Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
,
This invention relates to adhesives. In particular this inYen-
tion concerns starch-silicate compositions useful as adhesives in the
rabrication of corrugated paperboard boxes and similar applications.
Starches and s:Llicates have been used separately for many years
ns adhes:Lves for maAy applications. It is thereEore surpr:Lsing that
starch-sil:Lcnte composit:Lons have not been tested as adhegives. Sillcate-
clay-starch combinations have been used as adhesives'. United States
Patent No. 2,669,282 issued 16 February, 1954 to KREYLING ~;
discloses'such an adhesive that is stable at tempera-
tures of 55 - 90C. and contain 3 to 30~ raw starch,`4 to 30% clay or
diatomaceoùs earth and at least 65% sodium silicate. United States .
Patent No. 2,772,996 issued'$ December, 1956 to SAMS
discloses'a borated silicate-clay-starch adhesive
that is formed at 55 to 80C. and contains 1.5`to 10%.starch, 1 to 25% `
clay, 0.2 to 5% alkali metal borate and at least 50% sodium silicate. In
these systems the starch'is included'in predominantly silicate adhesives ~ '
to provide release properties and dusting control. .
A few starch-silicate composites'have been used in paper coat~
.
ings. United States'Patent No. I,080,143 issued'2 December, 1913
to DUNHAM discloses a starch-clay composition,
used as a sizing agent for paper'which contains up to 5% silicate as a
viscosity control agent. 'United States Patent No. 2,02~,123 issued .
10 December, 1935 to- BA~ER.
discloses a process for preparing a paper coating composition involving
.
the'addition of sodium silicate:to a starch which has.been'mildly dextrin-
ized and esterified by.an acid treatment. Upon application of the:com- ''
position to paper the'silicate reacts with the'acid of the composition .~ ~ -
and the acidic paper'surface to form silicic acid. Neither of these
..
- patents relate to starch-silicate compositions that would be useful as ' . .
30 . adhesives.
A number of reasons appear to be responsible for the lack of
interest in starch-silicate compositions. 'Pure starch compositions have
- 1 - :
L07
generally been adequate adhesives and only minimal problems are encoun-
tered with such systems once they are established. Also starch has been
relatlvely inexpensive in the past. Further~ the starch adhesive art has
ta~lght that the presence oE any silicate during the preparation of pre-
(lominantly sturch a~hesLv~s will cause complete gelation before the pre-
pnra~Lon 1~ complete or the adhesives can be applied. (See ~erner and
Roseli~ls, Corrugated Fiber Box Manufacturer's ~landbook, Published by S&S
Corr~lgated Paper Machinery Company, Brooklyn, N.Y., page 2~.)' Therefore
the use of silicates in any quantity with largely starch adhesives has
been avoided in the past.
It has now been found that adhesive compositions containing
starch and silicate can be'prepared'with 8 to 40% of the solids as alkali
metal silicate and 60 to 92% of the'solids as starch, and that these
compositions are especially useful in forming corrugated paperboard,
coolmonly used in boxes. The compositions can be prepared by adding sili-
cate solutions to a prepared starch adhesive. Other methods of preparing
the compositions include mixing, dissolving or slurrying the various com-
ponents with water and combining the solutions and slurries to provide
the adhesive; or sequentially mixing, dissolving or slurrying the compon- '
ents with water in a single container. A preferred method of preparing
the compositions involves prepàring a mixture of the dry components and ~
then dispersing these mixtures'in water and processing. ~ '
It is surprising that the'compatibility of starch and silicate
and the'use of the conbination as an adhesive has not been discovered and
reported previously. 'However, it appears that the combination in the ~ ~
disclosed proportions has been prepared for the first time and the use `
thereof as an adhesive has been proposed herein-for the first time. This
new combination has numerous advantages'over both silicate and starch
adhesives. The preparation of the'composition of an aspect of this inven-
tion is somewhat easier than the`preparation of the usual starch adhesive
and it is not necessary to heat the composition of an apsect of this
invention to the'same èxtent as starch'adhesives during the preparation.
