U.S. patent application number 12/572683 was filed with the patent office on 2010-04-08 for methods and compositions for coating pipe.
This patent application is currently assigned to Uponor Innovation AB. Invention is credited to Luke J. Brickweg, Jan S. Ericsson.
Application Number | 20100084037 12/572683 |
Document ID | / |
Family ID | 41572579 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100084037 |
Kind Code |
A1 |
Ericsson; Jan S. ; et
al. |
April 8, 2010 |
METHODS AND COMPOSITIONS FOR COATING PIPE
Abstract
Compositions and methods for producing multi-layered plastic
pipes are described. Some embodiments of the compositions comprise
a cross-linkable polymer system (for example, based on either
acrylate or epoxy chemistry), a photoinitiator, and one or more
additives such as a pigment, an antioxidant, a light stabilizer, or
other additive. In an exemplary method of producing a multi-layered
plastic pipe, a base pipe, for example comprising cross-linked
polyethylene, is conveyed through an oxidizing step in which at
least the outer surface of the base pipe is oxidized, through a
coating step in which a pre-polymer system is applied to the outer
surface of the base pipe and through a curing step in which the
pre-polymer is cured to form a layer of the pipe.
Inventors: |
Ericsson; Jan S.;
(Lakeville, MN) ; Brickweg; Luke J.; (Farmington,
MN) |
Correspondence
Address: |
FAEGRE & BENSON LLP;PATENT DOCKETING - INTELLECTUAL PROPERTY
2200 WELLS FARGO CENTER, 90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
Uponor Innovation AB
Fristad
SE
|
Family ID: |
41572579 |
Appl. No.: |
12/572683 |
Filed: |
October 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61102636 |
Oct 3, 2008 |
|
|
|
Current U.S.
Class: |
138/137 ;
138/143; 138/146; 427/457; 427/508; 428/36.91 |
Current CPC
Class: |
B32B 27/18 20130101;
B32B 15/08 20130101; B05D 7/546 20130101; C08J 7/048 20200101; F16L
2011/047 20130101; B32B 1/08 20130101; B05D 3/067 20130101; B32B
15/20 20130101; B32B 2255/26 20130101; C08J 7/0423 20200101; B32B
27/32 20130101; C08J 7/0427 20200101; C08J 7/046 20200101; B32B
2307/7244 20130101; Y10T 428/1393 20150115; B32B 27/16 20130101;
B32B 2255/06 20130101; B32B 2307/546 20130101; C08J 7/043 20200101;
B32B 2597/00 20130101; B32B 27/20 20130101; F16L 11/04 20130101;
B32B 2307/71 20130101; C08J 7/044 20200101; F16L 9/121 20130101;
B05D 1/28 20130101; C08J 2323/06 20130101; C08J 2433/00
20130101 |
Class at
Publication: |
138/137 ;
427/508; 427/457; 138/143; 138/146; 428/36.91 |
International
Class: |
F16L 11/02 20060101
F16L011/02; F16L 11/20 20060101 F16L011/20; C08F 2/48 20060101
C08F002/48 |
Claims
1. A flexible tubular member comprising: a flexible tubular
polymeric substrate, the substrate having an outer diameter of at
least 5/16 inch and a burst strength of at least 475 psi at
23.degree. C. and; a coating disposed on an outer surface of the
tubular substrate, the coating comprising at least one radiation
cured crosslinked polymeric layer having a thickness of less than
100 microns thick.
2. The flexible tubular member of claim 1 wherein the polymeric
substrate comprises a polyolefin.
3. The flexible tubular member of claim 2 wherein the polyolefin is
polyethylene.
4. The flexible tubular member of claim 2 wherein the polyolefin is
a cross-linked polyethylene.
5. The flexible tubular member of claim 1 wherein the layer is less
than 60 microns thick.
6. The flexible tubular member of claim 1 wherein the coating
comprises at least 2 layers, and each of the layers is individually
less than 60 microns thick.
7. The flexible tubular member of claim 1 wherein the coating
comprises an oxygen barrier or a colorant, or combinations
thereof.
8. The flexible tubular member of claim 1 wherein the coating
comprises a photoinitiator.
9. The flexible tubular member of claim 1 wherein the at least one
crosslinked layer comprises an acrylate.
10. The flexible tubular member of claim 1 wherein the at least one
crosslinked layer comprises a carboxyethyl acrylate.
11. The flexible tubular member of claim 1 wherein the peel
strength between the tubular substrate and the crosslinked
polymeric layer is at least 300 psi.
12. A flexible tubular member comprising: a flexible tubular
substrate comprising a cross-linked polyethylene; a coating
disposed on an outer surface of the tubular substrate, the coating
comprising a radiation cured cross-linked acrylate base polymer
layer disposed on an outer surface of the tubular substrate and a
radiation cured cross-linked polymer topcoat layer disposed over
the base layer wherein the base and topcoat layers each have a
thickness of less than 60 microns thick and a total thickness of
less than 100 microns wherein the peel strength between the tubular
substrate and the crosslinked polymer layers is at least 300
psi.
13. The flexible tubular member of claim 12 wherein the coating
layer comprises an oxygen barrier material or a colorant, or
combinations thereof.
14. The flexible tubular member of claim 12 wherein the coating
layer comprises a photoinitiator.
15. The flexible tubular member of claim 12 wherein at least one of
the base or topcoat layers comprises crosslinked carboxyethyl
acrylate.
16. A flexible tubular member comprising: a polymeric flexible
tubular substrate; a metallic layer disposed over an outer surface
of the flexible tubular substrate; a coating disposed on an outer
surface of the metallic layer, the coating comprising at least one
radiation cured crosslinked polymeric layer having a thickness of
less than 100 microns.
17. The flexible tubular member of claim 16 wherein the metallic
layer comprises aluminum.
18. A process for producing a flexible tubular member having a
cross-linked coating including: oxidizing an outer surface of a
flexible tubular substrate, the substrate comprising a cross-linked
polyethylene; disposing a first layer of a radiation curable
pre-polymer formulation on the oxidized outer surface; and exposing
the first layer to radiation to produce a first crosslinked coating
layer, having a thickness of less than 60 microns thick.
19. The process of claim 18 wherein the oxidizing step comprises
heat oxidation.
20. The process of claim 18 further comprising disposing a second
curable pre-polymer formulation on the first coating layer and
curing the second formulation with radiation energy to form a
second coating layer.
21. The process of claim 20 wherein the first formulation is
partially cured prior to disposing the second formulation on the
first coating layer.
22. The process of claim 18 wherein the exposing step comprises
exposing with UV radiation.
23. The process of claim 18 wherein in the process is continuous
process further including the steps of: prior to the oxidizing
step, dispensing the flexible tubular substrate from a first
roller; and after the curing step, receiving the flexible tubular
member onto a second roll.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 of provisional application No. 61/102,636 filed Oct. 3,
2008 and entitled "Methods and Compositions for Coating Pipes",
which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This invention relates to radiation curable coatings applied
to layered plastic piping or tubing products.
