Style: feature
Strap head: filter media
UV curable resin
system in filter
paper and media
Knowlton Technologies is a manufacturer thermoset/thermoplastic resin impregnated filtration media. By
utilizing a UV (ultra-violet) curable resin system there may be some environmental and manufacturing benefits.
These benefits are already being observed in other industrial markets. Potentially solvent materials could be
reduced from the system. Also by moving towards a UV system, a reduction in floor space would allow
Knowlton have better utilization of the existing space.
Five types of filtration media, and a glass veil sample were saturated with the UV resin system and cured using a
UV beam to cure the resin. All samples were improved in the basic strength properties such as burst, tensile and
stiffness when compared to the raw unsaturated samples. As a filtration media, the test results were similar to
the current resin systems which require a % resin input, strength tests and air permeability and met most current
filtration media specifications.
It is concluded that a UV curable resin system could effectively replace the solvent based saturation process
utilized during the manufacture of Knowlton Technologies filtration media if the cost of installation and cost of
the raw materials (resins) can be justified. The safety issues surrounding the use of UV curable resins must be
considered as well. Any skin contact must be thoroughly cleansed immediately. Any eye contact can cause
significant impairment of vision. Also to be considered is the clean-up of the resins and would it differ from the
current resin system. If there is any incapability in this area then this must be considered.
Background
The potential of ultraviolet (UV) and electron beam (EB) curable chemistries have been realized for some years in
markets such as printing and durable flooring. It is only in the last five to ten years that UV & EB curable
chemistries have made significant inroads into applications like composites, high end electrical
devices/components and durable coatings for metals, plastics, stone and concrete, among others. UV and EB
curable chemistries are now utilized in three-dimensional parts such as 20 lb propane cylinders and drive shafts.
The numerous process and environmental benefits of UV & EB curable technologies are what make them a
sustainable and a technology worth looking at in today’s marketplace. Some of these benefits include reduced or
near zero volatile organic compound (VOC) and potentially hazardous air pollutant emissions, significantly
reduced energy consumption, high processing speeds, good finished product performance quality and less floor
space. On the other hand is the cost and installation of the new equipment, increased electrical usage and
developing new formulations for the wide range of products being the manufactured.
Knowlton Technologies, LLC of Watertown, NY conducted a feasibility study to develop and to quantify the
benefits of a 100% solids UV curable resin system(s) that would replace the standard thermally cured resin blends
in a number of their specialty filter papers/media.
A UV curable resin system is potentially capable of replacing Knowlton's standard thermally cured solvent based
thermoset and thermoplastic resin systems in some products, may potentially provide significant environmental
and processing benefits in the process of manufacturing specialty filter and filtration media. At the same time, it's
projected that a UV curable resin could possibly result in an equal product that is less expensive to produce, giving
Knowlton an opportunity to increase market share and business as whole. There are areas in how the final media
is processed that must be answered though in order to make this a viable system.
Knowlton Technologies, LLC is a privately held company that now employs over 100 people within New York
State. Knowlton's history dates back over 200 years to 1808 when the company was started by John Paddock and
Gurdon Caswell. The company has since undergone many transformations, but at the core of these evolutions is
the paper mill capable of producing thousands of pounds of wet laid non-wovens, filter and composite media now
being utilized in everything from automotive transmissions to medical filtration.
Problem and solution
Knowlton owns and operates two composite media manufacturing lines and one saturation line. More than half
of the filter paper and composite media that is manufactured by Knowlton is impregnated with a resin to add
additional value to the product and provide the customer with a product of a desired quality. The addition of a
resin to a paper, filter or composite media can significantly increase the strength, heat and chemical resistance
and long term durability of the product.
Knowlton has identified two filter product lines as candidate products for qualification of a UV curable resin as
a replacement for the traditional resin systems. B oth of which are proprietary filter formulations sold to major
manufactures of fluid filter manufacturers. For these products the customer(s) are generally most concerned
with cost and performance. Knowlton has secured a verbal commitment from their primary customer of these
grades, who asked to remain unnamed, to evaluate and qualify any new filter products that have the potential
to make Knowlton's manufacturing process ‘greener,’ while maintaining performance and ideally reducing
costs.
The saturation line, as currently configured and operated, requires significant floor space and energy to
impregnate filter and composite media with thermally cured resins.
Secondary concerns with the current system include the flammability issues associated with the resins and the
solvents that they contain. F lue detection and suppression systems have been installed as the current
chemistry is flammable. Also, since phenolics generally contain some amount of free phenol and
formaldehyde, there is a safety factor associated with humans handling these chemicals. In certain locations,
such as the room that contains the saturator bath, respirator systems must be used when interacting with these
chemicals to prevent exposure to the respiratory tract. Third, as most of the phenolics currently purchased by
Knowlton are supplied as 50% - 60% solids a significant weight and volume of the purchased product is material
that has no function in the finished product and simply adds to shipping costs and storage space. This means that
up to 50% of the volume taken up on a shipping container, commercial truck or storage tankage does not add
value to the end product.
