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Патент USA US3093616

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United States Patent 0
3,093,607
1
ICC
1
Patented June 11, 1963
2
lignins are all soluble in alkali, apparently producing so
3,093,607
dium lignate.
PLYWOOD ADHESIVE SOLUTIONS AND EX
TENDER COMPOSITIONS THEREFOR
The lignin components of the oxidized lignins of ap
plicant’s compositions are both acid-insoluble and water
insoluble and are referred to as being “extracted,” for
Los Augeles, Cali?, a corporation of Delaware
they are products which have been separated from the
No Drawing. Filed June 30, 1960, Ser. No. 39,816
wood or other llignocellulose material. Sulfonic acid de
15 Claims. (Cl. 260-171)
rivatives, or lignin sulfonates, such as are obtained in
This invention relates to novel extender compositions
the sul?te process of paper production being acid- and
for sale to and use by plywood fabricators, and also to 10 water-soluble are not included Within the scope of said
synthetic resin adhesive solutions and their production
term. Only through the use of lignin in extracted form
using these extender compositions. More speci?cally, it
can the quality and the performance of the adhesive com
relates to extender compositions based on vegetable shell
positions of the invention be attained and maintained.
?our having mixed therewith two additional components
To produce commercially acceptable results, experience
which improve the properties of the glue solutions in sev 15 has shown that it is essential that not only must the lig
eral respects and also the properties of plywood bonded
nocellulose extender be of known constitution and uni
with the glue solutions, all as hereinafter brought out.
form character, but alas the oxidized lignin component
As set forth in my copending applications Serial No.
must be of a de?nite and known quality.
425,051, issued January 16, 1962, as US. Patent No.
Suitable extracted ignins are described in the booklet
Joseph W. Ayers, Easton, Pan, assignor to Agrashell, Inc.,
3,017,303, and Serial No. 643,501, ?led March 4, 1957, 20 entitled “Indulin” issued by the West Virginia Pulp and
and now abandoned, having been replaced by application
Paper Co., Charleston, West Virginia (1951). Other
Serial No. 391,812, ?led June 30, 1960. I have hereto
fore discovered that extender compositions composed of
suitable lignin products contemplated are disclosed in the
booklet entitled “Commercial Lignins” by Robert S. Aries
and Anthur Pollak issued by he Northeastern Wood Uti
vegetable shell flour containing an addition of a minor
amount of a ?nely divided, extracted lignin, either in un 25 lization Council, New Haven, Connecticut (1949).
oxidized form or in oxidized form, can improve the prop
The oxidized lignin preferably used in the practice of
erties of phenolic resin and other glue solutions when
added thereto, by increasing the viscosity of the solution
and decreasing the penetration of the glue into soft or
porous surfaces of core woods.
The addition of the ex
tracted lignin in oxidized form produces exceptionally
high grade plywood of the most varied construction (as
the invention may be obtained by oxidation in neutral
solution, in alkaline solution or, under certain circum
stances, in an acid solution, but it can also be accom
30 plished electrolytically or by enzymatic action. Prac
to both thickness and number of veneers), even when
the core wood is of low grade or rough stock. The c0m~
positions and solutions of the present invention may con 35
tain basically these same ingredients.
An immediate object of the present invention is to pro
vide extender compositions and adhesive solutions con
taining the same which constitute improvements over said
prior compositions and solutions particularly as to more
tically considered, the oxidation is accomplished under
aqueous alkaline conditions simply by introducing oxy
gen into the aqueous alkaline suspension of the extracted
lignin.
The oxidized extracted lignins are those extracted lig
nins hereinbefore described which have been oxidized to
a point where they impart an increased viscosity of prac
tical effect to aqueous glue solutions in which they are
incorporated. The oxidation effected imparts stability to
glue solutions to which the oxidized lignin has been add
ed, by preventing loss of glue at the glue lines due to ex
cessive penetration into the pores of the surfaces of the
effective and uniform application of the glue solution
from the rapidly rotating rolls of the glue spreading ma~
chines used in plywood manufacture.
