Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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S P E C I F I C a T I O N
This invention relates to carbohydrate-based ~ ;~
condensation resins and a process for producing same, and
more particularly to a phenolic-carbohydrate resol resin. ~-~
Condensation resins based upon phenolic compounds
such as phenol and aliphatic aldehydes have been in widespread
use for many years. As is well known, the aldenyde, usually
formaldehyde, is reacted with phenol in the presence of an
acid or basic catalyst to form a condensation resin. There
are generally two recognized types of phenol-formaldehydc
resins currently in use for various applications. One orm
o~ resin, referred to in the art as a novolak res;n, is
prepared by reaction of excess phenol with formaldehyde to
form a resin capable of thermosetting by the addition of a
catalyst. The other form of phenol-formaldehyde resin is
referred to in the art as a resol. Those resins are prepared
by reaction of phenol with excess farmaldehyde to form a ~ ;
resin system having greater water solubility than the
novolak resin.
Resol resins are widely used as the base for
adhesives in, for example, paper laminating applications
and in the manufacture of plywood.
I~e basic raw material for phenolic resins,
whether they be novolak or resol resins, is petroleum.
Supplies of petroleum a.e becoming increasingly limited,
and prices have accordingly increased significantly.
There is thus a need to re?lace at least a portion of the
petroleum-b2sed components of the phenolic resinx with a
less expensive, more abun~ant material. Carbohydrates,
s~,~
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rea~ily ava;lable from plant sources, are thus one typ~ of
renewable resource ideally sui~ed for use in the manufacture
of novolak and resol resins.
It has been proposed, as described in U. S.
Patent No. 1,753,030, to employ starch as a component or
phenolic resins in which starch is reac~ed with pheno7 in
the presence o~ an acid catalyst to form a solid, infusible
resi.n which can be rendered water soluble by thereafter
reacting the resin with fo~maldehyde. ~o proportions of
reactants are set forth, and consequently it is not possible
to determine whether or not the foregoing patent is directed
to the production o a resol resin.
One o~ the dif~iculties which has been incurred
in the production of resol resins by first forming a
condensation resin by reaction of a carbohydrate such as
starch with phenol followed by reaction with formalde~de
resides in the apparent lack of reactivity of the phenol-
carbohydrate condensation product. In U. S. Patent No. ;~
3,215,653, there is described an adhesive composition
prepared by a complex reaction scheme wherein a phenol-
formaldehyde resin said to be useEul in bonding applications
is prepared by reaction of a phenol-formaldehyde resin, a
formaldehyde-reactive filler and resorc;nol are reacted
under alkaline conditions. The procedure described by the
~oregoing patent is a very cumbersome one, requiring complex
reaction procedures.
It is accordingly an obJect of the present
invention ~o provide a low cost ~esol resin system incor-
porating an inexpensive carbohydrate at relatively high
levels of substitution.
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It is a more specific object of the invention to pro-
vide a resol resin useful in bonding and laminating applications
and a process for the production of same wherein a substantial
portion of the resol resin is made up of a caxbohydrate mate-
rial wherein the resol resin has improved adhesive and water
resistant properties.
The concepts of the present invention reside in a
phenolic-carbohydrate resol resin produced in a two-stage
reaction. In the first stage, a phenolic compound is reacted
in the presence of a basic catalyst with a carbohydrate to
form a furan-type resin intermediate, in the second stage,
that intermediate is reacted with a lower aliphatic aldehyde
to produce a resol resin having good solubility, low viscosity
and excellent water resistant properties. The resol resins
of the present invention have been found to be particularly
suitable for use in th~ manufacture of adhesives. !;
It is an essential feature of the present invention
that the second stage reaction between the furan-type resin and
the aldehyde be carried out under basic conditions, that is in
the presence of a ba~ic cataly~t. Without the use of a basic
catalyst, the aldehyde is apparently not sufficiently reactive
with the furan-type intermediate resin for complete solubili-
zation of the resin.
