Note: Descriptions are shown in the official language in which they were submitted.
10~5981
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PROCESS FOR MAKING PR~PASTED VINYL WALL COVERI~G
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BACKGROUND OF THE INVENTION
Field of the Invention
This invention is directed to a process for making
prepasted vinyl wall covering.
Description of the Prior Art
- Many articles of manufacture are made with re-
-moistenable adhesive backings, such items include: postage
stamps, envelopes, gummed labels, tape, wall paper
(including cotton-scrim backed vinyl coated wall paper)
and other cellulosic sheet. The remoistenable adhesive
can apparently be applied to the paper articles without
detrimentally changing the length and width dimensions of
the paper articles. The use of water based adhesive on
paper articles, however, does appear to cause curling.
See U.S. Patents 2,477,344; 3,200,091 and 3,425,968.
Vinyl wall covering is available with an adhesive backing,
but the adhesive is generally a pressure sensitive type
;of adhesive. Attempts to apply starch water solutions to
cotton-scrim backed vinyl wall covering have resulted in
a nonuniform change in dimension of the wall covering.
The nonuniform change in dimension was probably due to a
shrinking of the cotton-scrim backing when the cotton
scrim-backing was impregnated with the water solution then
dried. This lack of dimensional uniformity in the wall
covering results in patterns in adjacent sheets not matching
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when the sheets are hung on the walls and also in the edges of the sheets
not meeting properly.
Starch particles suspended in an organic solution of a binder
polymer are appl;ed to a fabric backing of vin~l wall covering. The solvent
is then removed leaving the starch e~bedded in an organic binder pol~mer
matrix. The binder matrix holds the starch particles in place with respect
to each other and onto the cotton-scrim backing.
Accordingly, the mvention provides a process for prepasting
a wall covering consisting essentially of a flexible vinyl film having a
fabric backing which process comprises applying to the fabric backing a
composition comprising 100 parts of a water moistenable starch, 10 to 35
parts of an organic polymer characterized by a tangent mLdulus of elasticity
in bending at 5~ of from 10 to 3,000 M Pa and 100 to 300 parts of an organic
liquid having a boiling point of frQm 45 & to 150C which liquid is a solvent
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~ for the o~ganic polymer and a non-solvent for the pregelatinized starch.
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When the matrix containing staxch particles is brought into con-
tact with water the starch particles are wetted and become adhesive. The
vinyl wall coveri~ng produced does not shrink due to the application of the
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non aqueous adhesive to the fabric backing resulting in good pattern match in
` 20 use. In addition, good edge match is achieved. The organic solvent causes
neither shrinking nor stretch of the fabric backing.
BRIEF DESCRIPTION OF THE DR~WING
~- Figure 1 is a schematic drawing of a typical vinyl wall covering
design printing machine containing an additional adhesive application stage.
The one additional stage employs the use of a turnaround roller and an adh~sive
applicator. The turnorownd roller turns the wall covering fr~m vinyl side
down to fabric backing side down so that the adhesive applicator can
apply the supended starch and binder in organic solvent to the fabric ~acking.
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The drying stage of the device is conventional.
Figure 2 is an isometric view of the adhesive appli-
cator section of the machine of Figure 1.
; DESCRIPTION OF THE PREFERRED EMBODIMENT
A prepasted fabric backed vinyl wall covering is
made by applying an adhesive to the fabric back. The
adhesive, as applied, contains a water moistenable pre-
gelatinized starch suspended in an organic solution of a
binder polymer and is substantially free of water. The
solvent has essentially the same volatility as the solvent
for the ink used to print the vinyl so that the binder
solvent will be moved at about the same time and rate that
the solvent ink is removed. The term pregelatinized starch
as used herein also includes water moistenable adhesive
starches prepared by chemically modifying starches which
- modification usually also involves pregelatinization.
,' The vinyl film used in making the wall covering is
- conventional. It is composed of polyvinyl chloride con-
taining plastizers, fillers and other conventional com-
pounding ingredients. The film has a thickness of from
about 5 to 15 mils. The film has a fabric backing applied
directly to the film with no intermediate paper layer.
The fabric backing again is conventional in vinyl wall
- covering. The vinyl is calendered onto the fabric backing
in the known conventional manner using heat and pressure.
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- The fabric backing which is employed in the practice
of the present invention can be cotton scrim or any of the
non-woven fabrics made from long filaments. By long
filaments is meant filaments having an average length of
at least 5 mm. The preferred non-woven fabrics are those
made from polyester filaments These non-woven fabrics
are well known and generally used in making fabric backed
vinyl wall covering. The problems which the present
invention solve however are primarily in the area of
- 10 cotton-scrim backed wall coverings and hence for the pur-
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poses of the present invention cotton scrim is the preferred
fabric backing.
