Note: Descriptions are shown in the official language in which they were submitted.
S.~3~
This inVention rel~tes to reinfoxced plastic articles
hav~ng at least one sur~ace ~hich includes a supplQ~entary lining
and/or outer coating integrally formed therewith, and a method
for producing same. ~ great need exists for pipes, pipe fittings,
and other related components which are capable o transporting
corrosive or abrasive materials. Past practice ln fabricating
such components has included steel or cast pipings and fittings
having an abrasion resistant liner bonded to the material wall
thereof. Another approach has been the use of resin bonded,
fiber reinforced structures, again ~aving an abrasion resistant
or corrosion impervious lining bonded to the interior wall. One
of the largest problems faced by each of the above mentioned
techniques has been in maintaining the integrity of the bond
between the inner lining material and the outer structural portion
of the pipe. A void or other imperfection in the bond or a tear
in the liner almost inevitably would lead to the entry of the
material being transported into the space between the liner and
the outer shell and eventually partial or sometimes complete
separation of the liner from ~he pipe.
According to the present invention, a resin bonded,
composite structure comprises a resin bonded structural portion
having an inner and an outer ~all; an inner lining contiguous
with the inner wall of said structural portionS and a fibrous
reinforcing material extending partially into said inner wall of
said resin bonded structural portion and partially into said
inner lining.
~s~3a~
Pigu~e 1 is ~ cXoss sectional view of a pipe section
having an inner lining inte~rall~ interconnected with the pipe
wall according to the principle of the invention;
Figure 2 is a vie~ similar to Figure 1 of a pipe having
only an outer covering î and
Figure 3 is a view similar to Figure 1 of a pipe having
both a liner and a cover.
Before proceeding with a detailed description of ~he
invention, it should be understood that the ~ords "plastic and
"resin" as used in the description of the present inven~ion are
considered to be essentially interchangeable. That is, for a
particular material the unfabricated or uncured material being
the "resin" and the fabricated or cured article a "plastic".
The term plastic i5 meant to include any of the many non-metallic
compounds, synthetically produced which can be molded into
various forms and hardened for commercial use.
Referring to Figure 1, there is sho~n a section through
a cylindrical pipe fabricated according to the principles of
the present invention. While a pipe section is used for
illustration purposes, it should be understood that other
reinforced plastic structures such as pump bodies, valve bodies,
etc. may also be fabricated according to the principles which
~ill hereafter be discussed.
Referring to Figure 1, the partial longitudinal cross
section of a typical pipe 10 is broken do~n into three generally
distinct regions for purposes of explanation; i. e., the
inner liner 12, the outer plastic shell 14, and the
interface region 16 wherein some form
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of fiber reinforcemant material 18 partially included in both the outer
plastic shell and the inner liner ~orms a mechanical interlock between
the shell and the liner. This mechanical int0rlock results in a unitary
structure in which the inner liner and the outer structural shell are
not likely to separate from one another. A supplemental reinforcing
fiber 20 is provided in the outer plastic shell in this embodiment. This
material is typically glass filament or a similar materi~1.
Figure 2 shows another typical pipe section 10' wherein an
outer layer 22 of elastomer material or the like has been attached to
the base structural shell 14' in a like manner with the fiber reinforcement
material 18'.
Figure 3 shows a third pipe section 10" which ha3 been provided
with both an inner liner 12' and a protective outer covering 22'. The
liner and outer covering are each mechanically interlocked with the
structural shell 14" through the fibers 1~" contained in fibrous
interface arrangements 16". As in the Figure 1 embodiment, supplementary
reinforcing material 20' is provided in the structural 14".
The method of fabricating components according to the present
invention may vary depending upon the types of materials used for the
liner, the reinforcing material in the interface and the outer plastic
shell. The materials selected are dependent, among other considerations,
upon the application to which the finished product is to be put. A number
of possible materials, their advantages, disadvantages and special
characteristics will first be discussed and then representative techniqueæ
for fabricating components according to the invention will be set forth.
The structural shell 1l~ is normally formed from a reinforced
plastic material. Typically, a thermosetting resin is used, preferably a
polyester, however, epoxies and vinylesters may also be used in piping
applications. Typical polyester resins include: Hetron ~o~. 72, 92 and
; 30 197 produced by the Durez Division of Hooker Chemical Company, and
~OS~3~;~
Atlac Nos. 382 and 711 produced by ICI United States, Inc., Specialty
Chemicals Division. All of the above resins exhibit good corrosion
resistance and ~lso have excellent fire retardant ~ualities. In most
applications the plastic outer shell contains some type of reinforcement;
such reinforcement varying depending on the service requirements of the
pipe. For piping where internal pressure is to be experienced, fil~nent
~inding with glass filaments is preferably used. For non-pressure
applications a hand laid-up shell using glass cloth or woven roving is
satisfactory. Also, in some non-pressure applications a thermoplastic
non-reinforced outer shell made from, for example, PVC ~Poly Vinyl Chloride)
may be used.
