Note: Descriptions are shown in the official language in which they were submitted.
)5~.5;3
BOOK BINDING PROCESS_INVOLYING PR_IMER
AD~IESIVE CONTAINING STARCH
. . . ~ _ . . _ . _
Cross-Reference to Related Apelications
This application is related to U.S. Paten~ No.
~,564,6~9, filed April 16, 198~. ;
Field of the Invention
The present invention relates to an improved book-
binding process comprising the use of an aqueous primer
adhesive composition containing ungelatinized starch. A
layer of the primer adhesive is coalesced to a resilient
hinge by the application of a hot covering adhesive without
the need for an intermediate drying step. The coalesced
film of primer adhesive provides a suitable underlying
substrate for the adherent covering adhesive which binds the
cover stock to the finished book.
Backqround of t_e Invention
The automation of book binding has allowed book produc-
tion to proceed ~s an essentially continuous process fromthe printing and compilation of the pages, or signatures,
into book blocks, through the gluing of the block spines, to
the application of the cover stock and trimming. Typically,
individual pages or signature folds are collated into a
compressed stack, or "block". The block may be sewn prior
to further processing. Prior to application of the primer
adhesive, the outer surface of the spine area can be cut and
roughe)led by a ro~ating blade to yield an absorptive, planar
surface. The block is next provided with a flexible hinge
by the application of a coating of a primer adhesive, which
may be a latex comprising an emulsified polymeric adhesive
resin, or an aqueous animal glue adhesive. The primer is
~ ~ ~5 ~'33
applied in one or more applications by brushing, rolling or
a similar process so as to coat and penetrate the roughened
spine. A portion of the wet primer wicks between the sheets
to form a matrix which when dry, binds the sheets into the
body of the flexible film which forms a part of the spine of
the block.
The coating of wet primer is next dried and set by expo-
sure of the coating to an intense, high temperature heat
source. At least one coating of a covering adhesive, which
may be a natural or synthetic animal glue or a polymeric
hot-melt type adhesive, is then applied over the dried
primer layer to provide the backbone. The cover is adhered
to the backbone and the bound pages are trimmed.
The maximum speed at which the adhesive application
steps can be accomplished has been limited by the time
needed to dry and set the water-based primer layer prior to
application of the covering adhesive layer. However, the
use of elevated temperatures to speed the drying of the wet
primer coatings is limited by a number of factors. Primers
based on animal proteins resist moisture release at low tem-
peratures but are subject to extensive thermal degradation
at high application or drying temperatures~ When dried,
these primer layers can exhibit defficiencies with respect
to film strength, flexibility and absolute adhesion to the
paper.
Latex-based primers skin over when exposed to intense
heat sources; the wet coating becomes surfaced with a thin
polymeric membrane. The water entrained in the interior of
the primer layer vaporizes and lifts this dried membrane
3û into large blisters which can break and burn as they
approach the heat source. If the subsequently-applied
covering adhesive fails to adhere fully to these blistered
or burned layers of primer, the binding process cannot be
completed satisfactorily. The damaged, partially-bound
books often jam in the assembly line and must be removed and
~LX~
--3--
discarded, resulting in substantial economic losses.
Furthermore, if the primer coating is not sufficiently
dried, application of a hot-melt adhesive at conventional
temperaures of about 150-200~C can cause splattering and
blistering of aqueous primer adhesives.
Recently, improved latex-based aqueous primer adhesives
which resist blistering and charring when exposed to high
drying temperatures, have been developed which address this
problem. See U.S. Patent No. 4,536,012. These adhesives
contain an amount of ungelatinized starch granules effective
to complex a major portion of the water in said primer com-
positions during the drying process. As the temperature of
the wet primer coating rises, the starch swells by absorbing
contiguous water. At the same time, the primer adhesive
coating is coalesced into a uniform plastic filrn. As the
temperature continues to increase, the bound water is
released uniformly and relatively slowly from the swollen
starch granules. This controlled water release allows the
resultant film to resist the formation of large blisters and
their subsequent charring. A multiplicity of much smaller
bubbles form and burst, cratering the surface of the prirner
film. The primer coating dries into a uniform, resilient
layer which possesses a surface which is well-suited for the
application of further adhesive coatings.
In spite of this advance, however, it will be appre-
ciated that the speed of the book binding process would be
improved if the need for an intermediate drying step between
the application of the primer adhesive and the covering
adhesive could be entirely eliminated. Such a simplifica-
tion would substantially reduce the production time required
for each book. It would also allow manufacturers to reduce
the energy input required by eliminating the need for
thermal energy during the drying step, thereby lowering pro-
duction costs.
It will be further appreciated that additional advan-
tages can be achieved by reducinq the high temperatures
5~ 3
required in the application of conventional covering adhe-
sives. For example, in the process disclosed in U.S. Patent
No. 4,536,012, the hot-melt is applied to the dried primer
layer at about 1~50-200C. If the covering adhesive could be
handled and applied at substantially lower temperatures, the
burn hazard to workers would be diminished. In addition,
less time would be required to cool the covering adhesive
prior to the cover pick up step.
Brief Description of the Invention
The present invention is directed to an improved book-
binding process comprising the use of a latex-based primer
adhesive composition containing ungelatinzed starch. A
layer of the wet primer is applied to the spine area of the
book block and is coalesced to a resilient hinge by the
application of a hot covering adhesive without the need for
an intermediate drying step. The coalesced film of primer
adhesive provides a suitable underlying substrate for the
adherent covering adhesive which binds the cover stock to
; 20 the book block. In addition, a covering adhesive such as a
natural or synthetic animal glue, may be employed which can
be applied to the wet primer adhesive coating at tempera-
tures substantially below about 150C.