The starch, which is used in making the paste, is
a water moistenable starch and preferably has a particle
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size less than 250 microns. The lower limit of particle
size is not critical though dusting occurs at lower levels.
The preferred starch is a pregelatinized amioca starch
- having an amylopectin structure and a particle size of
; about 180 microns. Pregelatinized starches such as those
derived from corn, wheat, rice, potato, and tapioca may be
used. Also included are the known chemically modified
starches used in adhesiues such as starch esters and starch
ethers. Examples are starch acetate, hydroxy ethyl or
hydroxy propyl starch and sodium carboxy methyl starch.
The starch is present at a level of 100 parts. By a
"moistenable starch" is meant a starch that will become
adhesive upon contact with water for one minute at room
temperature. The term also includes British gums and
dextrines but these latter two materials are not preferred.
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In addition to the starch, from 10 to 35 parts of
an organic polymer are present in the paste. Organic
polymers which can be employed include those which will
adhere to the vinyl, are tack free in the solventless state
and are pliable sO that the coated wall covering can be
- rolled up. Such polymers have a tangent modulus of elas-
ticity in bending at up to 5~ of from 10 to 3,000 MPa (mega
Pascals) The modulus is determined according to ASTM
method D 790-71. The test is run at room temperature
(15C-25C). The polymer is preferably an acrylic polymer
such as a copolymer of ethyl acrylate and of methacrylate,
or a terpolymer of methyl methacrylate, ethyl acrylate
and acrylic or methacrylic acid. Rubbery copolymers such
as those of butadiene and styrene are also useful, as are
mixtures of polymers.
The solvent for the organic polymer, which is also
the non-solvent suspending agent for the pregelatinized
~tarch has a boiling point of from 45C to 150C preferably
55C to 120C. The preferred solvents are methyl ethyl
ketone or methyl isobutyl ketone and mixtures of one or
more of the recited ketones with 1 - 10~ by weight based
upon total solvent weight of isopropol alcohol. Other
solvents such as methanol, ethanol, isopropanol, toluene,
zylene, benzene and mixtures thereof can also be used.
Alcohol is normally present because it is used to solubilize
the waxy stripping agent used.
Cellulosic materials can be used as a "slip agent"
to aid in sliding the covering into place on the surface
being covered. Hydroxyethyl cellulose, hydroxypropyl
cellulose, carboxymethyl cellulose, hydroxypropyl
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; methyl cellulose and the methyl ether of cellulose can be
used for this purpose with minor adjustments in the formu-
lation.
When the preferred combination of ingredients is
used, the remoistened wall covering can be adjusted in
position on wallboard up to ten minutes after application.
The slip agent is present at a level of from 1 to 30
preferably 10 to 20 parts.
Biocides can also be present in amounts of 0.1
to 10.0 parts preferably 1 to 5 parts. These materials are
known in the starch adhesive art. They include among
other things arsenics, mercurials and phenols.
Biocides which can be used are specifically exemplified
by tributyltin oxide, phenyl mercury acetate N-trichoromethyl
thio-4-cyclohexane 1,2-dicarboximide, parachlorometacresol,
- 3,5-dimethyltetrahydro 1,3,5, 2-H-thiadiazine-2-thione,
dodecylguanidine hydrochloride, dimethoxane, pentachloro-
phenol, and 1-(3-chloroallyl)-3,5,7-triaza-1-azonia-
adamantane chloride.
The preferred compositions also contain a release
agent to allow the wall covering to be removed from the
- wall when it is no longer wanted. Such release agents are
present at a level of 0.1 to 10 parts and preferably 1 to
5 parts. They include hydrocarbon waxes such as a Carbo-
wax release agent as well as other well known release
agents.
The adhesive is applied to the fabric back of the
vinyl wall covering at a level of from about 5 to 40 grams
per square meter (gms/mz). The preferred method for
1075981
applying adhesive is by using a 14 to 24 line per centimeter trihelical
applicator roll. A doctor knife is positioned on the roll to provide uniform
application of the adhesive.
In the Examples which follow as elsewhere in the specification,
all parts and percentages are by weight unless otherwise specified.
To a container equipped with a *Cowles mixer was added 171 parts
of methyl ethyl ketone. Then was added with stirring a ccpolymer of methyl
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` methacrylate and ethyl acrylate. The ratio of monomers was 64 moles of
methyl methacrylate to every 36 moles of ethyl acrylate. The estimated
flexural modulus was 1,400 M2a. m e mLxture was stirred for 15 minutes
to dissolve the oopiolymer. To a separate contalner was added 1.8 parts
of isopropanol and 1.8 parts of methyl ethyl ketone. Then 2.34 parts of
*Carbowax 20M were added and the mixture was heated to 60C to form a solution.
