U.S. patent number RE39,399 [Application Number 10/420,569] was granted by the patent office on 2006-11-14 for segmented die for applying hot melt adhesives or other polymer melts.
This patent grant is currently assigned to Nordson Corporation. Invention is credited to Martin A. Allen.
United States Patent |
RE39,399 |
Allen |
November 14, 2006 |
**Please see images for:
( Certificate of Correction ) ** |
Segmented die for applying hot melt adhesives or other polymer
melts
Abstract
A segmented die assembly comprises a plurality of side-by-side
and separate units. Each die unit, includes a manifold segment and
a die module mounted thereon. The manifold segments are
interconnected and function to deliver process air and polymer melt
to the modules. Each module including a nozzle through which the
polymer melt is extruded forming a row of filament(s). The
filaments from the array of modules are deposited on a substrate or
collector. The die assembly is preferably used to apply a hot melt
adhesive to a substrate, but also may be used to produce meltblown
webs.
Inventors: |
Allen; Martin A. (Gainesville,
GA) |
Assignee: |
Nordson Corporation (Westlake,
OH)
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Family
ID: |
26759661 |
Appl.
No.: |
10/420,569 |
Filed: |
April 22, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60077780 |
Mar 13, 1998 |
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Reissue of: |
09138039 |
Aug 20, 1998 |
06220843 |
Apr 24, 2001 |
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Current U.S.
Class: |
425/7; 425/378.2;
425/378.1; 425/72.2; 425/192S |
Current CPC
Class: |
B05B
7/0861 (20130101); B05C 5/001 (20130101); B05C
5/0279 (20130101); D01D 4/025 (20130101); D01D
5/0985 (20130101); B05C 5/0237 (20130101) |
Current International
Class: |
B29C
47/10 (20060101); B29C 47/12 (20060101) |
Field of
Search: |
;425/7,72.2,186,192S,378.1,378.2 ;118/302,315 ;156/167 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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8534594 |
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Dec 1985 |
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DE |
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85 34 594 |
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Dec 1985 |
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DE |
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0701010 |
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Mar 1996 |
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EP |
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WO94/01221 |
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Jan 1994 |
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WO |
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WO 94/01221 |
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Jan 1994 |
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WO |
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Other References
Trends (1993) The CF 800 Metered Head. cited by examiner .
Nordson Corporation, The CF800M Metered Head, Trends, 1993, 2 pgs.
cited by other .
European Patent Office, Partial European Search Report, Application
No. EP 03 07 9172. cited by other.
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Primary Examiner: Davis; Robert B.
Attorney, Agent or Firm: Wood, Herron & Evans,
L.L.P.
Parent Case Text
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
Ser. No. 60/077,780, filed Mar. 13, 1998.
Claims
What is claimed is:
1. A segmented die assembly, comprising: (a) a plurality of
manifold segments, each manifold segment having a polymer flow
passage and an air flow passage formed therein; said manifold
segment being interconnected in side-by-side relationship wherein
said air passages and polymer passages are in fluid communication,
respectively; (b) a die module mounted on each manifold segment,
said die module comprising a die body having a polymer flow passage
and an air flow passage in fluid communication with said polymer
flow passage and said air flow passage of its associated manifold
segment, respectively; and a die tip or nozzle mounted on said die
body and having a polymer flow passage in fluid communication with
said polymer flow passage of its associated die body for receiving
the polymer melt and discharging a filament or filaments therefrom;
(c) means for delivering a polymer melt to at least one manifold
segment whereby the melt is distributed through said other
interconnected manifold segments and flows through each die module
discharging as a filament or filaments from each die tip or nozzle;
and (d) means for delivering air to at least one manifold segment
whereby air is distributed in said interconnected manifold segments
and flows through each die module discharging through said die tip
or nozzle.
2. The die assembly of claim 1 wherein said die tip or nozzle is
selected from the group consisting of meltblowing die tip, spiral
spray nozzle, spray nozzle, bead nozzle, and coating nozzle.
3. The assembly of claim 2 wherein said die tip on at least one
module is a meltblowing die tip.
4. The die assembly of claim 1 wherein said die tip on each die
module is air assisted having air passages formed therein, said air
passages of said die tip being in fluid communication with said air
flow passages of said die body on which it is mounted.
5. The die assembly of claim 1 wherein each die module has an air
actuated valve mounted therein to open and close said polymer flow
passage therein and each manifold segment having instrument air
flow passages formed therein for delivering air to and from said
air actuated valve, said assembly further comprising control means
for selectively delivering air to and from said instrument air
passages of said manifold segment.