The method of the present invention is particularly
well-adapted to the assembly of books which have conven-
tionally employed primers based on animal glues to hinge
blocks formed of uncoated, highly moisture absorbent papers.
Such books include mass-market paperbacksg catalogs, tele-
phone directories, and the like. Unlike aqueous primers
based on animal glues such as bone glue, the present starch-
latex primers adhere well to coated paper stocks, thus per-
mitting the inclusion of coated, or glossy inserts into such
books without weakening the page strength of the finished
assembly. The present primers are also highly effective
with respect to their adherence to blocks which are formed
of coated stock.
5~5~
--5--
The preferred primer composition for use in the present
method comprises an adhesive latex and an amount of ungela-
tinized granular starch effective to complex the latex water
upon application of the hot covering adhesive so that no
intermediate drying step is required prior to application of
the covering adhesive. Instead of complexing and then
evaporating the residual water from the coating of primer
adhesive in a discrete drying step, the covering adhesive is
applied directly onto the wet primer layer at a temperature
lû which is sufficient to coalesce the primer adhesive to a
resilient, flexible film. The covering adhesive can be
applied at about 35-100C~ preferably at about 50-~0Co
The absence of an intermediate drying step which drives
off essentially all of the primer ~ater, does not preclude
the external application of heat following primer applica-
tion to the extent necessary to gel a portion of the starch
in the liquid primer layer. It is to be understood, how-
ever, that when the covering adhesive is applied, the primer
has not been completely coalesced or dried. It is believed
that the melding of the-liquid or quasi-liquid primer layer
with the liquid layer of the covering adhesive contributes
substantially ta the greatly increased total strength of the
finished books.
- The eli~ination of the need for an intermediate drying
step between the application of the primer adhesive and the
application of the covering adhesive permits a substantial
increase in the speed at which the adhesive application
steps can be accomplished, and consequently increases the
speed of the entire continuous book binding process. In
eliminating the drying step, the use of thermal energy is
also reduced, thereby lowering the overall manufacturing
costs.
The use of covering adhesives which can be applied at
temperatures below about 150C reduces the time required
to cool the covering adhesive prior to cover pick up.
~L~75~L53
Furthermore, the exposure of the hot covering adhesive to a
relatively cool, unheated layer of primer decreases the time
necessary for the covering adhesive to cool and become
tacky. In addi~tion, the application of adhesives at lower
temperatures improves plant safety, because workers are not
exposed to the danger of burns caused by high-temperature
liquid adhesives.
A preferred covering adhesive is an aqueous animal glue-
` based adhesive which comprises a hide glue in admixture with
a humectant-plasticizer. Another covering adhesive for use
in the invention is a synethetic animal~ glue adhesive com-
prising about 25-75% by weight of an aqueous phase and about
25-75~ of a solid component which contains a lignin sulfon-
ate composition and a polyvinyl alcohol composition.
Preferably, there are about 1 to 8 parts of the lignin
sulfonate composition per each part of the polyvinyl alcohol
composition. The liquid covering adhesive can be-applied
hot by conventional means to form a coating of about 0.1 to
100 mils in thickness. Following cooling of the adhesive
layer to a tacky film or gel, it is brought into contact
with the book cover. The assembly is clamped, and trimmed
to complete the book binding process.
While we do not wish to be bound by any theory of
action, it is believed that sufficient heat is transferred
from the covering adhesive to the primer adhesive to cause
the ungelled starch to swell and adsorb the residual latex
water. This causes the primer adhesive to coalesce to form
a uniform flexible film on the spine of the book block which
acts to firmly bind the pages thereto. Thus, the latex
3û water bound by the gelled starch is not available to disrupt
the integrity of either the primer or the covering adhesive
layers.
~t7~ ~
Detailed Description of the Invention
Primer Compositions
Latexes
. _
The present primer compositions are modified adhesive
latexes. The major portion of the latex solids are
emulsified particles of adhesive polymeric resins. Any
suitable water-dispersible polymeric resin may be employed
` as the polymeric solid phase, including, but not limited to
polychloroprene (neoprene), styrene-butadiene rubber, vinyl-
vinylidene chloride, ethylene-vinyl chloride copolymers,
ethylene-vinyl acetate copolymers, vinyl acetate-acrylic
acid copolymers and acrylonitrite-butadiene copolymers.
Preferred polymeric latex adhesive bases include the alkali-
soluble vinyl acetate-acrylic acid copolymer available as a
55% aqueous emulsion as CovinaxTM 106 from the Franklin
Chemical Co., Columbus, OH and DowTM 620 styrene-butadiene
latex (Dow Chemical Co.). Especially preferred latex adhe-
sives include the ethylene vinyl acetate copolymers avail-
able as 47-55% aqueous dispersions as the AirflexTM series
(Air Products Corp., Allentown, PA), or the ethylene-vinyl
acetate copolymer available as ElvaceTM 1875 (54.5% solids)
from Riechhold Chemical, Dover, Delaware.
Primer compositions are commonly prepared by dosing such
latexes with minor but effective amounts of surfactants,
biocides, foam-control agents and plasticizer, and by adding
water, if necessary, to bring the solids content into the
desired range.
