition of the binder
and coupler.
[0041] According to a further aspect of the invention there is
provided microbeads for use in the production of a retroreflective
ink, the microbeads having silicate (optionally sodium silicate)
and/or silane (optionally an amino silane such as
bis-[gamma-(trimethoxysilyl) propyl] amino) and/or stannous
chloride applied thereto.
[0042] The microbeads may be metallised, optionally with a coating
of aluminium, the metal being superposed on the stannous
chloride.
[0043] The microbeads may be metallised, optionally with a coating
of aluminium, the silicate and/or silane being superposed on the
metallised beads and the silane where present being superposed on
the silicate where present.
[0044] Also within the scope of the invention is an ink
incorporating such microbeads and substrates such as fabrics coated
or printed with inks in accordance with the various aspects of the
invention.
[0045] For certain applications, notably where printed or coated
with retroreflective inks, for example for backdrops and special
effects screens in film and television studios, it is desirable
that fabrics used are fireproof, or fire retardant.
[0046] The specialised nature of some retroreflective inks,
however, raises problems in connection with many normally fireproof
or fire retardant fabric materials.
[0047] Another aspect of the invention is concerned with a
fireproof or fire retardant fabric printed or coated with
retroreflective ink that is particularly satisfactory as a backdrop
or screen in the applications in question.
[0048] The invention comprises a fireproof or fire retardant fabric
printed or coated with a retroreflective ink which comprises
retroreflective elements in a polymeric matrix, the fabric
comprising a structural component that chars before it melts.
[0049] The fabric may be made fireproof or fire retardant by
application of a fire retardant agent, such as the commercially
available Proban.RTM. or Pyrovatex.RTM., to cellulosics, or it may
be naturally fireproof or fire retardant, such as an aramid.
[0050] The ink is desirably non-burning, at least once applied to
the fabric. The polymeric matrix may comprise polyvinylidene
chloride (e.g. in the case of an aqueous-based ink), or polyvinyl
chloride or other non-flammable plastisol.
[0051] Examples of suitable inks for this purpose are given
hereinafter in Tables 2 and 3.
[0052] Substrates coated with inks in accordance with various
aspects of the present invention may find use in a variety of
applications such as flexible tape having a retroreflective
coating, for instance tape as used in defining boundary lines
and/or cordoning off areas such as crime scenes, construction
sites, road works and other hazards.
[0053] Another important application is retroreflective materials
for use as studio background material for chroma-keying and like
purposes, as disclosed in GB-A-2312565 and GB-A-2321814 the
disclosures of which are incorporated herein by this reference.
Thus, a substrate in the form of a flexible sheet material may be
coated or printed with an ink in accordance with the present
invention to produce a studio background material exhibiting a
normalised retro-reflectivity of at least about 1/4 at an angle of
incidence of at least 60 degrees to the normal, i.e. as described
in GB-A-2312565 and GB-A-2321814.
[0054] A substrate provided with a retroreflective coating in
accordance with the present invention may be provided with an
additional coating or coatings for protecting the retroreflective
coating against scuffing and/or moisture (i.e. a water repellant
coating), e.g. a fluoropolymer coating applied over the
retroreflective coating. An anti-static coating may also be applied
to the substrate. Alternatively, instead of coating the substrate
with such coatings after printing or coating the substrate with
retroreflective ink, the ink may incorporate ingredients which will
confer anti-scuffing, water repellant and/or anti-static
properties.
[0055] The substrate may be selected from a wide range of materials
including textile fabrics (e.g. woven or knitted) such as cotton,
polyesters, nylons, silk, wool, viscose and acrylics.
[0056] Inks and methods for making them, according to the
invention, will now be described with reference to the accompanying
drawings, in which FIG. 1 is a diagrammatic illustration of the
production of metallised beads; and FIG. 2 is a block diagram of a
process for making an ink.
