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Inks Technical News inks
Environmental Resin's Performance in Low Rub Black
Offset Inks
INTRODUCTION
The development work covered in this article compares the use of American Gilsonite Company's product,
Environmental Resin ER-125, in rub- resistant web offset blacks, versus the Asian and European use of rosin
modified phenolics. While phenolic systems are not common in the U.S., they can produce inks of ultimate rub
resistance. With the use of suitable gelling agents, phenolic systems can be made to lithograph extremely well at
very high speeds on all types of presses.
Secondly, the work looks at using combinations of ER-125 and Gilsonite to alter flow and rheology to produce
inks that are suited to all common ducts systems including overshot, undershot, and rail system without the
need for flow agents such as treated clay.
MODIFIED PHENOLIC SYSTEMS
The introduction of high-speed web offset presses for the printing of high quality newspapers in Europe,
Australia, and parts of Asia over the last decade has seen the development of inks that truly have almost no
scuff in time frames as low as four hours after printing. This unique performance has in some cases been
achieved by the use of high viscosity rosin modified phenolic resins that retain good solubility in low aromatic
distillates and compatibility in vegetable oils such as Soy and Canola oils. These inks, because of the binding
capacity of the resin, are able to use low-cost carbons normally only associated with the rubber industry . The
final balance of ingredients produces an ink of superb transfer, good strength, easy water balance, and above all,
fast set and the ultimate in scuff resistance.
These systems employ Gilsonite to aid in pigment wetting and, because of the predominance of overshot ink
ducts, generally prefer the lower viscosity grades such as American Gilsonite Company's Selects 300 Grade.
One such system is described as follows:
Modified Phenolic Varnish: High Molecular Weight Modified Phenolic Resin
Hydrocarbon Resin (MP 120ºC)
Alkali Refined Soy Oil
Haltermann PKWF 30.33¹
25% Solution of Chelate OAO² in PKWF 30/33
Butylated Hydroxy Toluene
Equals
30.00%
15.00%
10.00%
41.00%
3.00%
1.00%
100.00%
Gilsonite Selects 300 Varnish:
Gilsonite Selects 300 Grade
Alkali Refined Soy Oil
Haltermann PKWF 30.33¹
Equals
40.00%
20.00%
40.00%
100.00%
Using the above varnishes, the ink formulation becomes:
Elftex Pellets 115³
Phenolic Varnish
Gilsonite Selects 300 Varnish
Isophthalic Linseed Alkyd (40 poise)
Tixogel VP(4)
Water
Pronap 280(5)
Alkali Refined Soy Oil
Haltermann PKWF 30/33¹
Equals
20.00%
27.00%
17.00%
5.00%
1.00%
1.00%
13.00%
5.00%
11.00%
100.00%
The ink is adjusted to the specification:
Tack (800 rpm)
Laray Viscosity (ASTM 4040)
Brookfield Viscosity 7/2.5 rpm
5.0
36 poise/700 dynes
2000 poise
All tests are conducted at 32°C with the ratio of the Laray viscosity to the Brookfield value being controlled
within a tolerance to suit the type of press. ER-125 SYSTEM
Environmental Resin ER-125 from American Gilsonite is a refined natural fossil resin that has been extensively
cleaned and de-aromatized. It is
not Gilsonite but made from Gilsonite. Via solvent extraction, ER-125 Resin is
almost totally pure aliphatic hydrocarbon with less than 0.05 percent impurity content. The final result is a low-
cost resin, bituminous in nature, with excellent pigment wetting and long flow. ER solutions are totally stable in
aliphatic and vegetable oils and require little, if any, filtration.
Using ER-125 Resin as a replacement for the modified phenolic resin results in the following varnish formula:
Environmental Resin Varnish:
ER-125 Resin
Alkali Refined Soy Oil
Haltermann PKWF 30.33¹
25% Solution of Chelate OAO² in PKWF 30/33
Butylated Hydroxy Toluene
Equals
50.00%
10.00%
31.00%
8.00%
1.00%
100.00%
Using this ER-125 svstem as a replacement for the modified phenolic and Gilsonite varnish results in the
following ink formulation and specification:
Elftex Pellets 115³
Environmental Resin ER-125 Varnish
Isophthalic Linseed Alkyd (40 poise)
Tixogel VP(4)
Water
Pronap 280(5)
Alkali Refined Soy Oil
Haltermann PKWF 30/33¹
Equals
20.00%
36.00%
4.00%
1.00%
1.00%
16.00%
5.00%
17.00%
100.00%

Tack (800 rpm)
Laray Viscosity (ASTM 4040)
Brookfield Viscosity 7/2.5 rpm
5.0
32 poise/243 dynes
1750 poise While the viscosity is lower than the phenolic system, the ratio of the Laray to Brookfield viscosity is 55 in both
cases, indicating similar flow characteristics.
To further evaluate the products, the two inks were subject to a range of tests including scuff resistance at two
hours and 24 hours, lithographic emulsion stability using the Prufbau Lithomat and Duke Tester and print
strength using the Prufbau Printability Tester. Table I indicates the results achieved.
Table I
Scuff Percent
4 Hours 24 Hours
Lithomat
Duke
Print Density 100 mm³
Product
Phenolic System
1.9%
1.1%
75/100
45%/10m
1.12
ER-125
2.2%
1.8%
85/100
39%/10m
1.12
SCUFF TEST PROCEDURE
Each ink was printed on the Prufbau at 100 mm
³ on Fletcher Challenge 43 gsm newsprint and the density
measured using a Techkon Colorsens Densitometer model R412 fitted with Status E filters. After four hours,
each print was subject to 20 rubs with clean newsprint using the Holmes Empirical Scuff Tester. The density of
the ink transferred to the clean panel was then measured for density using the Techkon Densitometer and the
ratio of the two readings expressed as a percentage. This procedure was repeated with separate prints after 24
hours.
It should be noted here that conventional web offset blacks yield a scuff percentage according to this procedure
at four hours of 16-20 percent. So called low rub inks yield 6-8 percent while the phenolic system as illustrated
can yield results as low as 1-2 percent. At this level the ink transfer to the hands or clothes of a newspaper
reader is below the background level and hence not discernible. Thus, the difference between the phenolic and
ER-125 systems is so small as to be insignificant.
PRUFBAU LITHOMAT EMULSION STABILITY
The inks were tested for resistance to pile in accordance with a well documented procedure(6) where the
performance of each ink is scored out of 100 points. Fifty points are allotted if the ink shows no sign of pile on
any roller in a given period with the balance being allotted to tack retention, resistance to bleed or
contamination of the fountain solution and resistance to stripping. Any ink achieving better than 60 points is
considered commercially acceptable, while those scoring above 85 points are considered excellent products with
robust lithographic tolerance and a wide window of press performance.
The test is conducted over 10 minutes at high speed at 20-22°C using distilled water. Table I indicates that the
ER-125 system achieved a top end result and additionally, did so without the use of hydrophobic additives of
any kind. DUKE WATER TAKE UP
Both inks were tested for water take up over 10 minutes using distilled water as a control. Graph 1 illustrates
clearly the difference in the two systems. The ER-125 produces a near perfect "C" curve with rapid initial water
take up and a definite end point at around 10 minutes. Again, this balance was achieved without the use of
additives.
The result of this laboratory work indicates that American Gilsonite's ER-125 is indeed an excellent
replacement for the modified phenolic system. The ER-125 produces an ink of lower viscositybut with similar
flow to the alternative and with better lithographic water balance and resistance to pile, all without the need for
the use of hydrophobic additives so common with modified phenolic products.
The fast set characteristics of ER-125 are comparable, if not better, than the competitive system. While the scuff resistance is quite marginally inferior, the difference in the commercial sense is so small as to be
indiscernible.
The first part of this development program has been involved in the replacement of modified phenolics in very
rub-resistant inks with American Gilsonite's Environmental Resin ER-l25. The rheology of both inks was
designed to be long flowing and suited to overshot duct systems, as this has been the predominant feed system
adopted by machine manufacturers in Europe in recent years. Part two of this study looks at the influence of
Gilsonite (or ER-125 Resin) choice on the rheology of web offset coldset blacks and how ink may be
formulated to suit other duct systems such as undershot and rails, without the need for common expensive
additives such as Tixogel(4) and fumed silicas.
What are the differences in the various feed systems and why do they require different ink rheology?
OVERSHOT SYSTEM
In the Overshot System the ink is picked up by the pan roller and lifted into contact with a metering roller
which allows a small amount of ink to pass through the nip for distribution to the plate. The excess ink is
forced to return to the ink duct or pan by the force of gravity subject to the ink's rheology. Short, paste-like inks
b