6. The die assembly of claim 1 wherein said manifold segments are
identical.
7. The die assembly of claim 1 wherein said assembly comprises from
2 to 100 die segments.
8. The die assembly of claim 1 wherein each manifold segment and
said die module mounted thereon is from 0.25 to 1.5 inches in
width.
9. The die assembly of claim 1 wherein each manifold segment
includes electric heaters for heating said polymer and said air and
wherein said air flow passage of a particular manifold segment is
in fluid communication with said air passages of said other
manifold segments whereby air flows through each manifold segment
before flowing to said die module mounted on said particular
manifold segment.
10. A meltblowing die comprising: (a) a manifold with at least two
manifold segments, each segment having a polymer flow passage and
an air flow passage, said polymer flow passages and air flow
passages being interconnected, respectively; (b) a die module
secured in each manifold segment, each die module having a polymer
flow passage which registers with its associated manifold segment
polymer flow passage, an air flow passage which registers with its
associated manifold segment air flow passage, a die tip or nozzle
for discharging polymer as a filament or filaments, and an air flow
discharge for delivering air onto said filament or filaments; (c)
means for delivering a polymer melt to at least one of said
manifold segments whereby said melt flows through said
interconnected polymer flow passages of each manifold segment and
is delivered to said associated die modules; and (d) means for
delivering air to at least one of said interconnected manifold
segments whereby said air flows through each manifold segment and
is delivered to said associated die modules.
11. The meltblowing die of claim 10 further comprising valve means
for selectively controlling the flow of polymer melt through each
die module independently.
12. A segmented die assembly comprising a plurality of separate
air-assisted die units interconnected in side-by-side relationship,
each die unit comprising: a) a manifold segment having formed
therein (i) a process air flow passage, (ii) a polymer flow
passage, and (iii) and instrument air flow passage, said process
air flow passages and said polymer flow passages respectively being
in fluid communication; b) a die module having a die body
detachably mounted on said manifold segment, and an air-assisted
die tip or nozzle mounted on said die body, said die body having
formed therein (i) a process air flow passage, (ii) a polymer flow
passage and (iii) an instrument air flow passage which,
respectively, are in fluid communication with said process air flow
passage, said polymer flow passage, and said instrument air flow
passage of said manifold segment, said die body further having an
air-actuated valve mounted therein for opening and closing said
polymer flow passage thereof, which is in fluid communication with
instrument air flow passage thereof; said tip having (i) a process
air flow passage and (ii) a polymer flow passage which,
respectively, are in fluid communication with said process air flow
passage and said polymer flow passage of said die body; and c)
means for selectively delivering air to and from said instrument
air flow passages of said manifold segment for actuating said
air-actuated valve.
13. The segmented die assembly of claim 12 wherein said die
assembly comprises from 5 to 50 die units.
.Iadd.14. A die assembly comprising: a manifold having first and
second sections, a fluid passageway in said first section for
conveying therethrough a material to be dispensed, and an air
passageway in said second section for conveying therethrough
process air to be discharged adjacent the material being dispensed,
first and second heaters respectively contained in said first and
second sections and configured to separately heat the material in
said fluid passageway and the process air in said air passageway to
different temperatures, a plurality of holes positioned between
said first and second sections to disrupt the flow of heat between
said fluid passageway and said air passageway, a dispensing valve
coupled with said manifold for receiving and dispensing the
material conveyed through said fluid passageway of said first
section and for receiving and discharging the process air conveyed
through said air passageway of said second section..Iaddend.
.Iadd.15. A segmented die assembly comprising first and second side
by side die units, each of said first and second die units
comprising: (a) an integral manifold block formed from a single
piece of material having first and second sections, a fluid
passageway in said first section for conveying therethrough a
material to be dispensed, an air passageway in said second section
for conveying therethrough process air to be discharged adjacent
the material being dispensed, a front wall and a pair of oppositely
disposed side walls, (b) first and second heaters respectively
contained in said first and second sections and configured to
separately heat the material in said fluid passageway and the
process air in said air passageway to different temperatures, (c) a
thermal isolator hole positioned between said first and second
manifold block sections to disrupt the flow of heat between said
fluid passageway and said air passageway, and (d) a dispensing
valve mounted upon said front wall of said manifold block for
receiving and dispensing the material conveyed through said fluid
passageway of said first section and for receiving and discharging
the process air conveyed through said air passageway of said second
section, and a fastener connecting one of said oppositely disposed
side walls of said manifold block of said first die unit to one of
said oppositely disposed side walls of said manifold block of said
second die unit..Iaddend.