The overall object of the invention is to provide novel
adhesive solutions containing new extender compositions,
possessing to a unique degree all of the desirable proper
plies during curing. This retention of viscosity during
ties for producing plywood of consistently high quality
dized condition.
heating to the setting temperature and the prevention of
excessive ?ow into the pores constitutes the primary ad
vantage of the presence of the extracted lignin in the oxi
Oxidation to an extent providing any
appreciable degree of viscosity increase in the aqueous
suspension improves the retention at the glue line.
cores, which properties include high glue viscosity and 50
As is indicated in the hereinbefore mentioned Indulin
viscosity stability, uniform transfer and spreading from
booklet (page 18), the oxidation may be effected satis
factorily by introducing oxygen into an alkaline solution
the applicator rolls, stability of ?lm during assembly and
both as to strength and water-resistance, from all grades
of wood including soft wood and non-uniform or rough
lack of excessive penetration into wood pores.
The extender compositions of the invention are mix
in water or other solvent until about I to 7 mols of oxy
gen per mol of lignin (M.W. 840) has taken up. The
tures containing (1) a vegetable shell Hour, (2) a ?nely 55 alkalinity may be imparted by the addition of any alkali,
suitably sodium hydroxide, in a quantity of from 1-16
divided extracted lignin, preferably in oxidized form and
(3) a non-?brous bark phloem ?our.
mols per mol of extracted lignin. As is also pointed out
in said booklet, the rate and extent of oxygen absorp
The vegetable shell ?our used is exempli?ed by nut
tion is increased with increasing alkali content. If the
shells, as those of English and black walnuts and pecans,
oxidation is continued too long, the gel is advanced in
fruit pit shells, as those of apricots and peaches.
structure
too far, and drying and further processing be
The extracted lignin component hereinbefore men
comes
‘very
diilicult or practically impossible. Thus it
tioned is exempli?ed by the so-called “alkali lignin” pro
is the practical problem of handling which limits the per
duced as a by-product from Wood pulping processes em
ploying alkali, the most common procedure being known 65 missible amount of oxidation. In all instances, the oxi
dation is terminated, of course, before any drastic break
as the kraft process. Extracted lignins produced by bio
down of the lignin occurs and destroys ‘their viscosity
logical and selective solvent action, as well as those pre
imparting qualities.
pared by chemical action can be employed, and in com
An oxidized lignin found particularly effective was
mon the lignin products are free or substantially free of
produced
by concentrating a spent black cooking liquor
combined cellulosic constituents, wood sugars and other
products of the wood or other ligno-cellulosic materials 70 obtained from a kraft paper process to provide a liquid
containing 18 to 20% solids. Cooled carbon dioxide gas
from which the lignin is obtained, and such extracted
was then bubbled through the concentrated solution while
8,093,607
3
4
The three components to be combined to form the ex
said solution was being continuously circulated, to pre
tender composition may be blended merely by mixing the
cipitate the lignin. Upon completion of the precipita
tion, the carbonated liquor was heated at ‘a temperature
close to boiling to bring about coagulation of the lignin.
After being cooled, the coagulated liquor was separated
by ?ltration and the lignin was puri?ed by washing.
The washed cake was then repulped in water and suf
?cient sodium hydroxide was added to adjust the pH of
the suspension to an approximate value of 9. There
upon air was blown into the solution during vigorous
agitation until oxidation had occurred, this result being
determined by the viscosity increase of the suspension.
After oxidation, the suspension was concentrated, ?ltered
same in ?nely divided form in a standard ribbon type
blender until a homogeneous product is obtained.
The extender compositions hereinbefore described can
be employed very advantageously with plywood glue
solutions of conventional types which are generally
aqueous alkaline emulsions of arti?cial resins. Under
some conditions, the amount of alkali already in the glue
solution is sufficient, but ordinarily the addition of caustic
alkali or sodium carbonate in amounts somewhat in ex
cess of that which reacts with the extender components
improves the bonding quality of the glue solution. Al
though 5% of either or both of said alkali materials
spray drying. The ?nal product thus obtained can be 15 (calculated in relation to the amount of extender com
position present) may be su?icient in some glue solutions,
described as a technically pure, oxidized, extracted alkali
and dried, this latter result preferably being obtained by
the amount may be increased to 15 to 20% or more, as
lignin.
to each of said alkaline materials.
The completion of the oxidation step in the above
Plywood fabricators obtaining the extender composi
described process was determined by a standardized test
involving adding 60 grams of the oxidized product and 20 tions hereinbefore described can produce the adhesive
solutions of the invention by gradually adding such com
300 grams of distilled water to a 600 cc. beaker. The
positions to the water to be used for dilution of the resin
mixture in the beaker was then stirred for three minutes
to which has already been added the sodium hydroxide
with an electric stirrer. Next a sodium hydroxide solu
or other caustic alkali ordinarily employed, and the mix
tion made up of 50 grams water and 2 grams of solid
ture is agitated until uniform ?uidity is obtained, 20 to
25
sodium hydroxide was added. The resulting mixture was
30 minutes usually being suf?cient. When sodium car
then electrically stirred for a period of five minutes.
bonate is to be employed, it is preferably introduced im
Thereupon, the mass was adjusted to a temperature of
mediately after the extender composition has been added.
