Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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H~UFACTURING HETHOD 0~ ReLEAS~ PAPER
TECH~ICAL YIELD OF THE INVE~TIO~
The present invention relat~s to a metho~ for manufacturing a release
paper by an extruslon laminating process, and more partlcularly to an
e~icient and ~conomlcal method for man~facturin~ a releasQ paper by an
extrusion laminating proce3s.
T~C~NICAL B~C~ROUND
Prior methods used to manufactu~e sil~cone relsase papers ccn~lsted
mainly of coating, the method consisting of forming ~ resln layer, 8 normally
a polyethylene laminate, on a substrate such as paper and coat~ng a layQr gf
release agent on its surface. ~he release agant used in this metho~ consists
of, for instance, polymethyl hydrogen siloxanes and vinyl ~roup-contalnin~
polydimethyl siloxanes. An addition reaction taXe5 place in the pr~sence of
platlnum catalysts unaer heating, and the reaction pro~uct sats to form a
release film.
Also, as in the present invention, there is known a method of formlng
a ralease layer on a substrate b~ an extrusion laminatlng process in a slngle
passl but when this method ls used, the resin laminate ltself has release
properties. ~s such a release resin, there is used for exampl2, ethylene~~
olefin copolymer elastomer, and it is suitable for acrylîc adh~sives.
When the for~er coating process is adopted, Eirst polyethylene
lamination is carried out on the substrate and then the coating of the release
a~ent, such as silicone, is carried out in a separat~ step. Thus, the process
is a two step process, this being disadvantageous in terms of e~uipment~ time
and costs. Furthermore, the release agent applied by coating is ganerally
used together with an organic solvent, which can be accompanied by ~rave
production problems such a5 fire, explosion and environmental pollutlon.
~ n the other hand, in the latter extrusion laminating process usin~
an ethylene- ~~olefin copolymer elastomer etc. there is concern about heat
resistance and resistance to solvents etc. at the time of coating, about
dimi~ishing of release potential with re~ard to acrylic adhesives, and
furthermore the release potential increases with the lapse of time. ~lthough
e~hylene-~ -olefin copolymer elastomer is difficult to extrude whén it is used
alone, and h~nce is used, mixed wlth polyethylene, the release effect
diminishes with a decrease in the proportion of the elastomer present, whereas
PAT 8283-1
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an increase in its proportion results in stronger elastomer charactar~tics
causing loss in film strength and givin~ rise to workin~ difficultie~ such as
blocking.
ThQ present inventors trie~ that method for extrud;ng the r01ea e
a~ent hitherto used in the coating proces5 in combination with polyethylene to
attempt to eliminate the defects of bvth methods. It ~urned out to lack
cowpatibility and to be extremely difficult to extrude due to its poor film
formin~ prop~rty and poor stretch. Also curin~ was extremely dif~icult even
i~ laminatlon should have been ~easible. Continuin~ thelr in~nsive stu~ies,
they discovered that extrusion could be marke~ly improved by a~ing a ~e~tain
substance to the compo--nd, and that then curing could be easily accomplished
effectively an~ thus resulted the present invention.
DISCLOSURE OF TH8 I~VENTIO~
The present lnvention relates to a method of manufacturing a release
paper characterized in that a mixture o~ polyolefin snd a sllicone release
agent compatible th0rewith comprislng the r~action product of polymathyl
hydrogen slloxane and a vinyl group-contaln~ng poly-dimethyl siloxano w~th at
least one olefin or polyolefin having one or more double-bonds i9 extrudad
onto a substrate of paper, fabric, film etc., the laminate is then heat
treated to cause the release agent contained in the mixed layer of the
above-mentioned laminate to bleed onto the surface of the mixed layer to be
thus localized and that the localized release agent is fixed by cur~ng.
As a release agent suitable for use in the method of the prasent
invention, preferred is a silicone release agent co~patible with polyolefin,
being the reaction product of polymethyl hydrogen siloxane, a vinyl group-
containing polydimethyl siloxane, and at least one olefin or polyolefin having
one or more double-bonds as the third component.
As olefins containing one or more double-bonds there can be used
those having 16-24 carbon atoms such as octadecene, while the polyolefins
which can be used, for instance, include 1,4-polybutadiene alone or mixed with
1,2-polybutadiene, polyisoprene, polybutene etc. and mixtures tharsof.