.Iadd.16. The segmented die assembly of claim 15, wherein said
thermal isolator comprises a plurality of holes in said manifold
block, said holes located between said first and second
sections..Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to dies for applying hot melt
adhesives to a substrate or producing nonwovens. In one aspect the
invention relates to a modular die provided with at least one
air-assisted die tip or nozzle. In another aspect, the invention
relates to a segmented die assembly comprising a plurality of
separate die units, each unit including a manifold segment and a
die module mounted thereon.
The deposition of hot melt adhesives onto substrates has been used
in a variety of applications including diapers, sanitary napkins,
surgical drapes, and the like. This technology has evolved from the
application of linear beads such as that disclosed in U.S. Pat. No.
4,687,137, to air-assisted deposition such as that disclosed in
U.S. Pat. No. 4,891,249, to spiral deposition such as that
disclosed in U.S. Pat. Nos. 4,949,668 and 4,983,109. More recently,
meltblowing dies have been adapted for the application of hot melt
adhesives (see U.S. Pat. No. 5,145,689).
Modular dies have been developed to provide the user with
flexibility in selecting the effective length of the die. For short
die lengths only a few modules need be mounted on a manifold block.
(See U.S. Pat. No. 5,618,566). Longer dies can be achieved by
adding more modules to the manifold. U.S. Pat. No. 5,728,219
teaches that the modules may be provided with different types of
die tips or nozzles to permit the selection of not only the die
length but also the deposition pattern.
At the present, the most commonly used adhesive applicators are
intermittently operated air-assisted dies. These include
meltblowing dies, spiral nozzles, and spray nozzles.
Meltblowing is a process in which high velocity hot air (normally
referred to as "primary air") is used to blow molten filament
extruded from a die onto a collector to form a nonwoven web or onto
a substrate to form an adhesive pattern, a coating, or composite.
The process employs a die provided with (a) a plurality of openings
(e.g. orifices) formed in the apex of a triangular shaped die tip
and (b) flanking air plates which define converging air passages.
As extruded rows of the polymer melt emerge from the openings as
filaments, the converging high velocity hot air from the air
passages contacts the filaments and by drag forces stretches and
draws them down forming microsized filaments. In some meltblowing
dies, the openings are in the form of slots. In either design, the
die tips are adapted to form a row of filaments which upon contact
with the converging sheets of hot air are carried to and deposited
on a collector or a substrate in a random pattern.
Meltblowing technology was originally developed for producing
nonwoven fabrics but recently has been utilized in the meltblowing
of adhesives onto substrates.
The filaments extruded from the air-assisted die may be continuous
or discontinuous. For the purpose of the present invention the term
"filament" is used interchangeably with the term "fiber" and refers
to both continuous and discontinuous strands.
Another popular die head is a spiral spray nozzle. Spiral spray
nozzles, such as those described in U.S. Pat Nos. 4,949,668 and
5,102,484, operate on the principle of a thermoplastic adhesive
filament being extruded through a nozzle while a plurality of hot
air jets are angularly directed onto the extruded filament to
impart a circular or spiral motion thereto. The filaments thus
assume an expanding swirling cone shape pattern while moving from
the extrusion nozzle to the substrate. As the substrate is moved in
the machine direction with respect to the nozzle, a circular or
spiral or helical bead is continuously deposited on the substrate,
each circular cycle being displaced from the previous cycle by a
small amount in the direction of substrate movement. The
meltblowing die tips offer superior coverage whereas the spiral
nozzles provide better edge control.
Other adhesive applications include the older non-air assisted bead
nozzles such as bead nozzles and coating nozzles.
SUMMARY OF THE INVENTION
The segmented die assembly of the present invention is of modular
construction, comprising a plurality of side-by-side and
interconnected die units. Each die unit includes a manifold segment
and a die module mounted on the manifold segment. The die module
has mounted thereon an air-assisted die tip or nozzle. The die tip
may be a meltblowing type and the nozzle may be a spiral nozzle or
a spray nozzle. For convenience of description, the term "nozzle"
is used herein in the generic sense, meaning any air-assisted die
tip or nozzle; and the term "air-assisted" means a nozzle through
which is extruded a molten thermoplastic filament or filaments, and
air jets, air streams, or air sheets which contact the molten
filaments to divert, attenuate or change the flow pattern of the
filament(s) and impart a desired characteristic to the filaments,
either in terms of the size of the filaments or the deposition
pattern.
