Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
The invention relates to a resilient compressible element having at
least two lamina, one of which is a compressible layer and the other of which
is a thermosol. The preferred compressible material is that shown in United
States Paten~ 3,147,698, which patent shows the material used in laminates.
United States Patent 3,652,376 discloses additional laminates utilizing the
compressible element of the aforesaid United States Patent 3,147,698. Thermo-
sol materials using polyvinyl chloride plastisol together with the crosslink-
ing monomers 1,3-butylene dimethacrylate and trimethylolpropane trimethacrylate
are shown in the sales brochure of Rohm and Haas Company, CM-32.
It is an object of the present invention to provide an improved
printers packing that will outperform all known packings.
It is the Eurther object of the present invention to provide a new
composition of matter that will make possib:Le the accomplishment of the afore-
said object.
A still further object of the pre~3ent invention is to provide a
superior method of manufacturing printers packing and similar printers ele-
ments. Such a superior method should have as few disadvantages as possible,
for example, substantially eliminating pollution, reducing cost, and conserv-
ing energy. The present invention in particular increases the productivityof labor, manufacturing equipment and space.
To give just some view of disadvantages inherent in prior procedures
known to have been used in producing printing elements, solvent laid elasto-
mers generally require a number of coating passes or a number of in-line
coatings to enable the expeditious removal of the solvent. Elastomers
applied by milling have the disadvantage of poor adhesion, trapping air and
difficult caliper control. While plastisols are not known to have been used
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to produce resilient compressible printing elements they would have the ob-
vious disadvantage of being subject to heat deformation, poor solvent resist-
ance and poor impact resistance.
It might be thought that thermosols would also have disadvantages
such as instability of solution viscosity and likely precuring prior to good
lamination, but surprisingly it has been found that the thermosols are not
only easily coated on to the desired compressible laminas but the thermosols
can be formed into sufficiently resilient lamina with sufficient integrity to
give improved resistance to collapse over long usage compared to the laminate
structures of the prior art.
Summary of the Invention
By an aspect of the invention a new thermosol composition is pro-
vided having about 30 to about 95% by weight polyvinyl polymer containing
plastisol, about 2 to about 20% by weight poly acrylate monomer crosslinkable
with said polyvinyl polymer to form a thermoset polymer and about 2 to about
30% by weight phenolic resin. The thermosol preferably includes a peroxide
free- radical initiator. The polyvinyl plastisol polymer is preferably a
polyvinyl chloride and the acrylat0 monomer is preferably a di- or tri-acrylate.
The plastisol's plasticizer is preferably dioctyl phthalate present in an
amount of about 15 to about 65% by weight of the plastisol.
By yet another aspect of the invention a resilient compressible
printing element is provided that has a compressible lamina and a thermosol
lamina. Preferably the compressible lamina contains voids and is a fibrous
sheet impregnated with an epoxy. The voids preferably comprise at least
about 20~ of the volume of the compressible lamina. The thermosol is prefer-
ably ~he polyvinyl plastisol and poly acrylate monomer type previously des-
cribed.
By other aspects of the present invention other laminas of thermosol
7~
and compressible material and laminas of woven textile may be added. A
thermosol lamina may form an outer wo~king face for the resilient compress-
ible printing element in so~e preferred constructions.
~ y other aspects of the in~ention any material that will crosslink
with the polyvinyl polymer of the plastisol to -orm a thermoset polymer may
be used. Further the thermosol could in some instances be replaced by what
at present is considerad a less desirable flexible material so long as ~he
tensile stress is at least about 800 psi, preferably at least about 1000 psi.
The highly porous compressible lamina is preferably at least 10
mils thick and the thermosol lamina is preferably at least 2 mils thick.
By yet another aspect of the present invention a new and
advantageous process is provided for manufac~uring a resilient compressible
printing element. The process involves simply coating a liquid thermosol
coating at least 2 mils thick onto a lamina, solidifying the thermosol
coating throughout, plying a second lamina over the solidified thermosol
coating, and activating the thermosol coating to adhere the laminas
together and themoset the thermosol. The solidifying is preferably
accomplished by heating to cause gelling and said thermosetting is by
heating to a higher temperature. The preferred thermGsol is the one des-
cribed above.