[0057] Examples of ink formulations according to the invention are
given in Tables 1 to 4. TABLE-US-00001 TABLE 1 Inks based on a
acrylic copolymer binder system and (3-aminopropyl) silanetriol
coupling agent Ingredient/Ink reference C202 C205 C208 Urea
(Humectant) 10 10 10 Water 154 179 179 Ammonium phosphate buffer 20
20 20 Alcoprint PDN (Dispersant) 2 2 2 Agitan 218 (Defoamer) 2 2 2
Alcoprint PT21 (Thickening agent) 8 8 8 2,3 Propane diol
(Humectant) 25 25 25 Alcoprint PFL (Trimethoxymethyl 15 15 15
melamine cross-linking agent) Alcoprint PSM (Softening agent) 30 30
30 Alcoprint PBA (Acrylic copolymer 300 225 225 binder) Ammonium
hydroxide 1 1 1 Silquest VS-142 (3-aminopropyl 25 25 25 silanetriol
coupling agent) [20% in water] Alcoprint PT21 (Thickening agent) 6
3 4.6 Metallised beads (40 micron) treated 400 450 400 with sodium
silicate and Silquest A-1170 (Bis[trimethoxysilylpropyl] amine)
Nonmetallised beads (40 micron) -- -- 50 treated with sodium
silicate and Silquest A-1170 Total 997 995 996.6 Binder volume % 12
9 9 Bead volume % 16 18 18 Binder volume/bead volume % 75 50 50
Viscosity 20.7 16.2 23.2 Temperature 16.6 16.6 16.6 pH 8.4 8.9
8.8
[0058] TABLE-US-00002 TABLE 2 Inks based on a polyvinylidene
chloride copolymer binder system and (3-aminopropyl) silanetriol
coupling agent Ingredient/Ink reference V246 V248 V251 Urea
(Humectant) 10 10 10 Water 128 288 288 Ammonium phosphate buffer 20
20 20 Emulsifier WN (Dispersant) 3 3 3 Agitan 218 (Defoamer) 2 2 2
Alcoprint PT21 (Thickening agent) 8 8 8 2,3 Propane diol
(Humectant) 25 25 25 Polidene 33-048 (Binder) 273 163 163 Ammonium
hydroxide 1.4 1.4 1.4 Silquest VS-142 (Coupling agent) 25 25 25
[20% in water] Alcoprint PT21 (Thickening agent) 3 5 3 Metallised
beads (40 micron) treated 500 450 400 with sodium silicate and
Silquest A-1170 Non-metallised beads (40 micron) -- -- 50 treated
with sodium silicate and Silquest A-1170 Total Weight of Ink (g)
998.4 1,000.4 998.4 Binder volume % 15 9 9 Bead volume % 20 18 18
Binder volume/bead colume % 75 50 50 Viscosity (pascals) 25.6 14.2
12.3 Temperature (.degree. C.) 17.7 17.6 17.2 pH 8.6 8.7 8.7
[0059] TABLE-US-00003 TABLE 3 Inks based on a polyvinylidene
copolymer binder system and a combination of (3-aminopropyl)
silanetriol and blocked hexamethylene diisocyanate trimer coupling
agents Ingredient/Ink reference V253 V254 V257 Urea (Humectant) 10
10 10 Water 91 183 183 Ammonium phosphate buffer 20 20 20
Emulsifier WN (Dispersant) 2 2 2 Emulsifier HVN (Dispersant) 2 2 2
Agitan 218 (Defoamer) 2 2 2 Alcoprint PT21 (Thickening agent) 9.3 8
8 2,3 Propane diol (Humectant) 25 25 25 Polidene 33-048 (Binder)
273 181 181 Ammonium hydroxide 1.4 1.4 1.4 Silquest VS-142
(Coupling agent) 25 25 25 [20% in water] Trixene BI 7986 (Coupling
agent) 40 40 40 Alcoprint PT21 (Thickening agent) -- -- --
Metallised beads (40 micron) treated 500 500 400 with sodium
silicate and Silquest A-1170 Non-metallised beads treated with --
-- 100 sodium silicate and Silquest A-1170 Total Weight of Ink (g)
1,000.7 999.4 999.4 Binder Volume % 15 10 10 Bead Columes % 20 20
20 Binder Volume/Bead Volume 75 50 50 Ratio % Viscosity (pascals)
22.5 22.1 21.2 Temperature (.degree. C.) 19.3 19.0 19.0 pH 8.4 8.3
8.4
[0060] TABLE-US-00004 TABLE 4 Inks based on a polyurethane binder
system and a blocked 1,6 Hexamethylene diisocyanate trimer coupling
agent Ingredient/Ink reference P96 P98 P102 Urea (Humectant) 10 10
10 Water 62 187 187 Sodium Phosphate Buffer 10 10 10 Emulsifier WN