',;
- 2 -
Actually, heating the starch-silicate adhesive of aspects of this inven-
tion to the temperatures usually used to prepare starch (above 70C.)
will lead to unacceptable final adheslve prodllcts. 'Lo~er, more economical
heatlng temperatures wLth resultant energy conservation are among the
desLrnble Eea~llres vf this new technology. ~nother advant~ge i9 that it
~g posslble to prepare the starch-silicate adhesive compositions of
aspects of this in~ention at higher'solids c'ontents than is usually
possible with pure starch adhesives, allowing more flexible conditions
for application of the adhesive.' It is also possible significantly to ~ '
reduce and in some formulations substantially completely to eliminate
borax which is usually included in starch compositions to provide gel body
properties. In many cases the bonds obtained when the composition of
aspects of this invention have beèn used are stronger than those of pure
starch adhesives. The`bonds of specimens prepared with the composition
of aspects of this invention that have been'subjected to high humidity and '~
then redried are much stronger'than those prepared with starch and treated
similarly. Further the composition of aspects of this invention does not
significantly build up and adhere to metal parts as silicate adhesives do.
Another advantage over'silicate adhesives is a quicker set time.
By one aspect'of this invention, an adhesive composition is pro- '
vided having a pH of 11.0 to 11.9 and an adhesive solids content of 15 to
30% by weight and consisting of ~on a weight basis): ~a) 12 to 23% of a
starch that contains less than 20% protein and selected from those
starches which swell by hydration before going into solution at tempera-
tures'between 55 and 80C;; ~b~'1.5 to 12% of sodium or potassium sili-
cate solids, the silicate having a mol ratio of 1.5 to 4.0 parts of SiO2
per 1 part M20, wherein M is sodium or potassium; the weight ratio of
starch solids to silicate solids being within the range of l.S to 12 parts
of starch per part of silicate,' ~c) 0.5 to 2.5% of an alkali source
selected from the group consisting of sodium hydroxide, potassium hydrox-
ide and sodium metasilicate; ~d~ 0 to 2% borax; and ~e) 70 to 85% water.
By a further'aspect of this invention, an adhesive composition
- 3 ~
L07
is provided having a pH of ll.O'to 11.9 and an adhesive solids content
of 15 to 30% by weight'and consisting of ~on a weight basis): (a) a
gelled carrier portion constituting 15 to 30% by weight of the total
adheslve and contalning 10 to 20% of the adhesive sollds consisting of
(~y weL~ht): (:L) 0.5 to 2.5% of a source of alkall selected from the
group conslsting oE sodium hydroxide, potassium hydroxlde,'and sodium ~.;
metasilicate, (2) 1.5'to 6.0% of starch and silicate, the weight ratio
of starch solids to silicate solids being 1.5'to 12 parts of starch per
part of silicate,'the starch containing less than 20% protein and selec-
ted from those starches which swell by'hydration before going into solu-
tion at temperatures between'55 and 80C., and the silicate being sodium
silicate or potassium silicate having a mol ratio of 1.5 to 4.0 parts of
SiO2 per part of M20 wherèin M is sodium or potassium, and (3) 14 to 34%
water; and (b) a slurry portion blended wi~h th'e gelled carrier, the
s~urry portion constituting 70 to 85% by'weight'of the adhesive and con-
taining 80 to 90% of the'adhesive solids consisting of (by weight): (l~
13.5'to 24% of the'starch and the silicate,'the'weight'ratio of starch
solids to silicate solids being 1.5'to 12 parts of starch per part of
silicate, (2) 42 to 68% water, and (3) 0 to 2% borax.
In one variant of these-two aspects, the'starch is selected `;
from the'group consisting of corn starch,'rice starch, potato starch, ~ ~ -
sago, tapioca and casava starches, arrowroot, acorn and moss starches, `
starch esters, starch ether, methyl cellulose and sodium palconate, and
especially where the'starch is selected from the group consisting of corn
starch,'rice starch and potato starch.'
In another variant of these two'aspects, the silicate constit-
utes 8 to 40% of the adhesive solids, especially where the silicate con-
stitutes 10 to 30% of the'adhesive solids.
In yet another'variant of these two aspects, the weight ratio
of starch solids to silicate solids is 2.5 to 7.0 parts of starch per part
of silicate.
By another'aspect of this invention, a process is provided for ' ~
`` ': .,
-- 4 --
.. :. - .-. - .. - -... .- .. . : .. -.. . . . ... . . ..
~L~.35~L07
preparing an adhesiYe composition haYing a pH of 11.0 to 11.9 and an
adhesive solids content of 15 to 30% consisting of ~on a weight basis~:
(a) 12 to 23% of a starch that contains less than 20% protein and
s~lectcd Erom those starches'wllich swell by hydration beEore golng :Lnto
~o:lu~:Lon nt tempern:tures'between 55 and 80C.; (b) 1.5 to 12% of sodlum
or potass:Lum sillcate sol:Lds, the silicate having a mol ratio of 1.5 to
.O parts of SiO2 per'part of M20, wherein M'is sodium or potassium;
(c) 0.5 to 2.5% of a source'of alkali; (d~ 0 to 2% borax; (e~'70 to 85%
water; the process comprising the'steps of: (A) forming a gelled carrier
portion that constitutes 15 to 30% by'weight of the total adhesive and
contains 10 to 20% of the adhesive solids by: (1) dissolving the source
of alkali selected from the'group consisting of sodium hydroxide, potas- :
sium hydroxide and sodium metasilicate thereby forming an alkaline solu-
tion; (2) heating the'alkaline solution to a temperature of 50 to 65C.; . .