The inner liner and/or the outer protective coa-ting, as the
case may be, may be made from essentially any material compatable with
the interlocXing, attaching feature of the invention. In applications
where it is desired to have the inner lining highly abrasion resistant,
a soft material of an elastomeric nature i6 preferable. 0~ the many
elastomeric materials that have become available to designers and
engineers in recent years, the most versatile are those included in a
group known as polyurethanes. There are three basic forms in which
polyurethanes may be manufactured. The first is a millable gum urethane
which may be processed like conventional rubber materials; i.e., it may
be milled, calendered, extruded and compression molded. A second form
is a thermoplastic material which is handled the same as many other
thermoplastics, such as polyethylene and polypropylene. Typical
manufacturing processes for the thermoplastic polyurethanes are in~ection
molding and transfer molding. The third type is what is known as a
liquid cast elastomer. With a liquid material it is possible to produce
intricate parts which would be impractical with other materials. The
liquid cast polyurethanes are the most versatile of the three types
and offer the highest combinations of physical properties.
~o5z3~2
TypicAl of the many commercially available materials which could
successfully be used as the inner lining material are the ~llowing
elastomers: Solathane 291 available from the Thiokol Chemical Corporation,
Cyanoprene D-7 available from the American Cyanamid Corporation, Nordel
~420 and Hytrel available from Dupont Corporation. All of these
materials possess good abrasion resistance. Of particular application
to the present invention ~re a series of cast polyurethane products
manufactured by the McCreary Indu~trial Products Company identified by
the trademark Scothane.
Several Plternate embodiments for fabricating components
according to the principles of the invention will now be described. One
method of fabricating straieht piping sections is to first preform the
hollow elastomer inner liner by extruding the elastomeric material through
an extrusion die according to conventional techniques. The inter~ace or
interlocking material, preferably, a glass mat is then placed about the
preformed elastomer tube and thereafter passed through a squeeze die which
acts to imbed the reinforcing fiber mat partially into the outer surface
of the elastomer material. The outer structural plastic shell is then
formed about the elastomer liner/reinforcement material assembly so as to
impregnate the outer portion of the reinforcing fiber mat thereby forming
the mechanical interlock between the liner and outer structure. Using
an uncured plastic resin, the resin would be applied in any accepted
fashion to the portion of the fiber interface material not embedded in
; the elastomeric liner and built up until the outer shell was the desired
thickness for proper structural integrity. If no additional reinforcing
material were desired in the outer shell, the entire structure would
then be allowed to cure.
If, however, it was desired to further reinforce the structural
portion of the pipe section, the reinforcing material, such as a filament
wound gla5s (see Figure 1 numeral 20) or hand laid up glass cloth, would
be applied to the outer reinforcing resin prior to curing of the structure.
~:)S'~302
Another technique for forming a pipe structure according to the
principles of the invention, is to form the elas-tomer inner liner by
centri~ugal casting techniques using a liquid cast elastomer, Scothane
97O5, Por example, would be a material having high abrasion resistance
which would be used ~or lining pipes used for transporting fly ash flurry.
Before introducing the liquid elastomer in the centrifugal casting mold,
the interface material, such as a glass mat, is placed ~ithin the centrifugal
casting appsrstus about the inner surface of the mold ca~ity. The viscosity
of the liquid elastomer~ the rotational speed of the centri~gal casting
apparatus and other variables in the centrifugal casting process are then
controlled so as to assure that the cast elastomer penetrates only
partially, to the desired depth in the interface reinforce~ent material
thereby leaving a portion o~ the rein~orcing material on its outer surface
unimpre~nated with the liquid elastomer so that it may be ~ubsequently
impregnated with the plastic resin used in fo~ming the outer structural
~ shell. Forming of the outer structural shell with the plastic resin is
; then carried out in the same manner as described above.
In order to form components having unusual shapes, such as ~oints,
fittings, pump bodies, etc. the elastomer inner lining would normally be
formed in a static molding or casting operation. Again, the interface
reinforcement material, glass mat or the like, would be placed within the
molding or casting equipment prior to introduction of the fluid elastomer
and the variables of the molding process would be controlled such that the
elastomer material would penetrate only partially into the reinforcement
material. ~he outer plastic structural shell would then again be ~ormed
~ according to the technique described above.
; In all of the above examples, i~ it is desired to also have an
outer protective layer of an elastomer or similar material, a second layer
of interface rein~orcing material such as a glass mat may be partially
imbedded in the outer surface of the structural plastic layer prior to
10523~2
the curing thereof. ~he outer protective la~er of elastomer or the like
is then applied as a liquid, by spray or dipping. The entire structure
is then cured and results in an inner elastomer liner and an outer
elastomer protective coating bath mechanically interlocked through the
interface reinforcement material such that separation of the lining and
coating from the structural body would not be likely.
~ hile these preferred embodiments of the invention ha~e been
shown and described, it Nill be unaerstood that they are merely illustrative
and that changes may be made without departing from the scope of the
invention as claimed.
What is claimed is:
