Note: Descriptions are shown in the official language in which they were submitted.
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WALLCOVERING ~IATERLAL CON~ PREPASTE AD~ESIVES
Background o f the Invention
1. Field of the ~nvention
The presen~ invention relates to novel aqueous polymer emulsions which are preferabbJ
partially or fully hydrolyzed and are particularb suited as wallsovering prepaste a~hesives.
5 More speciffcally the invention comprises forrning an aqueous emulsion of a vinyl ester
with an amount of one or more water soluble monomers to yield a produc~ which has
adhesive properties. Particularb preferred emulsions have a viscosi~y of 12ss ~han 1000
centipoises.
10 2. Technolo~y Description
A number of materials have been proposed for wallcovering paste materials and ;;
particularly for wallpaper prepaste adhesive~. A wallpaper prepaste adhesive is a
material which is applied to one side of the wallpaper subs~rate and ~hen is dried on the
15 substrate. To adhere the paper to a wall the substrate side with the prepaste adhesive
or more commonly the entire wallpaper sheet is moistened typically with water to cause
the adhesive material to swell. Tlle adhesive side is applied to the sur~face to be covered.
An altemative method of appfying wallpaper to a surface is to use a brush on adflesive
which is applied to an uncoated surface of the paper just prior ~o application of tlle
20 paper to the wal~ While both methods for applying wallpaper ~o a wall are used the
wallpaper prepaste method is far more common.
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Known prepaste adhesives for wallcoverings include stanch based materials, modified
cellulose materials, alk~line-soluble oil-in-water (O/W) emulsion materials and cross-
linked acrylamide-sodiurn acrylate materials in a water-in-oil (W/O) emuls1on. In
selecting a prepaste adhesives, the material selected should possess ~he following
at~ributes: can be applied in one pass, i~ environmental~ safe, is cost effective, is easy
to handle, is non-~oxic; demonstrates good paste properties and is compatible with
commercially available coatlrlg machines. Despite the success of tlle above materials,
none can satt'sJy all of the above criteria
A representative example of a starch based adhesfves is described in US. Patent Na
3,696,065. Starch adhesives are typically applfed to wallcoverings in either powder or
aqueous form. These materials can be environntentalb deleterious as they can produce
dust upon application to ~he substrate and when app~ying the covering to a surface
Further, starch based adhesives are not necessarib heat stable and as such are limited
in their use. For example, they cannot be used in applica~ons which involve hot
embossing procedures. U.S. Patent No. 3,696,065 specificaUy discloses the addi~fon of
a small amount of a vinylpyrrolidone/vinyl acefate solid copoiymer to the starch to
improve its adhesiveness.
A representative example of a modified cellulose based adhesive is described in U.~
Published Applica~'on No. 2,054,628. Modified cellulose adhesives are typical~y applied
to wallcoverings in either powder or aqueous forrn. These materials can be
environmentalb deleterious as they can produce dust upon application ~o the substrate
and when appbing the covering to a sur~ace. Further, modified cellulose based adhesives
are not necessarib heat stable and as sr ch are limited in their use. For example, they
cannot be used in applications which involve hot embossing procedures. These materials
often do not provide as much adhesion as desired.
A representative example of an alkaline-soluble oil-in~water emulsion ~ype adhesive is
described in U.S. Paten~ 4,741,790. To produce a wallcovering having one side coated
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wifh the prepaste adhesive, a two pass coating ~echnique is used. In a first pass, an ionic
material which is acidic in nature is coated onto a sllbstr~te. Thereafter, in a second
pass a layer of base, typically Na2C03 is coated over ~he initial coa~ing to neutralize the
acid present in the ionic materiat. This method, while practiced commercially, suffers
S in that it requires two precise coatfng passes ~o yield a satisfactory finat product. This
can prove to be both cumbersome and costb~.
,4 representative exarnple of a cross-linke l acrylarnide-sodium acrylate polymer ma~enal
in a water in oil emulsion fs descrtbed ln Canadian Patent No. 1,304,185. The adhesive
10 polymerfcmaterialsarecoatedontoasubstrateinamineralspiritsolvent. Whflesuch
materials have gained wide commercial accepfance, they contam an orpanic solvent,
which causes the volatile organic content (VOC) of ~he resulhng emulsion to be highe~
than idealty desired. As such, these organic solvent-based materiats are su~ject to
environmental scrutiny.
I5
Hybrids of the above-described prepaste adhesives have been proposec~ ~or exarnple,
U.S. Patent No. 4, 7l9,?64 teaches an adhesive cornposition made from a blend of an
aqueous emulsion of a po~mer of vinyl acetate, an organic solven~ solution of a
copolymer of vinyl acetate a>ul vinyl pyrrotidone having dextrin dispersed theKin and an
20 aqueous emulsion of an ester gum taclafier. Such materials still face scru~ty because
of the VOC issue. Further, the starch present in these materiats can cause the above-
described heat stability problem. Accotdingly, these may not be ideal candidates for
prepaste adhesives
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25 Copol;ymers and blends of homopolymers of vinyl acetate with one or more monomers
are known for a variety of uses. ~or example, U.S. Patent Na 3,345,320 discloses a
solid vinyl pyrrol~done/vinyl acetate copolymer which, when combined with u plasticizer,
is useful as a hot mel~ adJIesive. U.S. Patent No. 5,122,582 discloses the use of a clear
aqueous solution containing a copolymer of N-vinyl pyrrolidone and vinyl acetate which
30 is useful as a hair se~ttng lotion or gel. rhe article ~'Polymers of N-~nylpyrrolidone~
Synthesis, Characterkation and Uses', Pohvmer Journal. Vol. 17, No. 1, pp. 143-152
(1985), sug~,~ests ~hat copolymers of N-vinylpyrrolidone can be used as adflesive sticks and
as re-moistenable adhesives. T7te article fails ~o disclose ~he use of such copo~mers Ut
aqueous emulsion form.
..