77° F. and allowed to stand at this temperature for ?f
The application of heat is not ordinarily required. Upon
teen minutes. At the end of this period, the viscosity was
measured with a Brook?eld viscosimetcr equipped with a 30 completion of the mixing operation the resin glue solution
is added and the mass is again agitated ‘for a few minutes
No. 4 spindle, at 6 rpm. The reading was 90,000
or until a homogeneous mass is obtained.
centipoises.
The resin glue solutions in which the extender composi
Using this test for the determination and control of
tions are particularly effective may be described as
the oxidation, oxidized extracted lignins operable ‘for the
purposes of the present invention have revealed viscosities 35 aqueous colloidal solutions of thermosetting aldehydic
resin glues. Such solutions are produced and sold by
as low as 5000 centipoises and viscosities much higher than
several companies (usually in solutions of 40-50 resin
the 90,000 centipoises reading.
solids content) and their production constitutes no part
No invention is claimed as to the bark phloem ?our
per se, for examples of such materials as are utilized in 40 of the present invention. The resins used include con
densation products of phenolic compounds such as phenol,
the practice of the invention are disclosed in the patent
cresol, and resorcinol, or amino-compounds such as urea
literature, as in the Heritage Patents No. 2,574,784 and
and melamine with an aldehyde, such as formaldehyde
2,574,785.
and acetaldehyde.
The bark phloem may be obtained, for example, from
In the glue solutions produced in accordance with the
pine, hemlock, ?r and cedar trees. The distinctive fea
present invention, conventional ratios of resin to ex
ture of these bark materials is that they are non-?brous
and generally contain a very much higher percentage of 45 tender composition to water can be employed. When
conventional phenolic resin glue aqueous emulsions
lignin than the wood itself and also other naturally oc
(about 40-50% solids) are employed the weight ratio of
curring ligno-cellulosic materials. A typical commercial
resin to extender to water is, suitably, 5/ 1/ 1.75. The
ly available bark phloem ?our has the following analysis
and properties:
Content:
ratio of extender and Water in the compositions can be
Percent by weight
Cellulose ____________________________ __
29
Lignin (from ?r) ______________________ .._
59
50 greatly increased to provide solutions having ratios of as
high as 5 / 4/ 7, and such glue solutions are economically
acceptable for the production of plywood of one type or
another, but all of high grade.
Properties:
In accordance with a modi?cation of the invention, the
Sol. in cold water 24 hrs ________________ .._ 7.54 55 extender compositions and adhesive solutions contain in
Sol. in hot water 2 hrs __________________ __ 11.98
addition to the oxidized lignin, also some plain or un
Sol. in 1% NaOH 1 hr _________________ __ 56.70
oxidized extracted lignin, all or part of which may be in
Sol. in 10% H2804 1 hr _________________ __ 17.85
the form of sodium lignate, as Indulin C. The unoxidized
Particle size distribution:
On 100 mesh _________________________ _..
100-200 mesh _________________________ __
6 60
45
200—325 mesh
___
Through 325 mesh _____________________ __
24
25
extracted lignin will ordinarily replace part of the oxi
dized extracted lignin in the compositions herein de?ned.
The amount of the oxidized lignin which can be replaced
by unoxidized lignin depends upon a number of factors
including the grade or porosity of the wood and viscosity
requirements of the glue solution. Displacement in great
over a very wide range. In the extender compositions, 65 est amounts is possible when plywood products of thin
the bark ?our content can be present in an amount as
construction, as 3746 inch, are being produced. From 5
low as 5%, but the quantity can be increased to about
‘to 75% of the oxidized lignin may be replaced by the
75% under favorable circumstances, and the extracted
unoxidized lignin (and/ or sodium lignatc), and when thin
lignin content, whether in its oxidized form or not, may
plywood is fabricated, the displacement may reach as
The proportion of the bark flour employed can vary
amount to from about 5% to 50%, and preferably from 70 high as 90%.