Description of the Drawings
Figure 1 is a diagrammatic cross section viaw of a resilient
compressible printing element laminate of the present invention labelled to
assist easy following of the description.
Figure 2 is a schematic diagram of a preferred method for carrying
out the invention.
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Description of t]ie Prèferred`Embodiments
First, a defini~ion of the word thermosol: a thermosol as used in
this application means a thermosetting plastisol.
The new thermosol composition of the present invention, in its pre-
ferred form, comprises about 30 to about 95% by weight polyvinyl plastisol,
more preferably about 70 to about 90% and most preferably about 75 to about
85% by weight. The polyvinyl polymer is preferably polyvinyL chloride and
the plasticizer is preferably dioctyl phthalate present in an amount of about
15 to about 65%, more preferably about 25 to about 55% by weight of the plasti-
sol. The composition also contains an acrylate monomer crosslinkable with thepolyvinyl polymer to form the thermoset polymer. The acrylate monomer is
preferably a di- or tri-acrylate and is preferably present in an amount of
about 2 to about 20% by weight, more preferably in an amount of about 3 to
about 10% and most preferably about 5 to about 9% by weight of the total
composition. The acrylate monomer is preferably trimethylolpropane tri-
methacrylate. The thermosol composition pre;Ferably includes a peroxide,
free-radical initiator, preferably present in an amount of .01 to 1% by weight.
The peroxide is preferably a peroxyketal.
An important componentJ and in its preferred form, a critical ingre-
dient of the thermosol compositioll is a phenolic resin. The phenolic resinis preferably present in an amount of about 2 to about 30% by waight, more
preferably about 8 to about 15% and most preferably about 11 to about 13% by
weight. The phenolic resin is preferably of the thermosetting two-step type.
When the phenolic resin is present the composition is, in its thermoset
condition, stiffer but still very resilient and flexible and the composition
provides oetter characteristics as a press packing work surface or interlay
lamina over pliesof resilient compressible material, particularly those plies
or laminas made from highly porous fibrous material.
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~7~9
The thermosol composition can also, of course, contain other
ingredients such as stabilizers, fillers, pigmenting agents and the like.
Turning now to a detailed description of the resilient compressible
printing element which is especially a press packing laminate, one embodiment
is shown in Figure 1. The labeling in Figure 1 is particularly designed to
show the basic structure and indicate additional laminas that may be added
to expand the usefulness of the present invention. The order designations
of the laminas, 1st, 2nd and 3rd, are strictly for illustrative purposes and
not to depict any required order of assembly.
The basic structure is a thermosol lamina which is preferably
directly adhered to a compressible lamina. The preferred thermosol composition
is the one descr:ibed earlier. The thermosol material containing the phenolic
material is adhesive]y very aggressive, particularly with regard to the epoxy
impregnated compressible laminas. Epoxy impregna~ted laminas are usually very
difficult to obtain good adherence with.
The compressible lamlna is preferably that shown in United States
Patent 3,147,698 which is a highly porous Eelted fibrous sheet impregnated
with an elastomeric material. The preferred elastomeric impregnant is one
that includes an epoxy resin. Other compressible materials having voids
therein can also be used; for example, impregnated paper materials, foamed
lamina and even other material such as cork laminas can be used as compressible
layers~ The voids preferably comprise at least about 20% of the volume of
the lamina. While not preferred, the compressible lamina itself can be a
composite material formed of two or more laminas or plies.
As shown in Figure 1, the basic structure can have a woven textile
secured to the compressible lamina of the basic structure. The woven textiles
usedto date are rubber impregnated and in order to provide the desired adhesion
to the textile a rubber adhesive layer about 2 mils thick is used to secure
~ ~ -5-
79
the textile to the compressible lamina. Ilowever, a preferred securing
adhesive layer would be a thermosol. The textile gives additional lateral
strength to the lanlinate. A pressure sensitive adhesive is then applied
to the exposed face of the woven textile and this is covered with a release
sheet. The thus constructed resilient compressible printing element would
normally be utilized by removing the release sheet and sticking the element
to the impression cylinder with the thermosol lamina facing the type face.