Fiberglass composites have been produced at roughly 0.0500 in (50 mm) thickness and containing anywhere from
40%-60% resin based on weight. The key to UV curing is that it is a ‘line-of-sight’ curing technology. In other
words, the resin must see or be directly exposed to UV light in order to cure, or crosslink. UV transmission
measured through an 80 mm fiberglass veil produced by Knowlton Technologies showed more than sufficient
UV energy passing through the random chopped fiber media.
Table 1 shows that data obtained by measuring the UV transmission through the 80 mm glass veil of a 500
W/in microwave powered Fusion UV light fitted with an iron (D) doped bulb at roughly 2.5 in from the bottom of
the irradiator housing. The data was measured with an EIT Power Puck II A2. Keep in mind that the optimum
distance from Fusion focused irradiator is 2.1 in.
UV Range
UVB
(280-320nm)
UVA
(320-390nm)
UVA2
(375-415nm)
UW
(395-445nm)
Peak Irradiance
Total Energy
mW/cm2
mJ/cm2
mW/cm2
mJ/cm2
mW/cm2
mJ/cm2
mW/cm2
mJ/cm2
Control
Through Media
% Transmission
865
956
2423
2836
1546
1658
2355
2726
32
20
920
817
719
589
1240
1094
4%
2%
38%
29%
47%
36%
53%
40%
Table 1 – UV transmission through 80mil chopped fiber veil.
In this particular application, the use of a 100% solids UV curable resin will eliminate solvents from the
saturation and curing process and the need for a thermal oxidizer. From an environmental and health and safety
standpoint this is a benefit to switching to a UV curable resin system. This feasibility study is not designed to
research and develop a UV curable resin system(s) to replace all of Knowlton's saturation resins as some products,
such as friction papers, require very high temperature resistance and the UV light source cannot penetrate this
substrate. However, this feasibility study will show that a UV curable resin system can successfully be
formulated to replace thermally cured resin systems in many filter applications as UV cured epoxy acrylates and
epoxy novolac acrylates have good thermal resistance and excellent chemical and moisture resistance.
Secondly, the UV curable resins will be formulated to cure almost instantaneously with the specified
wavelength and energy of UV light to meet or exceed current production rates. The energy consumption of the
required number of UV lights is expected to be significantly less than the energy required to run the thermal ovens
to cure the thermo resin systems and power the material handling equipment. Once a formulation is developed
that meets all of the performance specs and fits within the cost model it will be determined how much UV energy
is required to sufficiently cure the chemistry. In this case, an EIT MicroCure will be utilized to quantify the
amount of UV energy necessary to cure the resin and ultimately determine the number of UV lights to meet the
processing speeds. Once this information is determined a comparative analysis of energy consumption of the two
different resin systems can be thoroughly performed.
A I00% solids UV curable resin system will eliminate the flammability hazard and safety equipment required
for such products. 100% solids UV curable resins are not flammable and have flash points well over 200°F.
From a safety and handling standpoint, UV curable resins can at worst case be considered skin
irritation/sensitization hazards, and this property is generally a result of low molecular weight monomers and
not higher molecular weight oligomers.
Since no solvents will be present in the UV curable resins, no special respiration equipment will be required,
meaning a better working environment for the employees. Lastly, 100% of the resin shipped to Knowlton will be
utilized in the final product. In the big picture, this means that Knowlton could technically use 50% less volume of
resin compared to the thermoset resins utilized today. This means less storage space is required and more
efficient transport of raw materials to Knowlton Technologies.
Project benefits
This p r o j e c t is a proof of concept and the final UV curable resin formulation and UV energy requirements to
cure this composition will not be established until well into the research and development process. As a result,
it is difficult to project accurate estimates of cost and energy benefits at this time. However, during the latter
stages of the project, after a UV curable resin has been developed and quantified, measurable energy savings,
reduction in solvent usage, reduction in maintenance costs, the potential for increased market share and overall
growth of Knowlton can be evaluated.
Energy S a v i n g s : while difficult to quantify at this point, certain energy savings can be identified through
discontinued use of the thermal oxidizer, curing ovens, material handling equipment and environmental
controls in these areas. Additional quantifiable energy benefits may include reduced resin shipments and reduced
storage space.
Environmental benefits: the environmental benefits would be significant by reducing the use of solvent borne
chemistries originating from the saturation process.
Economic benefits: a UV curable resin system has the potential to allow Knowlton to manufacture the same
products for less money, meaning Knowlton can improve margins or use the lower costs of manufacturing to
gain market share both domestically and overseas. Either way, the company can improve the bottom line and
be in a better position grow/expand, hire more employees in upstate New York and develop new products and
processes that help diversify the company and keep them competitive in today's global marketplace.
Cost benefit projection: once a UV curable resin formulation has been qualified, detailed comparative
analysis will be performed to determine potential energy savings, actual solvent reductions and process benefits,
such as reduced maintenance costs. Included in this analysis will be the difference in natural gas and electricity
consumption resulting from the shutting off of larger energy sinks like the thermal oxidizer, ovens and material
handling equipment. At the same time, the actual reduction in solvent consumption will be evaluated to see if
savings on permitting or any other emission related issues can be realized. It would be desirable from Knowlton's
standpoint that this proof of concept result in a technology that can be commercialized in a relatively short
period of time and have a return-on-investment (ROI) of less than three years on the capital cost to integrate such
a technology into the production line.
