U.S. patent application number 12/740114 was filed with the patent office on 2010-12-09 for use of zero-order diffractive pigments.
This patent application is currently assigned to BASF SE. Invention is credited to Ralf Knischka, Urs Lehmann, Marc Mamak, Urs Leo Stadler.
Application Number | 20100310787 12/740114 |
Document ID | / |
Family ID | 39135202 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100310787 |
Kind Code |
A1 |
Lehmann; Urs ; et
al. |
December 9, 2010 |
USE OF ZERO-ORDER DIFFRACTIVE PIGMENTS
Abstract
The invention relates to the use of tungsten oxide or of
tungstate to increase the heat-input amount of near infrared
radiation in processes selected from laser welding of plastics, NIR
curing of coatings, drying of printing inks, fixing of ink toners
to a substrate, heating of plastic preforms, laser marking of
plastics or paper.
Inventors: |
Lehmann; Urs; (Basel,
CH) ; Stadler; Urs Leo; (Madison, NJ) ; Mamak;
Marc; (New City, NY) ; Knischka; Ralf;
(Lorrach, DE) |
Correspondence
Address: |
BASF Corporation;Patent Department
500 White Plains Road, P.O. Box 2005
Tarrytown
NY
10591
US
|
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
39135202 |
Appl. No.: |
12/740114 |
Filed: |
October 23, 2008 |
PCT Filed: |
October 23, 2008 |
PCT NO: |
PCT/EP2008/064335 |
371 Date: |
August 27, 2010 |
Current U.S.
Class: |
427/517 |
Current CPC
Class: |
B29C 66/71 20130101;
B29K 2995/0026 20130101; B29K 2023/0641 20130101; B29K 2023/083
20130101; B29K 2067/00 20130101; C01P 2002/70 20130101; B29K
2023/0608 20130101; B29C 66/7392 20130101; B29K 2023/0616 20130101;
B29K 2023/12 20130101; B29K 2067/046 20130101; B29K 2023/06
20130101; B29C 66/71 20130101; B29C 66/71 20130101; B29C 66/71
20130101; B29K 2069/00 20130101; B29K 2023/10 20130101; B29K
2081/06 20130101; B29K 2025/08 20130101; B29K 2027/16 20130101;
B29K 2067/006 20130101; B29K 2023/12 20130101; B29K 2033/08
20130101; B29K 2055/02 20130101; B29K 2033/12 20130101; B29K
2309/08 20130101; B29K 2069/00 20130101; B29K 2023/04 20130101;
B29K 2067/003 20130101; C09C 1/00 20130101; B29K 2023/00 20130101;
B29C 66/71 20130101; B29C 65/1674 20130101; B29C 66/73366 20130101;
B29C 66/71 20130101; B29C 66/73921 20130101; B29C 65/1616 20130101;
B29C 66/71 20130101; B29C 66/7212 20130101; B41M 5/26 20130101;
B29K 2077/00 20130101; B29C 66/71 20130101; B29C 65/16 20130101;
B29K 2055/02 20130101; B29K 2023/0683 20130101; C01G 41/00
20130101; B29K 2077/00 20130101; B29C 66/71 20130101; C09K 5/14
20130101; C09D 5/32 20130101; B29C 2035/0822 20130101; B29C 66/71
20130101; B29C 66/71 20130101; B29K 2023/0625 20130101; B29C 66/342
20130101; B29C 66/71 20130101; B29C 65/1677 20130101; B29C 66/71
20130101; B29C 66/71 20130101; B29K 2023/065 20130101; B29C 66/7212
20130101; C01P 2004/38 20130101 |
Class at
Publication: |
427/517 |
International
Class: |
C08F 2/50 20060101
C08F002/50 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2007 |
EP |
07119940.0 |
Claims
1. A process of NIR curing or drying a coating on a substrate by
adding into said coating f a tungsten oxide of the formula WO3-x
wherein W is tungsten, O is oxygen, and x is 0.1-1 and/or the
tungstate of the formula MxWyOz wherein M is one or more element
selected from NH4, H, Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo,
Nb, Ta, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In and TI, W is
tungsten, O is oxygen, 0.001.ltoreq.x/y.ltoreq.1, and
2.0<z/y.ltoreq.3.0.
2. The process according to claim 1, wherein the tungsten oxide or
tungstate is selected from the group consisting of WO.sub.2,72
H.sub.0.3-0.7WO.sub.3 Na.sub.0.2-0.5WO.sub.3 and
Cs.sub.0.2-0.5WO.sub.3.
3. The process according to claim 1 wherein the tungstate is
Cs.sub.0.2-0.5WO.sub.3
4. The process according to claim 1, wherein the coated substrate
is a coil coating.
5. The process according to claim 1, wherein the coating is
pigmented.