(3) adding starch and silicate to the heated alkaline solution, the weight
ratio of starch solids to silicate solids be;ng 1.5 to 12 parts of starch
per part of silicate; and (4) blending at 50 to 65C. for a period ~ .
sufficient to produce a gel; (B) forming a slurry portion constituting
70 to 80% of the total adhesive composition and containing 80 to 90% of ~ -
the adhesive solids, by'blenaing starch and silicate into water between
room temperature and 45C. wherein the weight ratio of starch solids to '
silicate solids is between'1.5'and 12 parts of starch per'part of silicate; - :~
and (C) blending the slurry portion and carrier portion to provide the
final adhesive composition. `~ ;
By another aspect of-this invention, a process is provided for
preparing an adhesive composition having a pH of 11.0 to 11.9 and an
adhesive solids content of 15 to 30% consisting of (on a weight basis): ~'
(a) 12 to 23% of a starch`that contains less than 20X protein and selec~
ted from those starches'which swell by hydration before going into solu- ~'' ,
tion at tem~eratures between 55 and 80C.; (b) 1.5'to 12% of sodium or
potassium silicate solids,~the silicate having a mol ratio of 1.5 to 4.0
parts of SiO2 per part of M20 wherein M is sodium or potassium; (c~ 0.5
- 5 - "'
' . ` ': :'
37
to 2.5~ of a source of alkali; (d) 0 to 2% borax; and (e~ 70 to 85%
water, the process comprising the steps of: (A) dissolving a source of
alkali selected Erom the'group consisting of sodium hydroxide, potassium
hydroxide and sodium metasilicate in water thereby for~ing an alkaline
solu~:Lon; tB) 'heating the alkaline sollltlon to.50 to 65C.; tC) add~ng
~ e star.h antt s:Lllcflte to the alkallne solution, whereln the weight
ratio of starch so.llds to sillcate solids Is~1'.5 to 12 parts of starch
per part of slllcate; (D) blending at 50 to 65C. for a period suffl- .
clent to form a gel; (E? adding water'thereby diluting the gel; (F)
'10' adding more of the starch and silicate to the'diluted gel wherein the
weight ratio of starch solids to silicate solids is 1.5 to 12 parts of
starch per part of silicate;' and ~G) blending at a temperature between
room temperature and 45C. for a period sufficient to produce the final
adhesive composition.
By yet another'aspect of the'invention, a process is provided
for preparing an adhesive composition having a pH of 11.0 to 11.9 and an
adhesive solids content of 15 to 30%.consisting of (on a weight basis):
(a) 12 to 23% of a starch that contains less than 20% protein and selec- :
ted from those starches'which swell by'hydration before going into solu-
tion at temperatures between 55 and 80C.; (b) 1.5 to 12% of sodium or
potassium silicate solids, the silicate having a mol ratio of 1.5 to 4.0
parts of SiO2 per part of M20 wherein M is sodium or potassium; (c) 0.5
to 2.5% sodium metasilicate; (d~ 0 to 2% borax; and (e) 70 to 85% water; '
the process comprising the'steps of: (A) preparing a first uniform mix-
ture composed of 50 to 75% of the starch, 10 to 25% of the sodium or ~ -
potassium silicate (the silicate having 15 to 20% water) and 10 to 25%
sodium metasilicate by blending the components; (B~ mixing sufficient of
the uniform mixture with 14 to 34% of water to provide 10 to 20% of the
total adhesive solids and heating at 50 to 65C. while blending for a '
period sufficient to produce a gel; (C? preparing a second uniform mix-
ture composed of 70 to 90% of the'starch and 10 to 30% of the sodium or .
potassium silicate ~the'silicate having 15 to 20% water? and 0 to 1.5% ` ~ .
,, , . . . . - .- .. . . :
.: ~ .. . : . :~ -
~s~
borax; (D) mixing sufficient of the second uniform mixture to provide
~0 to 90% of the adhesive solids with 42 to 68~o water at a temperature
between room temperature and 45C. to provide a slurry; and (E) blending
the slurry and gel for a period sufficient to provide the final adhesive
composltion.
