Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a method for
~mak~ng printahle sel-adhesive tapes, ha~ing a supporting
film made of polypropylene.
It is known -that a film of polypropylene is not
receptive to printing inks and cannot be printed.
It is also known that, in order to m~ke printing
possible, it is necessary to process the surface of the film
with electric charges, or by flame processing, in such a way
as to modify the surface of the film, so as to provide the
chemical-physical conditions suitable for receiving and
holding inks.
This process is carried out to increase surface
tension of the film up to 40 dynes/cm (on the surface of the
unprocessed film it is 30 dynes/cm), to provide a more wettable
film with respect to the printing inks.
By means of the aforesaid processing, the contact
angle is increased between the film (which is solid) and the
inks (which are liquid), so as to facilitate the adhesion of
the inks, ~ccording to the first adhesion law. The measure-
ment of the surface tension is carried out with conventionalsurface tension liquids, according to the methods of TAPPI
and ASTM.
Printing inks are known in the trade which are
suitable for printing processed polypropylene. Such printing
inks are conventionally used for printing materials for pack-
aging applications and the like.
In the case of self-adhesive tapes having a polypropylene
supporting film, as provided for printing applications, it is necessary to
process the film on a surface, in such a way as to allow film to receive
the a~hesive layerj either ~ith or without an i~termediate anchoring layer,
and on the other s~rface thereof, to receive the printing.
.. ' ~
However, this two-step processing may cause
-- 1 --
the so-called blocking phenomena to occur, due ko the strong
adhesion of the self-adhesi~e layer on the back, with conse-
quent breakage during the unwinding of the rolls.
In order to eliminate the above mentioned disadvan-
tage, the application on the adhesive free surface of an anti-
adhesive layer, the so-called "release coat" may be considered.
This antiadhesive layer, however, has the disadvantage of re-
pelling the printing inks.
In some cases it is possible to solve this problem
by applying a lacqueron the back of the tape or by making said
tape of, a mono- or bi--lacquered supporting fï~m.
These lacquered supporting films are commercially
available and mainly used, to make the tape material thermo-
sealable, in addition to being printahle. However, apart from
the cost, the application of theselacquer6 which are general-
ly based on acrylic and vinyl copolymers, in maklng self-
adhesive tapes printable, require the use of a primer. Thus,
the applicatio~ of the lacquer has to ~e carrie~ out in two
steps.
This two step method, however, is different from
the presently used method for making self-adhesive tapes having
a polyethylene supporting film, in which all of the opera-
tions are carried out by a single stepO
It is well known that, the presently used method
for making self~adhesive tapes having a processed polypropylene
supporting film consists of applying, on a face of the film,
an anchoring layer and an adhesive layer and, on th~ other face
of the film, and antiadhesive layer. More specifically, the
anchoring layer, whIch, in some cases may be omitted, is
~enerall~ a solution o~ dispers~on of elastomeric and/or plas-
tics materials. The adhesive layer, however is a solution of
elastomeric materials, modified ~y tackifying resins, in
- 2 -
7~7
organiC solyents, or of aqueous dispersions of elastomeric
and/or plastics mater~als ~l~ernatiYely, said layer may be
adhesive materials based on block elastomeric copolymers, or
plastics materials (e g. acrylic, and polyesters,), or of
solvent free adhesives, based on acrylic prepolymers, poly-
urethane prepolymers, and the like which may be cross-linked
by chemical methods or by radiation, such as U.V and E.B
radiation.
The materials used to provide the antiadhesive layer
are vinyl esters, long chain ~ligher alcohols, preferably
including from 14 to 22 carbon atoms, or polyvinyl carbamates,
also of the long chain type.
These compounds, however, as discussed above, repel
printing inks, so that the self-adhesive tapes obtained can
not be printed.
Accordingly, the present invention provides a self-
adhesive printed tape which is a film of polypropylene, an
~- adhesive layer applied to one surface of said film and an
antiadhesive lacquer applied on the other surface of said
film, said antiadhesive layer being in the amount of 0.5-
1.5 g/m of said tape and being one member selected from the
group consisting of acrylic and methacrylic resins, poly-
urethane resins, polyamide copolymers, and modified cellulose
ethers and esters, and being printed on.