Starch
The highly-desirable properties exhibited by the present
primer compositions are achieved by the incorporation
therein of an amount of ungelatinized (nonswollen) starch
granules effective to complex or absorb the water in a layer
of the primer composition when the hot covering adhesive
~;~75~L53
layer îs applied thereto. It is believed that this com-
plexation causes the adhesive particles dispersed in the
primer coating to coalesce, forming a uniform, resilient
film which firmly binds the individual sheets of the book
block theretoO
Starch is a high molecular weight carbohydrate of the
general formula (C6H1005)n. Starch granules exhibit a
structure of concentric sheets which contain an elutable
amylose fraction in the inner layers and an amylopectin
fraction in the outer layers. ~hen starch granules are con-
tacted with water and heated above a temperature designated
as the gel point, the granules begin to bind water and
swell. The gel temperature for a particular starch variety
depends on a number of factors, including particle size, pH
and absolute concentration. If the weight ratio of starch
to water is high enough, the effect of exceeding the gel
temperature will be to gel substantially all of the water
into a thick paste.
Starches useful in the present primer compositions will
be chosen from any of those which can be mixed with the base
primer composition at a concentration effective to complex a
major portion of the free water present, while not overly
increasing the viscosity of the primer compositions prior to
the application of the covering adhesive.
Useful starches may be selected from any of a wide
variety of commercially-available products including but not
limited to barley~ corn, potato, wheat, rice, waxy maize,
sago, sorghum, arrowroot, tapioca or mixtures thereof.
These raw starches typically have granules sized within the
range of about 2-150 microns, as measured along the longest
axis, and exhibit gel temperatures of about 55-~CDC. Since
these starches can bind about 600-1000% of their weight of
water, for most binding applications useful amounts of the
starch additive will fall within the range of about 1-20%,
preferably about 2-15% and most preferably about 3-10% of
. ~ , .
the total wet weight of the primer composition. Although it
is preferred to add an amount of starch within these ranges
which will complex a major portion of the water in the com-
position, amoun~s of starch effective to absorb 50~ or less
of the composition water have been found to be effective in
the present method, particularly when the primer adhesive is
applied to a block formed of highly water-absorbent paper.
Surfactants
Although the commercially-available latexes useful as
starting materials for primers often comprise minor amoun-ts
of dispersing agents for the polymeric adhesive particles
therein, it is often desirable to add additional amounts of
surfactants to enhance the ability of the polymeric disper-
sion to wet the paper fibers and help to maintain the starch
additive in suspension. The added surfactants can be
anionic, cationic, nonionic or amphoteric and should be
selected to be compatible with the surfactants already pre-
sent in the latex, if any.
Examples of useful nonionic surfactants include poly-
ethylenoxy esters and ethers of alkylphenols, alkanols and
mercaptans, as well as polyethylenoxy compounds with amide
links. One useful class of nonionic surfactants is the
TergitolTM series, available from Union Carbide, which are
formed by condensing about 3-10 moles of ethylene oxide with
a C12-C15 alkanol. Another useful class of nonionic surfac-
tants is the GlycoperseTM series, available from Glyco, IncO,
Green~ich, CT, which are formed by condensing sorbitol and
sorbitol anhydride mono- or tri-fatty acid esters which with
about 4-25 moles of ethylene oxide. For example,
GlycoperseTM 0-20 is polysorbate 80.
Examples of anionic surfactants include (a) carboxylic
acids such as soaps of straight-chain naturally-occurring
fatty acids, chain-substituted derivatives of fatty acids,
branched-chain and odd-carbon fatty acids, acids derived
~.~75153
--10--
from paraffin oxidation, and carboxyllc acids with inter-
mediate linkages; and (b) sulfuric esters such as sodium
lauryl sulfate, tallow alcohol sulfates and coconut alcohol
sulfates.
Examples of cationic surfactants include nonquaternary
nitrogen bases such as amines without intermediate linkages 7
and quaternary nitrogen bases. The quaternary nitrogen
bases are preferably those which also function as biocides,
since such "quats" act to inhibit the growth of microorgan-
isms which would attack the bindings of the finished books.
Especially preferred quaternary ammonium surfactants are the
Cg-C20-alkyl(dimethyl)-(benzyl or substituted-b~nzyl)
ammonium halides such as benzalkonium chloride, cetalkonium
chloride, methylbenzethonium chloride, cetyl(dimethyl)ethyl
ammonium bromide, domiphen bromide, gentian violet, dicoco-
(dimethyl)ammonium chloride3 cetyl(trimethyl)ammonium bro-
mine and the like.
Biocides
-
Apart from the antimicrobial action imparted to the
latex primer adhesive by any added surfactants, it is often
desirable to add an effective amount of one or more addi-
tional biocides, particularly in cases where a quat surfac-
tant cannot be employed. Such agents include chlorhexidine
gluconate, glutaral, hexachlorophene, nitrofurazone, nitro-
mersol, thimerosol, Cl-C5-parabens, chlorophene, phenolics,
mefanide acetate, aminacrine hydrochloride, oxychlorosene,
metabromsalene, merbromine and dibromsalan. Preferred
biocides include sodium bisulfite, formaldehyde (formalin),
cresols, sodium ortho-phenyl phenol (DowicideTM A, Dow
Chemical Co.), 2,2'-methylene-bis-(4-chlorophenol), which is
available as CuniphenTM 2778 from Ventron Corporation,
Beverly, MA and 1,2-dibromo-2,4-dicyanobutene (TektamerTM 38
A.D., Merck Chemical Div., Rahway, NJ).
iL;~7S~3
Plasticizer
The present primer compositions preferably will include
an amount of plasticizer effective to maintain the polymer
particles in a~flexible state, thus maintaining the
resiliency of the dried, set primer adhesive. Useful
plasticizers may be selected from any of the commercially-
available benzoates, hydroxylated benzoates or hydroxylated
benzyl esters of alkanols. One useful plasticizer is the
mixed dibenzoate of dipropylene glycol and diethylene
glycol, available from Velsicol Corp., Chicago, IL as
BenzoflexTM 50. Another useful plasticizer is butyl benzyl
phthalate available from Monsanto Co. as SanticizerTM 160.