BACKGROUND
[0003] Extruded plastic pipe or tubing is used for a variety of
applications. For example, such plastic pipes are utilized for the
transportation of water, more specifically delivery systems for hot
and/or cold potable water, radiant floor heating, waste water and
fire sprinkler systems, among other uses. Such plastic pipes can
also be used as district heating pipes and as process pipes in the
food industry, and other applications include the conveyance of
liquids other than water, such as gases and slurries. Examples of
thermoplastic polymers used for the manufacturing of such plastic
pipes include polyolefins such as polyethylene (PE) (e.g.,
PE-raised temperature, or PE-RT), polypropylene (PP), polybutylenes
(PB), and any copolymers thereof; polyolefin copolymers such as
poly(ethylene-co-maleic anhydride); poly(vinyl chloride) (PVC); and
chlorinated PVC, i.e., CPVC; etc. Such thermoplastic polymers may
or may not be crosslinked, depending on the polymer system used and
the desired properties of the finished pipe.
[0004] As one example of a cross-linked polymer, cross-linked
polyethylene (PEX) is commonly used for plastic pipes. There are
several varieties of PEX that utilize a number of different
crosslinking chemistries and processing technologies. Various PEX
grades further contain other additives such as antioxidants and/or
stabilizer packages in different concentrations and combinations.
Three known varieties of PEX for pipe applications are PEX-a,
PEX-b, and PEX-c.
[0005] In the PEX-a process ("Engel Method"), the crosslinking is
induced by peroxide under the influence of heat and high pressure.
The resultant PEX-a composition is crosslinked through
carbon-carbon bonds to form the crosslinked polymer network. The
PEX-a crosslinking process occurs in the melted stage, as opposed
to the primary crosslinking processes for PEX-b and PEX-c. The
primary reaction is the formation of free radicals upon
decomposition of the peroxide, which has to be present by
definition for PEX-a, and subsequently, the free radical abstracts
hydrogens from the PE polymer chains. The latter gives new carbon
radicals, which next combines with neighboring PE chains to form
stable carbon-carbon bonds, i.e., crosslinks. The crosslinking,
which is considered to be homogeneous and uniform for PEX-a, gives
degrees of crosslinking (typically referred to as CCL) in the range
of 70-90% for practical applications. Requirement for CCL is to be
above 70% for PEX-a as defined in ASTM International's Standard for
Crosslinked Polyethylene (PEX) Tubing, F 867-04 (approved May 1,
2004).
[0006] In the PEX-b process, the crosslinking is induced by
moisture and heat over extended pre-determined times typically
conducted in a "Sauna atmosphere". The most commonly used methods
are referred to as the Sioplas (two-steps), and the Monosil (one
step) methods, respectively. In the Sioplas method, a silane, such
as for example a vinylsilane is grafted to a HDPE resin prior to
pipe extrusion. In the Monosil method, a silane is blended with the
HDPE resin during pipe extrusion. In both methods, which are
chemically different in the pre-crosslinking steps, the fundamental
principle for the actual crosslinking are practically identical,
i.e., the crosslinking occurs in a secondary post-extrusion process
that is accelerated by a combination of heat and moisture. The
latter combination is the active "reagent", which is involved in
the primary hydrolysis and condensation reaction. In principle, the
extruded pipe is exposed to hot water and a steam bath. A
fundamental difference to PEX-a, is that for PEX-b, the resultant
crosslinks are not between carbon-carbon bonds, but instead,
oxygen-silicon covalent bonds (siloxane "bridges") are formed. In
comparison with PEX-a, the crosslink density (CCL) are somewhat
lower for PEX-b (65-70%), and the crosslinking is also less
uniform.
[0007] In the PEX-c process, the crosslinking is commonly referred
to as a "cold" method. In the PEX-c process, no chemicals are
needed in order to facilitate the crosslinking process, but instead
high energy electron beam (EB) irradiation is utilized to create
the free radicals necessary for the hydrogen abstraction and
subsequent crosslinking to take place. The high energy electron
beams are non-selective, i.e., chemical bonds are cleaved in an
un-controlled fashion. The latter has the consequence of creating
side reactions, together with the reaction aimed for, i.e., the
crosslinking of HDPE. The crosslinking density for PEX-c is
typically in the 70-75% range, and caution has to be taken with
irradiation time since a too long exposure may give discolored
products and/or brittleness. PEX-c has been successfully used for
many years despite the somewhat challenging production
conditions.
[0008] Presently, PEX tubing has temperature and pressure ratings
of 160 psi at 73.4.degree. F. (23.degree. C.), 100 psi at
180.degree. F. (82.2.degree. C.), and 80 psi at 200.degree. F.
(93.3.degree. C.). Minimum burst ratings are at 475 psi at
73.4.degree. F. (5/8 inch and larger). Additional performance
characteristics and requirements for PEX pipes and tubing are given
in the Standard for Crosslinked Polyethylene (PEX) Tubing; F 876-04
(approved May 1, 2004) and ISO 9080.
[0009] A variety of plastic pipes may be produced in the form of
multi-layer plastic pipes, wherein at least one of the layers
comprise the extruded thermoplastic plastic pipe as described
above. Multi-layer plastic pipes are well known in the industry and
have been used for all applications described herein. Additional
layers are currently used to provide various desired properties,
for example oxygen barrier properties, UV light protection, scratch
resistance and enhanced mechanical performance, long-term stability
(known as chlorine resistance in accordance with F876 and ASTM
2023), visual appearance in order to create esthetic values and/or
for labeling purposes, etc.
[0010] In one example, for an oxygen barrier, such additional
layers may be produced from thermoplastic non-crosslinked
poly(ethylvinylalcohol). For the same purpose, metallic layers can
be used, for example aluminum or stainless steel. The metal layer
in such cases will provide oxygen barrier properties but also
selected visual appearance. In some instances, metal coatings may
be applied using vacuum deposition, from which the final metal
coatings will have thicknesses in the nanometer range. The metallic
layer may also act as a strengthening layer, and in such cases, the
metal layer will be thicker, i.e., in the micrometer range. In
addition, colored low density polyethylene resins are commonly used
to create colored pipes, typically blue for cold potable water
applications, and red for hot water. Furthermore, outer coating
layers may be applied in the form of crosslinked polyethylene, for
example PEX-b.
[0011] In any case, where thermoplastic polymers, such as EvOH,
polyethylene, PEX-b pre-polymers, etc., co-extrusion technology is
commonly used for this purpose. Co-extrusion is a process whereby a
coating layer is applied to a polymeric pipe (e.g., a PEX pipe) by
extruding a polymer-based material through a ring shaped die as the
polymeric pipe is passed through the die. Because of difficulties
in obtaining thin coating layers with the co-extrusion process, the
practical lower limit for the coating layer thickness is about 100
.mu.m. Co-extrusion also presents other challenges, for example
limited flexibility in operating conditions and in potential raw
materials, high energy requirements, costly start-up times and
purge requirements, and general difficulties with quality control
such as obtaining a consistent coating layer thickness and an
inability to effectively level the surface of the pipes. In the
case where PEX-b technology is used for the outer layers, a
secondary time-consuming and costly operation step is
necessary.
SUMMARY
[0012] In some embodiments, a flexible tubular member comprises a
flexible tubular polymeric substrate, the substrate having an outer
diameter of at least 5/16 inch and a burst strength of at least 475
psi at 23.degree. C., and a coating disposed on an outer surface of
the tubular substrate, the coating comprising at least one
radiation cured crosslinked polymeric layer having a thickness of
less than 100 microns thick.