15 to 20%, based on the total weight of the three com
In a special embodiment of the invention leading to
ponent extender composition. In the compositions pre
ferred at the present time, the vegetable shell ?our is
present as the major component, the other two com
nonents being present in minor amounts.
the production of particularly high grade plywood, a
minor or small amount of epoxy resin is incorporated in
75 the compositions hereinbefore de?ned. The epoxy resin
5
33093307
need be present in an amount as‘ little as .4 to 1%, by
weight, of the phenolic resin content to impart worth
while improvement in quality of the bond. Amounts as
high as 20% can be used, but such higher amounts are
now economically unfeasible. The epoxy resin is pref
erably introduced by preliminarily coating the shell ?our
particles with 2 to 7% resin, but such resin may be mixed
in solution form with the phenolic resin solution. The
epoxy resin used can be any of the commercial adhesive
products such as may be produced by reacting bis-phenols
or other polyhydroxy compounds with either of the usual
chlorohydrins, epichlorohydrin or dichlorohydrin, spe
ci?c examples of the same being disclosed in the herein
before mentioned copending application Serial No. 643,
501.
Other epoxy resins utilizable are disclosed in the
book entitled “Epoxy Resins” by Henry Lee and Kris
6
wood may be quite porous in character, (3) does not lose
too much water by evaporation and (4) retains its bind
ing qualities over a substantial period, providing long as
sembly time life.
This application is a continuation-in-part of my co
pending application Serial No. 643,514 ?led March 4,
1957, and now abandoned.
It should be understood that the invention is not lim
ited to the exact compounds, proportions, procedures and
10 conditions herein described but that it extends to all
equivalents which will occur to those skilled in the art
upon consideration of the scope of the claims appended
hereto.
I claim:
1. A composition of matter for adding to and improv
ing the viscosity, wood penetration, bonding and other
Neville published by the McGraw-Hill Book Company,
properties of plywood adhesive and other laminating ad
Inc., New York, in 1957.
hesive solutions, which comprises a homogeneous mix
Example 1
ture of a major proportion of a vegetable shell ?our ex
20 tender and minor proportions, each of at least 5% by
Sixty parts of English ‘walnut shell ?our, 15 parts of
weight, of ?nely-divided extracted lignin in oxidized form
?nely divided oxidized ‘lignin produced from alkali lignin
containing about 1 to 7 mols of added oxygen per mol
of lignin, and of a non-?brous bark phloem ?our.
2. A composition of matter for adding to and improv
derived in a kraft paper prmess, and 25 parts of the bark
phloem flour hereinbefore described are mixed in a rib
bon blender until a homogeneous product is obtained.
25 ing the viscosity, wood penetration, bonding and other
Example 2
properties of plywood adhesive and other laminating ad
hesi-ve solutions, which comprises a homogeneous mix
The procedure of Example 1 is repeated using 10 parts
ture of a major proportion of a vegetable shell ?our ex
of oxidized lignin and 10 parts of extracted lignin (un
tender and minor proportions, each of at least 5% by
oxidized) in place of the 15 parts of oxidized lignin.
30 weight, of ?nely-divided extracted lignin at least 10% of
Example 3
which is oxidized lignin containing about 1 to 7 mols of
The procedure of Example 1 is repeated except that
added oxygen per mol of lignin, and of a non-?brous bark
phloem ?our having a lignocellulose content in which
only 10 parts of oxidized lignin are used, and 10 parts
of sodium lignate are adde .
about 59% is lignin and 29% is cellulose, by weight.
35
3. A composition of matter for adding to and improv
Example 4
ing the viscosity, wood penetration, bonding and other
An adhesive solution is prepared by introducing 115
properties of plywood adhesive and other laminating ad
parts of the extender composition of Example 1 into a
hesive solutions, which comprise a homogeneous mix
mixing tank into which has already been placed 200 parts 40 ture of a major proportion of a nut shell ?our and minor
of water and 30 parts of an aqueous sodium hydroxide
proportions, each of at least 5% by Weight, of a ?nely
solution of 50% concentration and the mass is continu
divided extracted lignin in oxidized form containing about
ously agitated during the introduction. Next 15 parts of
1 to 7 mols of added oxygen per mol of lignin, and of a
non-?brous bark phloem ?our.
sodium carbonate are added and the mixing is continued
for about 20 minutes. Thereupon, 500 parts of a phenol
4. A composition of matter for adding to and improv
formaldehyde glue solution in aqueous alkaline emulsion
ing the viscosity, wood penetration, bonding and other
form (viscosity G; solids content 40.8%) are added to
properties of plywood adhesive and other laminating
the mixer and agitation is continued for about 5 minutes.