Foam Control Agents
In addition to the plasticizer and biocide7 the primer
compositions preferably contain one or more foam control
agents in an amount effective to substantially prevent the
primer adhesive from foaming when it is applied to the
roughened spine area, e.g., by rotating brushes. Any agent
usefwl to control the surfactant-induced foaming of aqueous
emulsions may be employed in the present primers, including
but not limited to polysiloxanes such as simethicone,
dimethicone copolyol 9 cyclomethicones and the like. Other
useful foam-control agents are the proprietary
FoamasterTM VF defoamers available from Diamond Shamrock
Corp., Morristown, NJ9 and the NopcoTM defoamers available
from Nopco Chemical Division, Newark, NJ and ColloidTM 5759
711 and 796 available from Colloids9 Inc., Newark, NJ.
pH Ad~justment
The present primer compositions may also include a minor
amount of a basic metal salt, e.g., sodium or potassium
hydroxide9 effective to lower the gel temperature of the
starch employed. Amine bases such as urea, hydroxyethanol
amines or ammonium hydroxide may also be employed. The use
~7S9~5;3
-12-
of such bases is indicated when a starch which swells at
relatively high temperatures, e.g., rice or barely starch,
is employed in primer compositions which are exposed to
relatively low ~emperature covering adhesives. From about
0-5% of the base can preferably be employed in the present
compositions. For example, the use of ammonia to increase
the pH of a barley starch primer from about 3.5-4.5 to about
7.0-7.5, decreases the gel point of the starch from about
65-7ûC (150-16ûF) to about 57-62C (135-145F). The sub-
sequent addition of urea can further lower the gel point ofthe primer to as low as about 46--51C (115-125F) without
further decrease in the pH.
Thus, the primer compositions of the present invention
will comprise about 50-97%, preferably about 75-95% of an
adhesive latex; about 3-10% starch; about 0.05-5%, pre-
ferably about 0.1-1% of a biocide; about 0.05-2'~, preferably
about 0.07-1% of foam control agent; and about 1-10%, pre-
ferably about 2-7% plasticizer. Optionally, the primers can
comprise about 0.02-5~, preferably about 0.05-2.5~ of added
surfactant and about û.1-1% of an alkali metal hydroxide
salt or an amine base. The starch-containing primers will
comprise about 30-80% total solids, preferably about 45-65%
total solids and most preferably about 55-63% total solids.
Primer adhesives of this type and their use in conventional
book-binding processes are disclosed in U.S. Patent No.
4,536,012.
Preparation
- 30 The present adhesive primer compositions can be prepared
by dispersing the starch and other adjuvants in the latex
component in any convenient manner. Typically, an appro-
priate liquid mixer is charged with the latex, followed by
addition of the plasticizer with stirring. After the poly-
meric granules have been adequately plasticized, e.g., after
.,
I
~` '.
~ I
~x~
about 0.25-0.75 hours of stirring at 20-30C, defoamer is
added, followed by the surfactants, if any, and the biocide.
Slow stirring is continued until the mixture is homogeneous
and then the powdered starch is gradually added. After
about 0.25-0.75 hours of slow mixing, water is added, if
necessary, to adjust the viscosity and bring the total per-
cent solids into the desired range. After screening the
slurry to remove any agglomerated material, the composition
is ready for use.
Primer Application
The finished starch-containing primer adhesives are
applied to the spine area of the book block to a thickness
of about 2-35 mils (50-875 microns), preferably about 25-30
mils (125-75û microns), by methods which are well-known to
the art; for example, by moving the block over a rotating
brush or wheel.
- Covering Adhesive
The primer layer is next coated with a layer of a cover-
ing adhesive, such as a natural or synthetic animal glue-
based adhesive, or a hot-melt adhesive7 which functions to
adhere the cover stock to the backbone of the book.
Typically, the covering adhesive will be applied to the
primer adhesive as a liquid heated to a temperature which is
effective to coalesce the primer adhesive, e.g., to about
35-lOûC, most preferably about 5n-80c. After application,
it may be necessary to cool or dry the liquid covering adhe-
sive until it attains the required degree of tackiness. The
coverstock is then applied to the individual book blocks and
the books are trimmed. In a continuous binding operation,
the covering adhesive is generally applied to the individual
book blocks by passing them over a heated reservoir of the
adhesive which is fed onto a rotating wheel and doctored to
the necessary thickness. It may also be sprayed on or
applied in any other conventional manner.
~L~7~i~LS;~
Hot-Melt Adhesives
Hot-melt adhesives employed in book binding typically
comprise combinations of a polymeric component with a
tackifying wax gr.resin and, optionally, an oil and a minor
amount of resinous or monomeric plasticizer.