The main components of each die unit, the manifold segment and the
module, are provided with (a) air passages for delivering air to
the nozzles and (b) a polymer flow passage for delivering a polymer
melt to the nozzle. In the preferred embodiment, the nozzle is a
meltblowing die tip provided with a row of orifices and flanking
air slits, so that as a row of filaments are extruded through the
meltblowing die tip, they are contacted with converging sheets of
hot air that attenuate or draw down the filaments to microsize. As
described in detail below, the nozzle may also be a spiral or spray
nozzle. In practice, the die assembly may include segmented units
having different types of nozzles.
The segmented die units are assembled by interconnecting several
identical manifold segments, wherein the air passages and the
polymer flow passage of each segment are in fluid communication. In
the assembled condition, the interconnected manifold segments
function much in the manner of an integrated manifold. A die module
is mounted on each manifold segment and, in combination with other
die modules, form a row thereon. Thus, polymer melt is extruded as
a row of filaments from the array of modules and deposited on a
moving substrate positioned under the assembly.
In a preferred embodiment, each module is provided with an
air-actuated valve to selectively open and close the polymer flow
passage. The instrument air for activating the valve is delivered
through each manifold segment to the module. The valves may be
individually actuated or actuated as a bank, depending on the
instrument air passages and the number of control valves used.
The segmented die assembly of the present invention offers several
advantages over the prior art: (a) Die modules may be repeated by
merely removing an existing module from an assembled manifold
segment, and replacing it with a new module. This feature not only
permits the replacement of faulty modules, but also permits
changing the die nozzle. (b) The length of the die assembly
determines the effective length of the die discharge (i.e. length
of the row of nozzles). In prior art designs, the length was
determined by the manifold length which had to be preformed. For
example, a manifold would be built to accommodate a maximum number
of modules. Frequently, however, less than the maximum number would
be required. This meant that several manifold sites (i.e. those
without modules) would have to be sealed off. In the present
invention, the manifold is made up of only the active manifold
segments (i.e. those which have modules mounted thereon). (c) The
manifold segments are substantially identical and interchangeable,
and are simple in construction. The machining of the small segments
is much easier than that required for bulky integrated manifolds.
(d) If a manifold segment becomes plugged or damaged, it can easily
be replaced by a new manifold segment. In the prior art device, the
entire manifold would have to be replaced. (e) The solid block
manifold of the prior art, in some operations, any may include
dormant polymer flow passages, as in situations where the active
die length is substantially less than the length of the manifold.
These dormant passages at the end of the manifold could become
partially or completely plugged.
These and other advantages of the assembly of the present invention
will be apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a segmented meltblowing die
constructed according to the present invention showing polymer flow
lines.
FIG. 2 is a top plan view of the present segmented die showing
process air (primary air) flow lines.
FIG. 3 is front elevation view of the segmented die illustrating
the discharge of filaments onto a substrate.
FIG. 4 is an enlarged sectional, view taken along plane 4--4 of
FIG. 1 illustrating middle section of the segmented manifold.
FIG. 5 is a sectional view taken along cutting plane 5--5 of FIG. 1
illustrating an end plate of the segmented manifold.
FIG. 6 is a sectional view taken along cutting plane 6--6 of FIG. 1
illustrating the end plate of the segmented manifold opposite that
shown in FIG. 5.
FIG. 7 is a sectional view of the segmented manifold taken along
plane 7--7 of FIG. 4 illustrating the polymer flow passages.
FIG. 8 is a sectional view of the segmented manifold taken along
section 8--8 of FIG. 4 illustrating the process air flow
passages.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIGS. 1, 2 and 3, the meltblowing die 10 of the
present invention comprises a plurality of side-by-side die units
15 comprising manifold segments 11 and die modules 12. (In FIGS. 1,
2 and 3, the manifold segments are labeled 11A through 11F and the
die modules are labeled 12A through 12F for the 6 segment
structure.
In FIGS. 4 through 8, the manifold segments are labeled 11, it
being understood that all the manifold segments are substantially
identical).
In the embodiment illustrated in FIGS. 1, 2 and 3, each die unit 15
comprises a manifold segment 11, a die module 12 mounted thereon,
and a valve actuator 20 for controlling the flow of polymer melt
through the die segment. As shown in FIG. 3, each die module 12,
has a die tip 13 which discharges filaments 14 onto a moving
substrate (or collector) forming a layer or pattern of filaments on
the substrate in a somewhat random fashion.