adhesive solutions, which comprises a homogeneous mix
An aqueous glue solution is thereby obtained in a con
dition ready for pumping to the Well of the glue blending
machine for application to the plywood veneer,
ture of a major proportion of a vegetable shell ?our ex
50 tender, 5 to 20% > y weight of ?nely-divided extracted
lignin in oxidized form containing about I to 7 mols of
added oxygen per mol of lignin, said lignin being de
Example 5
The procedure of Example 1 is employed using an
English walnut shell ?our which has been modi?ed by
coating ‘the same with an epoxy resin glue produced by
rived from wood by the kraft process and subsequently
55
puri?ed by the removal of non-ligneous materials, and at
least 5% by weight of a non-?brous bark phloem ?our.
5. Plywood- and laminating-adhesive solutions compris
ing a thermosetting aldehydic resin glue selected from the
phenol) propane in aqueous alkaline solution.
group consisting of phenolic-aldehyde resins and amino.
The components of the extender compositions and the
aldehyde resins in aqueous alkaline colloidal solution,
glue solutions herein referred to, other than the bark 60 having dispersed therein an extender composition compris
the reaction of epichlorohydrin and 2,2 bis (parahydroxy
phloem product component are described in more detail
along with additional examples, procedures and advan
tages in the hereinbefore mentioned prior applications.
The glue solutions of the present invention have several
outstanding advantages:
ing a major proportion of a vegetable shell ?our ex
tender and minor proportions, each of at least 5% of the
weight of said composition, of extracted lignin at least
10% of which is oxidized lignin containing about 1 to
7 mols of added oxygen per mol of lignin, and of a
non-?brous bark phloem ?our.
6. Plywood- and laminating-adhesive solutions com
more exact and uniform quantities of glue spread in the
prising a thermosetting aldehydic resin glue selected from
?im applied to the core wood and to greater resistance to
the group consisting of phenolic-aldehyde resins and
the centrifugal force of the rapidly revolving spreader
rolls of the glue applying machine, which force has a 70 amino-aldehyde resins in aqueous alkaline colloidal solu
tion and having dispersed therein an extender composi
tendency to throw glue solution oil the rolls. After the
They have an exceptionally high viscosity, leading to
tlon comprising a major proportion of a vegetable shell
?our extender and minor proportions, each of at least
5% of the weight of said composition, of extracted lignin
gel structure, thixotropic in character, and thus (2) does
not penetrate too deeply into the wood even though the 75 of which at least 10% is oxidized lignin containing 1 to
7 mols of added oxygen per mol of lignin, and of a non
glue solution has ?owed over the Wood surfaces in an
even spread, it (1) ceases to flow and assumes a limpid
8,093,607
?brous bark phloem ?our, said solutions having said
lignin and said bark ?our dissolved therein together with
a minor amount of free alkali.
7. Plywood- and laminating- adhesive solutions com
8
pound selected from the group consisting of epichlorohy
drin and dichlorohydrin, and containing free epoxy groups,
having dispersed therein an extender composition com
prising a major proportion of .a vegetable shell ?our ex
tender and minor proportions, each of at least 5% of the
weight of said composition, of extracted lignin in oxi
dized form containing about 1 to 7 mols of added oxygen
prising a thermosetting aldehydic resin glue selected from
the group consisting of phenolic-aldehyde resins and
amino-aldehyde resins in aqueous alkaline colloidal solu
ger mol of lignin and of a nond?brous bark phloem
tion, having dispersed therein an extender composition
our.
comprising a major proportion of a vegetable shell ?our
12. A composition of matter for adding to and im
10
extender and minor proportions, each of at least 5% of
proving the viscosity, wood penetration, bonding and
the weight of said composition, of extracted alkali lignate
other properties of plywood adhesive and other lami
oxidized to contain 1 to 7 ‘mols of added oxygen per mol
nating adhesive solutions, which comprises a homogeneous
of lignin, and of a non-?brous bark phloem ?our, the
mixture of a major proportion of a vegetable shell ?our
lignate and the bark ?our being substantially dissolved
extender and minor proportions, each of at least 5% by
in said solutions by the action of alkali in said solutions.
weight, of a non—?brous bark phloem ?our and of both
8. Plywood- and laminating-adhesive solutions com
a ?nely divided substantially unoxidized extracted lignin
prising a theromsetting aldehydic resin glue selected from
and a ?nely divided oxidized extracted lignin containing
the group consisting of phenolic-‘aldehyde resins and
at least 1 to 7 mols of added oxygen per mol of lignin.