Substances useful as the polymeric component of hot-melt
adhesives include ethylene-vinyl acetate copolymers, block
copolymers of styrene with isoprene, butadiene or ethylene-
butylene midblocks, polyamides, polyisobutylene, polyacryl-
ates or polyesters. Of these polymers, ethylene-vinyl
acetate copolymers are preferred, due to their compatibility
with the preferred ethylene-vinyl acetate latexes used to
form the primers. The tackifiers commonly used in hot-melt
adhesive formulations includes rosins, rosin-resin esters,
polyterpenes, terpene phenolics, aliphatic and aromatic
hydrocarbons, asphalt and the like. Hot-melt adhesives of
this type are commercially available as the HM series from
H. B. Fuller Co., St. Paul, MN, i.e., HM-1922, HM-1330,
HM-1832 and HM-3415.
Animal Glue-Based Adhesive
Animal Glue
Animal glues useful in this invention are the hydrolysis
products of the protein collagen which is extracted from
animal tissues such as skin, hide, bone, sinew, and tendon.
These glues are available as granular powders or flakes
which include 80-9û% glue protein, and which exhibit a jelly
value of greater than about 299 bloom grams. Their general
utility depends on the nature of the hydrolytic breakdown
that takes place during manufacture. Preferred animal glues
include the hide and bone glues available from Hudson
Industries, Corp., Johnson, NY.
53
-15-
Humectant Plasticizer
The animal glue adhesives and the lignin sulfonate-
polyvinyl alcohol adhesives of this invention can contain a
material that p~asticizes the mixture. Plasticizers are
defined as materials incorporated into a composition that
can increase its workability and flexibility or distens-
ability. Plasticizers that can be used in the covering
adhesives of this invention include the humectant plasti-
cizers that can complex a suffi.cient plasticizing amount of
lû water, thus insuring the flexibility and toughness of the
adhesive film. The most preferred group of plasticizers
include polyhydroxy compounds having 2 or more hydroxyl
groups and 2 or more carbon atoms. Typical examples of such
plasticizers include ethylene glycol, diethylene glycol,
triethylene glycol, propylene glycol, 1,2-butylene glycol,
1,4-butylene glycol, sorbitol, glycerin, glucose, sucrose,
invert sugar, glycerol monomethyl ether, polyoxyalkylene
glycols and mixtures thereof.
Therefore, animal glue-based adhesives preferred for use
in the present invention will comprise about 25-50%, most
preferably about 30-45% by weight of animal glue; about
20-40%, most preferably about 25-35% of a humectant plasti-
cizer and about 15-~0%, most preferably about 20-35% water.
Optional ingredients for modification of the properties of
these glues include about 0.5-2% foam control agent, about
0.1-1% biocide and minor but effective amounts of pigment,
surfactant, fragrance and/or binder. The surfactant~ foam
control agent and biocide may be selected from those dis-
closed to be useful in the primer compositions described
hereinabove.
Preparation
The animal glue-based adhesives can be prepared by
mixing the water, animal glue, the glycol or glycerin
plasticizer and any biocide or defoamer at about 20-45C
~L2751S3
-16-
for about 5-15 min., followed by heating the stirred mixture
to about 70-75~C (160-165F). The sugar humectant plasti-
cizer~ if any, is then added, rollowed by adjuvants such as
fragrance, bind~er, and additional defoamer and water, as
needed.
Synthetic Ani~al Glues
Covering adhesives which may be considered synthetic
animal glues include aqueous adhesives which contain about
25-75% by weight of an aqueous phase and about 25-75% of
solid component dispersed therein consisting essentially of
a lignin sulfonate composition and a polyvinyl alcohol com-
position. Preferably, there are about 1 to ~ parts of the
lignin sulfonate composition per each part of the polyvinyl
alcohol composition. These adhesives exhibit substantially
improved heat and biological stability, extended pot life,
easy clean up, low odor, elevated tack, extended open time,
and have a substantially lower cost than glues based upon
natural animal protein. After manufacture the synthetic
~0 adhesives can be dimensionally stable, biologically stable
and flexible. Adhesives of this type are fully disclosed
with respect to their formulation and use in conventional
bool<-binding processes in U.S. Patent No. 4,564,649.
Li~nin Sulfonate
Lignin is a major constituent of wood and woody plants
comprising about one-quarter of the dry weight of such
materials. It appears to function as a natural plastic
binder for the cellulosic fibers which make up the struc-
tural units of the plant. During the pulping process,
lignin is made water-soluble by reaction with sulfite
resulting in sulfonation. The products derived from the
solubilized sulfonated lignin are referred to as lignin
sulfonates. The structure of these lignin sulfonates cannot
~' ,.
.. ,. :
5~53
be completely determined; however, they appear to be a mix-
ture of polymers containing units of aromatic rings, methoxy
groups, aromatic and aliphatic hydroxyl groups and ketone
and aldehyde carboxyl groups. It appears that the basic
monomeric unit of lignin is a sulfonated substituted
guaiacyl propane.
Lignin sulfonates commonly contain many sulfonated com-
pounds with a broad range of molecular weights and degrees
of sulfonation. They can contain small amounts of natural
sugars such as mannose, glucose, xylose, and galactose, and
can contain small amounts of higher moLecular weight poly-
saccharides. Lignin sulfonates are commonly available, from
a number of commercial sources, as light brown dried powders
or as viscous aqueous solutions.