U.S. Patent No$ 3,166,525 tmd 3,691,125 disclose aqueous emulsions of copo~mers of
vinyl ace~ate with N-vinyl pyrrolidone prepared in the absence of an emutsifier or
protective colloid. U.S. Patent No. 3,166,525 suggests a number of uses for the
emulsions, ot the copo~mers recovered afterremoval of water including texnle and other
f nishes, anti-snag f ntshes for hosiery, sizings for cloths and f bers and as adhesn~e base
materials for paper, plashcs, metals, ceramics and the like. Accvrding to the exa nples,
the viscosity of the emulszons pro~uced are extremely high (80,000 cps). As a resul~, the
emulsions could not be used as wallpaper prepaste adhesives as it woukl be impossible
to use them with commercial coaters.
US. Patent No. 3,691,125 produces the above copolymers in emulsion form an~ uses an
amount of a poly-N-vinyl lactam, preferably poly vinylpyrrolidone as a seed material.
According to the examples, the viscosity obtained when producing a copofymer of viryl
acetate and N-vinyl pyrrolidone rangesfrom about l3,200 to about l4,700 cps (lixample
1) and abou~ 4060 cps (Example 2). These emulsions could not be used as a wallpaper
prepaste adhesive as it would be impossible to use them with commercial coaters.
US. Patent No. 4,251,400 discloses adllesives based upon po~vinyl acetate. More
specifically, the adhesive compnses an emulsion blend of polyvinyl ace~ate,
polyvinylpyrrolldone and a plasticizer. Tlle adhesive is suggested for use by children as
it can easily be removed from clo~hing. This product cannot swell in water, and as such,
i5 not usefi~l as a prepas~e.
Despite the above, there still exists a need in the art for a~t environmentally safe aqueous
emulsion which can be used as a wallcovering prepas~e adhes~ve.
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Summary of the Invent~on
In accordance wi~h the presen~ invention novel aqueol s emulsion(s) having a lowS viscosity and adhesive properties are provided. The emulsions primari~ funcnon as
adhesives and more specifically as wallcovering prepaste adhesives. Also provided are
~he process for preparing ~he novel emulsions a wallcovering having at leos~ one side
coated with the emulsion to render it adherable ~o a surface an(d the process for
preparing the wallcovering. Final~ ~he present invennon provides additional novel
I 0 emulsions which may be used as wallcover~ng prepas~e adhesives or as brush on pastes.
One embodimen~ of ~he present inven~ion comprises a s~able aqueous emulsion
comprising
(1) be~ween about 20 and about 50 weigh~ percent syn~hetic polymer soli~s said solids
comprising a copo~ymer or a ~erpo~ymer derived from~
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(a) between ubou~ 60 and aSout 90 mole percen~ of a Yinyl es~er op~ionalh ;~including vinyl alcohol derived from said vinyl ester;
(b) behYeen about 10 and abou~ 40 mole percent of one or more water soluble
monomers; and ~-
(c) between about 0 and about 10 mole percent of an alkyl acryla~e or alkyl
methacrylate wherein alkyl represents an alkyl group containing between 1 and
20 carbon atoms;
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(2) between about 0.5 and about 5.0 weight percen~ of one or more surfactants orprotective colloids; and
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(3) ~he balance water;
whereir~ said aqueous emulsion has a viscosity of less than I 000 cps at 25C and wherein
said emulsion can provide adhesive propern'es.
In partfcularly preferred embodiments, the po~mer fs partfal~y or fully hydrolyzed and the
solids before hydrolysis are either a copolymer of vinyl ace~ate and vinyl pyrrolfdone, a
terpolymer of vinyl acetate, vinyl pyrrolidone and acrylarnide or a terpob~rner of vinyl
ace~ate, vinyl pyrrolidone and ethyl acrylate. Further"o yield a superior product, the
10 polymer solids may be crosslinkeçl A preferred ~se of the aqueous emulsion is as a
wallcovering adhesive, and particularly a wallpaper prepas~e adhesive. In ~he preferred
hydrolyzed embodiments(ie., co-or terpolymer), the emulsions are extremely heat stable;
a property which is required in wallpaper manufacturing (e g. heat emboss~ procedures
and expandable processing for polyvinylchloride expandable wallpapers.)
Another embodiment of the present invention comprises the process for producing the
above emulsion by copolymerizing the monomers of (a) an~ (b) in an aqueolls medium
having a polymer solids content by weight of about 20 to 50 percent and contauu'ng
between about 0.5 and about 5.0 weight percent of one or more surfactants or protective
20 colioids.
Still another embodiment of the present invention comprises a wallcovering material
comprising a substrate having a water remoistenable adhesive on at least one of its
surfaces, said adhesive being derNed from the clbove defined stable aqueous emulsion.
In preferred embodiments, the wallcovering material mc~y take fhe form of stn'ppable
wallpapefi vinyl wallpaper, peelable wallpaper, foil wallpaper, cloth fabnc and silk with
stnppable wallpaper and vinyl wallpaper being pa~cularly preferred.
30 Another embodiment of ~he present invention comprises producing a wallcovering
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comprising a substrate having a water remoistenable adhesive on at least one of i~s
surfaces compr~ing the s~eps of app~ing the above defined aqueous emulsion onto at
least one surface of a substrate and then drying the emuls~on on the surface. :
S In preferred embodiments, application of the emulsion ~o the surface may take place by
means of a Myer rod, grav~re roller, reverse roller, ~lexo-coater, an Air ~Cnife coater or
a rota~y screen. ; ;
Accordingly, it is an object of the present invention to provide novel aqueous stable
emulsions having adhesive properties which can be applied onto a substrate in one pass, :
are environmentally safe, are cost effective, are easy to handle, are non-tox~c,demonstrate good paste properties and are compa~ible with commercially availablecoating machines.
15 It is a further object of the present invention ~o provide a process for pr~ducing the novel
stable aqueous emulsions.