In one varlant of these process aspec~s, the carr~er portion of
~ep ~ consLsts o~ 0.5 to 2.5~ of the source of alkali dissolved in 14
~o 3~1% water and 1.5 to 6.0% starch and silicate, and the`slurry portion
of step (B) consists of 13.5 to 24% starch and silicate mixtued in 42 to
68% water.
In yet another variant of these process aspects, the'composi-
tion is prepared by: (a) forming the carrier gel portion by tl~ prepar-
ing a dry blend of the alkali source, the starch and the silicate, (2)
blending sufficient of the dry blend with water`at 50 to 65C. to provide
15 to 30% of the`adhesive composition containing 10 to 20% of the adhe-
sive solids; and (b) forming the'slurry portion by (1) preparing a dry
blend of the'starch and silicate,'~2) blending sufficient of the dry
blend with water at room temperature to 45C. to provide 70 to 85% of the
adhesive composition containing'80 to 90% of the adhesive solids.
By a variant of these process aspects, 0.5 to 2.5% of the
alkali source is dissolved in 14 to 34% water to form the àlkaline solu- ~ ~'
tion; 1.5 to 6% of the starch and silicate are blended with the'alkaline ~ '~
~ ,.. . . . ~ , . : .
solution to form the gel; 42 to 68% water' is used to dilute the gel;
and 13.5 to 24% of the starch and silicate are added to the diluted gel.
By another variant of these process aspects, the starch is
selected from the group consisting of corn starch, rice starch,'potato
stzrch, sago, tapioca and casava starches, arrowroot, acorn and moss
starches, starch esters, starch ethers, methyl cellulose and sodium '
palconate, especially where the starch is selected from the group consis-
ting of corn starch,`rice starch'ànd potato starch.' ;
All types'of commercial raw starches'can be'used as the starch '`~
component of the'adhesive of aspects of this invention provided they do '
`~; ~',''`
- 7 - ';
, ~ ,.
37
not contain a signif-lcant amount of protein. '~ey should preferably
contain less than 20% protetn~ 'In general, starches that have the prop-
erty of swelling by'hydration before going into solution at temperatures
between 55 and 80C. are useful. Specific examples of starches that can
be used include corn starchJ rice starch, potato starch, sago, tapioca
nnd casava starches, arro~root, acorn and the so-called moss starches.
Chemlcally modiEled starches such as, for example, esterified starches
and those containing ether groups are also useful. Also useful are
sodium palconate, the sodium salt of palconic acid extracted from red-
wood bark, and starch derivatives such as, for example, methylcellulose.
It has been found that starches of all physical form can beused in the process of aspects of this invention. Pearl, powdered or
granulated starches are usually used in the compositions of aspects of
this invention.
The silicates found useful in the composition of aspects of
this invention include both solutions and apparently dry silicates that
contain some water of hydration and anhydrous silicates and have mol
ratios of 1.5 to 4.0 parts of SiO2 per part of M20 wherein M stands
for sodium or potassium. Examples of useful alkali metal silicate sol-
utions include:
Ratio SiO2/M20
Silicate Wt. Ratio Mol'Ratio
B-W sodium silicate I.6 1.6~
RU " " 2.4 2.47
K " " 2.9 2.97
N " " 3.2 3.30
'S 35 " " 3.8 3.92
KASIL #6 potassium silicate 2.1 3.29
KASIL #l " " 2.5 3.92
(B-W~ RU, K, N, S 35 and KASIL aretrademarks of the Phila-
delphia Quartz Company.~ The granular silicates used as compoDents in ~; '
the compostiQns include~
~, :,,.
` ~ ~
- . ~ - . ~, . . . . .
iti107
Ratio SiO2/M 0
Silicate Wt. Ratio Mol'~at-lo ' Water Content~%)
SS sodium silicate powder 2.0 2.06 0.0
GD sodium silicate 2.0 2.06 18.5
BRITESIL C 20 sodlum silicate 2.0 2.06 18.5
BRITESIL C24 " " 2.4 2.47 18.5
BRITRSIL H 24 " ~ " 2,4 2.47 18.5
G sodium silicate ~ 3.2 3.29 18.5
SS-C sodL~Im sLlicnte powder 3.2 3.29 0.0
~SS, SS-C, GD, G and BRITESIL are ;~trademarks of the Philadel-
ph~ Quart~ Company.)