[0013] In other embodiments, a flexible tubular member comprises a
flexible tubular substrate comprising a cross-linked polyethylene
and a coating disposed on an outer surface of the tubular
substrate, the coating comprising a radiation cured cross-linked
acrylate base polymer layer disposed on an outer surface of the
tubular substrate and a radiation cured cross-linked polymer
topcoat layer disposed over the base layer wherein the base and
topcoat layers each have a thickness of less than 60 microns thick
and a total thickness of less than 100 microns wherein the peel
strength between the tubular substrate and the crosslinked polymer
layers is at least 300 psi.
[0014] In other embodiments, a flexible tubular member comprises a
polymeric flexible tubular substrate, a metallic layer disposed
over an outer surface of the flexible tubular substrate and a
coating disposed on an outer surface of the metallic layer, the
coating comprising at least one radiation cured crosslinked
polymeric layer having a thickness of less than 100 microns.
[0015] In yet other embodiments, a process for producing a flexible
tubular member having a cross-linked coating includes oxidizing an
outer surface of a flexible tubular substrate, the substrate
comprising a cross-linked polyethylene, disposing a first layer of
a radiation curable pre-polymer formulation on the oxidized outer
surface, and exposing the first layer to radiation to produce a
first crosslinked coating layer, having a thickness of less than 60
microns thick
[0016] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention.
Accordingly, the drawings and detailed description are to be
regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows a perspective view of a multi-layer plastic
pipe according to some embodiments of the present invention;
[0018] FIG. 2 shows a cross-sectional view of another multi-layer
plastic pipe according to some embodiments of the present
invention; and
[0019] FIG. 3 is a flow chart depicting a process of producing
multi-layer plastic pipes according to some embodiments of the
present invention.
DETAILED DESCRIPTION
[0020] According to some embodiments of the present invention,
radiation cured coating layers are applied to a surface of a base
pipe in order to provide a desired property. The radiation cured
coating layers are crosslinked to various degrees depending on the
particular application, and may be produced with a pre-determined
coating layer thickness and/or multiple layers.
[0021] In some embodiments of the present invention, one or more
layers are disposed on a base pipe. In some such embodiments, the
base pipe comprises a polyolefin material. Such pipes may be
manufactured from polyethylene, for example high density
polyethylene (HDPE). However, the present invention is applicable
where any type of polyethylene is used for the production of
multi-layer plastic pipes, including low density polyethylene
(LDPE), medium density polyethylene (MDPE), ultra-high molecular
weight polyethylene (UHMWPE), PE 100, and PE 80. With each of the
above polyethylene grades, the polymer chains may be cross-linked
to form three-dimensional polymer networks (e.g., PEX pipe such as
PEX-a, PEX-b, or PEX-c).
[0022] The radiation cured coating layers described herein, and the
processes used to apply these coating layers, are applicable for a
wide range of pipe dimensions and constructions conventionally
employed, for example, as related to the outer diameter (OD), inner
diameter (ID), wall thick thickness, number of layers in the
complete pipe construction, and any combinations thereof.
[0023] The finished pipes described herein may have particular
burst strength ratings (for example, the burst strength ratings
provided in ASTM 876-04). For example, the burst strength at
23.degree. C. may be at least 400 psi, at least 475 psi, or at
least 550 psi.
[0024] FIG. 1 shows a perspective view of a multi-layer plastic
pipe according to embodiments of the present invention. The
multi-layer plastic pipe 20 includes a tubular member 22 with a
first layer 24 disposed on an outer surface thereof. The first
layer 24 may be any of the coating layers discussed herein.
[0025] In addition, other coating configurations are also possible.
For example, FIG. 2 shows a cross-sectional view of another
multi-layer plastic pipe 20' according to some embodiments of the
present invention. The pipe 20' comprises a tubular member 22' with
a first coating layer 24' and a second coating layer 26 disposed
over the first coating layer 24'. As discussed further below, such
multi-layered pipes 20' may be produced by passing the tubular
member 22' through multiple coating stages. In addition, the
multiple layers may be combined to provide various properties, with
the first layer 24' providing one or more properties and the second
layer 26 providing the same, or different, property or properties
as the first layer 24'.
[0026] In other embodiments, a base polymeric pipe (e.g., any of
the base polymeric pipes described herein) has a metal layer
disposed on an outer surface of the base polymeric pipe. A coating
consisting of one or more layers may then be disposed on the outer
surface of the metal layer. For example, any of the coating systems
described herein, including any of the different coating
formulations described herein, any of the numbers of coating layers
provided below, and any of the combinations of coating layers
described herein, may be used as the coating system disposed on the
outer surface of the metal layer. The metal layer itself may
comprise any suitable metal, such as Aluminum or stainless
steel.
[0027] For specific embodiments, the plastic pipes can be produced
with thin cured coating layer thicknesses with very precise control
over thickness. For example, the entire coating may be less than
100 microns thick, less than 80 microns thick, less than 60 microns
thick, less than 50 microns thick, less than 40 microns thick, less
than 30 microns thick, less than 20 microns thick, less than 10
microns thick, between 7 microns and 80 microns, between 7 microns
and 60 microns, between 7 microns and 40 microns, between 7 microns
and 30 microns, between 7 microns and 20 microns, or between 7
microns and 15 microns. The entire coating thickness may be formed
by one coating layer, or formed by multiple coating layers, each
layer individually having a thickness of less than 50 microns, less
than 40 microns thick, less than 30 microns thick, less than 20
microns thick, less than 10 microns thick, between 7 microns and 50
microns, between 7 microns and 40 microns, between 7 microns and 30
microns, between 7 microns and 20 microns, or between 7 microns and
15 microns. In contrast, typical co-extrusion systems provide a
minimal thickness between 100 and 200 microns, with a concomitantly
higher variability in the layer thickness, and therefore higher
variability in the outer diameter of the pipe.
[0028] In some embodiments changes between grades may be
implemented simply and conveniently in a short time relative to
co-extrusion processes. For example, different pre-polymer
formulations may contain different additives that provide for
different characteristics. The time and materials to remove the old
formulation from the coating system and introduce a new formulation
would be relatively small compared to co-extrusion processes.
[0029] Some of the coating layers described herein may have
color-adding materials. Furthermore, the multi-layer plastic pipes
can be equipped with optional gloss level and/or with a smooth
finish. In some embodiments, the coating composition is
transparent, and in other embodiments, the coating composition
includes color. The degree of color is optional and the flexibility
in color design is unlimited. In some embodiments, the color layer
may be semi-transparent. Such a semi-transparent coating layer
allows print on the pipe to be visible through the coating layer
and the print is thereby protected from abrasion and physical
damage.
[0030] In some embodiments of the present invention, the
multi-layered plastic pipes can be provided with one or more layers
that yield UV Resistance. UV resistance can be obtained by adding,
for example, hindered amine light stabilizers (commonly referred to
as HALS compounds), nano-particles such as zinc oxide, or other
compounds or substances that reduce UV damage.
[0031] In some embodiments, one or more of the coating layers
provides oxygen barrier properties. Oxygen barrier coatings may be
applied to PEX tubing and other plastic pipes, which in some
embodiments are used for under floor heating systems. The oxygen
barrier prevents or slows oxygen from crossing through the plastic
pipe to the fluid within the pipe. Generally speaking, less oxygen
entrained in the fluid within the pipe protects boilers, piping and
other accessories that contain ferrous components from
corrosion.
[0032] In addition, one or more of the layers may provide for
scratch and abrasion resistance, enhanced mechanical performance,
anti-microbial functionality, anti-static performance, adhesive
attributes and leveling of a surface of the pipe. Also, more than
one of the above functions may be provided in a single layer.