A draw sheet or tympon sheet would usually be engaged over the thus exposed
1st compressible lamina, looking at Figure 1. However, the thermosol lamina
in preferred embodiments can itself function as an excellent working surface
and is a considerable improvement in press packing elements, in this sense,
eliminating the need for draw sheets and the like. The compressible lamina
provides for the good compressibility of the printing element and the thermosol
lamina enhances this even more than the prior art facings, in ways not entire-
ly understood.
It is also frequently desired to build up multiple layers of
compressible laminas alternating with laminas of thermosol. It has been
found that the individual lamina of compressible material should preferably
~; be between about 10 and about S0 mils thick, more preferab]y about 20 and
about 30 mils thick to give optimum compressibility qualities. Preferably,
the individual thermosol lamina is at least about 2 mils thick and more
preferably it is held to about 5 to about 75 mils thick, most preferably
about 10 to about 20 mils thick, particularly when employed with multiple
compressible plies. The thermosol's thickness contributes to both overall
lamlnate thickness ~nd the quality of impact resistance.
To build up the multiple alternating layers it is preferable to
join each compressible lamina to the next adjacent compressible lamina by
means of directly engaging each with the opposed faces of a single thermosol
--6--
lamina without the use of or necessity Eor intervening layers or means.
Thus, 1st, 2nd and 3rd compressible laminas may be joined together by 1st
and 2nd thermosol laminas as shown in Figure 1. If a thermosol working face
is desired this composite structure or subassembly can be faced with a
thermosol on one face. If desired for lateral strength the other face of
the sub-assembly may be faced with a woven textile and pressure sensitive
adhesive as previously described and as shown in Figure 1. Alternatively
the thermosol working face may be replaced with a woven textile working
face. The woven textile can be secured by rubber adhesive to the
compressible lamina or in proper instances and preferably by a thermosol.
Obviously, only several variant constructions of the resilient
compressible printing element of the present invention have been described.
Many others are possible. In some applications it might be desirable to add
additional alternate intermediate laminas of compressible material and
thermosol or even other materials such as, for example, dimensionally
stabilizing woven textiles and it will be obvious to those oE ordinary skill
in the art how this can be done using the description given in this patent
application.
Another aspect of the resilient compressible printing element which
is unexpected is that it can have a lamina with a tensile stress at least as
high as about 800 psi or even the more preferred at least as high as about
1000 psi disposed between the printing member or other impinging force
member and the compressible lamina and still have the compressible operate
effectively. This is admirably done by the thermosol lamina of the present
invention hut it is witllin the scope of the invention to cover any resilient
compressible printing element having a new lamina with such unexpected
characteristics. Tensile stress as used in this application is to be under-
stood as determined by ASTM D142-61T.
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7~79
Turning now to a brief description of the process of the present
invention for manufacturing a resilient compressible printing element, it
will be understood that in a preferred form, the thermosol coating such as
the one previously described in this application is applied as a liquid by
coating onto a lamina such as the compressible lamina previously described.
A preferred form of the process is shown in Figure 2. As shown in Figure 2
the compressible lamina 10 may be withdrawn from a roll 11. The thermosol
coating would be applied by the simplest method giving a substantially
uniform coating thickness, as illustrated by the knife coater 12 and the
bank of thermosol 13. The coated lamina 10 is passed through an oven 14
where it may be heated to between about 200F and 220F to cause gelling
and the formation of a solid thermoplastic material. This laminate 15 is
then rolled up in roll 16. The procedure of forming laminate 15 is
considered to be a first stage 17 of the process. This laminate 15 would
be the basic structure of Figure 1 before it is thermoset and could, of
course, be thermoset in this configuration.