An additional object of the present invention i~ to provide a wallcovering rnaterial having
at least one surface coated with the above aqueous emulsion and which rnay be easUy
20 applied to a surface by wetting the emulsion and applying the wallcovenng material to
the surface. ~ ; -
Still ano~her object of the present invention is to provide a process for prodl4cing the
wallcovering muterial.
These and other objects will be readily apparent to those shlled in the art as reference
is made to the detailed description of the preferred embodiment.
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Detailed Description of the Preferred Embodimen~ :
In describing ~he preferred embodiment, certain terminology ~vill be utilized for ~he sake
of clarity. S~lch terminology is intended to encompass the recited embodirnent, as well ; -~ -
as all technical eauivalents which operate in a sirnilar mannerfor a similar purpose fo : -
achieve a similar result.
The present invention comprises an aqueous emulsion containing between about 20 ancJ
about 50 percent polymer solids of a copolymer or terpolymer formed between a viryl
ester, one or more water soluble monomers and, optional~, an alkyl acrylate or alkyl
rnethacrylat~ As will be discussed ir~ greater detail, the solids may be par~zally or fulfy
hydrolyzed such that some or all of the vinyl ester is converted to vinyl alcohol. In
particularly preferred embodiments, the level of potymer solids in the emulsion ranges
from about 20 to about 35 percen~. In addition, the emulsion should prefeJably have
a viscosity of below 1000 cps at 25C as measured by a Brookfield Vscometer (spindle
#3, 60 rpm) and should provide adhesive properties.
The vinyl ester, which comprises between about 60 and abou~ 90 mole percent of the ~:
copolymer or terpolymer, is preferably vinyl ace~ate. However, other higher homologs of
vinyl acetate may be selected such as vinyl 2-ethylhexanoate, vinyl propionate, vinyl
pivala~e, vinyl neononanoa~e and vinyl neodecanoate. The vinyl ester is preferably
present in amounts ranging from about 70 to about 80 mole percent and even more
preferably between about 70 and 75 mole percent or between about 75 and about 80mole percen~ of the formed polymer.
2S
The other monomer(s) used to form the copo~mer or terpolymer is one or moK watetsoluble monomers which combines with the vinyl ester to yield the polymer solids of the
emulsion. Examples of watersoluble monomers which may be copolymerized with vinyl
esters, and particularly vinyl acetate include vinyl pyrrolidone, acrylic acid and sodium
acrylate, itaconic acid and sodium methylene succinate (sodium salt of itaconic acid),
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methacrylic acid and sodium met5tacrylate, 1-allyloxy-2-hydroxypropyl sulfonic acid and
sodium l-allyloxy-2-hydro~propyl sulfonate, 2-acrylamido-2-me~hylpropyl sulfonic acid
and sodium 2-acrylamido-2-methylpropyl sulfonate, diacetoneac~ylamide, N-vinyl
formamide, dimethacrylarnide and acrylamide. Mixtures of the above monomers may
5 also be selec~ed. Other water soluble monomers which may be selected will be
appreciated by those sh'lled in the nrt.
The water soluble monomers comprise 10 ~o 40 mole percen~ of ~he po~mer formed.
Particularly preferred water soluble monomers include vinyl pyrrolidone and aaylamide.
10 When using vinyl pyrrolidone, it should be preferabb present in amounts rtmging from
20 to 40 mole percent of the po~mer, more preferably between 20 and 39 mole percent
of the polymer. When combined with vinyl acetate to form a copolymer, the molar
amoun~ preferably ranges from between about 25 to abo~t 30 mole percenf. When
combined with vinyl ace~ate and another monomer, such as acrylamide or an alkyl
acrylate such as ethyl ncrylnte to form a terpolymer, the amount of vinyl pyrrolidone
preferably ranges from about 25 to about 30 mole percent.
While acrylnmide may be present in amounts ranging from 0.1 to 40 mole percent and
may form a copolymer with a vinyl ester such as vinyl aceta~e, it is particulnrly preferred
20 that acrylcmtide be used in amounts ranging from ctbout al to about 10 mole percent
and in combination wiJh vinyl pyrrolidone and vinyl acetate ~o form a terpoiymer.
Although believed to be novel~ emulsions containing copolymers of vinyl acetate cmd
acrylamide having more than 10 mole percent of acrylamide tend to Itclve very hig~t
viscosities. While Jhese maferials may be useful as "brush on" adhesives, they are not
25 ideal candidates as prepnste ad5tesives. Even more prefeJred amounts of acrylami~e
when used to forrn a terpolymer range from about 1 fo about S mole per~ent.
While not as thoroughly Jestecl, it is further hypothesized thnt a vinyl acetate/N-vinyl
formamide copolymer m~yyield a pc~ticularly desirable emulsion for use as a wallpaper
30 prepaste aclhesive. In such use, the amount of vinyl acetate is preferably between about
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60 and 70 mole percent and the amount of N-vinyl formamide is preferably besiween
about 30 and 40 mole percent.
In another embodiment, a terpolymer derived from a vinyl ester, one or more water
S soluble monomers and up to 10 percent of an atkyl acrylate or alkyl methacryla~e,
wherein alkyl represents an atkyl group contauung between I and 20 carbon atoms is
provided. Examples of alkyl acrylates and methacrylates mclude e~hyl acrylate, butyl
actylate, methyl methacrylate, methyl acrylate7 ethylhexylacrylute, hydroxyethylactytate,
hydroxyethylmethacrylate, hydroxypropylacrylate, hydroxypropylme~hactylate, stea yl
10 methacrylate and lauryl methucrylate. Parhculat~y preferred is a terpo~ymer of vinyl
acetute, v~ryl pyrrolidone and any of the above alkyl aaylates or methacrylutes. In thls
embodiment the amount of vinyl pyrrolidone preferably ranges from about 25 to about
30 percent, und the amount of alkyl acrylate or methacrylate, such as ethyl acrylate,
ranges from abou~ 0.1 to about 10 percent, und even more preferred between about I
15 and about S percenL
To enable the novel emulsions to be more heat stabte, it is desired that they be partial~
orfulty hydrotyzed so that part or all of the vir~l estet is converted to vinyl alcohot, with
partial hydrotysis being especially preferred. Hydrolysis may be accomplished by add~ng
20 either acid or base ~o the emulsion, with a base addition being the preferred route. The
degree of hydrolysis can be controlled by the arnount of acid or base added. 7'fie
hydrolysis reaction may be performed at temperah~res ranging from 10 ~o 80C, with a
range of 50C-60C being preferred. The pre~erred degree of hydrolysis based upon the
amount of vinyl ester present in the polymer solids ranges frorn about 30 to about 80
25 percent, with a more preferred range being between about 50 and about 75 percent, aru~
a most preferred range being between abou~ 60 and abou~ 70 percent. It has further
been discovered that when hydrolyzing the solids to a level beyond about 80 percent the
emulsion inverts, formin~ a solu~ion w11ich, llowever, retuins its adhesive properties.