Each of the main components, manifold segment, die module, and
controls is described in detail below.
Die Modules
The preferred die modules 12 are the type described in U.S. Pat.
Nos. 5,618,566 and 5,728,219, the disclosures of which are which
are incorporated herein by reference. It should be understood,
however, that other die modules may be used. See, for example, U.S.
patent application Ser. No. 09/021,426, filed Feb. 10, 1998,
entitled "MODULAR DIE WITH QUICK CHANGE DIE TIP OR NOZZLE."
As best seen in FIG. 4, each die module 12 consists of a die body
16 and a die tip 13. The die body 16 has formed therein an upper
circular recess 17 and a lower circular recess 18 which are
interconnected by a narrow opening 19. The upper recess 17 defines
a cylindrical chamber 23 which is closed at its top by threaded
plug 24. Valve assembly 21 mounted within chamber 23 comprises
piston 22 having depending therefrom stem 25. The piston 22 is
reciprocally movable within chamber 23, with adjustment pin 24a
limiting the upward movement. Conventional o-rings may be used at
the interface of the various surfaces for fluid seals as
illustrated at 28.
Side ports 26 and 27 are formed in the wall of the die body 16 to
provide communication to chamber 23 above and below piston 22,
respectively. As described in more detail below, the ports 26 and
27 serve to conduct air (referred to as instrument gas or air) to
and from each side of piston 22.
Mounted in the lower recess 18 is a threaded valve insert member 30
having a central opening 31 extending axially therethrough and
terminating in valve port 32 at its lower extremity. The lower
portion of insert member 30 is of reduced diameter and in
combination with the die body inner wall defined a downwardly
facing cavity 34. Upper portion 36 of insert member 30 abuts the
top surface of recess 18 and has a plurality (e.g. 4) of
circumferential ports 37 formed therein and in fluid communication
with the central passage 31. An annular recess extends around the
upper portion 36 interconnecting the ports 37.
Valve stem 25 extends through body opening 19 and axial opening 31
of insert member 30, and terminates at end 40 which is adapted to
section valve port 32. The annular space 45 between stem 25 and
opening 31 is sufficient for polymer melt to flow therethrough. End
40 of stem 25 seats on port 32 with piston 22 in its lower position
within chamber 23 as illustrated in FIG. 4. As discussed below,
actuation of the valve assembly 21 moves stem end 40 away from port
32 (open position), permitting the flow of polymer melt
therethrough. Melt flows from the manifold 11 through side port 38,
through 37, through annular space 45 discharging through port 32
into the die tip assembly 13. Conventional o-rings may be used at
the interface of the various surfaces as illustrated in the
drawings.
The die tip assembly 13 comprises a stack up of four parts; a
transfer plate 41, a die tip 42, and two air plates 43a and 43b.
The assembly 13 can be preassembled and adjusted prior to mounting
onto the body 16 using bolts 50.
Transfer plate 41 is a thin metal member having a central polymer
opening 44 formed therein. Two rows of air holes 49 flank the
opening 44 as illustrated in FIG. 4. When mounted on the lower
mounting surface of body 16, the transfer plate 41 covers the
cavity 34 and therewith defines an air chamber with the air holes
49 providing outlets for air from cavity 34. Opening 44 registers
with port 32 with an o-ring between these providing a fluid seal at
the interface surrounding port 32. Holes 49 register with air holes
57 formed in die tip 42.
The die tip 42 comprises a base member which is co-extensive with
the transfer plate 41 and the mounting surface die body 16, and a
triangular nose piece 52 which may be integrally formed with the
base.
The nose piece 52 terminates in apex 56 which has a row of orifices
53 spaced therealong.
Air plates 43a and 43b are in flanking relationship to the nose
piece 52 and define coverging air slits which discharge at the apex
of nose piece 52. Air (referred to as process air) is directed to
opposite sides of the nose piece 52 into the converging slits and
discharge therefrom as converging air sheets which meet at the apex
of nose piece 52 and contact the filaments 14 emerging from the row
of orifices 53.
The module 12 of the type disclosed in FIG. 4 is described in more
detail in the above referenced U.S. Pat. No. 5,618,566. Also usable
in the present invention are modules disclosed in U.S. Pat. No.