Results
Knowlton Technologies chose six samples to be saturated to our standard input levels. The samples were chosen
across our typical grade mix of air filtration, liquid filtration and glass veil type grades. The samples were then
cured under the UV light at a speed of 10fpm to a saturated fully cured state. These samples were then tested for
physical properties and compared to our current specifications for each specific grade.
Based upon all testing completed the samples saturated with the UV resin were equal in all ways to the traditional
phenolic saturated products and the specifications that the grades were compared against were met.
INITIAL SAMPLE TESTING
SAMPLE ID
BsWt
CAL
DEN
FRAZ
MULLEN
MD STIFF
CD STIFF
AVE.
INPUT
B TARGET
125.9
19.1
6.59
2.74
67.5
7600
4000
12.7
D HIGH
146.3
31.1
4.70
43.8
37.8
10800
7200
44.7
D TARGET
104.1
31.0
3.36
110
32.8
9600
3600
19.0
E HIGH
177.6
22.1
8.04
1.09
50.8
10800
6800
40.5
E TARGET
130.6
21.6
6.05
1.83
53.3
10400
4400
18.3
F TARGET
132.7
24.8
5.35
6.34
53.0
14400
6000
14.0
G HIGH
181.0
26.4
6.86
3.42
47.0
15200
9200
46.7
G TARGET
133.3
26.5
5.03
5.96
51.0
12400
6000
21.5
H HIGH
174.2
34.7
5.02
38.6
51.3
20000
13200
38.5
H TARGET
129.3
33.5
3.86
52.4
34.5
15200
5600
13.4
Table 2. Physical property results with UV resin.
SAMPLE ID
BsWt
CAL
DEN
FRAZ
MULLEN
MD STIFF
CD STIFF
AVE.
INPUT
B1
142.1 19.1
7.44
1.9
99
8800
3600
20.4
B2
145.2 19.1
7.60
1.69
94.5
9600
4800
18.6
B3
145
19.7
7.36
1.85
86
9200
4000
18.3
D1
108.1 26.5
4.08
99
67.5
10000
4000
24.1
D2
107.1 26
4.12
96.2
65
9600
4800
22
D3
108.1 26.8
4.03
91.6
65.0
7600
5200
23.3
E1
141.7 21.4
6.62
1.35
66.0
9600
5600
19.7
E2
140.8 21.5
6.55
1.27
64.5
10000
4400
20.6
E3
137.5 20.6
6.68
1.3
60.5
9200
4800
20
F1
129.7 24.4
5.32
10.2
80.5
15200
6000
16.1
F2
131.5 23.6
5.57
9.77
78
14800
6400
17.9
F3
128.4 23.7
5.42
10.6
75
12800
5200
17.5
G1
126.3 26.3
4.8
4.85
42
12800
6400
23.5
G2
120.6 26.1
4.62
5
55
10400
4800
21.4
G3
123.5 26.2
4.71
4.93
58
10000
4400
21.8
H1
138.5 33.3
4.16
60.2
64
20000
8800
20
H2
138.7 34.7
3.99
55.8
61
19200
10400
18.2
H3
135.9 35.6
3.82
61.2
74.5
15200
6800
19
AIM
INPUT
14.0%
23.0%
20.0%
16.0%
21.5%
19.0%
Table 3.
Conclusions
Based upon the results obtained through this testing, it appears that the UV curable resins have a true potential
for the saturation of filtration media. Properties such as tensile strength, Mullen burst, and Elmendorf stiffness
were improved equal to the thermoset resin systems, while at the same time maintaining Frazier air permeability.
Should Knowlton Technologies go forward with this project, an investigation of the costs associated with this
technology is required. This would include the need to determine cost of the UV equipment necessary, the
projected costs of the raw materials, energy consumption and how these might be incorporated into the
Knowlton manufacturing plant layout.
Lastly, the safety needs of handling the UV curable resin and operating the UV light systems would need to be
thoroughly investigated. The UV systems would allow some reduction of solvent based resins from the operation
however not all. Many of the products manufactured would still require thermoset resin systems as the UV light is
not visible through 100% of the non-woven media manufactured at Knowltons. Therefore there would still be
some solvent based systems in house and it may result in problems switching between the systems.
Contact
John Crimi
Director of sales and product development
Knowlton Technologies, LLC
213 Factory Street
Watertown, NY 13601
Work (315)755-2640
Fax (315)782-7517
www.knowlton-co.com
Caption
The filters are used primarily for fuel filtration, coalescing (water removal) filtration, and lubrication oils filtration.
One of Knowlton’s largest product lines is aviation fuel filtration. The company manufactures roll stock of grooved
material, which its customers will typically convert into a cartridge. Picture courtesy of Ozgur
Coskun/Shutterstock.com