The present invention also provides a method of manu-
facturing a printable self-adhesive tape which comprises:
processing a film of polypropylene to increase the surface
tension thereo~ to a value of 4Q dynes/cm; applying to a sur-
face of the processed fil~ an adhesive layer; applying to the
oppos~te surface, an antiadhesive lac~uer receptive to print-
~ng inks, $aid antiadhes~ye lac~uer being a solution of a
member selected from the group consisting of acrylic resins,
~,~
~ - 3 -
;{~
methacrylic resins, polyurethane. resins obtained by conden-
sation o~ polyenes and ~socyanatesi, pol~amide copol~mers,
and mod~ie.d cellulose ethe~s and esters in an oryanic solvent
and eYaporatin~ the solvent to ~o~m an antiadhesive layer.
Thus according to the present invention, applying
on the surface of the processed supporting polypropylene
film, opposite to the surface provided with the adhesive
layer, a layer of a lacquer ~ased on resins having a good
adhesion to the
-~ - 3a -
~L~g;.~3~7~7
pr~cessed polypropylene film and good antiadhesive or releasing
properties, in such a way as not to deleteriously affect the
tapes unwindin~ characteristics, very good receptivity for
printing inks is achieved.
There are several resins having the above mentioned
properties and which, accordingly, may be used for forming the
self-adhesive layer on the self-adhesive printable tapes.
These resins include acrylic or methacrylic ester copolymers
obtained from acrylic and/or methacrylic acid and alcohols,
polyurethane resins obtained by a condensation of polyenes
and isocyana~es, lacquers based on modified cellulose ethers
and esters, polyamide copolymers and cellulose ester modified
polyamide copolymers.
Such resins thus include 1) arylic or methacrylie
resins, obtained by polymerizing or copolymerizing the following
eompounds: methyl methacrylate, ethyl methacrylate, butyl
methacrylate methyl acrylate, ethyl acrylate butyl acrylates
whieh are commercially available under the trademarks "ELVACITE"
(Du Pont de Nemours), "PARALOID" and "ACRYLOID" (Roehm & Haas),
and "DEGAN LP" ~Degussa Geschaftsbereich Chemie), whieh may be
modified by alkyd, cellulos~, epoxy and, phenoxy resins.
These modified resins are dissolved in organic solvents, such
as methylethylketone, ethyl acetate, toluene, and butyl
aleohol with a solids content of about 20%. 2) Polyurethane
resins, obtained by condensation or polyenes and isocyanates,
commerically available under the trademarks "LIOFOL UK" (Henkel),
and "PENTACOLL" (Wikolin Polymer~. 3) Polyamide copolymers,
commercially available under the trademarks "VERS~ID" (Shering)
and "REAMM~DE" (Chem Plast), modified by plastifiers such as
sulphonamides and cellulose resins, such as nitro-cellulose.
Typical formulations of the lacquers used, are pre-
paring the antiadhesive printable layer are the following:
~3
- 4 -
. .~
7~L~
FORMULATION A
- Paraloid ~ a trademar]c of Roehm ~ Haas, 80 ppm's
Philadelphia)
- Vinylite VMCH, a chloroacetovinyl copolymer
(U.C.C.C., New York) 20 "
- Epoxy resin 828 (a trademarki of Shell Chimica, 5
Milan)
- Metnylethylketone 200 "
: - Ethyl acetate 200
- Toluene 150 "
- Isopropyl alcohol 50
- TS=15%
FORMULATION B
.
- Pentacol PR 19.24 (a trademark of Wikolin 100 ppm's
Polymer Chemi.e, Bremen)
- Hardener MK 40/32 (a trademark of Wikolin
Polymer Chemie, Bremen) 6 "
- Diluent, a mixture of methylethylketone and
toluene 70 "
TS= 15~
FORMULATION C
- Versamid 961 (a trademark of Shering, Milan) 100 ppm's
- - Nitrocellulose l/2 sec (Hercules, Milan) 10 "
- Isopropyl alcohol 300
- Ethyl acetate 300
TS= 15.5%
For preparing self-adhesive tapes provided with a
printable polypropylene supporting film, the expanded mono-
or bi-oriented film, processed on a portion of the film in
such a way as to present a surface tension of about 40 dynes/
cm, is passed to a three headed coating machine, for applying
the so-called "release coat" (thereinafter called RC), an
anchoring layer and a self-adhesive layer, according to con-
ventional methods.