An example of the manufacturing method for the release sgent consists
in mixing polymethyl hydrogen siloxane (including polymethyl hydro-d~methyl
siloxane copolymer), a vinyl group-containing polydimethyl siloxane and the
above-mentioned third component, adding di-tertiary butyl peroxide as
PAT 8283-1
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cntalyst, proceedln~ wi~h the renction under heatin~ and stoppin~ th~ reaction
simultaneously with the recognition of the start of ~ellin~. AlternatiYely,
polymethyl hy~ro$en siloxane and the third component may be pr~liminarily
cause~ to react under hea~in~ with ~i-tertiary butyl peroxi~e as a catalyst
and the reaction product further reactea with ~he vinyl group-contain~ng
polydimethyl siloxane or the third component may be simultaneously mix~ and
reacted under heatin~ wlth di-tertiary butyl peroxi~e as t~a catalyst and t~e
reaction may be stopped simultaneously with the recognitlon of the start of
~ellin~. If t~e reaction is stopped before the start of gelling, the later
curin~ is imperfect, w~ile, if gellin~ is allowed to proceed too far,
localization o~ bleeding onto the surface of the r~lease ~gQnt becomeg
difficult. After stopping the reaction, the rea~tion proauct is ref~ne~ by
vacuum treatment to eliminate the unreacted volatile components.
The release agent synthesized by the above-mentioned mathod ls mixed
with polyolefin resin a~ a rate of approx. 1 to 10 wei~ht ~, more preferably
2 5 wei~ht ~ based on tho polyolefin resin, and kneaded and p~lleti~ed by a
pelletizer to form the resin for the mixed layer ~resin for extru~lon).
Through adjustment of the amount added, it can be made efPective for use as a
release a~ent for various adhesives and urethane hard foams etc.
As the polyolefin to be used in the method of the present invention,
polyethylene, polypropylene, 4-methyl pentene-l resin, ethylene-vinyl acetate
copolymer resin and mixtures thereof can be mentioned. As the polyethylene,
linear low density polyethylene with a density of 0.910-0.935 g/cm is
particularly suited for its low speed peeling property and, since it can be
heat treated ana cured at a high temperature, it is sdvantageous in that it
can be heat treated and cured in a short len~th of time. To accelerate
localized bleedin~ it is possible to add ethylene-vinyl scetate copolymer
resin, polyvinyl ether or the like which acts on polyolefin as a sort of
plasticizer.
The release layer resin thus obtained can be extruded onto the
substrate by an extrusion laminator and a release layer is formed thereby on
the subs~r~te. As the substrate for the p~esent invention, paper, fabric,
film, metallic foil and laminatss thereof can be used.
The laminate formed on the substrate is heat-treated. Heat treatment
is done by allowing the laminate to stand for approximately 10-60 minutes
PAT 8283-1
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after its qurface temperatur~ has reache~ approxlmately 70-120 C. By heat
treatment the rele~se a~ent contained in tbe mixed lay~r bl~s towards the
surface of the layer ~o be lccalized, and simulate the state in which the
release agent is coa~sd on the surface of polyethylane layer as in the
conventiDnal process. This is confirmed by measurement of ~he FT-ATX-I~.
The thus localized release agent is perfectly cured and fixed by
catalytic ~reatment by the use of, for instance, c~iloroplatinic acid. Curin~
temperature is preferably approximately 100-130 C and curin~ time
approxi~ately 1-60 minutes. Hence in a range in which the temperature and
time of hea~ tr~atment and curin~ are overlapped, localixation an~ curing msy
be carried out simultaneou~ly. The aose of chloroplatsnic acid is preferably
~n a range of 2 x 10 to 3 x 10 m~m . Fixing by curing of th~
release agent is no~ li~ited to the use oE platinum as atalyst but fixing by
curing by the use of other catalysts, such as ultraviolet rays, electron
beams, gamma rays, etc. is also feasible. The method of applying the catalyst
is not limited to surfaca coating.
~ccor~ln~ to the present invention, an adhes~on enhancing layer such
of polyethylon~ may be provlded between the release agent and the substrate
for improving the adhesive stren~th therebetween.
OPTI~UI~ EUBODIMENT FOR EXECUTING THE INVENTIO~
Uereafter the present invention i5 explained by ~ivin~ examples and
control examples, but, needless to say, the present invention is not limited
thereby. Parts and percentages given hereafter mean parts by wei~ht and
percent by wei~ht unless otherwise specified.
Example 1:
6.6 parts of polymethyl hydrogen siloxane ~P=5-7~, 90.1 parts of
vinyl group-containing polydimethyl siloxane (P=150, vinyl group 0.7%), and
3.3 parts of polybutadiene ~MW=1600, 1,4 bondage accountin~ for 99%) were
charged into a reactor, 0.286 parts of di-tertiary butyl peroxide was added as
catalyst w~en the mixture was heated to 120 C, and reaction was allowed to
proceed for 10 hours at 120 C, and the reactor was cooled simultaneously
with start of gelling to stop the reaction. The reaction product was treated
by refinin~ for S hours st 110 C at a reduced pressure of 5 mmH~ for the
elimination of unreacted ~olatile components.