Polyvinyl Alcohol
Polyvinyl alcohol (PVA), a polyhydroxy polymer having a
polymethylene backbone with pendent hydroxy groups, is a
water-soluble synthetic resin. It is produced by the hydro-
2û lysis of polyvinyl acetate. The theoretical monomer(CH2=CHOH) dDes not exist. Polyvinyl alcohol is one of the
few high molecular weight commercially-available polymers
that is water-soluble. Polyvinyl alcohol is made by first
forming polyvinyl acetate and removing the acetate groups
using a base catalyzed alkanolysis~ The production of poly-
vinyl acetate can be done by conventional processes which
controls the ultimate molecular weight. Catalyst selection
temperatures, solvent selection and chain transfer agents
can be used by persons skilled in the art to control molecu-
lar weight. The degree of hydrolysis is controlled by pre-
venting the completion of the alkanolysis reaction. It is
commonly available as a dry solid and is available in granu-
lar or powdered form. PVA grades include both the fully
hydrolyzed form (99%~ removal of the acetate group), a form
~;~75~S3
-18-
of intermediate hydrolysis (about 98 to 91% removal of ace-
tate group), and a partly hydrolyzed (about 90 to ~5%
removal of the acetate group) polyvinyl alcohol.
The proper~ies of these resins vary according to the
molecular weight of the parent polymer and the degree of
hydrolysis. Polyvinyl alcohols are commonly produced in
nominal number average molecular weights that range from
about 20,00û to about 100,000. Commonly, the molecular
weight of commercial polyvinyl alcohol grades is reflected
in the viscosity of a 4wt-% solution measured in centipoise
(cP) at 20C with a Brookfield viscometer. The viscosity of
a 4% solution can range from about 5 to about 65 cP. Varia-
tion in flexibility, water sensitivity, ease of solvation,
viscosity, block resistance, adhesive strength and dispers-
ing power can all be varied by adjusting molecular weight ordegree of hydrolysis. Solutions of polyvinyl alcohol in
water can be made with large quantities of optional lower
alcoholic cosolvents and salt cosolutes. Polyvinyl alcohol
is made in the United States by Air Products Chemicals,
Inc. under the trade name VinolTM, by duPont under the trade
name ElvanolTM, and by Monsanto under the trade name
GelvitolTM .
Fibers
In some cases, the bond strength and the adhesion of the
lignin sulfonate~PVA composition can be improved by the
addition of an effective amount of fiber. Both synthetic
and natural fibers can be used. Useful synthetic fibers can
be made from metal, glass, graphite, nylon, polyester, poly-
olefin, boron, and the like. Examples of natural fibers
include wool, flax, bamboo, etc. A preferred fiber for
reasons of ease of use and utility is a cellulosic fiber.
Cellulose can be derived from another number of sources.
However, cellulose derived from hard or soft wood or cotton
~.27~;~53
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tends to have exceptional purity and performance character-
istics in the context of the present adhesives. The pre-
ferred form of the cellulosic fiber used in the adhesives of
this invention çomprise elongated fibers, fiber units or
fiber bundles having dimensions of from about 1 to about 100
millimeters in length and a diameter of about 0.5 to 450
microns. Since the cellulose is a polymer of repeating car~
bohydrate units having pendent hydroxyl groups, the hydroxyl
` groups can interact, by hydrogen bonds 9 with the polyvinyl
alcohol compositions in the invention to increase the film
strength of the adhesive.
The lignin sulfonate-polyvinyl alcohol adhesives of this
invention can also contain a variety of well-known adhesive
constituents including thermoplastic and thermosetting
resins, natural and synthetic rubbers, boric acid and salts
thereof, preservatives, anti-foam agents, sequestering
agents, surfactants, perfumes, dyes, pigments, and the like.
The lignin sulfonate-polyvinyl alcohol adhesive compo-
sitions useful in the present invention are made in an
aqueous base. Typically, the adhesive can contain 75 to 25
wt-% of solids and about 25 to 75 wt-% water. The solids
generally comprise a polyvinyl alcohol composition and a
lignin sulfonate composition wherein there are about 1 to 8
parts by weight, preferably 1 to 5 parts by weight, of the
lignin sulfonate per each part of the polyvinyl alcohol. I~
substantially greater than ~ parts by weight of the lignin
sulfonate per each part of the polyvinyl alcohol is used,
the tack of the adhesive is not sufficiently strong to
result in successful adhesion in many applications. Most
preferably, the adhesive comprises about 30 to 55 wt-%
solids, and contains about 2 to 5 parts of the lignin
sulfonate per each part of the polyvinyl alcohol for reasons
of ease of preparation and enhanced adhesive properties.
Further, the adhesives are often unable to maintain suffi-
ciently long open time to be useful in all adhesive appli-
cations. In high solids adhesives, at proportions of
75~;3
-20-
greater than about equal parts of polyvinyl alcohol and
lignin sulfonate, the adhesive tends to increase in visco-
sity such that it is difficult to handle and apply.
The lignin sulfonate-polyvlnyl alcohol adhesive com-
positions of the invention can have a viscosity that fallsin a broad range including from about 2,500 to about 100,000
cP, depending on the percent solids and the ratio of lignin
sulfonate to polyvinyl alcohol.
The lignin sulfonate-polyvinyl alcohol adhesives of the
invention can contain an effective amount of the humectant-
plasticizer such as a polyhydroxy plasticizer compound at a
concentration of about 2-lû% by weight. Most preferably,
the adhesive contains an ethylene glycol, glycerin, or
polyalkylene oxide plasticizer at a concentration of about
3-20% by weight.
The lignin sulfonate-polyvinyl alcohol adhesive com-
positions of the invention can contain the cellulosic fibers
at a concentration of about 0.01-25% by weight based on the
fully-compounded formulation. The preferred adhesives con-
tain about 0.5-5% by weight of celluosic fibers, and most
preferably, for reasons of strength and flexibility, the
adhesives contain about 1-5% of a cellulose fiber derived
from wood.