6. A process of laser marking plastic or paper by adding to said
plastic or paper a tungsten oxide of the formula WO3-x wherein W is
tungsten, O is oxygen, and x is 0.1-1 and/or a tungstate of the
formula MxWyOz wherein M is one or more element selected from the
group consisting of NH4, H, Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn,
Mo, Nb, Ta, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In and TI; W is
tungsten, O is oxygen, 0.001.ltoreq.x/y.ltoreq.1, and
2.0<z/y.ltoreq.3.0.
7. The process according to claim 6, wherein the tungsten oxide is
WO.sub.2,72 and the tungstate is selected from the group consisting
of H.sub.0.3-0.7WO3, Na.sub.0.2-0.5WO.sub.3 and
Cs.sub.0.2-0.5WO.sub.3.
8. The process according to claim 6 wherein the tungstate is
Cs.sub.0.2-0.5WO.sub.3.
9. A process of laser welding of plastics by adding to said plastic
a tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the a tungstate of the formula MxWyOz
wherein M is one or more element selected from NH.sub.4, H, Li, Na,
K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Me, Nb, Ta, Ni, Pd, Pt, Cu, Ag, Au,
Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0.
10. The process according to claim 9, wherein the tungsten oxide is
WO.sub.2,72 and the tungstate is selected from the group consisting
of H.sub.0.3-0.7WO.sub.3 Na.sub.0.2-0.5WO.sub.3 and
Cs.sub.0.2-0.5WO.sub.3.
11. The process according to claim 9 wherein the tungstate is
Cs.sub.0.2-0.5WO.sub.3.
12. The process according to claim 1, wherein the coating is an
adhesive or sealant.
13. The process according to claim 12, wherein the tungsten oxide
is WO.sub.2,72 and the tungstate is selected from the group
consisting of H.sub.0.3-0.7WO.sub.3 Na.sub.0.2-0.5WO.sub.3 and
Cs.sub.0.2-0.5WO.sub.3.
14. The process according to claim 12 wherein the tungstate is
Cs.sub.0.2-0.5WO.sub.3.
15-17. (canceled)
18. The process according to claim 1, wherein the coating is a
printing ink or fixing of ink toner.
19-20. (canceled)
21. The process according to claim 1, wherein the coating
additionally contains a dithiolene metal complex of the formula I
or II ##STR00004## wherein M Ni, Pd, Pt, Au, Ir, Fe, Zn, W, Cu, Mo,
In, Mn, Co, Mg, V, Cr and Ti, X.sub.1, X.sub.2 and X.sub.3
independently of one another are sulfur or oxygen; R.sub.1,
R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 independently of one
another are hydrogen, NR.sub.7R.sub.8, C.sub.1-C.sub.18alkyl, aryl,
aralkyl, heteroarylalkyl, wherein R.sub.7 and R.sub.8 independently
of one another are C.sub.1-C.sub.18alkyl, aryl, aralkyl,
heteroarylalkyl.
22. The process according to claim 1, wherein the coating
additionally contains at least one organic IR absorber selected
from quinone-diimmonium salt, aminium salt, polymethines
phthalocyanine, naphthalocyanine and guaterrylene-bisimide or in
addition at least one anorganic IR absorber selected from lanthanum
hexaboride, indium tin oxide (ITO) antimony tin oxide or pigments.
Description
[0001] The invention relates to the use of tungsten oxide or of
tungstate to increase the heat-input amount of near infrared
radiation.
[0002] In principle the IR absorbing properties of tungsten
sub-oxides and tungsten bronzes are known. EP 1 847 635 discloses,
for example a particle dispersion of Cs.sub.033WO.sub.3 as heat
absorbing material.
[0003] It was found that these materials exhibit a distinct higher
effect than other known IR-ab-sorbers although absorbing the same
amount of energy. This is very surprising and cannot be explained
so far. Tungsten bronzes e.g. incorporated in coatings led to a
much higher temperature increase upon irradiation with IR than
expected according to its spectral absorption capacity. The
temperature increase measured was distinctly higher than found with
other known IR absorbers and reached almost the temperature
observed with carbon black. Or for laser marking of paper tungsten
bronzes or sub-oxides proved to be more than 10 times more
efficient as lanthanum hexaboride, a well known almost colorless IR
absorber. This is in fact very surprising and the reason for is not
known.
[0004] Many technical processes (like laser welding and marking of
plastics, NIR curing and drying of coatings, drying of printings,
laser marking of paper, curing and drying of adhesives, fixing of
ink toners to a substrate, heating of plastic pre-forms etc.)
require an efficient, quick and focused local heat-input through IR
radiation. The conversion of IR radiation into heat is realized by
placing appropriate IR absorbers at the place where the heat is
required. Carbon black is a well known efficient IR absorber for
such processes. But carbon black has one big draw back: that's its
strong black colour. Thus carbon black cannot be applied for
coloured (other than black or grey), uncoloured, white or
transparent systems. For such systems a "white or colourless carbon
black" is a great technical need.
[0005] Accordingly the target was to find such a "colourless and
transparent carbon black".