~ ydrated flakes of silicate glass that contain 4 to 25% water
prepared as described in ~nited States Patent No. 3,840,359 issued
to can also
be used. Sodium metasilicate can also be used in preparing the composi-
tions of aspects of this invention. Anhydrous or hydrated metasilicate
can be used as long as the water associated with the hydrated materials
does not dilute the adhesive system. Examples of useful sodium metasili-
cates include:
Ratio SiO2/M 0
Silicate Wt Ratio Mol'~atio Water Content(%?
METS0 200 sodium silicate 0.50 0.51 0.5
METS0 anhydrous sodium silicate 0.93 0.95 0.5
METS0 BEADS 2048 " " 0.93 0.95 0.5
METS0 Granular " " 0.98 1.01 41.7
METS0 PENTABEAD 20" " 0.9~ 1.01 42.3
(METS0, METS0 BEADS and METS0 PENTABEAD are f- _ -' trademarks of the ' `
Philadelphia Quartz Company.
The starch-silicate adhesives of aspects of this invention can ~ ;
be formed by combining a gelled carrier portion with a slurry of the
remaining ingredients. The gelled carrier portionis somewhat less con- ' ~--
centràted than the finished adhesive since it contains only 10 to 20% of
the adhesive solids but constitutes 15 to 30% of the total composition.
It is prepared by forming an aqueoùs alkali solution, heating this solu~
tion, adding starch ànd silicate while blending, and maintaining the ;
temperature at 50 to 65C. for a period sufficient to produce a creamy
~
uniform gel. 'A slurry of the'remaining starch and silicate and if neces- ~ - '
sary borax is prepared'by mixing the'ingredients in water at room
_ 9 _
;,
- . . ~ , -
i , , ., . .~ . .. , , " ", ., ", . . .
temperature or 24 to 45C. The slurry is added slowly to the gelled
carrier portion while blending to complete preparation of the adhesive.
The alkali utilized to form the aq~leous alkali solution can be
alkali metal hydroxide such as, Eor example, sodium or potasslum hydro-
xlde, or highly alk~line silicate such as, for example, sodium metasili-
cate or tlle so-callcd subsiltcates'such as, for example, orthosillcate
or sesqulsillcate. The'alkaline material reacts with the'starch to form
the carrier gel. The silicate tothei- than the'metasilicate)'used in the
carrier portion and the'slurry portion can be either a solution or a dry
product. The weight'ratio of starch to silicate solids in both the
carrier portion and slurry can be 1.5'to 12 parts of starch per part of
silicate, preferably the ratio being 2.5 to 7 parts of starch per part
of silicate. This ratio is usually the`same for both components of the
adhesive.
The adhesive solids in the composition of aspects of this
invention can vary from 15 to 30% by~weight'based on the'total weight of
the'composition while the'silicate constitutes 9 to 40% o the'solids.
It is considered herein that starch and silicate solids are adhesive
solids~ but that other'materials such às, for example,'borax are not
adhesive solids. The adhesive preferably has a composition of 12 to 23%
starch, 1.5 to 12% silicate, 0.5 to 2.5% of a source of alkali such as,
for example,'sodium'hydroxide or sodium metasilicate, 0 to 2% borax and -
the balance ~70 to 85%) is water. The pH can vary between 11.0 and 11.9
while the'gel temperature varies between 65 and 75C. '~'~
A more detailed'description of the'process is as follows. ~ater
'(14 to 34%) is placed in a container and agitated. Then 0.5 to 2.5% of
source of alkali selected from the group consisting of NaOH, KOH and
sodium metasilicate is dissolved'in the water and the resulting solution
heated to a temperature between 50 and 65C. Then starch and silicate '
(1.5 to 6% total solids) with a starch to silicate weight'ratio of 1.5 to ~ '
12 part of starch per'part silicate are added. The'blending and heating -
are maintained'until a creamy gel'is formed. Then a slurry of water
;;~` ;' `
-- 10 ~
~35~,~L07
(42 to 68%), starch and silicate (13.5'to 24% solids with a starch to
silicate weight ratlo of 1.5'to 12 parts of starch per part of silicate)
and borax (0 to 2%~ is prepared. 'Thls slurry can be prepared at room
temperature or at 25 to 45C. This slurry is added to the'previously
prcpared carrier po~rtLon and blending ls continued until the composition
i9 unlEorm.
~nother process oE preparing the composition lnvolve~ the forma-
~ion oE ~he carrier portion as hereinbefore described. Then the addi-
tional water that would be'used to form the slurry is added'to the carrier
portion and the'!blending continued. 'The'starch and silicate are added and
the composition is blended until uniform. Borax may be added after all
of the other ingredients are blended'to uniformity. In some equipment
the prepared carrier portion may be'àdded to the slurry to form the com-
plete composition.