30 Examples of bases which may be used to fiydrolyze the emulsion include sodium
hydronde, sodium carbonaJe, potassium hydroxide, ammonium hydroxide and potassium
~o~e, w~th ~ n2 hy~ra~e h~ prcp~
When producing an emulsion having a viscosity of less than 1000 cps at 25~C; llil~
preferably less than 750 cps, even more preferabb less than 500 cps and most preferabb
less ~han 250 cps i~ is generally necessary to include one or more surfactants or protec~we
colloids. These materials are present in amounts ranging from about 0.5 to 5 weight
percent of t~e emulsion, wiJh amour1ts ranging between about 1 to 5 weight percent being
more preferred. Examples of suitable surfactan~s include ammonium lau~yl ethersulfa~
sodium lauryl ether sulfate, octyl phenol ethoxylates (30-50 moles of e~hylene o~de),
nonyl phenol e~ho~ylates (30-50 moles of ethylene oxide), sodium lau~yl sulfate, an~
phosphate esters such as arnmonium or sodi~rn salts of polyfoxy-1,2-ethanediyl),~
(nonylphenol)- ~-hydroxy-phosphate, poly(oxy-1,2-ethanediyl), ~-phenol- ~hydtoxy-
phosphate and poly(oxy-l,2-ethanediyl),a-(octylphenol)-6~hydroxy-phosphate. 771ese
materials are commercially sold by Rhone-Poulenc Inc. under the trade names AbexJKB, Abex VA-50, Abex 23S, Alkasurf NP-40, Rhodas~RP-710, Sipon LSB, Alkasurf
NP-50, Rhodafac R9-25A, Rhodasutf RE-610 and Rhodasu~f RE-960.
Mirtures of surfactun~s may ideally be used. A patticularly preferred surfuctan~ blend
includes two weight percent ammonium lauryl ethers~dfate and one weight percent nonyl
phenol ethoxylates (40 moles of ethylene oxide).
Examples of protectn~e colloids which may be selected include poly[vinyl alcohol~
hydtoxyethyl cellulose, polyfvinyl pyrrolidone], sodium polyacrylate and condensat~'on
products of polyethylene glycol with fatty aci~, long chain alkylene or polyhydroxy fatty
acids. Examples of the condensation products are sold by ICI under the Hypermer
name. ~;
The polymerformed in the aqueous emulsion may be crosslinked. ~his is accomplished
by adding between about 0.01 and about 3.0 weight percent of one or more crosslinking
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agen~s to the emulsion. Examples o~sui~a~le crosslinhng agents include ethylene glycol -
dimet~acrylate, pentaery~hrttol tetracryJate, dipentaer~tllritol pentacrylate,
trimethylolpropane trimethacrylate, ' pentaery~hritol triacrylate, polyethylene
diacrylate, divinylbenzene and triallyl isocyanurate, with ethylene glycol dimethacryl~
S and trimethylolpropane trimethacrylate being particularly preferred. Mi~tuKs of the
above crosslinking agents may be used.
Fu~ther, the final emulsion may include between about a01 and 3.0 weight percent of
other additives to improve paste properties such as anJifo~ning agents, fungicides~ paste
10 body enharlcers to incKase slip and the like. These materials are well known in the an.
To produce the emulsion the surfactant and/or protective colloid is added to water and
the solution is heated to between about 50 and aoout 70C, more prefer~bly to about
60C In a separate vessel, the vinyl es~er and water soluble monomers are mixed
IS together along with a crosslinl~ng agent, if desired. Before adding the -
monomer/crosslinkl'ng agent ~o ~he water/surfac~ant solution an amount of a
po~merization initiator is added to ~he water/surfactant soluh'on.
Tlle polymerization initiator may take the forrn of many known initiators such as azo,
20 peroxide, perester and redox initiators. The amount of initiator a~k~ed to the soluhon
typically ranges from between about Q05 to about 2 weight percent of the ernu,'sion with
amounts rangmg from about 0.1 to abou~ 0.5 weight percent being particularly preferred.
The free radical inifiator added Is preferably an azo (azobisnitn'le) type initiator (water
or oil soluble) such as 2,2'-azobis-(2-methylpropanenitrile), 2,2'-azobis-(2,4
25 dimethylpentanenitrile), 2,2'-azobis-(2-methylbutanenitrile), I,l '-azobis~
(cyclohexanecarbonitrile!, 2,2' azobis-(2,4-dimethyl-4.methoxyvaleronitrile) and 2,2'-
azobis-(2-amidinopropane) hydrochloride. Other free radical initiators which may be
selected include peroxide materiaf~ such as Senzoyl perox;~le, cumene hydroperoxide,
hydrogen peroxide, acetyl peroxide, lauroyl peroxide, and peresters such as t-
30 butylperoxypivala e, -cumylperoxypivala~e and ~-butylperoctoate. Examples of
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commercially suitaole ini~iators which may be selected include Wako V-50, Vazo 52,
Vazo 64, Vazo 67 and Lupersol 11. The inihators may be a~ded in an inert solvent such
as acetone. -
5 Once a portion of the inihator is added into the wa~er/surfactant solution, the
monomer/crosslinJct'ng agent mi~ure ls metered into fhe reactorat between aoout 50 and
about 70C, and more preferab~ at about 60C ~n prach'ce, the monomer/crosslinking
agent mixture addition can take from 30 minutes to six hours, with addition times
between 2 and 4 hours being preferred. rftereafter, a series of inihator additiorns and ~ ~ -
"hold " periods wherein the emutsion is maint~uned at the approx mate temperahlre of the
initic~l water/surfactant mixture for a period of h'me, for ex~mple 2 hours, are conduc~ed
until the monomers have fully polymerized. Anywhere ~rom two ~o seven sep~rate
initiator additions may be u~ilize~ Using the above me~hod can convert over 99.5% of
the monomers to pol:ymeric form.