(Dispersant) 3 3 3 Agitan 218 (Defoamer) 2 2 2 Alcoprint PT21
(Thickener) 3.0 3.1 3.0 2,3 Propane diol (Humectant) 25 25 25.1
Alcoprint PSM (Softener) 30 30 30 Witcobond 769 (Binder) 300 225
226 Trixene BI-7986 (Coupler) 50 50 50 Alcoprint PT21 (Thickener)
0.7 4.0 3.0 Metallised beads treated with 500 450 400 sod.silicate
and Silquest A-1170 Non-metallised beads treated with -- -- 70
sod.silicate and Silquest A-1170 Total Weight of Ink (g) 993.7
999.1 1,019.1 Binder Volume % 12 9 8.8 Bead Volume % 60 18 18.5
Binder Volume/Bead Volume 60 50 47.9 Ratio % Viscosity (pascals)
O/R 31.0 32.0 Temperature (.degree. C.) 18.8 18.2 18.5
[0061] Generally speaking, the ingredients are added in the
tabulated order given in Tables 1 to 4. The thickener is added in
two stages. Pigment, not tabulated, is added at the end in suitable
quantity to yield the desired colour.
[0062] Viscosities were measured with a Brookfield viscometer using
a number 5 spindle rotating at 10 rpm.
[0063] Table 5 lists the chemical nature and sources of proprietary
products used in the inks of Tables 1 to 4. TABLE-US-00005 TABLE 5
Proprietary Ink Component Product Chemical Nature Supplier Binder
Alcoprint PBA Aqueous emulsion of an Allied Colloids acrylic
copolymer Polidene 33-048 Aqueous emulsion of a Scott Bayer
vinylidene chloride/ acrylate copolymer Witcobond 769 Water based
polyurethane Baxenden dispersion Cross-linking/ Alcoprint PFL
Trimethoxymethyl Allied Colloids coupling agent melamine Silquest
VS-142 3-Aminopropyl OSi Specialities/ silanetriol Ambersil Ltd.
Silquest A-1170 bis-trimethoxysilylpropyl) OSi Specialities/ amine
Ambersil. Ltd. Trixene BI-7986 Blocked 1,6 hexamethylene Baxenden
diisocyanate trimer Softening agent Alcoprint PSM Allied Colloids
Thickening agent Alcoprint PT21 Dispersion of an acrylic Allied
Colloids copolymer in light mineral oil Dispersant Alcoprint PDN
Aqueous solution of an Allied Colloids anionic acrylic polymer
EmulsifierWN Nonionic arylpolyglycol Bayer ether Emulsifier HVN
BASF Defoaming agent Agitan 218 Munzing Chemie
[0064] Retroreflective microbeads are made, according to one aspect
of the invention, by a process which is generally similar to the
one that has been used commercially for many years, namely by
embedding glass microspheres in an adhesive layer on a substrate
and coating the exposed surface of the microspheres with an
aluminium layer in a vacuum metalliser. There are, however, subtle,
but important differences. The method according to the invention,
which is novel and inventive per se for the manufacture of
hemispherically coated microbeads, regardless of any ink
formulation in which they will be used is illustrated by way of
example in FIG. 1.
[0065] A carrier material 11, which is for example a polyester
film, supplied on a reel 11a, which may contain, say, 1000 m of
film of width 1500 mm, is coated by contact with a lick roller 12
dipping into a bath 13 with an 18 micron layer 14 of a
styrene/butadiene type adhesive 15, the coating thickness being
determined e.g. by a doctor blade/roller arrangement 16.
[0066] Beads 17 (see inset to FIG. 1) are scattered on the adhesive
layer 14 from a hopper 18 and pressed into the adhesive layer 14 by
a roller arrangement 19. Excess beads are removed e.g. by suction
arrangement 20.
[0067] Glass beads of refractive index 1.9, size 40 microns are
used, and, after the roller arrangement 19, appear, in
cross-section, as shown in the inset.
[0068] The beaded carrier material 11 is then passed through a
vacuum metalliser 21 to be coated with aluminium to a thickness of
about 0.3 microns. The material 11, wound on a reel, is placed in
the vacuum metalliser and run off on to a take-up reel to which it
is secured; then the metalliser is evacuated and the aluminium
source energised and the material passed reel-to-reel to expose it
to the aluminium vapour. The coated, beaded carrier 11 is then
passed through a bath 22 of aqueous solution (1%) of citric acid at
a temperature of 40-50.degree. C., passing over a series of rollers
23 to provide a dwell time in the bath of several minutes. The
material 11 also passes over an ultrasonic plate 24 which aids
release of the microbeads which fall to the bottom of the bath 22.
At the end of the run of 1000 m of carrier 11, the microbeads are
sucked out of the bottom of the bath 22, rinsed with water and
dried.
[0069] The effect of the citric acid bath is to cause the
styrene/butadiene adhesive to lose its tack and release the
microbeads. The material 11 regains its tack on drying, and can be
re-used for further runs of bead manufacture without the need for
further coating. The citric acid bath 22 can likewise be reused
without replenishment of the citric acid.
[0070] Prior to coating, the glass beads are pre-treated with a
dilute aqueous solution of stannous chloride, followed by drying
and resieving. It is found that this gives significant improvement
in the durability of the reflectivity of a printed design.
[0071] After coating, the beads are treated with a dilute aqueous
solution of sodium silicate. It is thought that the treatment
passivates the aluminium coating, reducing its susceptibility to
attack in aqueous environments, while, at the same time, the sodium
silicate reacts with the titanium/barium glass and/or the aluminium
increasing the number of reactive sites on the surface of the
coated microbeads that are available for reaction with the coupling
agent in the ink.
[0072] If this sodium silicate treatment is carried out close to
the metallisation process, the beads from that process can be used
after rinsing but before drying. About 40 kg wet metallised beads
(containing some 10 kg water) are mixed with a solution of 20 kg
water containing 1.4 kg sodium silicate and stirred for 5 minutes.
The beads are then allowed to settle, the sodium silicate solution
decanted off, the beads rinsed with tap water, with a final rinse
in deionised water.
[0073] Significant improvement in washfastness, especially with low
(e.g. below 0.5%) levels of certain coupling agents in the
formulation (which considerably improves shelf life), is obtained
by further treatment of the metallised beads with amino silanes,
significantly bis-[gamma-(trimethoxysilyl) propyl] amine.
[0074] The combined effect of these bead preparation treatments is
to provide an ink with a shelf life well in excess of 12 months yet
which exhibits insignificant loss of retroreflectivity after
multiple washings at 40.degree. C., even if the amount of coupling
agent is as low as 0.5%.
[0075] FIG. 2 is a block diagram of production steps for a typical
ink according to the invention, the steps being: [0076] 30 Glass
microbead production, with any necessary sieving to a desired size
range--about 40 microns is an ideal size; [0077] 31 Stannous
chloride pre-treatment, drying; [0078] 32 Metallising; [0079] 33
Recovery in citric acid solution; [0080] 34 Rinsing; [0081] 35
Drying; [0082] 36 Sodium silicate treatment of metallised beads;
[0083] 37 Rinsing; [0084] 38 Amino silane pre-treatment; [0085] 39
Mixing liquid carrier medium; [0086] 40 Add treated metallised
(and, if desired, unmetallised) beads to carrier medium; [0087] 41
Add pigment;
[0088] Ink formulations detailed herein, formulated by the methods
described, operating as one-pack systems, have long shelf lives,
being usable after more than six months, in many cases after more
than a year after formulation (based on accelerated ageing
measurements at elevated storage temperatures). They show higher
initial retroreflectivities at the lower binder/bead volume ratios
made possible by the various measures described.
[0089] Washfastness and abrasion resistance are acceptable with
binder volumes as low as 9%--reducing binder content in the
formulation containing polyvinylidene chloride and Trixene reases
abrasion resistance.
[0090] The various novel ingredients and combinations of
ingredients each have their contributions to make in connection
with the production of one pack inks and while the importance of a
binder combined with a coupling agent reacting only at elevated
temperature has been regularly noted, it is not intended to suggest
that that might be the only novel and inventive subject matter
disclosed herein. The pre-treatment of the beads both before and
after metallisation also has profound effects even with the
binder/coupler systems and is of advantage also in the preparation
of inks for printing on substrates which will not withstand
elevated temperatures. Here it is necessary to resort to a two-pack
system, with the coupling agent mixed into the ink just before
printing. A reactive polyisocyanate may be used as a coupling agent
in such circumstances. A two-pack arrangement is, of course, more
convenient to use than the old three-pack system, and is made
possible by bead pre-treatment.
[0091] Where unmetallised beads are added--giving the effect, quite
obviously, of reducing overall retroreflectivity, but reducing the
greyness associated with metallised beads and therefore enhancing
the colour brightness of pigmented inks, the unmetallised beads
also benefit from the bead pre-treatment, particularly treatment
with silicate and silane.
[0092] Unmetallised beads may also be used in similar formulation,
and having had similar pre-treatment, without metallised beads but
with flake particles having a mirror-like finish. Such a coating
composition, said to be suitable for application by brushing, was
described in U.S. Pat. No. 3,835,087, Searight et al, issued 10
Sep. 1974, and printing ink of this description is commercially
available.
[0093] According to the present invention, in another aspect,
one-pack inks containing unmetallised glass microspheres and flake
particles comprise a liquid carrier medium including binder
chemicals for attaching the microbeads and flake particles to a
substrate to which the ink is to be applied and a coupling agent
which couples the microbeads and cross-links the binder chemicals,
characterised in that the coupling agent is unreactive except at
elevated temperature at which the ink of the substrate is
cured.
[0094] Binder and coupler systems as described above are suitable,
and the microbeads benefit in the same way from the sodium silicate
and amino silane pre-treatment--the stannous chloride pre-treatment
is unnecessary.
[0095] A preferred flake material is Iriodin 123--mica flake coated
with titanium dioxide, supplied by Merck. The optimum particle size
is 5-35 microns, and the flake may be present in an amount about
7.5% by weight.
[0096] Mean glass microbead size may be 60 micron--larger beads,
e.g. up to 70 micron and larger, may be used but may not be
suitable for finer screen printing mesh sizes. Good quality, e.g.
1.9 refractive index, beads give better results than lower
refractive index beads, and best results are obtained using 60
micron TSTF (twice sieved twice fired) beads.
[0097] Coloured reflectivity can be achieved by using interference
pigments (Iriodin 200 series), while gold lustre mica pigments
(Iriodin 300 series) and metal lustre pigments (Iriodin 500 series)
give interesting effects particularly when printed on coloured
fabrics. Table 6 lists ingredients for a range of such inks.
TABLE-US-00006 TABLE 6 Ingredient/Ink reference NMB155 NMBI82
NMB185 NMB191 Urea (Humectant) 10 10 10 10 Water 79 134 94 91
Ammonium phosphate buffer 20 20 20 -- Sodium phosphate buffer -- --
-- 10 Emulsifier WN (Dispersant) -- 3 2 3 Emulsifier HVN
(Dispersant) -- -- 2 -- Alcoprint PDN (Dispersant) 2 -- -- --
Agitan 218 (Defoamer) 2 2 2 2 Alcoprint PSM (Softener) 30 -- -- 30
Alcopriny PT21 (Thickener) 4 4.8 3.3 3 2,3 Propane diol (Humectant)
25 25 25 25 Alcoprint PFL (Cross-linker) 15 -- -- -- Alcoprint PBA
(Binder) 300 -- -- -- [acrylic] Polidene 33-048 (Binder) -- 300 300
-- [polyvinylidene chloride] Witcobond 769 (Binder) -- -- -- 300
[polyurethane] Trixene BI-7986 (Coupling -- -- 40 50 agent)
Ammonium hydroxide 1 1.4 1.4 -- Silquest VS-142 (Coupling agent) 25
25 25 -- [20% in water] Alcoprint PT21 (Thickener) 3.5 -- -- 1
Iriodin 123 [Mica coated with titanium 75 75 75 75 dixoide] Beads
(60 micron) treated with 400 400 400 400 sod.sil. + A-1170 Total
weight (g) 991.5 1000.2 999.7 1000.0 Viscosity (pascals) 23.6 pH
8.5
* * * * *