The'previously described processes involve the dispersion and/or
dissolution of several sepàrate ingredients to form starch-silicate
adhesives. It has been found that stable blends of the materials required
to form the'components of the adhesives'can be prepared in advance and ~ ~ '
stored until the adhesive is required. The dry blend required to prepare '
the carrier portion comprises 50 to 75% raw starch, lO to 25% alkali ' ~'
metal silicate (15 to 20% water~ and 10 to 25% sodium metasilicate. These '~
materials are dry blended'until uniform and can be agglomerated by kno~n -- ' ' '
'methods if desired. The dry blend required to prepare the slurry com-
prises 70 to 90% raw starch, 10 to 30% alkali metal silicate (15 to 20%
water~ and 0 to 1.5% borax. These ingredients are dry blended until
uniform and can be agglomerated if desired. The carrier portion is pre- ,~
pared by dispersing sufficient of the first dry blend to provide lO to 20% , ', ''~ '
of the adhesive solids in an amount of water to provide 14 to 34% of the ,
total composition~ This dispersion is blended and heated at 50 to 65~C. ,`~
for a sufficient time to provide a creamy unifor~ gel composition. Suffi-
cient of the'second dry blena to provide 80 to 90~ of the adhesive solids
was slurried'with an amount of water'to provide 42 to 68% of the final ' '
.~', '.
.. . .
.. ' , . ~- ~, .
- 11 -
.`' ~' ' .
:. -.. -, . . -, .:- , ., . . : : :. :-, .. . ,.. ,, ,. :;~ :,,, ., :
~V5~
composition. The resulting slurry is then added slowly to the carrier
portion and blended to provide a complete composition. The'adhesives
prepared by this process were equivalent to those made by the processes
hereinbeEore described.
The ~tarch-Rillcate a(lhesive when prepared as Indicated ls
s~ablc and produccs strong bonds when used to bond paper products, parti-
cularly corrugated boxes.
... .
EXAMPLES
The following examples illustrate certain embodiments of the
composition of aspects of this invention as compared to the'prior art and
these examples should not be'considered'to restrict the present invention
in its various aspects to these specific embodiments. The proportions
used in the examples are parts by weight'(pbw) unless otherwise noted. '
The ratios of the silicates'are mol ratios of SiO2/M20. The following
procedure was carried out to prepare corrugated bond specimens and to ~`~
test them for tensile bond strength. A film of adhesive was spread on a
glass plate using a spreader`with 0.013" ~0.33 mm) clearance;' the flute;
tips of a piece of B single face board were pressed onto the'adhesive
film and then placed on a piece of kraft liner that had been preheated on
a hot plate at 171C. and a weight placed on the board assembly. After
15 seconds the weight'and board assembly were removed from the hot plate.
The bonded specimens were allowed to condition overnight at
22.8C. and 50% relative humidity. The specimens were cut to provide 6
identical sections, 1/2" tl.27 cm) wide and 12 specially bonded flute
tips in length. Three'sections were tested for tensile bond strength on
an Instron Tensile Tester using a special device designed by R. H. Sams, '
reported in TAPPI Routine Control Method 269-pin test of bond quality in ~ ' -
corrugator board. The'force causing separation of the bond was doubled -~
to convert it to pounds of tensile strength/12" length of flute tip and
will be reported as kg of tensile strength/30'.5 cm length of flute tip.