Thus in accordance with the invention there is pro-
vided a proce~s for producing a carbohydrate-phenolic resol
resin comprising (1) reacting in the presence of a basic catalyst
a carbohydrate and a phenolic compound having the formula
:
OH
~ 3 -
~ 3~
,. 'wherein R is selected from the yroup consisting of Cl to C3
alkyl, Cl to C3 alkoxy, halogen, hydroxy and hydrogen, to form
a resin intermediate, and (2) reacting the resin intermediate
with a lower aliphatic aldehyde in the presence of a basic
catalyst to form a resol resin.
The intermediate resin formed by the condensation
reaction between the carbohydrate and the phenolic compound
is preferably in liquid form: and preferably water is produced
in the condensation reaction in an amount between about 0.75
mole to less than about 5 moles, per mole of carbohydrate,
expressed as monosaccharide.
In the practice of this invention, a preferred carbo-
hydrate is starch. Suitable starches include all varieties of
starch, such as corn starch, tapioca starch, wheat starch,
grain sorghum, potato starch, rice starch, sago, etc. That
includes all types of grades of starch, such as waxy starches,
high amylose starches, non-waxy - ~
~ 1
- 4 -
... .. .. .. . .. . ...
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starches, etc. Also included in the practice of this
in~enticn are chemically modified starches, dextrins, thin
boiling sta~ches and pregelatinized starches. Starches
as used herein also include crude starches such as mill
st~rch, corn flour9 wheat flour, br~wer's grits, broken
rice, etc.
In general, use can be made of starches having
the following structure:
.
r~
C~2H I CH20H I ~H OH
H ~ O ~ I ~ ~ ~ I H ~ O~H
~OH ~i o ~ OH H~o - ~ OH
HO ~ ~ ~ ~
] [ ~H I ] I ~H ~ ~1 OH
wherein n> designating the number of repeating units, can
range up to 106.
In addition to starches~ use can also be made of
mono-, di- and trisaccharides such as dextrose, maltose, ~ -
maltotriose, lactose, glycogen, glucosides, corn syrups
and the like.
As the phenolic compound used in the practice of
this invention, preferred are the phenolic compounds having
the formula:
OH
~ '
wherein R is a group selected from Cl to C3 alkyl, Cl to C3
alkoxy, halogen, hydroxy and hydrogen. The preferred
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phenolic compound is phenol, but other phenolic compounds
include cresol, chlorophenol, bromophenol, resorcinol and the
like~
The relative proportions of phenol and carbohydrate
employed in the first stage reaction to produce a furan-type
resin can be varied within relatively wide limits. In general,
the amount of phenol employed ranges from 0.5 to 10 moles of
the phenolic compound for each mole of carbohydrate employed,
and preferably 0.75 to 5 moles of phenolic compound per mole
of carbohydrate (expressed as monosaccharide). One of the
advantages of the present invention stems from the fact that
the resin system of the present invention can incorporate
relatively high levels of carbohydrate without deleteriously
affecting the properties of the resulting resol resin.
The first stage reaction is generally carried out at
a relatively high temperature, preferably temperatures in excess
af 100C~ Best results are usually obtained when the reaction
temperature ranges from 109-200C. The reaction is best
effected by reacting the phenolic compound with the carbohydrate
in an a~ueous reaction medium, the preferred technique being
refluxing the reactants in the presence of the catalysts to
produce the first stage furan-type resin. Preferably the
reaction is continued for long enough to generate at least 0.75,
but less than 5 moles of water of condensation per mole of
carbohydrate reactant (expressed as monosaccharide) to form a
liquid intermediate resin.
In the second stage o~ the reaction, formaldehyde is
added in an amount sufficient to solubilize the furan-type
resin formed in the first stage and thexeby form a resol resin.
The amount of formaldehyde employed should be an amount
sufficient to solubilize the resin system. It has `been ~ourld
that best result3 can be obtained when the amount oE aldehyde
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(formaldehyde, acetaldehyde or propionaldehyde) ranges from
1.05 to 2.0 moles of aldehyde per mole of phenol, preferably
1.05 to 1.75 moles of aldehyde per mole of phenol.