5,728,219 and U.S. patent application Ser. Nos 08/820,559 and
09/021,426. Other types of modules may also be used. The modules
may dispense meltblown fibers, spirals, beads, sprays, or polymer
coatings from the nozzle. Thus the module may be provided with a
variety of nozzles including meltblowing nozzles, spiral spray
nozzles, bead nozzles and coating nozzles.
Manifold
As seen in FIGS. 1-3, segmented manifold 11 comprises end plates 61
and 62 having sandwiched therebetween a plurality of middle section
11A-F. End plates 61 and 62 are designed to provide fluid seals at
each end of the die as well as provide inlet ports for a polymer
melt at 64 and an inlet for process air at 66. Inlet 64 may have
removable filter cartridge 68 for removing impurities from the melt
stream. As described in detail below air inlet 67 in plate 62
provides air, referred to as instrument air for opening control
valves 20A-F in the modules 12A-F, respectively.
As seen in FIGS. 1, 2, 5 and 6 end plate 62 has threaded bolt holes
71a-d which align with countersunk bolt holes 72a-d in middle plate
11A (only 72a and b shown in FIGS. 1 and 2, respectively). End
plate 61 has countersunk holes 73a-d which align with thread holes
74a-d (only 74a, b shown) in middle plate 11F. Countersunk bolts 79
thus join plate 62 to plate 11A leaving surface 81 flush for
adjoining middle plate 11B to 11A, and flush surface 82 for joining
end plate 61 to middle plate 11F.
Adjacent middle sections 11A-F are joined by bolts 85 arranged in
an alternating pattern of threaded and countersunk bolt holes. As
seen in FIG. 4, middle section 11D has four bored and countersunk
bolt holes 86a-d and four threaded bolt holes 87a-d. Plates 11C and
11E flank 11D and have bolt holes which align with holes 86a-d and
87a-d, however, the pattern of countersunk holes and threaded holes
are interchanged in the flanking plates. The countersunk bored
holes 86a-d in plate 11D will align with threaded holes in plate
11C, and threaded holes 87a-d will align with bored and countersunk
holes in plate 11E (see FIGS. 1 and 2). This design of
interchanging the pattern of countersunk holes and threaded holes
in adjacent plates is repeated over the length of the die.
Countersunk holes 86a-d are of sufficient depth so that the heads
of bolt 85 do not protrude beyond the outer lateral surface of the
middle sections and thus permits the abutting surfaces of adjacent
sections to be flush when bolts 85 are tightened. Tightening of
bolts 85 establishes a metal-on-metal fluid seal between adjacent
plates. O-rings may also be used to seal adjacent plates.
Polymer Flow
Referring to FIGS. 1, 4 and 7, middle sections 11A-F have central
polymer flow passage 91 (see FIG. 4) which, when bolted together
define continuous flow passage 92 which extends the length of the
die. Polymer passage 92 interconnects manifold segments 11A-F. A
polymer melt enters the die through inlet 64 and flows into passage
92. Each middle plate has a hole 93A-F (see FIG. 7) which leads
from passage 92 into second continuous passage 94 and holes 96A-F
which is the outlet of the manifold and feeds polymer to die
modules 12A-F in parallel. The outlet of passages 96A-F register
with the polymer inlet 38 (see FIG. 4) of each die module. The
lateral surfaces of middle plates 11A-F and end plates 61 and 62
are precisely machined whereby a fluid seal is established at the
interfaces when the plates are bolted together by bolts 85 as has
been described.
Polymer melt thus enters the die through plate 61 at 64, fills
passage 92, flows in parallel through holes 93A-F, fills continuous
passage 94, flows in parllel through holes 96A-F, and enters die
modules 12A-F through passages 38 (see FIG. 4). The polymer which
enters the die modules is extruded to form filaments 14 as has been
described. The polymer manifold design wherein the polymer flows
between the two continuous passages 92 and 94 via a plurality of
parallel holes serves to equalize the flow over the die length.
Heating element 97 maintains the polymer of the proper operating
temperature.
Process Air
Referring to FIGS. 2, 4, 5 and 6. Heated process air enters through
inlet 66 which registers with the circular groove 101 (FIG. 6)
formed along the inner wall of end plate 62. Middle sections 11A-F
have a plurality of holes 102a-d which define continuous flow
passages 103a-d which travel the length of the die as seen in FIG.
2 (103c, d shown only). Air passages 103a-d interconnect manifold
segments 11A-F. The inlets of passages 103a-d register with groove
101 to that air entering the groove will flow the length of the die
from plate 62 to plate 61. The outlets of passage 103a-d register
with groove 106 in plate 61 passages which turns the air and feeds
the air passages 103e, f whereby the air flows back along the
length of the die in the direction opposite that a passages 103a-d.