Once the emulsion is prepared it rnay either be used "as is" as a bn6sh on wallcovering
adhesive but is more preferab~ used as a waltcovering prepas~e adhesive.
To produce a wallcovering material having a prepaste adltesive on one of its surfaces,
~he above low viscosity emulsion ~is coa~ed on~o one surface of the substrate and the
surface is dtied The st~bstrate typically comprises stn'ppc~ble wallpaper, vinyl wallpaper, ~ A '~ '`'
peelable wallpaper, foil wullpaper, cloth fabric orsilk wi~h strippable wallpaper and vinyl
wallpaper being particular~ preferred substrate materials.
Applicahon of the emulsion ~o the substrate surface carl be accomplished by any of the
commonly known methods. These include Myer rod, gravure roller, reverse roller, rotary
screen, Flexo-coaterand AirKnife coater. In pructice the coating wcight of the emulsion
applied to the surface ranges from about 2 to about 30 grams/meter2, preferably ranges
from about 5 to about 20 grams/meter2, with a coahng weight of from about 8 to about
15 grarns/meter2 being particularly preferre~ Achieving the desired coating weight can ~ ~ ;
13
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,;i: ::: :: -;:, i : ,:,,. , .. ,. : , ," : ': : . - :
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be accomplished in one pass.
After the emulsion has been coated onto the substrate, it is dried, typically by us~ng a
commercial paper dryer. Such ovens typically operate at an air temperature between
S about 70C and about 200C. 'rhereafter, the sllbstrate, particularly if it is wallpaper
may be sent to a printing station where decorat~ve printing is applied to the non-coated
surface (alternatrvely, the paper may be printed prior to coattng the prepaste onto the
non-printed surface). The wallcovering Is then paclcaged and shipped for cu~tomer use.
To use the wallcovering having the adhesive emulsion coated and dried on one surface
thereon, ~he surface con~aining ~he adhesive, or more commonly, ~he entire wallcovering
is immersed in water. The water causes ~he solids in ~he emulsion coattng to swel1,
yielding a thin adhesive film. The adhesive surface is then applied to ~he wall or other
surface to be treate~
The invention is described in greater detail by ~he fvllowing non-limi~ing examples.
Example 1
The aqueorls emulsion of crosslinked vinyl aceta~e-vinyl pyrrolidone (VA- VP) copolymer
is synthesized asfollows~
In a 1000 ml reaction flasJc which is equipped wi~h a dropping fi nnel, a
condenser, an agitator and a nitrogen inlet, is added demineralked water
(549.0 g), ammonium lauryl ether sulfate (1~0 g) and ethoxylated (40
moles ethylene oxide) nonylphenol (9.0 g). Ttle emulsifier (surfactant)
solution is heated ~o 60 under a slow nitrogen purgmg. The nitrogen
purging ~s maintained throughout the reaction. A vinyl acetate (204.1 g,
2.37 moles), vinyl pyrrolklone (65.9 g, 0.59 moles) and ethylene g~col
d~methacrylate (aS4 gJ monomer mixture is put in a dropping ~nneL
When ~he temperature reaches 60C, azobis-isobu~yronitrile AIBN (0.68
g in æs g ace~one) is added. Then the monomer mixture is immediately
14
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metered in to the reachon flask over two hours. Three equal porhons of ;
41BN (0.68 g each) are added every half-hour during ~he two llour
addition perio~ The reaction i5 held at 60Cfor 30 minutes following the
monomers addition Anotherporhon of A~BN (0~27g) is added and the
S reactionIsheldforanotherninetyminutes. Thereactionisfurtherchased
down wiJh another portion of AIBN (0.54 g), and is held for two hours.
Then ~he reac~ion is cooled down to 25C, and the mixture was filtered
~hrough a 100 micron ffl~ering ba~. A homogenous, lump~free, milk-like
s~able emulsion is obta~ned. The residual vinyl aceta~e (HPLC mefhod)
~s less than O.5 percent.
TJIe synthesis is repeated with either different types of emulsifiers (surfactants), different
monomer molar ratios, or differen~ crosslin~ang agents. The results are ga~hered in `
Ta~le 1.
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~ ~ E o o o o o ~ ~ ~, .
E ~ ~ ~ a ~ a ~ E ~
~ o
`o
O ~ o ~ ~æ ~
3 ~ ~ E~ E ~ ~ 3
;~ ~ E~ ;; % E ~ ~ E ~ E ~j; o ~ ~
,o : ::
~ o
I _ :::
~ ~ ,o~ 4' CO '" ~ ~ '` ~ ~ '' ':'
: :::: .
,.. ,., ., - , . . .. . .. ... ,; , ., .. . ,,. . .. . , ,, . .. .. - . . ,. . ~ .. . .. . .
~.~ : .. . ..
~ 2 1 ~ 3
X
æ æ æ æ ~e ~ æ ~ ~
., ,. :.~,
O O o O O o O O O O
~O ~ O ~e *, ~,~e, *, ~ ", ~-~;,.
O ~ a ~ o ~
E E E E .~ E ~ E 3
æ Oe~e Oe `
2 ~e 2~ 2 ~ `
o ~ o O ~o ~ ~ ~o ~ ~ ~o ~o ~ e ~
~ o ~ 5 E ~ ; E ~ o ~ ~ E
E ~gE--~ E ~ E ~ E ~ E
2 ,~, ~o ;a
., ..., ., ., ., " ....... .. ..