There was added 3~ of the resulting release agent to low-density
PAT 8283-1
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polyethyl~ne ("~-lOPt ~(TM~ of Hitsui Pclychemical, MI:9.5, density: 0.917
gJcm ) and p311ets for the mixed layes were prepared by a pell~tizer at a
die temperature of approx. 200 C. The samQ low-~en~;ity polyethylene as was
u~ed for the mixeB lay~r was used for the formation o~ the adhesion er.hancing
layer.
As a ~ubstrate 73 g~m "Clupa~' (T~) unbleac~d ~raft pap~r was
used. Pulyethylene for the adhesiv~ ~nhancing layer was extruded by an
ordinary co-a~trusion laminator at 8 die temperaturQ of 310 C with the
simultan~ous extrusion of pellets for ~he mixe~ layer at a d~e temperature of
280 C, and a 3-lay~r laminate of substrate-adhe~ion enhancin~ layer-mix~d
layer was thus prepared. The thickness of the mixed layer was 20 u~ and that
of the adhesion Qnhancing layer was 20 ~. The thus formed e~truslon`s
properties are shown in Table 2.
Then the 3-layer laminate was cut ln sheet form and was treated for
10 min. at 120C wlth the rolease layar up.
After heat treatment the surface of tha mlxed layer was coated w~th
1.7 x 10 mg/m chloroplatlnic aci~ (0.001~ IPA solutlon) and cured aga~n
for 20 minutes at 120C an~ the role~se papor was obtained.
Of the release paper thus obtained, the release pctential and
residual adhesion stren~th was measured as follows:
Adhesive tape:
For the test acrylic adhesive ~raft tape t"Elm (TM) tapa", Soken
KaXo) was cut to a size of 25 mm wide and 210 mm long.
~easuring conditions:
The above adbesive tape was stuck to the above-mentioned release
paper by pressing, one stroke and back, at a speed of S mmtsecond with a
rubber roller of 4.5 kg in wei~ht, and th~ release potential and residual
adhesive strength were measured under the following conditions. A~ter
stickin~ of the tape, the measurement was taken after sgeing for 20 hours
under a pressure of 20 g/cm in an atmosphere of 70 C and 65% RH.
Measuring method:
The force required for low speed S0.3 m/min.) peeling was measured by
autograph tension tester ("Strograph-R," (TM) Toyo Seiki~ and that for high
speed (3 m/min., 20 m/min~) peelin~ was measured by hi~h speed peeling tester
(Tester Sangyo (TM)3 both a peeling angle of lR0 . ~easurement was taken
PAT 8283-1
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under the conditions of 23 C and 65~ RUI.
The res~lts of measurement are sbown in Tab3e 1.
Example 2
In Example 1, polybutadiene was replaced by polyisoprene (~W = 29000)
and the r~actlon con~ltion was ~hanged to 120 C ~ 14 hours and with the
resultln~ release paper, testing was done as aescribed in Example 1. The
results are shswn in Table 1.
Example 3
Polymethyl hydrogen siloxane used in ~xample 1 was admixed w~th
polybutene ~W = 1450) and di-tertiary butyl peroxi~e was aa~sd as ~atalyst
and after 2 hours of prelimlnary reactlon at 120 C 9 ~inyl-~roup containlng
polyaimethyl siloxane usad in Exampl~ l was caused to react ~or 4 hollrs at
120 C and the release paper was obtained in otherwi~e the ~ame way, and with
it tests were carried out in the same way as describa~ in Example 1. The
mixin~ ratio of the indlvidual reaction components W8S the same as ln Example
1 and the coatin~ rate of chloroplatlnic acid was 1.8 x 10 lm~m . The
results are shown in Table 1.
Example 4
In Example 3, polybutene was replaced by octadecene and after 2 hours
of preliminary reaction at 120C, reaction was conducted for 3 hours at
120C and a release paper was preparea in otherwise the same way and with it
tests were made in the ~ame way as described in Exsmple 1. The coatin~ rate
of chloroplatinic acid was 1.6 x 10 mg/m . The results are shown in
Table 1.
Control example 1
Polybutadiene used in Example 1 alone was mixed at the same ratio
(0.099~) with low-density polyethylene, a 3-layer laminate was obtained in the
same way and it was heat-treated for 10 minutes at 120 C, and with it tests
were made in the same way as described in ~xample 1. The results are shown in
Table 1. hptitude for lamination was satisfactory.