[0006] Very surprisingly the tungsten oxide material of the present
invention comes quite near to this target profile--although it is
slightly bluish to grayish.
[0007] But due to its surprisingly high efficiency of conversion of
IR radiation into heat, this tungsten oxide material can be applied
at such a low concentrations that its own colour is acceptable for
most applications.
[0008] The same is true for transparency: the material (plastics,
coatings) containing this tungsten oxide remains also highly
transparent.
[0009] Tungsten oxides and tungstates are known as infrared
shielding material. The publications EP 1 676 890 and US
2007/0187653 (Sumitomo Metal Mining Company) disclose an infrared
shielding nanoparticle dispersion comprising tungsten trioxide
having reduced oxygen.
[0010] Thus, the invention relates to the use of tungsten oxide of
the formula WO3-x wherein W is tungsten, O is oxygen, and x is
0.1-1 and/or the use of tungstate of the formula MxWyOz wherein M
is one or more element selected from NH.sub.4, H, Li, Na, K, Rb,
Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd,
Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
NIR curing of coatings and NIR drying of coatings.
[0011] The heat-input amount is the thermal energy supplied by near
infrared radiation and corresponds to the temperature reached after
NIR-curing and drying of coatings.
[0012] Preferably y is 1. Examples are: H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, K.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3,
Ba.sub.0.33WO.sub.3, Rb.sub.0.33WO.sub.3
[0013] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,7), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0014] The tungsten bronzes can be prepared according to EP
1676890, wherein it is said that tungsten bronzes as expressed by
the formula M.sub.xWO.sub.3 can be prepared by heating an aqueous
solution of ammonium meta tungstate with metal salts to about
300-700.degree. C. and drying the aqueous mixture to obtain a solid
product.
[0015] Tungsten oxides powders, (e.g. WO.sub.2.7) are commercially
available e.g. from Osram Sylvania. WO.sub.2,7 may also be prepared
by reducing ammonium tungstate in a plasma reactor. The
commercially available WO.sub.2,7 may be dispersed and then this
dispersion is milled e.g. in a Dynomill mill with 0.4-.mu.m
zirconium balls to obtain particles having a particle size between
10 nm and 1 .mu.m, preferably between 10 nm and 500 nm, more
preferably between 10 nm and 200 nm.
[0016] The amount of tungsten oxide or of tungstate applied is
between 0.01 and 2.0 wt %. In this amount the slight blue color of
tungsten oxide is not relevant.
[0017] The NIR radiation used in the process according to the
invention is short-wave infrared radiation in the wavelength range
from about 700 nm to about 3000 nm. Radiation sources for NIR
radiation include, for example, conventional NIR radiation
emitters, which are available commercially (for example, from
Adphos) with the main emission in the range from 800 to 1500 nm,
diode lasers, fibre lasers or a Nd:YAG laser.
[0018] The NIR curing of coatings can be used for all type of
coatings including both pigmented and unpigmented coating
materials. Depending upon the nature of the organic binder,
coatings may comprise solvent and/or water or may be solventless or
water-free. They may also comprise fillers and other additives in
addition to the pigments. Any kind of coating is suitable in the
method according to the invention, for example, powder coatings,
clearcoats, high-solids coatings, effect coatings, high-gloss
coatings, silk-finish coatings, matt-finish coatings, spray
coatings, dip-coatings, pour-coatings etc. Corresponding raw
materials and compositions are known to the person skilled in the
art and are described, for example, in "Lehrbuch der
Lacktechnologie", Vincentz Verlag, 1998.
[0019] NIR Curing of coatings is state of the art in the field of
coil coatings. As coating formulations per se do not absorb
NIR-radiation, the heating rate of the coating during drying and/or
curing is therefore strongly dependent from several factors: [0020]
substrate [0021] pigmentation degree [0022] pigment chemistry
[0023] This leads to draw backs in certain coating processes. These
are: [0024] a) low energy efficiency due to loss of NIR radiation
[0025] b) different curing speeds of e.g. a black (FW 200)
pigmented against a white (TiO2) pigmented system. [0026] c)
NIR-drying can't be used for clearcoat applications [0027] d)
Especially white RAL shades as 9002, 9010 & 9016 show low
energy efficiencies during NIR curing.
[0028] In pigmented coatings, especially in TiO2 pigmented systems
it is important that the addition of NIR-Absorbers do not cause any
discoloration. Thus, one aspect of the invention is the use in
pigmented coatings.
[0029] There is therefore a need for near infrared absorbers that
are colorless as well as transparent to overcome the draw backs
a-d. State of the art materials are either colored (Lumogen IR 765,
788) or show a strong haze (Minatec 230 A-IR, Lazerflair 825,
LaB.sub.6) when incorporated into a coating formulation. Thus, an
additional requirement for the IR absorber used is to avoid
haze.
[0030] Minatec 230 A-IR consists of a specific antimony tin
composition (Merck), Lazerflair 825 is a mica based platelet type
pigment (Merck) and Lumogen IR 765 and IR 788 are organic
quaterrylene-bisimides (BASF). LaB.sub.6 can be purchased from
Aldrich.