- 5 -
The film side prayided for receiving the RC, in
particulax, is processed by means of the corona effect, in
such a way as to present a surface tension between 36 and 40
dynes/cm.
According to the method of the invention, instead
of the RC there is applied a layer of a lacquer having one of
the shown hereinabove formulations A, B or C, by the Gravure
or Mayer Bar system or any other suitable systems.
The dry end lacquer on the film is present in an
amount of 0.5 to 1.5 g/m
Then thelacquer layer is dried in an oven, in such
a way as to cause the solvents to evaporate.
On the film opposite side or surface there is applied
the anchoring layer, if necessary, and the adhesive layer, of
conventional composition and by conventional methods.
Upon drying the primer and adhesive layer, the
adhesive film is wound in rolls to be converted into tapes
having the desired width and length.
For the thus obtained lacquered tapes there are
determined the tacXifying characteristics on steel and on sup-
porting members, the unwinding force, the so-called "tack" and
lacquer transfer, according to AFERA and PSTC.
With the above formulations A, B and C, were obtained
the following values:
SAMPLES A B C
- Adhesion on steel, in g/cm220 236 200
- Adhesion on supports, in g/cm 160 200 155
- Unwinding force, in g/cm 290 320 220
` - Rolling ball, in tack cm 2 2 1.5
- Lacquer txansfer (upon accelexated
ageing at QC for 72 hl slight none none
The thus obtained lacquered rolls are printed using
- 6 -
suitable conventional printing inks.
There a~e generally used printin~ inks based on
polyamide resins, com,~ercially available, to adhere to the
lacquered surface.
The printing machine can be of the flexographic, Roto
gravure or screening type, suitably modified in order to assure
a complete and perfect drying of the ink and to permit the
application, either simultaneous or successive, of an addition-
al antiadhesive layer.
The antiadhesive layer is such as to permit an easy
unwinding of the tape and prevent backprinting, without dele-
teriously affecting the adhesive characteristics due to migra-
tion and/or transfer phenomena.
The application of the above mentioned antiadhesive
layer is carried out using solutions in organic solvents of
adhesive compounds, by means of the Mayer Bar, Rotogravure,
Kiss-Roll systems, or combinations thereof.
The most suitable antiadhesive compounds are long
chain fat alcohol vinyl esters, containing from 16 to 24
carbon atoms; polyvinyl carbamates; or hemiesters or hemiamides
of long chain aliphatic compounds, having from 16 to 30
carbon atoms, effective to provide a good anchoring to the
lacquered and inked surface.
The antiadhesive compounds are either dissolved or
dispersed in volatile organic solvents, such as aromatic and
aliphatic hydrocarbons, esters, ketones, and alcohols or in
aqueous dispersions with a solids content from 0.2 to 5~,
the dispersing phase being completely removed by evaporation.
Upon evaporating the solvents or dispersing phase,
the antiadhesi~e layer remaining on the lacquered and inked
surface'facil~t~tes the unwi,ndi,ng of the tape, without causing
backprintin~ a,nd without altering the characteristics of the
- 7 -
7~7
applied adhesiYe.
The sequence of the carried out printing operations
carried out on the self-adhesive tape provided with the
lacquered supporting film was the following:
- unwinding of the tape
- flexographic printing in one or rnore colours with suitable
ink~
- drying of the inks
- application of an antiadhesive layer
- drying
- cooling of the tape
- winding of the finished,printed tape.
The characteristics of the printed tapes, obtained by
using the above formulations A, B and C are as follows:
SAMPLES A B C
- Adhesion on steel, in g/cm 225 250 200
- Adhesion on supports in g/cm160 180 155
- Unwinding force, in g/cm 260 280 210
- Rolling ball, in tack cm 2.5 3 2
- Initial backprinting slight slight none
- Backprinting upon accelerated " " slight
ageing at 60C, 72 h.
The measurements have been carried out according to
the AFERA and PSTC Standards.
For "backprinting" it is meant the removing of the
printing or the lacquer by the adhesive.
From the above description and the examination of the
aforesaid characteristics of the printed tapes, the advantages
and technical progress characterizing the method for making and
printing self-adhesive tapes provided with a polypropylene
support~n~ film accordi,ng to the present invention are evident.
; ~ ~ 8 -
I~L