~ ~ ,~ oo ~ oo ~ ~ ~ ~
o~
o
~ ~ . .. ;. .
o~ ~9~
o~ .:
Example 2
The aqueous emulsion of crosslinked vinyl acetate-vinyl pyrrolidone-acrylamide
is prepared as follows:
. ~-
S In a 1000 ml reaction flask equipped with an agitator, a condenser, a dropping
funnel and a nitrogen inlet, is added deminerali~ed water (S90.l g), ammon~um
lauryl e~her sulfate (1%9 g), and ethoxylated (40 moles ethylene oxide) nonyl
phenol (9.0 g). A monomer mcrture consisting of vinyl aceta~e (ls%a g, ~18
moles), vinyl pynrolidone (80.7 g, 0.72 mole), acrylarnide (50 percent soluhon,
10. 7~, 0.075 moles), ~érsenex 80 (a chelating agent, 0.02 g), and eJhylene g~ycol
dimethacrylate (0.54 g) Is pu~ in a dropping ~nnel. The a~ueous solulion is
heated to 60C under a slow nitrogen purge (which is mainta}ned throughout the -
reaction). When the temper~ture reaches 60C, ArBN (0.68 g in 2.0 g acetone)
is added followed by immediately metering in the monomers solutfon from the
dropping funnel. The addition of monomers occurs over two hours at 60C.
Three equal AIBN portfons (0.68 g in æo g acetone) are added every half hour
during this two hour addition period. The reaction is held at 60C for thirty
minutesfollowing the monomers additlon. AnotherAlBN portion (0.28g in 1.2
g acetone) is added and the reaction is held a~ 60Cfor ninety minu~es. An e~ra
portion of AIBN (0.56 g in 1.6 g acetone) is added and the reaction is held at
60C for another two hours. The reaction mix~ure is cooled down to 25C, and
the emulsion is ~Itered through a 100 micron fil~ering bag. A homogeneous,
lump-free, milk-like stable emulsion is o~tained. The residual vinyl acetate
(HPLC method) is less than O.5 percent.
The synthesis using the above general procedure is repeated either with different
molar ratios, different emulsifiers or wi~h different crosslinking agents.
The results are shown in Table II.
19
2.~ 2 3
o ~o
o ~
~ ,
æ ~ æ a~ e æ
C r~
D
.,C ~
,o _ ,~ ~ ~ 2 o o C, ~o o ~ `
E ~ .~ ~ ~
c~ à j~ j
~ 2 ~
~,o ~ o ~ o ~ ~ ~ ~ '~
--E ~ t.--o ~ ~--o ~ o~--o ~ ~--o ~ o~ ~o ~ ~--o ~ o~-- ~ q, ~ `
!~ ¦ o ~ ~ o ~ ~ o ~$~ o ~ ~ ô ~ ~ o ~ ~ o ~r~
E 4 E ~ Y E ~a ~ E ~ E b ~ E ~ o E b ~ E ~ ~;
V) ~ V~ ~ 4~ ' .
;~
~ ol ~ O~ ~ _ _ ~ _ _
~1 ..
~o~ o
o
o o o o o
o ~ o~
æ o
O ~
O O~ C~ O
~ ~ 3 ~ E ~?.E
'
o -- ~ :
" o '_
g ~ E ~!, a E E g ~ E E
~, ~, X;. E
oo o~ o ~ ~
~::',,'"`.'.. '':''`''.','''''~ ' ;
2~ :
Example 3
Aqueous emulsions of crosslinked po~mers of vinyl ester with dimethacrylamide isprepared usu~g basical~ ~he same procedure as in Example 1.
Tlle results are shown in Table 111.
, . , ~ .,
: .
~ -," :~
'' ~"";,',',
: : . ~ : . .
: ~ , . . .; - .: :. .
E ~ ~; E E
o~
u~ u~ u~* ~*
_ o ~ o o ~ .~,
C~ E ' ~ à ~ ~ ~ ~
- I ~ q ~ q
E ~ ~ ~? E ~ E
a~ %
o ~ ~ o ~ ~ ~
a E, I EE b ~ E ~ ~ E ~ a a ~ ~ a ~ ~
~ ~ Q o~
C~ .
E ~
4, .
E:xample 4
The synthesis of crosslinked terpolymers of vinyl acetate - virlyl pyrrolidone - e~hyl ;'~
ncryla~e are done essentially following the same procedure as in Ex~unple 1.
The resul~s are shown in Table IV~ ~ -
:' ~.' ',.,
~ ;~''''`"""'''
2 4
i ~. 2 ~ ci ;
a
o~
~C
- E :
C R R ~63
- o
r~ O 0~ 0 O~ ~ ~ O 0 0 ~ O ~
o~
~, .E ~3 E 6 E ,~ E ~ ? 6 ~ ~ N
æ ae ~e ~e æ æ
~ ~ ~ ~ 2
~,. I o 3 c~ ~o ~ 0 ~0
, ~ o ~ ... ..
. I o ~ o o ~
I ~ o ~ ~-o
~C % ~ % % ~ ~ ~ %
';
. ~ ~ o ~ ~ o
.. .. .. .. .. .. ..
~ O ~ ,, "
~ ~ ~o~ 1o~ C~ ,
2 ~. J ~ ~ 2 ~
~ , -.. -
~
Example 5
l'J~e alkaline hydrolysis of many a~ueous emulsions of vinyl acetate polymers as :
synthesized in Examples I -4 is done as follows~
To an aqueous emulsion (about 33% total solids) of crosslinked v~nyl acetate-
vinyl pyrrolidone copolymer in a ~ask, ~s added sodiurn hydronde solution with
agitation over 20 minu~es at room temperature (about 25C). Then the mi~aure
is mainttained with agitah'on at room temperature for 18 hours.
l O Stable emulsions are obtained. Tfle viscosity, % solids and pH are measured. The pH
can be adjusted with acid to desired specifica~'ons. The residual monomer (HPLC)cannot be detected. The results are galhered in Table
The hydroly3i3 ~s repeated under a varie~y of conditions (e.g., different degree of
hydrolysis, different reaction temperature and time, different aqueous polymeremulsions,
different solids con~ents) with the above general procedure. The results of all these
e~periments are shown in Table ~
2 6
''':
2 ~
.. .
r
~o ~
~ ~0 ,~ o .