[0033] FIG. 3 shows a diagram of a process according to embodiments
of the present invention. In step 101, the base pipe is fed off of
a reel or other mechanism. The base pipe may be any of the types of
base pipe referred to above (e.g., any of the PEX pipes described
above). In other embodiments, the base pipe may be produced in-line
according to any of the processes described above.
[0034] In some embodiments, the base pipe is run through an
oxidizer process (step 103) in order to oxidize the surface of the
base pipe. This process may include one or more of a flame
treatment (as shown), a corona treatment, a plasma treatment, or
other appropriate processes to oxidize the outer surface of pipe.
The oxidation process generally raises the surface energy of the
surface being treated, for example to more than 50 dynes, more than
60 dynes, more than 70 dynes, more than 80 dynes, or increase the
surface energy by at least 20 dynes, by at least 30 dynes, by at
least 40 dynes, or by at least 50 dynes. In one embodiment, the
oxidation process increases the surface energy from about 30 dynes
to more than 70 dynes.
[0035] In some embodiments, as further described below, the
chemical composition of the coating layer is such that it will form
strong bonds with the higher energy, oxidized outer surface
relative to the bonds that would be formed with a lower energy,
non-oxidized surface. For example, acidic components in the coating
formulations described below may interact with the outer surface of
the pipe, possibly through either hydrogen bonding and/or covalent
bonding. Relatively higher levels of adhesion are beneficial for
some flexible pipe applications in order to accommodate the forces
resulting from flexing the piping material. Adhesion to polyolefins
is extremely difficult to achieve with any coating system,
especially with radiation cured coatings. The coatings and the
process described herein result in excellent adhesion
characteristics to polyolefins (greater than about 300 psi, greater
than about 350 psi, greater than about 400 psi, greater than about
450 psi, greater than about 500 psi, or greater than about 600 psi
pull-off adhesive strength, as tested with the PosiTest Pull-Off
Adhesion Tester used in accordance with ASTM D4541).
[0036] The pipe is then run through a coating process (step 105),
in which the pre-polymer composition for a first coating layer is
disposed on a surface (e.g., the outer surface) of the pipe. The
coating process employs a suitable mechanism for accurately and
evenly spreading a pre-polymer composition on a surface of the
pipe. For example, the coating process may employ a spray coating
system, a curtain coating system, a flood coating system, a wipe
coating system, or a vacuum coating system, or any other system
that will facilitate disposal of the pre-polymer composition on a
surface of the pipe. The pipe may run through the coating process
in a generally horizontal pathway or in a generally vertical
pathway.
[0037] In some embodiments, the coating system is a vacuum coating
system in which the pipe is run through a pre-polymer composition.
The pipe exits the coating system through a port and the vacuum
being drawn in through the port helps smooth the pre-polymer
composition along the surface of the pipe. Some examples of the
coating system are the vacuum coating systems produced by DV
Systems.
[0038] In some exemplary processes, the base pipe is run through
any of the coating systems mentioned above and the coating system
is generally enclosed and under vacuum. As such, as the base pipe
exits the enclosed coating system, air is drawn back along the
surface of the pipe, which tends to draw excess pre-polymer
solution back into the coating system and provide an even coating
of pre-polymer solution around the base pipe. Such an operation may
also provide for effective leveling of the surface of the pipe.
[0039] The pipe is then run through a curing apparatus (step 107).
In some embodiments, the curing apparatus is a chamber through
which the pipe runs, and the pre-polymer composition on a surface
of the pipe is exposed to radiation. The radiation may be
ultraviolet (UV) radiation and/or electron beam (EB) radiation. The
residence time of the pipe in the curing apparatus is sufficiently
long to partially or completely cure the pre-polymer solution to
form a coating layer on the surface of the pipe. In order to
provide sufficient curing, multiple curing stages may be placed in
series. A variety of different configurations for imparting
radiation on the coating layer may be used. For example, a number
of UV lamps or EB emitters may be used in series in order to
provide sufficient radiant energy to the coating layer. The speed
of the system, and the resulting residence time of the coating
layer in the curing portion of the system, can be adjusted for the
desired level of cross-linking of the coating layer formulation.
The coated pipe is then wound onto a reel (step 109).
[0040] It is noted that, although FIG. 3 shows a single
coating/curing stage, multiple layers may be disposed on the pipe
by placing multiple coating/curing stages in series. In some
embodiments, a first coating layer may not be entirely cured in
order to promote adhesion between the layers. The pipe may then be
passed through a subsequent stage (e.g., a stage as described above
with respect to FIG. 3) in which another layer is applied and
partially or entirely cured on the pipe. Any number of coating
stages can be provided in this process, for example one or more,
two or more, three or more, four or more, five or more, six or
more, between one and ten, between one and five, or between one and
three coating layers. In some embodiments, different layers of the
pipe impart different properties, while in other embodiments two or
more layers may impart the same or similar properties to the
pipe.
[0041] In some embodiments, each of the layers may be fully or
substantially fully cured, while in other embodiments all or some
of the intermediate layers may only be partially cured in order to
promote adhesion between the layers. In some embodiments in which
two or more layers are used and the intermediate layer(s) are not
fully cured, the oxidation step 103 may be omitted for the
intermediate layer(s).
[0042] Furthermore, leveling of the selected surface before
crosslinking of the radiation curable coating formulation is yet
another potential attribute of the radiation cured coatings. This
comes from the fact that radiation curable pre-polymer formulations
are truly low viscous liquids (no polymer included) before curing
(crosslinking), and therefore, the pre-polymer formulations will
indeed level the surface as opposed to co-extrusion processes.
[0043] It is also noted that many of the pre-polymer compositions
described herein can be cured with a relatively short residence
time in the curing apparatus (many such radiation-cured coating
layers cure in one second or less), which may allow for relatively
compact process layout and/or very rapid machine speeds. For
example, machine speeds of approximately 70-100 meters/minute or
faster are possible with some of the pre-polymer compositions and
process configurations described herein. In addition, the processes
of the present invention may consume less power than traditional
co-extrusion systems, and the time required to change between
product grades is typically greatly reduced due to the ease of
changing between pre-polymer systems compared to grade changes in
the traditional co-extrusion processes. Also, because some of the
processes of the present invention do not significantly heat the
pipe, no cooling apparatus (or any subsequent drying process after
a water cooling process) is required, and the finished pipe is
ready to wind on a spool immediately.
[0044] Furthermore, in some embodiments, the processes of the
present invention may provide more consistent and repeatable
dimensions for the pipe compared to traditional extrusion
processes. Because the application of the pre-polymer composition
is not performed with an extrusion operation, the layer of material
may be much thinner and more consistent than co-extruded layers.
The reduced thickness possible in some of the embodiments of the
present invention also provides for reduced material
consumption.
[0045] In some embodiments of the present invention, a radiation
curable pre-polymer formulation includes one or more polymerizable
components, various additives to enhance targeted properties of the
pipe and, optionally, a photoinitiator system that initiates a
cross-linking reaction when exposed to radiation. Some of these
formulations may be cured by UV radiation, while other formulations
may be adapted to be cured by other types of radiation such as
electron beam (EB) radiation. As further discussed below, in some
embodiments in which the pre-polymer system will be EB cured, the
formulation may exclude the photoinitiator system. Also, when
certain base oligomers such as Novacure radiation curable
compositions (Ashland Chemical) are used, no photoinitiator system
is needed for either EB or UV curing.