[0031] The temperature reached after NIR curing is nearly the same
using the above referenced tungsten oxides and tungstates or using
carbon black. This unexpected effect of the extremely high
temperatures that can be reached using the above referenced
tungsten oxides and tungstates can't be explained only with the
high near infrared absorption. Materials or concentrations having a
higher absorption integral in the near infrared are showing lower
temperature increases after a NIR curing cycle (Example 3.1).
EXAMPLE 1
Preparation of WO.sub.2.7 by Milling
[0032] 240 ml of 0.4-.mu.m zirconium balls are added to a
suspension of 106.5 g WO.sub.2.7 from Osram/Sylvania in 450 ml
water. The suspension is milled in a Dynomill for 8 h at 4500
r/min. The suspension obtained is filtered off and dried. Particle
size is mainly between 30 and 100 nm.
EXAMPLE 2
Preparation of a Hydrogen Tungsten Bronze (H.sub.0.53 WO.sub.3)
Using a Plasma Reactor
[0033] Ammonium paratungstate powder
((NH.sub.4).sub.10W.sub.12H.sub.2OO.sub.42.4H.sub.2O, Osram
Sylvania) was entrained into an argon carrier gas by a
vibratory-type powder feeder operating at 10 g/min. The fluidized
powder was fed into a plasma reactor with a Tekna PL-50 plasma
torch operated at a power of 65 kW. The temperature range typically
reached in the plasma hot zone of the reactor is between
5000-10,000 K. A mixture of 140 slpm argon, 0.5 slpm hydrogen, and
5 slpm helium [slpm=standard liters per minute; standard conditions
for the calculation of slpm are defined as: Tn 0.degree. C.
(32.degree. F.), Pn=1.01 bar (14.72 psi)] was used for the sheath
gas. The reactant vapor was cooled by a quench gas and the
resulting powder was collected in a bag filter. The resulting
hydrogen tungsten bronze powder was analyzed by powder X-ray
diffraction, electron microscopy, and UV-vis-NIR spectroscopy.
[0034] Particle size is between 30 and 200 nm. This material
exhibits very good dispersibility in coatings or plastics etc.
EXAMPLE 3.1
Application Example NIR Curing
[0035] The different NIR-Absorbers were tested in a 2P-PU
formulation concerning there temperature uptake during NIR-curing
as well as the final coating properties.
[0036] The NIR-Absorbers were incorporated into the millbase using
glass beads and a scandex shaker for 16 h according to the
following table (values are in g).
TABLE-US-00001 Millbase Laropal A 81 (urea-aldehyde resin available
from BASF) 15.7 g 60% in 1-methoxy-2propylacetate/xylene 3:1 EFKA
4401 (polymeric dispersant, available from Ciba Inc) 0.08 g
1-methoxy-2propylacetate (solvent) 4.62 g Butylglycolacetate
(solvent) 1.16 g NIR-A 0.19 g
[0037] The millbase was mixed with the letdown formulation and the
crosslinker was added according to the following table.
TABLE-US-00002 Amount in g LET DOWN Millbase 21.75 2p PUR
Clearcoat* 3.84 MPA/BGA (95/5) 7.61 Desmodur n 3390 (90%),
crosslinker, 7.50 aliphatic isocyanate from Bayer. 2p PUR
Clearcoat* Macrynal SM 510n (hydroxyfunctional 78.7 acrylic resin
available from Cytec Surface Specialties) EFKA 3030 (modified
polysiloxane to improve 0.15 levelling available from Ciba Inc.)
Dibutyltin dilaurate 10% in xylene 0.1 TINUVIN 292/TINUVIN 99-2
(65/35) 2.0 DABCO-33LV 10% in xylene 0.1 1-methoxy-2-propylacetate
14.45 butylglycolacetate 4.5
DABCO-33LV is a mixture of triethylenediamine and dipropyleneglycol
available from Air Products & Chemicals and used as catalyst
TINUVIN 292 is a hindered amine light stabilizers ("HALS")
available from Ciba Inc. TINUVIN 99-2 is an UV absorber available
from Ciba Inc.
[0038] The coating was applied by a wire bar using a WFT (wet film
thickness) of 80 .mu.m. The coatings were dried in an NIR-dryer
using different lamp settings (6 Adphos high-burn NIR-lamps, output
from 50-100%) and belt speeds (1-4 m/min).
[0039] The distribution of the NIR-A into the coating formulation
was checked via the measurement of haze over black. The lower the
value the better the distribution in the formulation and the less
impact on the visual film properties is observed.
TABLE-US-00003 NIR Absorber WFT (mm) Wt % on solids Haze Example 1
80 1 7.1 Example 2 80 1 8.0 LaB.sub.6 80 1 14.3 Minatec 230 A-IR 80
1 10.4 Lazerflair 825 80 1 15.7
[0040] The temperature of the coating surface was measured directly
after cure.