~ ~o :
o ~ ~ * ~ ~
~~ ~ ~~ ~~ ~~ o ~
1- ~ ~ * * * ~ * ~
~ ~ . '~
~.~
o ~
O ~*~ ~ o O O V~ O ~r~ ~ :: :
E ~:
o ,~
* ~ ~ _ ~ ~ ~ ~ . ~. ~. ~ o~ o, o~ ~
o ~ ~ ~ $ ~ E
r
~ ~ o, " :
C~ Cl Cl CS C~ Cl C~ Cl Cl q ~ ~ q Cl C~ ~ ~ Cl ~ ~ ~
~ ~ X ~ `~'. X X X ~ X X X X X ,. X ~ ~; X
~ o ~~ r~ ~ 'q -- o~ ~ ~ ~
O O~ ~ 00 0 O~ o o O
~e ~e * ~ æ ~ æ æ ~e æ
00 ~t O 0~ 9 o o ~ ~. o~
~ .
~ -. . ..
o o o o o o o o o o o o o o o o o o ~ -~
o o~ o V~ ~ o~ ~
~ ~ ~ ~ CO CO CO 00 CO o CO CO CO C~ CO ,~
O O ~ ~ ~ ~ V~ ~ ~ ~ O O O O
~.
~e æ æ ~ ~ æ ~ Oe æ ~o aOe ~ O ~Og O ~Oe O ~
co ~ ~ O ~ ~ ~ ~
C~ o -- ~ ~ ~ ~ ~O ~ CO O~ O _ ~, ~, ~, ~ ~ ,~ .:
:.' ,' . ',''
$ ~ ~ $ ~q lq $ ~ ~ ~ ~ $ c" ~ ,7 $
2 ~
. ~ .
~ .3 .~
~ ~ ~ _ _ _ _ _ _ _ _ ~ ,
2 ~ ~ CJ q ~ o q
O -- ~ ~ ~oo -- ~ ~ O O o O o ~ ~ ~
oo O Oo~ 0, o~ 0, o~ ~ O ~ O O _ _
~ æ ~ e æ ~ ~e æ ~ e æ ~
O O O OO~ O O O O O O O O O O~ O~
o o o o o o o o o o o o o o o o o o
- - - - - - - - - - - - - - - - - ~ :
e e ~ ~Oe ~ æ ~e Oe ae ~e æO æO Oe Oe Oe ~e
4~ `o
E E E E E E E E E E E E E E E E E E
,, " ~
.~ :
~ , ~
o~. ,,,
CO oo oo
ff
:--
~e ,
O O O ~l ~,~ :
:
o O O ~ :
,~ O
': ,:
. ~
~ b
~o ~ ~ ~ E
.~, o ~ :
O~ ~ e ~
E E ~ E
ample 6
Lab Evaluation Test:
5 The aqueous po~mer emulslons fltydrolyzed and unhydrolyzed) ~hat are prepared are
evaluated as pre-pasted wallpaper adhesives by simply perfornting draw-down ontowallpapers of coaf weight rattging about 10 g/m2. Tlte coated wallpaper (ei~her
stn'ppable or solld virryl types) is dried af 120C for 90 secon~s. 4fler soaking the pre-
pasted paper in water (about 30CJ for 10 seconds ~he paste properties ar~ examined
10 afler booking for 60 seconds. The wallpapers (with paste after soaldng~ tare also tested
for adhesion by hanging on a wall (coa~ed with five layers of a flat latex pamt). These
properties are given a subjectrve rating of I ~o 5 by a panel of technical exper~s with I
being worst and 5 being best. Results are gathered in Table Vl. ~ '
15 As recorded in Table Vl the hydrolyzed polymers grve much better paste properties than
~hose of corresponding unhydrolyzed product. Also be~ter pas~e properh'es are achieved
with crosslinked polymer t~lan tha~ of non-crosslinked However they all g~lve excellenf ' '~
adhesion on the wall. ; :
:.... ~ ..
' ~ '
~ ~ 2 ~
TABLE V7
Performance Results of Aqueous Po~mer Emulsions
S Pas~e Pr~perties Adhesion
Sample ~bodv and feel) ~wet and drv~ -
3 5 : .
2 3 5
3 2 3
6 3 5
7 3 5 ~ :-
8 3 5
9 3 5
3 5
1l 3 5
12 2 3 ~:
13 2 3
14 2 3
3 5
16 3 5
17 3 5 ;~
18 3 5
19 2 3
32
,. . ~ ~ , , , ... ,, , , . ., ~ . .
_ .
3 5
21 3 5
22 3 S
24 3 5 .
3 5 `
26 3 5 .
I5 27 3 5
.... .
28 3 5
29 3 5
3 5
31 3 5
:: ~
32 3 5
33 3 5
34 3 5
3 5
36 3 5
37 3 5
38 3 S
39 3 5
~0
3 5
42 3 5
_~ 2 ~ J ~
~`
44 3 5 :-
4 5
46 5 5
47 3 5
48 4 5
49 5 5
51 3 5
3 5
53 ~ 5
~`~
54 4 5 .
4 5
56 4 5
57 4 5 :~
58 5 5
:~:
59 5 5
61 5 5 -~
62 5 5
63 5 5
~:
64 4 5 ~:
3 4
3 4
~ ~ '
--~ 2 ~ 5
.