[0046] A combination of a photoinitiator system and an appropriate
monomer/oligomer formulation may be included in pre-polymer systems
that are UV cured. Some exemplary UV curable polymers include
carbon-carbon double and/or triple bonds capable of reacting with
free radicals, such as acrylates and methacrylates, allyl groups,
styrenes, thiol/enes, and/or, any combination of such
functionalities and/or any of their derivatives. The pre-polymer
system may also be a photoinduced cationic polymerization system.
Exemplary chemistries for cationically cross-linkable polymer
systems include cycloaliphatic epoxies and other cyclic ethers such
as oxetanes; vinyl ethers; and styrene derivatives. In addition,
photoinitiator-free systems based on maleimide chemistry may be
used. These and any other suitable radiation curable chemistry may
be employed to achieve the desired targeted properties.
[0047] In contrast to UV-curing where the light quantum normally is
absorbed by the chromophoric photoinitiator, electron beam (EB)
curing of the present invention takes advantage of the fact that
fast electrons lose their energy by coulomb interaction with the
bulk material itself. Simplified, this means that when a reactive
coating formulation is irradiated by an electron beam source, free
radicals are created in the bulk material and the polymerization
starts. Any of the formulations described herein may be utilized in
an EB curing process. As mentioned above, in EB curing the
photoinitiator may be excluded from the formulation.
[0048] The polymerizable components of the pre-polymer formulation
may comprise monomers (i.e., low-viscosity reactive diluents),
oligomers or pre-polymer systems, or a combination thereof.
Independent of polymerization mechanism chosen, oligomers or
pre-polymers used in the formulations may have from 1 to 250, from
1 to 200, from 1 to 100, from 1 to 75, from 1 to 60, from 1 to 50,
from 1 to 25, or from 1 to 10 monomeric units. The oligomers or
pre-polymers may have a molecular weight from 500 to 10,000, from
500 to 7,500, from 500 to 5,000, from 500 to 3,000, from 1,000 to
10,000, from 1,000 to 7,500, from 1,000 to 5,000, or from 1,000 to
3,000. One or more of the polymerizable components of the
pre-polymer formulation may be added to modify the glass transition
temperature of the cured coating layer. In some embodiments, it is
desirable that the glass transition temperature of the cured
coating layer be at or about the lowest service temperature of the
pipe. As such, the target glass transition temperature may be about
-5.degree. C., at least about -5.degree. C., at least about
-10.degree. C., between about -10.degree. C. and about 0.degree.
C., or between about -10.degree. C. and about 10.degree. C.
[0049] In some embodiments, all monomers and oligomers/pre-polymers
present in the formulation have at least one polymerizable moiety
per molecule, and in some cases at least one of the components
present (e.g., the oligomer/pre-polymer) is multi-functional to
facilitate crosslinking. These multi-functional components may be
adapted for free radical polymerization and may include acrylate
and/or methacrylate functionalities as the main polymerizable unit.
If cationic chemistry is utilized, the cationically induced
crosslinking may be facilitated by using cyclic ethers, such as
cycloaliphatic epoxies, as the main component. As is known in the
art, one unit of unsaturation and/or cyclic ether per molecule is
called mono-functional, two units of unsaturation and/or cyclic
ether per molecule are known as di-functional, and so on. In some
embodiments of the invention, one or more of the components of the
formulation has two or more ethylenically unsaturated groups and/or
cyclic ethers per molecule.
[0050] A curable composition can include up to 100% of one or more
oligomers and/or monomers. For example, the composition may include
from about 10% to 100%, from about 10% to about 99%, from about 50%
to 100%, from about 50% to about 99%, from about 70% to 100%, from
about 70% to about 99%, from about 80% to 100%, or from about 80%
to about 99% of the one or more oligomers and/or monomers. In some
embodiments, the pre-polymer formulation may have from about 10% to
about 80%, from about 20% to about 60%, from about 25% to about
50%, or from about 25% to about 40%, of the oligomer or
pre-polymer. In addition, in some embodiments the pre-polymer
formulation may have from about 10% to about 80%, from about 20% to
about 60%, from about 25% to about 50%, or from about 25% to about
40%, of the monomer or reactive diluent.
[0051] Particularly suitable monomers and reactive diluents include
acrylate or methacrylate based compounds. Examples include
1,6-hexanediol diacrylate, 1,3-bytylene glycol diacrylate,
diethylene glycol diacrylate, trimethylolpropane triacrylate,
neopentyl glycol diacrylate, polyethylene glycol 200 diacrylate,
tetraethylene glycol diacrylate, triethylene diacrylate,
pentaerythritol tetraacrylate, tripropylene glycol diacrylate,
ethoxylated bisphenol-A diacrylate, propylene glycol (mono)
dimethacrylate, trimethylolpropane diacrylate,
di-trimethylolpropane tetraacrylate, triacrylate of
tris(hydroxyethyl) isocyanurate, dipentaerythritol
hydroxypentaacrylate, pentaerythritol triacrylate, ethoxylated
trimethylolpropane triacrylate, triethylene glycol dimethacrylate,
ethylene glycol dimethacrylate, tetraethylene glycol
dimethacrylate, polyethylene glycol-200 dimethacrylate,
1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,
polyethylene glycol-600 dimethacrylate, 1,3-butylene glycol
dimethacrylate, ethoxylated bisphenol-A dimethacrylate,
trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate,
diethylene glycol dimethacrylate, pentaerythritol
tetramethacrylate, glycerin dimethacrylate, trimethylolpropane
dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol
dimethacrylate, pentaerythritol diacrylate,
aminoplast(meth)acrylates, acrylated oils such as linseed, soy bean
oil, castor oil, etc.
[0052] Other applicable polymerizable compounds include
(meth)acrylamides, maleimides, vinyl acetate, vinyl caprolactam,
thiols and polythiols. Styrene derivatives are also readily
applicable within the framework of this invention. A combination of
any of these monomers and reactive diluents may also be used.
[0053] Useful oligomers and pre-polymers include resins having
acrylate functionality. Such reactive compounds may have a similar
structure to, or be derived from, polyurethane acrylates, epoxy
acrylates, silicone acrylates, and polyester acrylates. Other
exemplary compounds are (meth)acrylated epoxies, (meth)acrylated
polyesters, (meth)acrylated silicones, (meth)acrylated
urethanes/polyurethanes, (meth)acrylated polybutadiene,
(meth)acrylated acrylic oligomers and polymers, and the like. In
addition, any combination of these oligomers or pre-polymers may
also be used.
[0054] For free radical chemistry based on acrylate chemistry,
specific examples of polymerizable components include a
difunctional urethane acrylate oligomer (such as Ebecryl 4833
available from Cytec), a monofunctional acrylate monomer (such as
CD 420, SR285, CD9055, all available from Sartomer), and a
monofunctional urethane acrylate monomer (such as Ebecryl 1039
available from Cytec).
[0055] In some embodiments, formulations also include reactive
intermediates for crosslinking by cationic polymerization.