amino-aldehyde resins in aqueous alkaline colloidal solu
13. A composition of matter for adding to and im
20
tion, having dispersed therein an extender composition
proving the viscosity, wood penetration, bonding and
comprising a major proportion of a nut shell ?our ex
other properties of plywood adhesive and other laminating
tender, at least 5% by weight of an alkali-dissolved, ex
adhesive solutions, which comprises a homogeneous mix
tracted lignin oxidized so as to contain about 1 to 7 mols
ture of a major proportion of a vegetable shell ?our
of added oxygen per mol of lignin and at least 5% by
extender and minor proportions, each of at least 5% by
25
‘weight of a non-?brous ibark phloem flour.
weight, of a non-?brous bark phloem ?our and of both
9. A composition of matter for adding to and improv
a ?nely divided substantially unoxidized sodium lignate
ing the viscosity, wood penetration, bonding and other
and a ?nely divided oxidized extracted lignin containing
properties of plywood adhesive and other laminating ad
about 1 to 7 mols of added oxygen per mol of lignin.
hesive solutions, which comprise a homogeneous mixture
14. Plywood- and laminating-adhesive solutions com
30
of a major proportion of a vegetable shell ?our extender
prising a thermosetting aldehydic resin glue selected from
coated with from 2 to 7% of an epoxy resin produced
the group consisting of phenolic-aldehyde resins and
by the reaction of a polyhydroxy hydrocarbon with a
compound selected from the group consisting of epi
chlorohydrin and dichlorohydrin, and containing free
amino-aldehyde resins in aqueous alkaline colloidal solu‘
tion, having dispersed therein an extender composition
comprising a major proportion of a vegetable shell ?our
epoxy groups, and minor proportions, each of at least 35 extender and minor proportions, each of at least 5%
5% by weight, of ?nely-divided extracted lignin at least
by weight, of a non-?brous bark phloem ?our and of
10% of which is oxidized lignin containing about 1 to
both an unoxidized extracted lignin and an oxidized ex
7 mols of added oxygen per mol of lignin, and of a non
tracted lignin containing about 1 to 7 mols of added
?brous bark phloem ?our.
40 oxygen per mol of lignin.
10. Plywood- and laminating-adhesive solutions com
15. Plywood- and laminating-adhesive solutions com
prising a thermosetting aldehydic resin glue selected from
prising a thermosetting aldehydic resin glue selected from
the group consisting of phenolic—aldehyde resins and
the group consisting of phenolic-aldehyde resins and
amino-aldehyde resins in aqueous alkaline colloidal solu
amino-aldehyde resins in aqueous alkaline colloidal solu
tion, containing 0.4 to 20% in relation to the Weight of 45 tion, having dispersed therein an extender composition
the aldehydic resin present of an epoxy resin produced
comprising a major proportion of a vegetable shell flour
by the reaction of a polyhydroxy hydrocarbon with a
extender and minor proportions, each of at least 5% by
compound selected from the group consisting of epichloro
weight, of a non- brous bark phloem ?our and of both
hydrin and dichlorohydrin, and containing free epoxy
sodium lignate aind an oxidized extracted lignin con
groups, having dispersed therein an extender composi 50 taining about 1 to 7 mols of added oxygen per mol of
tion comprising a major proportion of a vegetable shell
lignin.
?our extender and minor proportions, each of at least 5%
of the Weight of said composition, of extracted lignin at
References Cited in the ?le of this patent
least 10% of which is oxidized lignin containing about
UNITED STATES PATENTS
1 to 7 mols of added oxygen per mol of lignin, and of a
non-?brous bark phloem ?our.
11. Plywood- and laminating-adhesive solutions com
prising a thermosetting aldehydic resin glue selected from
the group consisting of phenolic-aldehyde resins and
amino-aldehyde resins in aqueous alkaline colloidal solu 60
tion, containing 0.4 to 20% in relation to the weight of
the aldehydic resin present of an epoxy resin produced
by the reaction of a polyhydroxy hydrocarbon with a com
2,161,748
2,506,486
Samaras ______________ __ June 6, 1939
Bender et a1. ________ __ May 2, 1950
2,507,465
Ayers ______________ __ May 9, 1950
2,669,522
2,781,327
2,878,197
Othmer ______________ __ Feb. 16, 1954
Ayers et al. __________ __ Feb. 12, 1957
Baxter et a1. ________ __ Mar. 17, 1959
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