66 3 5
~57 ~ 5
68 5 5
69 5 5
71 5 5
72 5 5
73 5 5
, ~,`, ` . ``
3 5
76 5 5
77 5 5
78 5 5
79 4 5
4 5
81 4 5
82 5 5
83 5 5
84 4 5
3 5
86 4 5
87 S S
2 ~
- ~:
88 2 3
89 q 5 ~-
S
91 4 5
92 5 5
93 5 5
94 3 5
3 S
96 3 5 --
97 5 5 `
98 5 5 ~-
99 5 5
Exam ple 7
~leat Sta~ilitv
The heat stability of the pa~te is evaluated as follows.
The aqueous polymer emulsions are coated onto a piece of wallpaper (either stnppable
or solid-vinyl) by a simple lab draw-down me~hod with a Myer rod. The coated
wallpcJper ~s fhen dried at 150C or at 210C for a prescribed time. The paste properhes
are then examined after soaking in waSer (30C) for 10 seconds and then booldng for I
minu~e. Tl~e paste coated on wallpaper and dried at 120Cfor 90 secor~s is used as the
standard for companson.
The results are shown in Table VII.
36
~-- 2 ~
''' ' ' ':
TABLE Vll
Results of Hea~ S~ility :
120C 150C 210C "
Sample ~90 seconds~ (5 minutes) (2 minutes)
. . .
stable unstable
2 s~able unstable ----
3 stable unstable ----
4 s~able unstable - - - -
stable unstable ----
6 sta~le ~nsta~le ----
7 s~able unstable ----
9 stable uns~able -- -
12 stable unstable ----
stable unstable ----
16 stable unstable ----
17 stable unstable ----
18 stable unstable ----
19 stable unstable ---~
stable unstable
stable unstable ----
.
28 stable unstable ----
~10
31 stable unstable ----
stable stable stable
37
2~1~
, ~ -
: :"
36 stable stable stable
37 stable stable stable
39 stable unstable
44 stable some degraded unstable
stable stable stable
' " '~ '":''.` . ',
46 stable stable stable
47 stable urtstable unstable ~ ~ -
48 stable stable same de~uded
49 stable stable stable
stable stable stable ;~
51 stable lmstable unstable
S2 stable stable some degraded
53 stable stable s~able
54 stable stable stable
5S stable stable s~able
56 s~able stable stable ~ ~ ;
57 stable stable stable
:: ~
58 stable stable stable
59 stable stable stable
stable stable stable
61 stable stable stable
62 stable stable stable
38
21 ~ ~2~
",
63 stable stable stable
64 stable stable stable - -~
stable stable stable
66 stable unstable unstable
67 stable s~able stable
68 stable stable stable
69 stable stable s~able
stable stable stable
71 stable stable s~able
72 stable stable stable
73 stable stable stable
74 stable unstable unstable
staSle stable stable -
76 stable stable stable
77 stable stable stable
78 stable stable stable
79 stable stable stable
stable stable stable
8I stable s~able stable
82 stuble stable stable
83 stable stable stable
84 stable stable stable
.
39 .~
;, ., . . ~ , ,
2 ~
. , ." . ,
stable unstable ~stable
86 stable stable stable
87 stable stable stable
88 stable stable somedegraded
89 stable s~able stable
:~ '
stable stable stable
9I stable stable stable
92 stable stable s~able -~
- 93 stable s~able stable
94 stable stable stable
stable stable stable
96 stable s~able stable
97 stable s~able st~ble
98 s~able stable somedegraded
99 stable stable somedegraded
; '
: ~ , :.,:
4 0
2 1 1 8 ~
,
ExamDle 8
Freeze-thaw Cvcle Test
5 Aqueous emulsion samples ~3 (unhydrofyzed) and #58 thydrobrzed) are used as
exarnples for ~he test. The samples are frozen at -10C for about 18 hours fhen ~hawed
at 25C Product viscosity is measured after the sample is completely ~hawed. Thefreeze-thaw cycle is repeated seven tlmes. The results are shown below.
Sample At S!art After 7 ~reeze-thaw cvcles
#3 Stable emulsion Pha~e-separahon occurred affer one
B.~ 405 cps cycle. B.V. after 7 cycles ~s
over I 50a cps.
$~58 Stable emulsion Stable emulsion; no obvious difference
B.V. 200 cps. after 7 cycles. B.~ 200 cps.
E~xample 9
.: ~ .
20 Microscopic Evaluu~ion
A number of aqueous emulsions are evaluated with a Zeiss Optical Microscope, phase
contrast, 650X The samples used are #2, #9, #47, #49, #50, #72, #74 and #75. In
each of ~he samples evaluated, part~cles are seen, evidencing the forrnahon of an
25 emulsion. The size of the purticles vary depending on the surfactant system used. For
example, Sample 2 has a larger average particle size (10-20 microns) whereas Sample
9 has a smaller average particle size (1-5 rnicrons) Further, in the hydrofyzed sarnples>
the particles tend ~o be less spherica~ At a hydrolysis level of grea~er than 80%, the
emulsion tends to inverf, forming a solution. Despite this inversion, the solution retains
its adhesive properties. ~ ~ ~
`: "~ ',: . ' .
4 1 ~
:' ~
' --: ':
-- 2 ~
Exam ple 10
An amount of Sample #59 is l~sed for ~he production of watlpaper. The wallpaper that
is produced is a solid vinyl ~ype, and the coater used is a Dahlgren reverse roll type. The
following pasting conditions are used: oven temperature 150C, paper speed 150
m/minute, transfer roller speed 750 rpm and coating weight 10 g/m2.
ArZ even coating is obtamed with desired paste body and feet. The resulting pasted viny~
wallpaper then undergoes printing and ho~ embosshg (abou~ I65C web temperature)procedures. No problems are encountered when performing either procedure ~e.g., no
paste transfer, dushng or heat instability). The prepasted wallpaper is immersed in wa~er
for 10 seconds and applied to a wall~ The paper hangs ~o watl very well, giving excellent
wet and dry adhesion and the paper does not curC
Having described the invention in detail and by r~ference to ~he preferred embodimen~s
thereof, it will be apparent that modifications and~ variations are possible without
departingfrom the scope of the appended claims.
42