Exemplary cationic systems of the present invention are based on
cyclic ethers, cycloaliphatic epoxies, oxetanes, polyols, and vinyl
ethers. Illustrative of the cycloaliphatic epoxides useful as base
materials in the present invention are
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (UVR
6110, Union Carbide), bis-(3,4-epoxycyclohexyl)adipate (UVR 6128,
Union Carbide), methyl 3,4-epoxy-cyclohexane-carboxylate, ethyl
3,4-epoxycyclohexane-carboxylate, propyl
3,4-epoxycyclohexane-carboxylate, isopropyl
3,4-epoxycyclohexane-carboxylate, n-butyl-, s-butyl-, and t-butyl
3,4-epoxycyclohexane-carboxylate; the various amyl and hexyl
3,4-epoxycyclohexane-carboxylates, methyl
3,4-epoxy-3-methyl-cyclohexane carboxylate, ethyl
3,4-epoxy-3-methyl-cyclohexane carboxylate, methyl
3,4-epoxy-4-methyl-cyclohexane carboxylate, ethyl
3,4-epoxy-4-methyl-cyclohexane carboxylate, butyl
3,4-epoxy-3-methyl-cyclohexane carboxylate, butyl
3,4-epoxy-4-methyl-cyclohexane carboxylate, methyl
3,4-epoxy-6-methyl-cyclohexane carboxylate, ethyl
3,4-epoxy-6-methyl-cyclohexane carboxylate, butyl
3,4-epoxy-6-methyl-cyclohexane carboxylate, dialkyl
4,5-epoxycyclo-hexane-1,2-dicarboxylates, as well mixed dialkyl
4,5-epoxycyclohexane-1,2-dicarboxylates, and the like. Mixtures of
any combination of the above compounds may also be used, including
mixtures of any of the above cycloaliphatic epoxides.
[0056] In order to facilitate the cross-linking process where
cationic systems are employed, polyols may be used along with any
of the above cationic or epoxy cross-linking compounds. For
example, the TONE (Dow Chemical) polyols, dendritic polyester
polyols (e.g., those sold under the name BOLTORN by Perstorp), or
other suitable polyols.
[0057] In some embodiments in which photoinitiators that are used,
the photoinitiators do not cause discoloration, have low
volatility, and do not lead to undesired side-reactions in the
curing process. Examples of suitable photoinitiators for use in the
present invention include photoinitiators that comprise
benzophenone derivatives, such as Esacure.RTM. ONE (Lamberti)
(difunctional-alpha-hydroxy ketone), Esacure.RTM. TPO (Lamberti)
(2,4,6 trimethylbenzoyldiphenylphosphine oxide), Esacure.RTM. KIP
100F (Lamberti) (oligo (2-hydroxy-2-methyl-1-4 (1-methylvinyl)
propanone and 2-hydroxy-2-methyl-1-phenyl propan-1-one
(monomeric)); Esacure.RTM. KT046 (Lamberti) (mixture of
trimethylbenzoyldiphenylphosphine oxide, alpha-hydroxyketones and
benzophenone derivatives); Irgacure.RTM. 2959 (Ciba)
(1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one);
and Irgacure.RTM. 819 (Ciba) (bis(2,4,6
trimethylbenzoyl)-phenylphosphine oxide); Esacure.RTM. KIP 150
(Lamberti) (oligo [2-hydroxy-2-methyl-1-[4-(1-methylvinyl) phenyl]
propanone]). In addition, synergists and/or co-initiators may be
used to improve the processing and curing conditions, and may
optionally be used for the purpose of this invention. Specific
examples include acrylated amine synergists such as Ebecryl.RTM.
P104, Ebecryl.RTM. P115, and Ebecryl.RTM. 7100, all supplied by
Cytec Industries.
[0058] Additional photoinitiators suitable in the present invention
include benzophenone derivatives; the class of benzoin alkyl
ethers, such as benzoin methyl ether, benzoin ethyl ether, benzoin
isopropyl ether, and benzoin isobutyl ether. Other useful
photoinitiators come from the class of dialkoxyacetophenones, for
example, 2,2-dimethoxy-2-phenyl acetophenones (Irgacure.RTM. 651 by
Ciba) and 2,2-dimethoxy-2-phenylaceto-phenone. Yet another group of
photoinitiators include the aldehyde and ketone carbonyl compounds
having at least one aromatic nucleus attached directly to the
carboxyl group. These particular initiators include benzophenone,
acetophenones, o-methoxybenzophenone, thioxanthone, isopropyl
thioxanthone acetonaphtalenequinone, methyl ethyl ketone,
valerophenone, alpha-phenyl-butyrophenone,
p-morpholinopropiophenone, hexanophenone, dibenzosuberone,
4-morpholinobenzophenone, 4'-morpholinodeoxybenzoin,
p-diacetylbenzene, 4-aminobenzophenone, 4'-methoxyacetophenone,
alpha-tetralone, 9-acetylphenantrene, 2-acethyl-phenanthrene,
10-thio-xanthenone, benzaldehyde, 3-acetylphenanthrene,
3-acetylindone, 9-fluorenone, 1-indanone, 1,3,5-triacetylbenzene,
thioxanthen-9-one, xanthene-9-one, 7-H-benz[de]-anthracene-7-one,
fluorine-9-one, 4,4'-bis(dimethylamino)-benzophenone,
1-naphtaldehyde, 1'-acetonaphthone, 2'-aceto-naphthone,
2,3-butedione, acetonaphthene, and benz[a]anthracene 7,12 diene.
Phospines such as triphenylphosphine, tri-o-tolylphosphine, and
bisacyl phosphine oxide derivatives, are also useful
photoinitiators. In addition, any combination of the above
photoinitiators may be used.
[0059] In some embodiments, the formulations include
photoinitiators for cationic polymerization including those coming
from triarylsulfonium and/or diaryliodonium salts. The fundamental
photochemical reaction mechanism involves several electron transfer
steps, but the practical consequence is that a strong protonic acid
is produced (super acid). The acid is the active moiety, which
subsequently initiates the cationic polymerization. Two examples of
such photoinitiators are triarylsulfonium hexafluoroantimonate
(Ar.sup.+ SbF.sub.6.sup.-) and triarylsulfonium hexafluorophosphate
(Ar.sup.+PF.sub.6.sup.-). These photoinitiators are typically
commercially available as 50% solutions in propylene carbonate. The
main difference between the two examples given is their effect on
the polymerization rate. The larger sized antimonate anion gives a
considerably higher polymerization rate than the phosphate counter
ion.
[0060] The corresponding diaryliodonium salts have a similar
photolysis mechanism, which again generates a super acid. In
addition, the iodonium salts may yield the super acid by a
catalyzed thermally activated process, as an alternative to the
photochemical route, which is not the case for the sulfonium
salts.
[0061] A curable composition can include up to 10% of one or more
photoinitiators. For example, the composition can include about
7.5%, from about 0.25% to about 4%, from about 2% to about 10%,
from about 4% to about 9%, or from about 6% to about 9%, of the one
or more photoinitiators. In other embodiments, the curable
composition is substantially free of photoinitiators.
[0062] The additives in the pre-polymer formulation (such as a
nano-sized material or other oxygen barrier additive, a UV
radiation absorber, a stabilizer, a colorant, a flame retardant, a
static electricity reducer, and/or a friction reducer) can affect
the strength, color, UV resistance, stability and other
characteristics of the composition. In addition, certain additives
or combinations of additives may result in a layer with any
combination of these properties. For example, some pigments may
provide some oxygen barrier properties, and pigments may also be
added to a formulation along with oxygen barrier additives and/or
UV protection additives to provide a combination or properties.