The process will now be described in terms of the preferred
embodiment, illustrated in its essential features in Figure 2, for forming
the assembly of Figure 1 when the two outer faces are of woven textile.
Only the three compressible laminas secured together by two thermosol
laminas subassembly, formation is illustrated in detail in Figure 2 with
a word description of how the additional laminas are applied being given
because this is basically considered to be done according to prior art
procedures.
To form the subassembly laminate the roll 16 is shown in Figure 2
to be divided into two rolls 16a and 16b by cutting means 18. Rolls 16a and
16b are then positioned for unwinding and processing in a second or curing
stage 19 o~ the process. A roll lla such as original roll 11 is positioned
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to be unwound providing a lamina lOa to be plied with the laminates 15a and 15b
as illustrated in Figure 2. Guide rolls 20 and 21 may be provided for directing
the feeds into parallel relation. Direction change rolls 22 and 23 may be
provided for directing the ~omposite about curing drum 24. The curing drum may
be operated at a temperature of 300F to 320F at its face. It has been found
preferable to engage the lamina lOa directly against the curing drum 24 to
reduce the risk of blisters forming at its interface with the thermosol layer
to which it is to be joined. Both laminates 16a and 16b preferably have their
thermosol laminas facing toward the curing drum. This orientation brings about
a curing o the thermosol laminas from their unattached faces inwardly. Thus
a good adherence of the thermoplastic thermosol composition is achieved with
the adjacent compressible laminas being pressed against it before the thermosol
becomes thermoset. The plied composite of lamina lOa and laminates 15a and 15b
is in contact with the surface of the drum for a time sufficient to bring about
the adherence of the composite and curing oE the thermosol, approximately 5
minutes in the Examples that follows. The composite is pressed together and
against the drum 24 by an endless rotocure belt 26 which is held in position
by rolls 27, 28 and 29. The newly formed compos:Lte or subassembly laminate 30
is then rolled up in a roll 31. It may be necessary to further heat the
laminate 30 after its formation to assure the complete curing of the thermosol.
This can be done by passing the laminate 30 through the oven 14. Many other
curing devices and procedures could obviously be employed but in these preferred
forms would use the principles of the presently preferred detailed process just
described. It is, for example, felt that it is of importance to cure the
thermosol laminas from their open or exposed faces inwardly for best results.
To apply the outer woven textile laminas to the outer faces of the
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79
subassembly 30 just formed at stage 19 the roll 31 may be positioned as roll
11 in stage 17 and drawn past knife coater 12 where a rubber adhesive is
applied as a solvent cement to its outer face to a thickness of about 2 mils.
The rubber coated composite is passed through the oven 14 to remove the
solvent and then the textile is substantially immediately laid over the
exposed face of the rubber and pressed thereon by passing between two rolls
after which the composite is wound up. The composite is then turned over
and a woven textile is applied to the other side of the subassembly 30 in
the manner just described for application of the first woven textile.
Thereafter a pressure sensitive adhesive is applied over one of the textile
faces by passing this latest composite back through stage 17 bu-t a release
sheet is applied over the exposed face of the pressure sensitive adhesive.
It is preferable to use a thermosol to secure the woven textile to the
subassembly 30 but its formulation for the rubber impregnated woven textiles
is not yet perfected.
If an outer face of the resilient compressible printing element
is to be a thermosl working face then the roll lla of stage 19 of Figure 2
would be coated on its face toward the curing drum 24 with a cured thermosol
lamina. This cured thermosol laminate is formed as shown in stage 17 except
the roll 16 is rerun through stage 17 without the operation of the coater 12
and with the oven operated at about, for example, 340-350F to cure the
thermosol. The laminate 15 with the thermosol cured is then placed in
stage 19 in the position of lamina lOa and fed into the composite with the
cured thermosol lamina disposed against the curing drum 24 and the exposed
face of the compressible lamina against the thermosol lamina of laminate 15a.
A woven textile can be applied to the side of the composite opposite the
working face in the manner previously described for applying such a woven
textile lamina.