The outlets to passages 103e, f register with groove 107 formed in
plate 62 which receives the air and turns the air to travel back
along the length of the die through passage 103g which discharges
into groove 108 of end plate 61. Groove 108 feeds passage 103h and
a portion of the air travels back along the die length through
passage 103h while the rest of the air flows towards the manifold
discharge through slot 109 in plate 61. Air which returns to plate
62 via 103h flows towards the manifold discharge through slot 111.
Thus the air makes three or four passes along the length of the die
before being discharge to the die modules. Central heating element
112 heats the multi-pass air to the operating temperature. Arrows
128 in FIG. 2 indicate the direction of air flow. Because the
process of temperature is hotter than the polymer operating
temperature a plurality of isolation holes 115 are provided in
plates 61, 62 and 11A-F to disrupt heat flow between the process
air flow and polymer flow passages of the manifold.
As seen in FIGS. 2 and 8, process air flows towards the manifold
discharge along both sides of the manifold through slots 109 and
111. Plates 11A-F have holes which define air passage 113 which
extends the length of the die. Slots 109 and 111 discharge from
opposite sides into passage 113 which feeds in parallel holes
114A-Fwhich in turn feed associated air input 39 in die modules
12A-F. The air flows through the die modules as has been described
and is discharged as converging sheets of air onto fibers 14
extruded at die tip apex 56.
Instrument Air
Each die module comprises a valve assembly 21 which is actuated by
compressed air acting above or below piston 22. Instrument air is
supplied to the top and bottom air chambers on each side of valve
piston 22 (see FIG. 4) by flow lines 116 and 117, respectively,
formed in each middle plate 11A-F. Three way solenoid valve 20D
with electronic controller 120D controls the flow of instrument
air. Instrument air inlet 118 is a continuous flow passage over the
length of the die. Passage 119 in each plate delivers the air in
parallel to each of solenoid valves 20A-F (shown schematically in
FIG. 4). The valve delivers the air to enter passage 116 or 117
depending on whether the valve 21 is to be opened or closed. As
illustrated in FIG. 4, pessurized instrument air is delivered via
line 116 to the top of the piston 22 which acts to force the piston
downward, while the controller 20D simultaneously opens the air
chamber below the piston to exhaust port 121 via lines 117 and 122.
In the downward position, valve stem 25 seats on port 32 thereby
closing the polymer flow passage to the die tip. In the open
position, solenoid 20D would deliver pressurized air to the under
side of piston 22 through line 17 and would simultaneously open the
upper side of the piston exhaust port 123 via line 124. The
pressure beneath the piston forces the piston upward and unseats
valve stem 25 to open the polymer flow passage to the die tip. Thus
in the preferred mode each die module 12 has a separate solenoid
valve such that the polymer flow can be controlled through each die
module independently. In this mode side holes 126 and 27 which
intersect passages 116 and 117, respectively, are plugged.
In a second preferred embodiment a single solenoid valve may be
used to activate valve 21 in a plurality of adjacent die modules.
In this configuration the tops of holes 116 and 117 (labeled 116a
and 117a) are plugged and side holes 126 and 127 opened. Side holes
126 and 127 are continuous holes and will intersect each of the
flow lines 116 and 117 to be controlled. This is the closed
position, pressurized air would be delivered to all of the modules
simultaneously through hole 126 while hole 127 would be opened to
the exhaust. The instrument air flow is reversed to open the
valve.
Assembly and Operation
As indicated above, the modular die assembly 10 of the present
invention an be tailored to meet the needs of a particular
operation. As exemplified in FIGS. 1, 2 and 3, six die segments
11A-F, each about 0.75 inches in width are used in the assembly 10.
The manifold segments 11 are bolted together as described
previously, and the heater elements 97, 112 installed. The length
of the heater elements 97, 112 will be selected based on the number
of segments 11 employed and will extend through most segments. The
die modules 12 may be mounted on each manifold segment 11 before or
after interconnecting the segment 11, and may include any of the
nozzles 13 previously described. FIG. 3 illustrates four modules
12b-e with meltblowing die tips and two end modules 12a, 12f with
spiral nozzles.