[0041] The Table below shows the results using a belt speed of 2
m/min, a 6 Adphos high-burn NIR-lamps, output 70%, a distance to
the lamp of 100 mm
TABLE-US-00004 Absorption Temp. Wt % on integral 100% after Curing
NIR absorber solid ref. FW200 (.degree. C.) Blanc (no NIR absorber)
-- 0 98 Minatec 230 A-IR 1 0.5 106 Lazerflair 825 1 n.d. 112
Lumogen IR 765 1 6 129 Lumogen IR 788 1 12 129 ##STR00001## 1 31
180 LaB.sub.6 1 2.5 151 H.sub.0.53WO.sub.3(Example 2) 1 27 216
H.sub.0.53WO.sub.3(Example 2) 0.1 3 136 FW 200 (Carbon black) 1 100
232
[0042] The Table clearly shows that H.sub.0.53 WO.sub.3 is able to
convert NIR radiation into heat to nearly the same extent as carbon
black does, 216.degree. C. compared to 232.degree. C. Thus, the
tungsten oxide material of the present invention comes quite close
to the target of a "colourless carbon black". Even near infrared
absorbers with a higher absorption integral in the NIR range
(800-1500 nm) show a significantly lower temperature increase
compared to the above referenced tungsten oxides and tungstates.
(e.g compared H.sub.0.53 WO.sub.3 in a concentration of 0.1% with
Lumogen)
[0043] This can be seen especially in an application with TiO2.
(Ex. 3.2)
EXAMPLE 3.2
Application Example NIR Curing
TABLE-US-00005 [0044] Millbase Letdown Dynapol .RTM. LH 530-02
35.00 Millbase 78.25 (60%) (Polyester resin) Dowanol .RTM. PM
(solvent) 1.00 Dynapol .RTM. LH 530-02 10.82 (60%) EFKA .RTM. 5010
(50%) 1.80 Cymel .RTM. 303 (98%) 5.75 (wetting agent) EFKA .RTM.
3772 (60%) 1.00 Solvent Naphta 150 0.88 (leveling agent) Aerosil
.RTM. 200 0.60 Dowanol .RTM. PM 1.00 Solvent Naphta 150 5.35
Butylglycoleacetate 1.10 Estasol .RTM./DBE (Solvent) 3.00 Dynapol
.RTM. Kat. 1203 0.70 (50%) 50% URAD .RTM. DD 27/50% 0.50 Tinuvin
.RTM. 123 1.00 Solvent Naphta 150 NIR-A/pigments 30.00 Tinuvin
.RTM. 400-2 0.50 (85%)
[0045] The millbase was prepared according to a standard process
using a dispermat for pre-mixing and additional milling for 1 h
using a Disperser DAS 200 from Lau. The coatings were applied onto
pre-primed white aluminium panels using a slit coater leading to
DFT's of around 80 .mu.m. Formulations with TiO.sub.2 and mixtures
of TiO.sub.2 and NIR-A' s were tested. Curing was done at different
belt speeds using 6 HB-NIR emitters from the company Adphos.
[0046] Especially in the field of coil coatings the main usage is
in the field of "white" shades e.g. RAL 9001, 9003, 9010, 9016. RAL
9010 being the most critical concerning the efficient absorption of
the emitted energy. To test the effect on curing speed by the
addition of NIR-A (Example 2), a 45 w %/w TiO.sub.2 pigmented
system was used as reference. The NIR-A can be added either
directly in the milling step or alternatively via a resin free
pigment paste based on Ciba EFKA.RTM. 4310 for solvent based
applications. The addition of the NIR-A leads to a strong reduction
of the curing time (see Tab. 1). This allows to either increase the
belt speed leading to a higher throughput of the coating line or to
reduce the lamp output leading to a reduction of electricity
costs.
TABLE-US-00006 w %/w NIR Rel. belt speed .DELTA.a .DELTA.b w %/w
TiO2 absorber of Ex. 2 to cure in % variation variation 45.0 0 100
0 0 44.95 0.05 250 -0.4 -0.8 44.75 0.25 350 -1.2 -2.8 44.50 0.5 450
-1.6 -4.2
[0047] The belt speed to cure was determined via the stability of
the cured coating against 100 MEK doublerubs.
[0048] The above Table shows that curing can be done by a higher
belt speed and that only slight changes in the b as well as a value
within the CIE-Lab color space are observed with an increased
addition level of NIR-A 1 compared to the TiO.sub.2 pigmented
system.
EXAMPLE 3.3
Application Example NIR Curing
[0049] The same formulation was used as in Example 3.2. The
formulation with 45 w % TiO.sub.2 on solids was used as
reference.
TABLE-US-00007 w % on Belt speed to NIR Absorber solids cure
[m/min] .DELTA.E none 0 0.75 0 Minatec 230 A-IR 1 1.00 1.9 Example
2 0.05 1.50 1.25
[0050] The belt speed to cure was determined via the stability of
the cured coating against 100 MEK doublerubs.