T~e'remaining 3 bond test sections were stored in a closed
container over'water to-approximate 100% r.h. One section was tested for -'
- 12 -
~o~ )7
bond strength after one hour. Another was tested after 3 days at 100%
r.h. 'The third sectionafter'3 days in the'closed'container'was recondi-
tioned at 22.8C~ and 50% r.h.' overnight before testing. 'The`gel tempera-
t~lre was measured'by weighing 20 g of the adhesive into a 25 x 100 test
~ube. This test tube was then immersed in a 600 ml beaker contalning
~ater con~rolled at 77C. A thermometer was ~Ised to stir the'adhesive
~In~Ll gelatlon occl~rred'and that tempera~ture'recorded. 'The`èase of
c~ean up was tested'by'smearing equivalent amounts of adhesives'on abraded
hot plate surfaces'at 171C. 'The'adhesive was allowed to bake dry and
pieces of kraft liner`were used`to scrape the residue from the'surfaces. "`
.......... ~
EXAMPLE 1
The'carrier'portion of a pure starch adhesive was prepared by
combining a solution of 0.4 pbw of caustic dissolved'in 1.9 pbw of water ' ,,~
with a slurry of 3.8 pbw of pearl corn starch in 7.6 pbw of water. The
resulting slurry was heated'to 74C. while mixing and then held at 74C. , ' . ,
for 15 minutes. 'Then an addition of 10.9 pbw of water was added and the ~` ,
mixture held for 1/2 hoùr. Then the'mixture was added to a starch slurry '`
containing 56.0 pbw of water, l9.0'pbw of pearl corn starch and 0.4 pbw of
borax. `T~le pH of this starch adhesive was found to be 12.3. A series of ,~
corrugated'bond specimens were prepared and tested for dry and humid
tensile bond strength. The'results of the prior art procedure were~
Tensile Bond Strength
'(Kg/30.5'cm'of'flute) ~ - ,
Conditioned overnight (22.8C., 50% r.h.) 24.8 `'
1 hour (100% r.h.) 23.4
3,days (100% r.h.) - 9.9
3 days (10070 r.h.)overnight(22.8C., 50% r.h.~ 20~7
The bond strengths are satisfactory except for the sample exposed to 100% -
r.h, The dried-baked'adhesive was easily scraped from a hot plate with
a piece of kraft liner. ~`
EXAMPLE 2
A starch-silicate adhesive was prepared using the'starch adhe- ~ ;
sive prepared'as describea in Example 1 by combining 10 pbw of "N" sodiu~ - ,
silicate (38% silicate solids)-with 90 pbw of the starch adhesive and ~
- 13 - ~,
iL07
mixing until uniform. The pH o~ the starch-silicate adhesive was 11.5.
A series of corrugated bond specimens were prepared and tested for dry
and humid tensile bond strength. 'The'results were:
Tensile B~nd Strength
_g 30 5'cm of flute)
CondltLoned overnight (22.8C, 50% r.h.) 27.9
l ho~lr (100% r.h.) 30.2
3 days (L00% r.h.) ' 9.0
3 days (100% r.h.) overnight (22.8C., 50% r.h,') 25.2
The drled baked adhesive was easily scraped from a hot'metal plate with a
piece of kraft liner.
EXAMPLE 3 '
A second starch-silicate adhesive was prepared using the starch ' '
adhesive prepared as described in Example 1 by combining 20 pbw of "~"
sodium silicate with 80 pbw of the'starch adhesive and mixing until
~miform. The pH was 11.3. A series of corrugated'bond specimens were
prepared'and tested for dry and humid tensile bond strength. The results
were~
Tensile Bond Strength
(Kg/30.5 cm of flute)
Conditioned overnight'(22.8C., 50% r.h.)' 23.4 '
3 days (100% r.h.)' 18.0 ~-
3 days (100% r~h.) overnight'(22.8C., 50% r.h.) 28.4 ~ ''
-EXAMPLE 4
A carrier portion of a prior art starch adhesive was prepared
by dissolving 0.53 pbw of caustic in 22.70 pbw of water, adding 3.40 pbw
of pearl corn starch and blending at 63C. until the mixture was creamy.
The adhesive composition was completed by addition of a starch slurry
containing 20.42 pbw of pearl corn starch,'52.52 pbw of water and 0.37 pbw
of borax. The slurry was added slowly and stirred for several minutes
until a uniform adhesive containing 23.82~ adhesive solids was formed. -'
The p~ of the starch adhesive was 12.2 and the viscosity wa~ 6 poises.
The gel temperature was 66C. 'Corrugated bond specimens were prepared
and tested for dry tensile strength and it was found to be'34.2 kg/30.5 '~
cm of flute.' The dried'baked'adhesive was easily removed'from a hot ~
plate. ' ~ -
..... .....
- 14 ~
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-- ~V~ 7 ~,
EXAM~LE 5
A Elrst series'starch-silicate adhesives'was prepared as
Eollows. 'A gelled carrier'portlon wns prepared by dissolving 0.53 pbw
oE cnustLc :Ln 22.70 pbw oE wnter', addlng various proportions of the pearl
oorn 8tasch nnd (G)' sodium silicate (3.29 SiO2/Na20 ratio and 18.5~ ~l2)
and mlxin~ at 63C. unt:Ll the mL~ture was creamy. 'rhs adhesive mixture ~'
was completed by addition of a slurry containing various proportions of
pearl corn starch and "~" sodium and silicate,'52.52 pbw of water and ~ `
0.37 pbw of borax. The'proportions of starch and silicate used in pre- " ``
paring the starch-silicate adhesive and the'composition and properties ~ '
of the final product are summarized'in Table 1.
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EXAMPLE 6
A second series of starch-silicate adheslves was prepared by a
process simLlar to that descrlbed'in Example 5 except that sodium meta-
slllcate (METSO BEADS 2048) was substituted for the NaO~I. Table 2
sulnmarL~s the dat~ for these runs.