The invention will be further described by reference to
the following detailed examples.
EXAMPLE I -- PRIMER COMPOSITION
~ . ~
A vertical kettle mixer was charged with 360 9 of a 15
ethylene-85% vinyl acetate copolymer latex, 55% solids,
(AirflexTM 400 latex) and 32 9 of cornstarch was slowly added
at 25C with stirring, followed by 2.0 9 of 37% formalde-
hyde, 0.8 9 of NopcoTM VF defoamer, 0.80 9 DowicideTM A
biocide and 4.4 9 water, to yield 400 9 of an opague white
primer adhesive having a viscosity of 2800 cP (Brookfield
viscosimeter, spindle 3, speed 20 at 36C) a pH of 5.0 and
containing 57.2% solids.
~75~
-21-
EXAMPLE II -- PRIMER COMPOSITION
A vertical kettle mixer was charged Y~ith 415 9 of
AirflexTM 400 latex and 15 9 oF butyl benzyl phthalate
(SanticizerTM lbO.) added with stirring. After 30 minutes of
stirring at 25C, 0.5 9 of NopcoTM VF defoamer was added,
followed by gradual addition of 40 9 of corn starch, 0.75 g
of 37% formaldehyde, 0.75 9 of DowicideTM A biocide and 28.0
g water. The opaque primer composition exhibited a visco-
sity of 80û cp (spindle 2, speed 20 at 36C), a pH of 5.0
and contained 56.5% solids.
EXAMPLE III -- PRIMER COMPOSITION -
A vertical kettle mixer was charged with 353 9 of a
vinyl acetate-acrylic acid copolymer latex, 55% solids,
(CovinaxTM 106 latex) and 17.6 9 of the mixed dibenzoate of
propylene and ethylene glycol (BenzoflexTM 50) was added to
the stirred latex. After 30 minutes of stirring at 25C,
5.6 9 of 37% formaldehyde was added, followed by 16 9 of
NopcoTM VF defoamer, 16 g of ColloidTM 711 defoamer, and 8 9
of a phenolic biocide (CuniphenTM 2778-I). After 10 minutes
of slow mixing, 27.2 9 of corn starch (Clinton Corn Products
121-B) was added and mixing continued another 0.5 hour. The
resultant primer was scree-ned (100 mesh) and exhibited a pH
of 4.5 and a total solids content of 60%.
EXAMPLE IV -- PRIMER COMPOSXTIONS
Exs. I and II are repeated substituting an ethylene-
vinyl acetate copolymer latex, 52.3% solids, (ElvaceTM 1875
latex) for the AirflexTM 400 to yield primers IVA and IVB,
respectively.
EXAMPLE V -- PRIMER COMPOSITION
A vertical kettle mixer was charged with 420 9 of a
vinyl acetate-ethylene copolymer latex (AirflexTM 416 DEV
latex), and 64.0 9 of barley starch was slowly added at 25C
~75~53
-22-
with stirring. After 20 minutes, 20.0 9 of FoamasterTM VF
defoamer was added, followed by 480 9 of AirflexTM 410 latex
and 3.0 9 of TektamerTM 38 A.D. biocide. After 10 minutes
of mixing, l.O~g of additional defoamer was added, followed
by an additional 30 9 of a 1:3.5 mixture of ethanol:water.
EXAMPLE VI -- PRIMER COMPOSITION
A vertical kettle mixer was charged with 900 9 of
ElvaceTM 1875 latexO To the stirred latex was added 80 9 of
Clinton 121-B corn starch, 5.0 9 of TektamerTM 38 A.D.
biocide and 2.0 9 of ColloidTM 675 defoamer. To the stirred
mixture was added a solution of 2.0 9 of DowicideTM A
biocide and 4.0 9 water, followed by 7.0 9 of additional
water. The finished primer exhibited a pH of 4.5 and con-
tained 57% solids.
EXAMPLE VII -- PRIMER COMPOSITION
A vertical kettle mixer was charged with 890 9 of
AirflexTM 401 latex. To the stirred latex was added sequen-
tially, 3.0 9 of NopcoTM VF defoamer3 32 g of barley starch,3.0 9 of TektamerTM 38 A.D. biocide, 30 9 of 1:3.5 mixture
of ethanol:water, 30 g of l,l,1-trichlorethane and 12 ml of
water.
EXAMPLE VIII -- ANIMAL GLUE-BASED COVERING ADHESIVE
A vertical kettle mixer equipped with steam-jacket
heating was charged with 260 ml of water. Stirring was
begun and 3.0 9 DowicideTM A biocide, 149 9 glycerin, 348.5
g hide glue (370-380 gram, Hudson Industries Corp.), 0.7 9
sodium bisulfite and 10 9 polysorbate 80 were added. The
reaction mixture was heated to 71-74C (160-165F). Sucrose
(198.1 9) was added, followed by 10.0 9 polyethylenimine
binder (50% actives, PolyminTM P, BASF), 0.3 9 methyl sali-
cylate, 1.5 9 of FoamasterTM VF defoamer and 18.5 ml of
water. The finished adhesive exhibited a pH of 8~0 and a
viscosity o~ 6-7x105 cps.