*Ca~bowax 20M is a polyethylene wax having a weight average molecular weight
of about two thousand. In this particular application it was a release
agent. m e Carbowax solutian was then added to the acrylate solution in
methyl ethyl ketone. Also added with agitation were 0.9 parts of
N-trichloromethylthio-4-cyclohexene 1,2 dicarbco3nide fungicide and 15 parts
of hydroxy propyl methyl oe llulose slip agent. m en 100 parts *Instant
Amioca starch was added and mixing was continued for 15 minutes. *Instant
Anioca is a pregelat mized, long chain carhohydrate with an amylopectin
structure. It is derived from
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10759~31
- waxy maize corn. The starch has a particle size of less
than 180 microns.
The adhesive prepared as described above was then
applied to cotton-scrim backed vinyl wall covering as
shown in the drawing and described below.
A cotton-scrim backed vinyl wall covering 1 was
run through a series of conventional printing rollers 2a,
2b, 2c and 2d in order to imprint a design upon the vinyl
, side of the wall covering. The wall covering 1 was then
run through a reverse roll arrangement 4 where the adhesive
6 of the present example was applied to the fabric side of
the wall covering by calender roll 5. Calender roll 5
draws adhesive 6 from pan 7. Doctor blade 8 limits the
amount of adhesive on roll 5. The adhesive was applied
at a level of 20.7 gms/m2 dry basis. The wall covering
was then passed over heated roll 9 and through drying oven
10 where the solvent is removed both from the printed sur-
face and from the adhesive surface by heated air. The
adhesive was applied at a 45~ total solvent content. The
air used for drying is first heated in heater 12, blown
through drying oven 10 by blower 14 and exhausted through
duct 16. The drying arrangement is conventional, known
in the art and only shown schematically here.
The wall covering was applied to new dry wall to
determine the ply adhesion. Prior to application to the
wall the strips were soaked in water for 30 seconds, then
drained for 30 seconds. The ply adhesion test consists of
cutting a 5.16 cm wide strip about 46.4 cm long in the
hung wall covering. The end is pulled away from the wall
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and the strip is pulled off with a tensiometer. A fish
scale calibrated in grams is convenient to use. The test
is run on the center and left and right sides. The results
reported are the average of the three.
; 5 The ply adhesions in force units were as follows:
After After After
16 hrs. 40 hrs. 1 wk
. . .
340 grams 556 grams 545 grams
The ply adhesion to painted plaster at the end of 16 hours
was 227 grams and at the end of one week was 113 grams.
The pattern matching and edge matching of the vinyl
wall covering produced according to this example was
excellent.
EXAMPLE 2
To a container equipped with a Cowles mixer was
added 138.5 parts of methyl ethyl ketone. To the methyl
ethyl ketone was then added with stirring a dry powered
; copolymer of methyl methacrylate and ethyl acrylate. There
was a ratio of 64 moles of methyl methacrylate to every 36
moles of ethyl acrylate in the copolymer. The estimated
flexural modulus was 1,400 MPa. The solution was stirred
for 15 minutes to dissolve the copolymer. To a separate
container was added 1.8 parts of isopropanol and 1.8 parts
of methyl ethyl ketone. Then 2.34 parts of Carbowax 20M
heated to 60C. are dissolved in the solvent mixture.
Carbowax 20M is a polyethylene having a weight average
molecular weight of about two thousand. In this particular
application it is a release agent. The Carbowax solution
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was then added to the acrylate solution in methyl ethyl
- ket3ne. Also added with agitation were 0.9 parts of
N-trichloromethylthio-4-cyclohexene 1,2-dicarboximide
fungacide and 15 parts of hydroxy propyl methyl cellulose
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sli~ agent. Then 100 parts of a pregelatinized hydroxy
propylated starch derived from a yellow dent corn having
a particle size of about 200 microns was added and mixing
was continued for 15 minutes.
A cotton-scrim backed vinyl wall covering was run
through a series of conventional printing rollers 2a, 2b~
2c and 2d in order to imprint a design upon the vinyl
side of the wall covering. The wall covering 1 was then
run through a reverse roll arrangement to apply the adhesive
and dried as in Example 1. The adhesive was applied at a
50~ total solvent content. There was some pick off when
embossing was employed on the embosser heating drum and
on t;he rubber embosser backup roll. The adhesive was
applied at a level of 22.4 gms/m2 dry basis.
The wall covering was applied to new dry wall to
~; 20 determine the ply adhesion. The ply adhesion test was the
same as that used in Example 1.
The ply adhesions in force units were as follows:
After After After
16 hrs. 40 hrs. 1 wk.
~` 25 556 grams 795 grams 880 grams
The ply adhesion to painted plaster at the end of 16 hours
was 340 grams and at the end of one week was 170 grams.
The pattern matching and edge matching of the vinyl
wall covering produced according to this example was
excellent.
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