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79
Variations in the process to produce other deslred combination
structures will be obvious to those of ordinary skill in the art. In addition
it is obvious that the process itself can be variously modified for convenience,
such as, for example, cutting the press packing laminate to size rather than
rolling it up in roll 31 or providing alternative coating as curing procedures.
The invention is further illustrated by the following examples:
EXAMPLE 1
A thermosol composition was prepared by charging the following
ingredients in the order in which they are listed to a reactor while stirring.
The reactor was maintained at 75F during the charging sequence and the rate
of charging was as rapid as reasonably possible allowing for their even
dispersion within the reactor.
% of Total
Rarts Composition
1. Dioctyl phthalate 60 78.7
2. Polyvinyl chloride resin, dispersion100
grade (Geon 121 , B. F. Goodrich)
3. Phenolic resin (SP6600 , Schenectady25 12.3
Chemical, Inc.)
4. Trimethylol propane trimethacrylate 15 07.4
monomer (X980 , ~ohm and Haas)
5. Stabilizer, barium-cadmium-æinc 3 01.5
(6V6A , Ferro Chemical Corp.)
6. 40% organic peroxide on inert filler0.3 00.1
(Luperco 231XL , Pennwalt Corp.)
203.3 100%
After complete mixing which required approximately 45-60 minutes the
thermosol composition was a thick liquid having the viscosity of about 20,000-
*T.M. -11-
: .
~7~7~
30,000 cps and ready fDr use. In actuality, the thermosol compound was retainedin barrels for about 3 days at ambient conditions prior to use. A highly
porous felted fibrous sheet impregnated with an elastomeric material Buna N
latex and an epoxy resin that is a condensation product of epichlorohydrin
and bisphenol A which is crosslinked with polyamide, was prepared in general
accordance with United States Patent 3,652,376.
As is illustrated in Figure 2, a 25 mil thick sheet of the highly
porous compressible material was drawn from a roll and through coating station
or stage 17. A conventional knife coater 12 applies the thermosol liquid
which is maintained in a bank 13 at the knife blade in conventional manner.
The thermosol was applied in a single pass to a thickness of 12 to 14 mils
and passed immediately through an oven for a dwell time of 5 minutes. The
thermosol was gelled to a non-tacky solid in the oven. After the now 2-ply
laminate exited the oven it was rolled up~ The coated material was then cut
into two rolls. This was actually done by unrolling part of a roll and cutting
it off rather than bisecting a roll as depicted for illustration in Figure 2.
The thus formed and identical lam:Lnates were then positioned in
relative position as depicted in Figure 2 and drawn from their respective
rolls as illustrated in Figure 2 with their thermosol laminas facing toward
the curing drum 24. A compressible lamina identical to the one described
above was then fed between the two laminate sheets and the drum 24 as also
illustrated in Figure 2. The thermosol coated sides of the laminates thus
engaged with unfaced exposed compressible lamina faces. The surface of a
curing drum 24 was maintained at about 320 F under a belt tension (belt 26)
of about 10,000 lbs. to provide a firm pulling together of the faces of the
separate plies producing an adhered composite having a thickness of 100 mils.
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This composite was then run back through the oven of station 17
operated at about 345F for a dwell time ot about S minutes to assure cure of
the thermGsol. The now thoroughly cured composite was then returned to
station 17 and coated with solution of nitrile rubber adhesive to a thickness
of 2 mils and passed through the oven 14 operated at about 220F with the
same in oven time as befoTe to remove the solvent. A 10 mil thick woven
textile impregnated with nitrile rubber was applied over the nitrile rubber
adhesive and firmed thereto by passing between closely spaced rollers. The
thus formed composite was turned over and run back through station 17 and the
procedure just described repeated except the woven textile was 5 mils thick.
The now formed composite was then passed back through station 17 and an
acrylic pressure sensitive adhesive was applied to the exposed face of the 5
mi]s thick textile to a thickness of approximately 2 mils and passed through
the oven at approximately 310-330F for a 5 minute dwell time and a release
sheet applied thereover in the same manner as the previous application of the
woven textiles.