:a~75153
-23-
EXAMPLE IX -- ANIMAL GLUE-BASED ADHESIVE
A. A vertical kettle mixer equipped with steam-jacket
heating is charged wi~h 233 ml of water. Stirring is begun
and 20 9 titani.um.dioxide pigment, 3.0 9 of Dowicide M G
biocide, 296 9 of glycerin, 1.0 9 of sodium bisulfite, 12.0
g of an additional anti-foam agent and 434.6 9 of bone glue
(315 gram) are sequentially added. Stirring is continued
for 10 minutes at 25C. The temperature of the reaction
mixture is then raised to 71-74C (160-165F) to yield the
finished adhesive composition.
B. A vertical kettle mixer equipped with steam-jacket
heating is charged with 233 ml of water which is maintained
at 43C. Titanium dioxide (16 9) is added to the water with
stirring, followed by 318 9 of 370-38û gram hide glue and
118 9 of 160-170 gram hide glue. The stirred mixture is
then heated at 71C and mixing is continued until the glue
is dissolved. Glycerin (220 9--88%), 8.0 9 SutroTM 970
sorbitol humectant, (ICI Americas, Wilmington, ~el.) 10 9 of
ColloidTM 796 defoamer, 5.0 9 of UconTM 50-HB-55 polyalkyl-
ene glycol, 3.0 9 of octoxynol-9 surfactant, 0.3 9 of methyl
salicylate and 4.0 9 of phenol are sequentially added,
followed by an additional lû.0 g of water. The hot mixture
is filtered and cooled to yield the finished adhesive com-
position.
EXAMPLE X -- LIGNIN SULFûNATE-PVA COVERING ADHESIVE
Into a 600-millileter stainless steel beaker having an
electrically-driven blade mixer immersed in a water bath at
99DC was placed 100 of a 50 wt-% dispersion of an ammonium
lignin sulfonate ~ûrzanTM AL-50, IIT Rayonier Forest
Products). The mixer was started and into the agitated
liquid was sprinkled gradually, at a rate to permit smooth
addition, 20 9 of a partially-hydrolyzed low molecular
weight polyvinyl alcohol (87.0-89.0 hydrolyzed - a 4%
aqueous solution of the PVA having a viscosity of 4 to 6 cP,
12~S~3
-24-
VinolTM 205, Air Products Chemicals, Inc.). The addition
took about 1.0 hr, and after the addition was completed, the
mixture was agitated until smooth, indicating the dissolu-
tion of all the_polyvinyl alcohol. At the end of the disso-
5 lution, the temperature of the mixture was about 90C. The
product had 65% by weight total solids.
A series of products were prepared by diluting the pro-
duct with 5 milliliter aliquots of water resulting in pro-
` ducts having total solids content ranging from about 58 wt-%
so~lids to 35 wt-% total solids, a total of 18 aliquot addi-
tions.
EXAMPLE XI -- LIGNIN SULFONATE-PVA COVERING ADHESIVE
Example X was repeated except that a mixture of 75 g of
ammonium lignin sulfonate (AL-50) and 25 g of a 50 wt-%
aqueous solution of a sodium lignin sulfonate
(OrzanTM SL-50, ITT Rayonier Forest Products) was substi-
tuted for the 100 g of AL-50.
EXAMPLE XII -- LIGNIN SULFONATE-PVA COVERING ADHESIVE
Example X was repeated except that 25 g of AL-50 and 75
g of SL-50 were used in place of 75 9 of AL-50 and 25 9 of
SL-50.
The adhesives of Examples X-XIII were evaluated for
quick tack, wet or green tack, speed of set, open time, and
bond strength by drawing a film having a thickness of about
2.5-8 mils ~et on an either ambient temperature or heated
glass plate and applying to the coating a substrate. In all
cases, the lignin sulfonate-polyvinyl alcohol composition of
3û the invention was superior to animal glue adhesives in these
characteristics.
The polyvinyl alcohol lignin sulfonate adhesives of the
invention were evaluated for pot life by maintaining a
stainless steel beaker containing 500 g of the adhesive at
88C for 4 days. ~ater loss by evaporation was repeatedly
53
-25-
replaced and no appreciable loss in viscosity, quick tack,
green tack, speed of set, open time, or bond strength was
apparent, indicating the thermal stability of the adhesive.
EXAMPLE XIII -- BOOK-BINDIN~
Book blocks (9" w x 11" 1 x 1" h) composed of uncoated
sheets of 20 lb. ground wood telephone stock were fed
through a binding machine at 180 books per minute. The
spines were sequentially roughed, trimmed and coated with
the primer of Example V. The blocks were then passed along
a clamp track and either we~e partially dried by exposure to
a combination of heating lamps and blown hot air or were
transmitted to the covering zone under ambient conditions.
The wet spines were then coated with a layer of the animal
glue-based covering adhesive oF Example IXB at an applica-
tion temperature of about 63-65C (145-150F) The blocks
were then covered and trimmed with no loss of integrity.
After two months' storage under ambient conditions, the
books prepared using the partially-dried primer required
about 28-32 lbs. of force to put out individual sheets,
which could also be flexed 660+220 times (1 Kg pull) without
separation from the spine. The books prepared employing the
undried primer exhibited a page pull of 26.8+2.3 lbs. and a
page flex of 812+238. A page pull of greater than 20 lbs.
; 25 and a flex of greater than 100-200 times is considered to be
normal, satisfactory performance for this type of book. The
angle section peel evaluation indicated that no failure had
occurred between the primer and the covering adhesive at a
force at which the cover separated from the spine.
The above description, examples and discussion provides ~-
a basis for understanding the invention. However, since
many variations and modifications of the invention can be
made without departing from the spirit and scope of the
invention, the lnvention resides wholly in the claims
hereinafter appended. ~
. ,, " ....