[0063] In some embodiments, the curable composition includes one or
more hindered amine light stabilizers (HALS), e.g., to protect the
cured composition from oxidation and degradation. Examples of
hindered amine light stabilizers include Tinuvin 123 (Ciba),
Tinuvin 622 (Ciba), Tinuvin 770 (Ciba), Cyasorb 3853 (Cytec),
Cyasorb 3529 (Cytec) and Hostavin PR-31 (Clariant). A curable
composition can include up to about 15% of one or more hindered
amine light stabilizers. For example, the composition can include
from about 0.1% to about 5%, or from about 0.1% to about 3% of the
one or more hindered amine light stabilizers. In other embodiments,
the curable composition is substantially free of a light
stabilizer.
[0064] In some embodiments, the curable composition includes one or
more materials capable of absorbing UV radiation ("UV absorbers"),
e.g., to protect plastic tube 22 from damage caused by UV
radiation. Examples of UV absorbers include benzotriazole
derivatives, titanium dioxide, zinc oxide, and cerium oxide. A
curable composition can include up to about 15% of one or more UV
absorbers. For example, the composition can include from about 0.1%
to about 5%, or from about 0.1% to about 3% of the one or more UV
absorbers. In other embodiments, the curable composition is
substantially free of a UV absorber.
[0065] In some embodiments, the curable composition includes one or
more color-adding materials such as pigments, pigment dispersions,
dyes, or other colorants. Examples of these color-adding materials
include Chromacure TPGDA Blue HS (Plasticolors), TPGDA Red 170
(Plasticolors) and TPGDA Purple (Plasticolors). A curable
composition can include up to about 15% of one or more color-adding
materials. For example, the composition can include up to about 5%,
from about 0.5% to about 5%, from about 4% to about 10%, or from
about 6% to about 8% of the one or more color-adding materials. In
other embodiments, the curable composition is substantially free of
a color-adding material.
[0066] In some embodiments, the curable composition includes one or
more nano-sized materials, e.g., dispersed to enhance the strength
of the cured composition, add resistance to UV damage, decrease the
build up of static electricity, improve resistance to scratch and
abrasion damage, provide anti-microbial properties, or to decrease
gas permeation. As used herein, "nano-sized" means having at least
one dimension smaller than approximately 100 nm. Examples of
nano-sized materials include clays, metal oxides, carbon nanotubes,
and organic particles. The form of the nano-sized materials can be,
for example, particles, fibers, and/or tubes. A curable composition
can include up to about 15% of one or more nano-sized materials.
For example, the composition can include up to about 10%, from
about 0.1% to about 5%, or from about 0.5% to about 3% of the one
or more nano-sized materials. In other embodiments, the curable
composition is substantially free of a nano-sized material.
[0067] In some embodiments, a curable composition contains
approximately 10-60% of a difunctional urethane acrylate oligomer
Ebecryl 4833 (Cytec); approximately 20-70% monofunctional acrylate
monomer CD 420 (Sartomer); approximately 0.1-8% of a mixture of
photoinitiators including benzophenone derivatives, alpha-hydroxy
ketone derivatives and/or bisacyl phosphine oxide derivatives;
approximately 0.1-5% of a benzotriazole UV absorber; approximately
0.1-5% of a hindered amine light stabilizer Cyasorb 3853 (Cytec);
approximately 0.1-15% of an organic pigment dispersed in a mono or
difunctional acrylate monomer; approximately 0-40% of a pigment
system including (e.g., consisting of) a pigment, a pigment
dispersant/stabilizer, a surfactant, a solvent, or a reactive
diluent/monomer, or dyes; and approximately 0-10% of a surface slip
additive to reduce the coefficient of friction of the cured
composition.
[0068] Following is a list of exemplary ranges for embodiments of
the present invention:
TABLE-US-00001 Topcoat Range #1 Material Purpose (wt %) Range #2
(wt %) Oligomer Base Resin 10-100 40-99 Reactive
Adhesion/Tg/viscosity 0.1-90 1-50 diluents/monomer adjustment
Photoinitiators* Photoinitiators 0.5-10 1-5 Slip aid** Slip
aid/surface 0.1-1 0.5-1 additive Scratch resistant Scratch
resistance 0.1-7.5 1-6 additive** *Optional photoinitiator when EB
curing is used **Optional components. One, all, or any combination
of these additives may be present in the formulation.
TABLE-US-00002 Basecoat Range #1 Material Purpose (wt %) Range #2
(wt %) Monomer Base resin/gas 10-99 50-99 Barrier Viscosity
modifier/ Viscosity Modifier 0.1-80 0.1-50 monomer TPGDA Red*
Pigment 0.1-7.5 1-5 TPGDA Blue* Pigment 0.1-7.5 1-5 Talc such as
platy Oxygen barrier 0.1-25 0.1-10 talc or leafing aluminum or
other fillers* Photoinitiators** Initiation 0.5-5 1-4 *Optional
components. One, all, or any combination of these additives may be
present in the formulation. **Optional photoinitiator when EB
curing is used
EXAMPLES
[0069] The exemplary curable compositions disclosed below were
prepared by combining the identified components of the composition
by, for example, mixing in batches using a high shear disperser or
a low speed liquid blender, until a homogenous composition was
formed. A PEX-a pipe was run through a flame treatment stage in
order to oxidize the surface of the pipe, and then the pipe was run
through a.sub.--------coating system that dispensed a layer of the
coating composition on to the surface of the pipe. The coating was
dispensed under to ensure that the formulation was evenly
distributed on the surface of the pipe.
[0070] The coated pipe was then exposed to UV radiation via a
commercially available UV lamp system for a sufficient period of
time to cure the coating composition on the pipe. The pipe was then
wound on a spool.
[0071] With the two-layer systems described below, the first layer
was not fully cured and was subsequently run through a second
coating system (which was similar to the first coating system). The
second, outer coating formulation was disposed on the first,
partially cured layer and cured with a UV lamp. The pipe was then
wound on a spool.
[0072] Various testing was then performed on samples of the
finished pipe. The PosiTest Pull-Off Adhesion Tester was used in
accordance with ASTM D4541 to test the adhesion of the coating to
the pipe. All of the examples shown below provided adhesion levels
of at least 300 psi indicating suitable adhesion for contemplated
applications.
[0073] When wound on a reel, Examples 1-8 had some delamination
occur. In addition, some of Examples 1/8 were subjected to an
Expansion Test, in which the pipe is cooled to 20.degree. F., an
expansion member is placed in the pipe and the pipe is expanded to
roughly twice the original diameter. For examples 1-8, delamination
occurred in the Expansion test as well when samples were wound onto
the spool. For examples 9-11, no delamination was observed either
with the Expansion Test or on the spool.