[0051] The above Table shows that the inventive NIR absorber (Ex.2)
has a low effect on the discoloration of a TiO.sub.2 pigmented
system.
[0052] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
laser marking of plastics.
[0053] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0054] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
laser welding of plastics.
[0055] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0056] Laser radiation is used in welding processes for producing
fusion bonded plastics. Typical laser wavelengths used are: 808 nm,
850 nm, 940 nm, 980 nm or 1064 nm. For the absorption of the laser
radiation and its conversion to heat for the melting process, it is
necessary to add an IR absorber. A common IR absorber is carbon
black. Due to the dark color welding of brightly colored or
transparent parts is impossible.
[0057] The concentration of the tungsten oxide or of the tungstate
is 10-800 ppm, preferably 100-300 ppm.
[0058] The tungsten oxide or of the tungstate may be incorporated
directly into the plastics parts by known processes like injection
molding, extrusion, and the like.
[0059] Examples of plastics used in a laser welding process are
polypropylene, polyvinylbutyrale, polyamide, polycarbonate,
polycarbonate-polyethylene terephthalate-blends,
polycarbonate-polybutylene terephthalate-blends,
polycarbonate-acrylnitrile/styrene/acrylnitrile-copolymer-blends,
polycarbonate-acrylnitrile/butadiene/styrene-copolymer-blends,
polymethylmethacrylate-acrylnitrile/butadiene/styrene-copolymer-blends
(MABS), polyethylene terephthalate, polybutylene terephthalate,
polymethylmethacrylate, polybutylacrylate,
polymethylmeth-acrylate-polyvinylidenedifluoride-blends,
acrylnitrile/butadiene/styrene-copolymere (ABS),
styrene/acrylnitrile-copolymere (SAN) and polyphenylenesulfone as
well as mixtures thereof.
EXAMPLE 4
Application Example Laser Welding of Plastics
[0060] The IR absorber according to Example 2 is incorporated by
means of an injection molding machine into a polycarbonate sheet
(thickness 2 mm) at a concentration of 500 ppm. The resulting
transparent slightly bluish sheet is welded together with a
polycarbonate sheet (thickness 1 mm) using a 250 watt Nd:YAG-laser.
The surface was scanned by laser beam at a speed of 20 mm/sec.
[0061] The resulting welding has an excellent connection, is highly
transparent, does not show any localized plastic deformation, does
not evolve bubbles during welding. No fracture of the welding seam
is induced due to mechanical stress.
[0062] With state of the art IR absorbers for laser welding of
plastics like Lumogen IR 765 or Lumogen IR 788 no welding takes
place under these conditions. This is also true for diode lasers at
e.g. 980 nm, 940 nm or 850 nm instead of a Nd:YAG laser (1064 nm).
Only at 808 nm welding with these IR absorbers takes place.
[0063] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
NIR curing of adhesives and sealants and NIR drying of adhesives
and sealants.
[0064] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0065] The addition of an NIR absorbing additive to a liquid
adhesive in particular water based adhesives but also solvent based
adhesives can improve drying performance of the liquid adhesive by
the concentrated absorption of the emitted NIR radiation.
[0066] The use of NIR radiation and NIR absorbing additive for
drying liquid adhesives can be used in addition to conventional
drying processes like hot air or IR radiation drying or as
independent drying step.
[0067] The addition of the NIR absorbing additive to a liquid
adhesive and subsequent irradiation with NIR under given constant
conditions, result in a lower content of residual liquid (water)
compared to the same adhesive without the NIR absorbing additive.
This is especially interesting in web coating applications of
liquid adhesives for example in the manufacture of label laminates
or tapes. Further in web laminating processes of non porous
materials like films or foils were the liquid adhesive needs to be
completely dry before the lamination step. Also with porous
substrates like paper or fabric, the complete adhesive drying
before lamination gives advantages with regards to flatness of
moisture or water sensitive substrates.
[0068] A further advantage is provided with the addition of NIR
absorbing additives, that the induced energy is mainly absorbed
within the adhesive layer itself which leads to lower substrate
temperatures compared to conventional drying operations. This opens
interesting possibilities to dry liquid adhesive coatings on
temperature sensitive substrates like low melting or shrinkable
films and fabrics.
EXAMPLE 5.1
Application Example NIR Curing of Adhesives and Sealants
[0069] A water based acrylic pressure sensitive adhesives (PSA),
Acronal V 212 from BASF Corp., with a solid content of 69% was
diluted with water. The NIR absorbing additive according to Example
2 was, with the help of an acrylic copolymer dispersant EFKA 4585
from Ciba, mixed in a speed mixer. With a stainless steel coating
bar a 50 micron adhesives layer was applied to a glass plate. The
weight of the adhesive was determined before and after multiple
passes under the NIR emitter.
[0070] The results indicate that the water based adhesive
containing the NIR absorbing additive dries faster than the same
adhesive without the additive.