Control example 2
In Control example 1, polybutsdie~e was replaced by polyisoprene used
in Example 2 and release paper was prepared in otherwise the samé way. The
results are shown in Table 1. Aptitude for lamination wss satisfactory.
Control example 3
PAT 8283-1
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In Control exampl¢ 1, polybutadi~ne was replaced by polybutene us¢d
in ~xa~ple 3 and release paper was prepared in othe~lise the same way. The
results are shown in Table 1. Aptltude for lamination was satisfactory.
Control example 4
In Control ex~ple 1, polybutadi~ne was r~plsced by oeta~ecene us~
in Example 4 and release paper WBS prepared in other~lise the same ~ay. Th2
results are shown in Table 1. AptitudQ ~or la~inaticln ~as satisfactory.
Control e~a~ple S
Low-density polyethylene use~ as base resin in e~mple 1 only was
extruded onto the same substrs~e for preparation of 1 lamlnate, and with it
tests were carried out in the ~ame way as described in Example 1. The results
are shown in Table 1. Aptitude for laminatlon was satisfactory.
Control sxample 6
A mixture of 1.7 parts of the mixture of polymethyl hydroger silox~ne
and 98.3 parts of vinyl group-containing polydimethyl siloxane was added in an
amount of 2.901~ to low-density polyethylene in the same way as descrlbod in
Example 1 and pellets for the mixed layer werQ prepare~.
Lamination W8S carried out by extr~dlng polyethylene for the adhesion
enhancing layer using a coextrusion laminator at a die temperature of 310 C,
and the layer thickness was adjusted to 20 ~. Using pellets for the mixed
layer an attempt was made for extruding it at a die temperatur~ of 280 C
with expected layer thickness of 20 ~. The ext~lsion rate was substantially
reduced and subject to marked fluctuation, and although extrusion was somehow
carried out, the film thickness was subject to marked scattering as was the
laminate film width and the resulting laminate was hardly useable in
practice. The extrusion performance is shown in Table 2.
Curing was not feasible although an attempt to cure wa.s made under
the same conditions as in the present invention, and the sillcone release
agent in the release layer migrated into the adhesive tape layer, this
resulting in the lowering of the release performance.
As is apparent from the above results, conventional silicone release
a~ent intended for coating has no aptitude for lamination, cannot be cured and
is not usable as a release agent of the present invention.
PAT 8283-1 7
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(1) Mea~ured values are all in unit of g/25 mm.
(2) Residual adhesion coefficient
= (A/B) x 103
where: A = Adhesive æ~reneth of standard adhesion tape aft~r
contact with release pa~per
B = Adhesive stren&th of standard adhesion tape
before contact with release paper
Table 2
Release agant of Conventional release agent
present invention
(Example 1) (Control example 6)
1. Compatibility Good Poor
w. polyethylene
2. E~trusion rate Slightly reducad Considerably decreased, and
sub~ect to marked fluctuation
3. Catching of Good ~ad due to screw slippage
resin by screw
4. Laminatlng No film deflection Some film deflection.
Good elongation Increased "neck ln" due to
decrease of extrusion rate
5. Aptitude for Positive Negative
lamination
(Overall
evaluation)
PAT 8283-1
~ii3~
As is apparent from Table 1, an olefin or a polyolefin having one or
more ~oubl2-~bonds as used in the present inven~ion is a minus factor in the
rel~ase effect but a5 seen ~rom Table 2, it is apparent that it plays an
important rQle with regard to improving laminstion in the process of
manufacture of releasc paper by the extrusion method. According to the
present invention, Exhibiting a good release effect a:re the two components of
the polyorganosiloxane type w~ich assume a three-dimensional crosslinklng
structure by fixation by curing.
IMDUSTRIAL POSSIBILITY OF UTILIZ~TIQ~
Ac~ording to the present inven~ion, compatibility ~ith polyolefin3,
the ilm forming pr~perty and stretching propertg were i~proved through
reaction of an olefin or a polyole~in having one or m~DrQ double bonds as a
third component with release components, and its extrusion properties can be
astonishinely improved. Also since the relaase agent is localized and fixed
at a hieh concentration on the surface of the release layer by heat treatm~nt
and curing, a remarkable release effect can be attained despite the small
proportion of relea~ agent to polyolefin and as a result a manufacturlng
method for release paper, which is che~p and high in product~vity can be
provided.
The release paper of the present invention, is widely used as a
release paper for adhesive tape, tack paper and stickers etc., as a "process
paper" for synthetic leatherette, urethane etc.
PAT 8283-1
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