Example 1
Colored Plastic Pipe (Blue)
TABLE-US-00003 [0074] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane diacrylate 32 oligomer SR285 Sartomer
Tetrahydrofurfuryl acrylate 21.75 CD420 Sartomer Monofunctional
acrylate ester 32 Esacure KIP100F Lamberti Photoinitiator blend 5
Esacure KTO46 Lamberti Photoinitiator blend 2.5 Ceraflour 988 Byk
Chemie Amide modified polyethylene 5 wax Byk 331 Byk Chemie
Silicone surface agent 0.5 TPGDA HS Blue Plasticolors Pigment
dispersion in TPGDA 1.25 TOTAL 100
Example 2
Colored Plastic Pipe (Blue)
TABLE-US-00004 [0075] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane 31.75 diacrylate oligomer Ebecryl
1039 Cytec Tetrahydrofurfuryl 50 acrylate Carboxyethyl acrylate
Cytec Adhesion promoter 8 Esacure KIP100F Lamberti Photoinitiator
blend 5 Esacure KTO46 Lamberti Photoinitiator blend 2.5 Ceraflour
988 Byk Chemie Amide modified 1 polyethylene wax Byk 331 Byk Chemie
Silicone surface agent 0.5 TPGDA HS Blue Plasticolors Pigment
dispersion in 1.25 TPGDA TOTAL 100
Example 3
Colored Plastic Pipe (Red)
TABLE-US-00005 [0076] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane diacrylate 31 oligomer SR285 Sartomer
Tetrahydrofurfuryl acrylate 21 CD420 Sartomer Monofunctional
acrylate ester 31.75 Esacure KIP100F Lamberti Photoinitiator blend
5 Esacure KTO46 Lamberti Photoinitiator blend 2.5 Ceraflour 988 Byk
Chemie Amide modified polyethylene 5 wax Byk 331 Byk Chemie
Silicone surface agent 0.5 TPGDA Red 170 Plasticolors Pigment
dispersion in TPGDA 3.25 TOTAL 100
Example 4
Plastic Pipe (Oxygen Barrier)
TABLE-US-00006 [0077] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane 31.75 diacrylate oligomer Ebecryl
1039 Cytec Tetrahydrofurfuryl 40 acrylate Ebecryl 1360 Cytec
Silicon acrylate 10 (Oxygen Barrier) Carboxyethyl acrylate Cytec
Adhesion promoter 8 Esacure KIP100F Lamberti Photoinitiator blend 5
Esacure KTO46 Lamberti Photoinitiator blend 2.5 Ceraflour 988 Byk
Chemie Amide modified 1 polyethylene wax Byk 331 Byk Chemie
Silicone surface agent 0.5 TPGDA HS Blue Plasticolors Pigment
dispersion in 1.25 TPGDA TOTAL 100
Example 5
Plastic Pipe (Oxygen Barrier)
TABLE-US-00007 [0078] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane 31.75 diacrylate oligomer Ebecryl
1039 Cytec Tetrahydrofurfuryl 50 acrylate Carboxyethyl acrylate
Cytec Adhesion promoter 8 Esacure KIP100F Lamberti Photoinitiator
blend 5 Esacure KTO46 Lamberti Photoinitiator blend 2.5 Ceraflour
988 Byk Chemie Amide modified 1 polyethylene wax Byk 331 Byk Chemie
Silicone surface agent 0.5 NanoByk Zinc Oxide Byk Chemie Oxygen
Barrier 5 TOTAL 100
Example 6
Plastic Pipe (Oxygen Barrier); Cationic Chemistry
TABLE-US-00008 [0079] Material Supplier Description Wt. % UVR 6105
Union Carbide Cycloaliphatic Epoxy 32 UVR 6000 Union Carbide
Cycloaliphatic Epoxy 38 Photomer 4006 Henkel Polyol 18 Epoxidized
Castor Oil Proprietary Aliphatic epoxy 7.5 Byk 307 Byk Chemie
Flowing agent 0.25 Byk 371 Byk Chemie Leveling agent 0.25 UVI 6990
Union Carbide Photoinitiator 4 TOTAL 100
Example 7
Plastic Pipe (Oxygen Barrier); Thiol/Ene Chemistry
TABLE-US-00009 [0080] Material Supplier Description Wt. % TMPMP
Bruno Trimethylolpropane 60.4 Bock tris(3-mercaptopropionate) SR
533 Sartomer 1,3,5-Triallyl-1,3,5-triazine- 37.7
2,4,6(1H,3H5H)-trione Esacure KTO46 Lamberti Proprietary
photoinitiator blend 1.9 TOTAL 100
Example 8
Plastic Pipe (Oxygen Barrier); Dual Coating Layer
Base-Coat:
TABLE-US-00010 [0081] Material Supplier Description Wt. % Acrylic
Acid Aldrich Acrylic acid 92.8 Jaylink JL-103M Bomar Polymerizable
cellulosic 5.2 thickener Esacure KTO46 Lamberti Proprietary
photoinitiator blend 2.1 TOTAL 100
Top-Coat:
TABLE-US-00011 [0082] Material Supplier Description Wt. % Ebecryl
4833 Cytec Aliphatic urethane acrylate 20.4 CD 420 Sartomer Acrylic
acrylate monomer 40.7 SR 285 Sartomer Tetrahydrofurfuryl acrylate
27.1 Esacure KIP 100F Lamberti Photoinitiator 2.5 Esacure KTO 46
Lamberti Photoinitiator 5.1 Byk 331 Byk Chemie Silicone slip ad 0.1
Ceraflour Byk Chemie Modified polyethylene wax 4.1 TOTAL 100
Example 9
(Blue Two-Layer Plastic Pipe, Base Coat); Two-Layered Coating (See
Top Coat Composition Below)
TABLE-US-00012 [0083] Material Supplier Description Wt. % CD 9055
Cytec Carboxyethyl acrylate 85 Esacure TPO Lamberti Photoinitiator
3 SR 238 B Sartomer Cross-linking agent 10 TPGDA HS Blue
Plasticolors Blue pigment dispersion in 2 TPGDA TOTAL 100
Example 10
(Red Two-Layer Plastic Pipe, Base Coat); Two-Layered Coating (See
Top Coat Composition Below)
TABLE-US-00013 [0084] Material Supplier Description Wt. % CD 9055
Cytec Carboxyethyl acrylate 83.20 Esacure TPO Lamberti
Photoinitiator 3 SR 238 B Sartomer Cross-linking agent 10 TPGDA HS
Red Plasticolors Red pigment dispersion in 3.80 TPGDA TOTAL 100
Example 11
(Oxygen Barrier Two-Layer Plastic Pipe, Base Coat); Two-Layered
Coating (See Top Coat Composition Below)
TABLE-US-00014 [0085] Wt. Material Supplier Description % CD 9055
Cytec Carboxyethyl acrylate; Oxygen barrier 81 Esacure TPO Lamberti
Photoinitiator 3 SR 238 B Sartomer Cross-linking agent 10 Nicron
674 Luzenac Platy talc, Oxygen Barrier 6 TOTAL 100
[0086] Top Coat for Examples 9-11:
TABLE-US-00015 Material Supplier Description Wt. % E20089 Sartomer
Monomer/Oligomer blend 79.00 DC 57 Dow Corning Silicone surface
additive 0.50 Esacure ONE Lamberti Photoinitiator 3.75 Esacure TPO
Lamberti Photoinitiator 1.75 SR 238 B Sartomer Crosslinking agent
10 Ceraflour 988 Byk Chemie Slip agent 5.00 TOTAL 100
[0087] Radiation cured coatings are typically known for being very
hard and protective, and flexibility is usually not one of the
favorable characteristics. It is well known that low flexibility
affects adhesion negatively, especially on plastics such as for
example polyolefins. However, for some of the coatings described
herein, the produced coatings are very durable and protective with
excellent mechanical performance, and at the same time, the
coatings are truly flexible giving excellent adhesion to
polyolefins such as PEX tubing. Furthermore, the coatings display
very good low-temperature flexibility and extensibility while
maintaining its abrasion resistance.
[0088] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. For example, while the embodiments described
above refer to particular features, the scope of this invention
also includes embodiments having different combinations of features
and embodiments that do not include all of the above described
features.
* * * * *