TABLE-US-00008 174/08 176/08 178/08 173/08 (0.1% 175/08 (0.1%
177/08 (0.1% (no NIR NIR (no NIR NIR (no NIR NIR Experiment-Nr:
additive) additive) additive) additive) additive) additive) NIR
setting HB 6, Distance 100 mm, Power (% 30% 30% 30% 30% 50% 50%
Belt Speed (m/min) 4 4 2 2 2 2 Adhesive Composition Acronal V 212
(69% solids) 90 90 90 90 90 90 Water 10 10 10 10 10 10 NIR-A 0.1
0.1 0.1 EFKA 4585 0.2 0.2 0.2 Adhesive thickness wet (micron) 100
100 100 100 100 100 Initial adhesive weight (g) 0.4942 0.4510
0.4381 0.4372 0.3841 0.3920 Adhesive weight after 1 pass (g) 0.4215
0.3697 0.3167 0.3020 0.2535 0.2541 Adhesive weight after 2 pass (g)
0.3602 0.3080 0.2828 0.2817 0.2419 0.2452 Adhesive weight after 3
pass (g) 0.3278 0.2917 0.2788 0.2779 0.2391 0.2424 Adhesive weight
after 4 pass (g) 0.3199 0.2877 Weight loos after Initial 0.00%
0.00% 0.00% 0.00% 0.00% 0.00% irradiation after 1 pass (%) 14.71%
18.03% 27.71% 30.92% 34.00% 35.18% after 2 passes (%) 27.11% 31.71%
35.45% 35.57% 37.02% 37.45% after 3 passes (%) 33.67% 35.32% 36.36%
36.44% 37.75% 38.16% after 4 passes (%) 35.27% 36.21%
[0071] In a further embodiment NIR absorbing additives can be added
to 100% solid, thermoplastic heat activated adhesive systems.
Typically a heat activated adhesive layer is created by coating or
extruding the corresponding adhesive system to one of the
substrates to be bonded or to a suitable intermediate carrier.
Alternatively a heat activated adhesive layer can be created by
coating and drying a corresponding adhesive from an aqueous or
solvent carrier. The so prepared adhesive layer may be sticky to
the touch but is typically non-sticky and can be converted into
smaller units e.g. slit rolls or sheets, for later activation and
bonding to the second substrate. Heat activated adhesives can also
be manufactured and provided as self supporting films (adhesive
film), webs (web adhesive) or powders (powder adhesives). To
establish a bond the so prepared heat activable adhesive layer or
the self-supporting adhesive structure has to be heated above its
activation temperature and then joined with the bonding
substrate(s). Typical adhesive activation methods are: flame
activation, hot air activation, IR activation, activation via
heated rolls or a heat calendar heated plates, wedges or
presses.
[0072] With the addition of NIR absorbing additives to heat
activated adhesives the activation can conveniently be done with an
NIR emitter. The suitably modified adhesive absorbs the NIR
radiation; heats up above it required activation temperature and
the bond can be established. As with the drying of liquid adhesives
the addition of NIR absorbing additives brings the further
advantage, that the energy is mainly absorbed by the adhesive and
not the substrates and therefore also temperature sensitive
materials are accessible to this bonding method. Typical
chemistries for heat activated adhesives involve: polyolefines,
amorphous alpha polyolefins, modified polyolefines like EVA, EAA,
BAA, polypropylene, co-polyesters, co-polyamides, thermoplastic
polyurethanes, polycaprolactones, styrene-blockcopolymer based
hotmelt adhesives
EXAMPLE 5.2
Application Example NIR Curing of Adhesives and Sealants
[0073] A typical heat activated hotmelt adhesive based on amorphous
poly-alpha-olefines (APAO) was mixed in a sigma blade kneader at
170.degree. C. for 1 hour. APAP polymers were obtained from Evonik
Industries, hydrocarbon resin and styrene blockcopolymer from Exxon
Chemical, Antioxidant from Ciba Inc. and the rosin ester tackyfier
from Eastman. The adhesives were coated with a hot melt slot-die
coater onto a siliconized paper and transferred to a steel plat
carrier. The adhesive samples were exposed to the NIR radiation and
the temperature of the adhesive surface was observed via laser
thermometer. The results show that the adhesive without NIR
absorbing additive according to Example 2 only reaches the
temperature as the blank steel carrier plate. Adding different
amounts of NIR absorbing additive boosts the adhesive surface
temperature to 99.degree. C., 109.degree. C. and 162.degree. C.
respectively.