A particularly advantageous feature of the present invention is
that it permits (a) the construction of a meltblowing die with a
wide range of possible lengths, interchangeable manifold segments,
and self contained modules, and (b) variation of die nozzles (e.g.
meltblowing, spiral, or bead applicators) to achieve a
predetermined and varied pattern. Variable die length and adhesive
patterns may be important for applying adhesives to substrates of
different sizes from one application to another. The following
sizes and numbers are illustrative of the versatility of the module
die construction of the present invention.
TABLE-US-00001 Preferred Die Assembly Broad Range Range Best Mode
Number of 2-1.000 2-100 5-50 Units (15) Length of each 0.25-1.50''
0.5-1.00'' 0.5-0.8'' Unit (15) (inches) Orifice (53) 0.005-0.050''
0.01-0.040'' 0.015-0.030'' Diameter (inches) Orifices/Inch* 5-50
10-40 10-30 Different Types 2-4 2-3 2 of Nozzles (13) *filaments
per inch per slot.
The lines, instruments, and controls are connected and operation
commenced. A hot melt adhesive is delivered to the die 10 through
line 64, process air is delivered to the die through line 66, and
instrument air or gas is delivered through line 67.
Actuation of the control valves 21 opens port 32 of each module 12
as described previously, causing polymer melt to flow through each
die module 12. In the meltblowing modules 15, the melt flows
through manifold passages 91, 93, 94, 96, through side ports 38,
through passages 37 and annular space 45, and through port 32 into
the die tip assembly 13. The polymer melt is distributed laterally
in the die tip 13 and discharges through orifices 53 as
side-by-side filaments 14. Multi-pass process air meanwhile flows
through manifold passages 103 where it is heated, into slots 109
and 111, through air passage 113 and is delivered to modules 20A-F
through ports 114A-F, respectively. Air enters each module 12
through port 39 and flows through holes 49 and 57 and into slits
discharging as converging air sheets at or near the die tip apex of
the nose piece 52. The converging air sheets contact the filaments
14 discharging from the orifices 53 and by drag forces stretch them
and deposit them onto the underlying substrate in a random pattern.
This forms a generally uniform deposit of meltblown material on the
substrate.
In each of the flanking spiral nozzle modules 12, the polymer and
air flows are basically the same, with the difference being the
nozzle tip. In the spiral nozzle, a monofilament is extruded and
air jets are directed to impart a swirl on the monofilament. The
swirling action draws down the monofilament and deposits it as
overlapping swirls on the substrate as described in the above
referenced U.S. Pat. No. 5,728,129.
Typical operational parameters are as follows:
TABLE-US-00002 Polymer Hot melt adhesive Temperature of the
280.degree. F. to 325.degree. F. Die and Polymer Temperature of Air
280.degree. F. to 325.degree. F. Polymer Flow Rate 0.1 to 10
grms/hole/min. Hot air Flow Rate 0.1 to 2 SCFM/inch Deposition 0.05
to 500 g/m.sup.2
As described above, the die assembly 10 may be used in meltblowing
any polymeric material, but meltblowing adhesives is the preferred
polymer. The adhesives include EVA's (e.g. 20-40 wt % EVA). These
polymers generally have lower viscosities than those used in
meltblown webs. Conventional hot melt adhesives usable include
those disclosed in U.S. Pat. Nos. 4,497,941, 4,325,853, and
4,315,842, the disclosures of which are incorporated herein by
reference. The preferred hot melt adhesives include SIS and SBS
block copolymer based adhesives. The adhesives contain block
copolymer, tackifier, and oil in various ratios. The above melt
adhesives may also be used.
Although the present invention has been described with reference to
meltblowing hot melt adhesive, it is to be understood that the
invention may also be used to meltblow polymer in the manufacture
of webs. The dimensions of the die tip may have a small difference
in certain features as described in the above referenced U.S. Pat.
Nos. 5,145,689 and 5,618,566.
The typical meltblowing web forming resins include a wide range of
polyolefins such as propylene and ethylene homopolymers and
copolymers. Specific thermoplastics include ethylene acrylic
copolymers, nylon, polyamides, polyesters, polystyrene, poly(methyl
metharylate), polytrifluoro-chloroethylene, polyurethanes,
polycarboneates, silicone sulfide, and poly(ethylene
terephthalate), pitch, and blends of the above. The preferred resin
is polypropylene. The above list is not intended to be limiting, as
new and improved meltblowing thermoplastic resins continue to be
developed.
The invention may also be used with advantage in coating substrates
of objects with thermoplastics.
The thermoplastic polymer, hot melt adhesives or those used in
meltblowing webs, may be delivered to the die by a variety of well
known means including extruders metering pumps and the like.
* * * * *