EXAMPLE 7
An attemp~ was made'by`prior art m'ethods to prepare a starch
adhesive at 21.6% total solids in the'following manner. A gelled carrier
portion was prepared'by dissolving 0.58 pbw'of NaOH in 19~61 pbw of
water, adding 5.14 pbw of powdered`corn starch to the`solution and mixing
at 60C. until homogeneous and creamy. The'slurry consisting of 53.83
pbw'of water, 15.37`pbw of powdered'corn starch and 0.58 pbw of borax,
was added slowly to the'carrier'portion and blended'until uniform. The
combination that resùlted from this preparation was unsatisfactory because
the viscosity was too high.' Repeated attempts to prepare this "starch '
`only" adhesive at 21.6% solids were unsuccessful. When'an adhesive was
prepared with starch solids of 19.8% a satisfactory adhesive resulted
with a gel temperature of 64.5C. and dry tensile bond strength of
26 kg/30.5 cm of flute.`
EXA~PLE 8
Starch ` silicate àdhesives'were prepared at 21.6% solids in
the following manner~ Sodium metasilicate pentahydrate (1.53 pbw of ~ ~
METSO PENTABEAD 20) was dissolved in 18.97 pbw of water, then 4.71 pbw of '
powdered corn starch was added and blended at 60C. until creamy and '
uniform to form a gelled carrier. The'slurry consisting of 57.93 pbw of
water, 11.53 pbw of powdered corn starch, 0.48 pbw of borax and 4.74 pbw
of dried sodium silicate, was added slowly and blended until uniform. Two '
starch-silicate adhesives were prepared in this way using as the silicate ~ `
BRITESIL C-20 sodium silicate (2.06 SiO2/1.0 Na20 mol ratio and 18.5% H20)
and BRITESIL C-24 sodium silicate (2.47 S102/Na20 mol ratio and 18.5% H20
The'gel temperatures were 70.5'and 75.0C. respectively. The tensile
bond strengths were both 31'.9'kgl30.5'cm of flute.' -~
- 18 - ' ~ "
~ '
~os6iO7
EXAMpLE 9 . `!
Starch-sllicate àdhesives were prepared'accordlng to the pro- '. .'cess of Example 8 except that onl~ 0.24 pbw o borax was used. The ''
propertles of the àdllesives were relatively unchanged.
; XAMP~E ln
Stareh-sil:Lcate adhes:lves were prepared accordlng to the pro- :
cess oE Example 8 except that no borax was uséd. The properties of the
a~hes~ves'were relatively unchanged.
EXAMPLE ll ~ .
A mixture of 26.6 pbw of pwoderèd corn starch, 5.7 pbw:of "G" :. .
sodium silicate and 8 pbw'of sodium metasilicate (METSO'BEADS 2048) was
prepared'and dry blended until uniform. 'A second mixture of 167.4 pbw
~f powdered corn starch and 36.3 pbw:of "G" sodium silicate was prepared
and dry blended until uniform. Ten'pbw of the first mixture was added
to 22 pbw of water'and blended'at 65C. until creamy, 10 pbw of the
second mixture was slurried in 52 pbw of water'and added'slowly to said '
creamy product and blenaed'until uniform. 'The pH of the completed starch-
silicate adhesive was 11.4'and the'gel temperature was 75C. Tensile
bond strengths'were 30.9,.and 37'.0 kgl30.5 cm of flute respectively for '
20~. dry, humid.and redried'specimens. The dried'and baked adhesive could be ~ ~
removed easily from a hot plate. ' '
EXAMPLE'12 .
Portions of the mixtures prepàred as described in Example 11 ~ :
were aged for six months and an adhesive prepared as previously described.
The pH of the adhesive was 11.4 and the gel temperature was 74.5C. Ten-
sile bond strengths were 31.5~ 13~7'and 37.3 kg/30~5 cm of flute respec-
tively for dry, humid, and redried specimens. The dried and bake:
adhesives could be removed'easily from a hot plate.
EXAMPLE'13 ' ~:
Starch-silicate adhesives'were prepared as described in Example
5 except that various types of starch were substituted'for the pearl corn ~ '
starch.' The'results were as follows~
- 19 - '
5~,~a.07
Tensile Bond Strength
(kg/30.5 cm of Elute~ ;
Type of Starch (overnight, 22.8C., iOX r.h.
Rlce 33,7
Potato 34~0
Taploca 32.9
R~erifled 33.0
' '
20..
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_ 20 - - :