The press packing laminate of ~xample 1 was tested on a standard
letterpress machine and found to perform in a superior manner to present
commercial press packing.
EXAMPLE 2
; The procedure of Example 1 was repeated except that a roll of the
gelled thermosol laminate produced in the first station 17 of the process
was cured by being passed back through the oven of station 17 without being
additionally coated. The ovcn was operated at about 345F and the laminate
had a dwell time of about 5 minutes in the oven. The thus formed cured
laminate was thcn taken to the compilation-curing station 19 and positioned
in place of roll lla with the cured thermosol lamina f~cing the curing drum
24. This composite was then run back through the oven of station 17 operated
79
at 3~l0 to 350 F for a dwell time of 5 minutes to assure cure of the thermosol.
The now thoroughly cured composite was then returned to station 17 and a woven
textile lamina and pressure sensitive adhesive and release sheet were added as
described in Example 1 to provide the laminate of Figure 1 having the thermo-
sol working face.
The press packing laminate of Example 2 tested on a standard letter-
press machine and found to perform in a superior manner to present commercial
press packing.
EXAMPLE 3
The procedure bf forming the cured laminate of the basic structure
of Figure 1 was carried out as described in ~xample 2 and then the woven
textile, pressure sensitive adhesive and release sheet were added to the ex-
posed face of the compressible lamina as described in ~xample 2 to produce a
more basic press packlng laminate having only the basic structure plus sub-
laminas directly adjacent to the compressible lamina.
The press packing laminate of Example 3 was tested on a standard
letterpress machine and found to perform in a superior manner to present
commercial press packing.
A single thermosol lamina 60 mils thick was Eormed and tested on a
~0 Scott Tester and found to have a tensile of 1,600-1,900 p.s.i., an elongation
of 200-250%, and a tensile stress at 100% elongation of 1,200-1,500 p.s.i. and
tested on a durometer and found to have a Shore A hardness of 83-85.
From a processing standpoint, the procedure of the present invention
eliminates the use of solvents for the laminas that are thermosol and also
the necessity of using adhesives of different characteristics on the facing
surfaces the compressible lamina and the resilient lamina (the thermosol) to
provide an adnesion between them that will withstand the long term use to
which printing elements are normally exposed. The phenolic component of the
*T.M. -14-
37~
thermosol has been pointed out to be important in this regard as well as lend-
ing stiffening properties o~ a desirable and generally indeterminant character.
In addition the identically same lamina that provides the adhesion between
laminas and internal stability can also provide a working face and vice versa.
This working face even lends itself to grinding when desired to achieve very
exacting caliper.
Further, the flexibility of the manufacturing procedure provided is
very great. Rolls of compressible material coated with gelled but unset ther-
mosol can be prepared in advance and then variously combined to meet order
needs on a tailor made basis. In addition multiple plies may be secured
together and the whole composite cured in a single pass over a curing drum.
Thus inventory requirements, labor productivity, plant space productivity and
energy productivity are greatly increased.
It has been found in printing test runs that when the thermosol
coating overlies the compressible lamina so that the thermosol lamina is en-
gaged either with the drawsheet or with the back of the material that is being
printed, the composite is extremely resistant to sinking over a long life,
providing an unexpectedly superior printing press packing. Even more
importantly, the print quality is superior - sharp and clear. I~hile the
compressible lamina provides good compressibility in the printing element, its
compressible performance is enhanced by the thermosol work surface of the
present invention compared to any of the prior art facings, in ways not
entirely understood. Furthermore, the integrity of the laminate is excellent.
No present day press packing offers such superior printing perform-
ance and long life or such superior adaptability to the simplest type of
assembly of a basic component into a multi-ply composite.
It will be obvious to those skilled in the art that various changes
and modifications may be made in the invention without departing from its true
7ii~
spirit and scope. It is, there~ore~ aimed in the appended claims to cover all
such equivalent variations~ as fall within the true spi~it and scope of the
invention.
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