TABLE-US-00009 137/08 138/08 139/08 136/08 (0.05% (0.1% (0.5%
Carrier (no NIR NIR NIR NIR Experiment-Nr: Plate additive)
additive) additive) additive) NIR setting HB 6, Distance 100 mm,
Power (%) 70% 70% 70% 70% Belt Speed (m/min) 2 2 2 2 Adhesive
Composition Escorez 5310 (Hydrocarbon resin) 25 25 25 25 Vestoplast
408 (APAO) 20 20 20 20 Vestoplast 828 (APAO) 26 26 26 26 Irganox
1010 (Antioxidant) 1 1 1 1 Vector 4111 (Styrene Blockcopolymer) 10
10 10 10 Permalyn 6110 (Rosinester tackyfier) 18 18 18 18 NIR-A 0.5
0.1 0.1 Adhesive thickness (g/m2) 0 96 94 95 95 Temperature after
irradiation (.degree. C.) 76 78 99 109 162
[0074] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation and the efficiency
in the process of laser marking of paper
[0075] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3 Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
EXAMPLE 6
Application Example Laser Marking of Paper
[0076] A colourless ink formulation composed of 45 parts of Tioxide
AH-R (Anatase), 54.9 parts of an acrylic varnish (prepared by
mixing together 20 parts Vinnapas C501 resin from Wacker, a solid
copolymer of vinyl acetate and crotonic acid, and 80 parts
propylacetate) and 0.1 parts of the material from example 2 is
applied to clay coated paper using a bar coater. Laser marking with
a Nd:YAG laser at various powers (14-25A, 20 kHz, 1500 mms, 4.2-7.6
W) gives excellent marking results with high contrast.
EXAMPLE 7
Comparative Example Laser Marking of Paper
[0077] Using lanthanum hexaboride instead of the material from
example 2 requires more than 10 times as much of the IR-absorber
(1.4 parts LaB6) in order to get the same laser marking
performance.
[0078] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
drying of printings or fixing of ink toners to a substrate.
[0079] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3 Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0080] In another embodiment the invention relates to the use of
tungsten oxide of the formula WO3-x wherein W is tungsten, O is
oxygen, and x is 0.1-1 and/or the use of tungstate of the formula
MxWyOz wherein M is one or more element selected from NH.sub.4, H,
Li, Na, K, Rb, Cs, Ca, Ba, Sr, Fe, Sn, Mo, Nb, Ta, Ni, Pd, Pt, Cu,
Ag, Au, Zn, Cd, Al, Ga, In, TI; W is tungsten, O is oxygen,
0.001.ltoreq.x/y.ltoreq.1, and 2.0<z/y.ltoreq.3.0, to increase
the heat-input amount of near infrared radiation in the process of
heating of plastic preforms.
[0081] Preferred is the use of tungsten suboxides (e.g.
WO.sub.2,72), and tungsten bronzes (e.g. H.sub.0.53WO.sub.3
Na.sub.0.33WO.sub.3, Cs.sub.0.33WO.sub.3). Especially preferred are
Cs.sub.0.2-0.5WO.sub.3.
[0082] In a further embodiment the invention relates to the use of
a blend comprising tungsten oxide and/or tungstate as defined above
and in addition a dithiolene metal complex of the formula I or II
as disclosed in the International publication WO2008/086931 to
increase the heat-input amount of near infrared radiation.
##STR00002##
wherein
M Ni, Pd, Pt, Au, Ir, Fe, Zn, W, Cu, Mo, In, Mn, Co, Mg, V, Cr and
Ti,
[0083] X.sub.1, X.sub.2 and X.sub.3 independently of one another
are sulfur or oxygen; R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5
and R.sub.6 independently of one another are hydrogen,
NR.sub.7R.sub.8, C.sub.1-C.sub.18alkyl, aryl, aralkyl,
heteroarylalkyl, wherein R.sub.7 and R.sub.8 independently of one
another are C.sub.1-C.sub.18alkyl, aryl, aralkyl,
heteroarylalkyl.
[0084] Examples for C.sub.1-C.sub.18alkyl are propyl, isopropyl,
n-butyl, sec. butyl, tert. butyl, n-hexyl, cyclopentyl,
cyclohexyl.
[0085] Aryl is phenyl, naphyl, anthryl or phenantryl. Arylalkyl ist
e.g. benzyl. Heteroarylalkyl is understood as heteroaryl groups
connected, as substituents, via a lower alkylene to a
heteroaromatic ring selected from imidazolyl, pyridyl, thienyl,
furyl, thiazolyl, indolyl, chinolinyl, pyrazolyl, pyrazyl,
pyridazyl, pyrimidinyl.
[0086] A specific example is
##STR00003##
[0087] The amount of dithiolen metal complex to tungsten oxide is
in the range of 5 to 90 wt %
[0088] In a further embodiment the invention relates to the use of
a blend comprising tungsten oxide and/or tungstate as defined above
and in addition at least one organic IR absorber selected from
quinone-diimmonium salt, aminium salt, polymethines such as cyanine
squaraine, croconaine; phthalocyanine, naphthalocyanine and
quaterrylene-bisimide or in addition at least one anorganic IR
absorber selected from lanthanum hexaboride, indium tin oxide (ITO)
antimony tin oxide such as Minatec 230 A-IR available from Merck,
or Lazerflair.RTM. pigments available from Merck.
* * * * *