The use of a basic catalyst in the second stage
reaction in which the aldehyde is reacted with the furan-type
resin intermediate is, as noted above, an important concept of
the invention. Any of a number of basic catalysts can be used
in the practice of this invention, all of which are well known ;
to those skilled in the art. Included are the alkali metal
hydroxides te.g. sodium hydroxide, potassium hydroxide, etc.), ;
alkaline earth metal oxides and hydroxides (e~g. calcium
oxide, barium oxide, magnesium oxide, etc.) as well as
ammonia and like bases. In general, the basic catalyst
should be used in an amount sufficient to adjust the pH of the
second ~tage reaction medium to at least 8Ø
Because the resol resins produced in the second
stage of the reaction tend to form gels under vigorous con-
ditions, it is generally preferred to employ relatively mild
reaction conditions in the second stage. Best results are
usually obtained when the temperature of the second stage
reaction medium is below 100C.
In accordance with the invention by conducting both
the first and second stage of the reaction in the presence of
a basic catalyst of the type described above, there is obtained
the advantage of avoiding neutralization of an acid catalyst
at the completion of the first stage of the reaction.
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This invention is further illustrated by thê
following examples, which, ho~.~ever, are not to be ta~en
as limiting in any respect. All parts and percentages,
unless expressly stated to be othen~ise~ are by weight.
~ .
- EXAMPI.E 1
Use o BaO as Cata~yst
310 g phenol (containing ~8 g water) 3 moles
180 g dextrose
9 g barium oxide
were placed in a 500 ml resin kettle equipped with a stirrer,
tnermometer and take-of condenser. The materiaLs were
heated wi.th stirring to 178C for 3,5 hours, and 83 cc
of water was collected ~about 3 moles of water/mole of
dextrose). The resulting resin was very low in viscosity
æt the reaction temperature. It ~as cooled to 70C and
284 g of 37% formaldehyde (3.5 mole) were added gradually.
Since no exotherm was noted, the temperature was raised to
reflux (103C) and 10 cc of concenkrated ammonia w~s added.
Refluxing was continued for 4 hours, until the viscosity
reached 24 centistokes. The resin was adjusted to 50%
solids with methanol and neutralized to pH 6.0 with ~2SO4.
The resin solution was then tested in laminates. The
resulting paper lamlnate withstocd a boiling water test for
24 hours without blistering.
Although the resulting laminate did not pass
the iinal test (48 hours), the example illustrates the
great stability of the resin and it shows an effective way
to control the exothermic reaction of formaldehyde with the
first stage reaction product.
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The following example demonstrates the necessity
of using a basic catalyst in the second stage of the reaction
in which the furan-type resin is solubilized with aldehyde.
In the following example, the teachings of McIntosh were
followed to the extent indicated, without obtaining satis-
factory results, employing an acidic catalyst in the first
stage.
EXAMP~E 2 ::~
315-g phenol (containing 33 g water)
10180 g dextrose
5 cc 5 ~ H2S4
were placed in a 1000 ml xesin kettle and heated with stirring
for 130 minutes at 160C. During this period, 83 cc of water
was distilled off, together with 15 cc of phenol. Allowing for
the 33 grams of water preqent in the phenol, the ~83 ~ 33 = : :
50) water corresponds closely to the removal of 3 moles of
water per dextrose unit to form HMF.
g _ ... ;
-: . -
. .
~ c
The resin so obta;ned ~as cooled to 70~C and18~ ~ forrnald~hyde (37%) was added. The t2mperatuLe ~-as
kep~ at 70C by means of a water bath for 4 hours.
The resin was then used to impregnate Kraft paper
as describe~ in the foregoing disclosurP. It did not cure
completely wllen pressed at 275F, and the laminate ~ell apart
when immersed in boiling water. This example illustrates
that: basic conditions are necessary to obtain a suitable
cure of the formaldehyde extended phenol~carbohydrate resin.
As an additional check on the procedure of U. S.
Patent No. 1,753,030, the procedure described by McIntosh
was followed. 100 g each of phenol, starch and water ~as
re~luxed for 5-1/2 hours in the presence of H2S0~. The
resulting liquid was separated in two layers. The lower
layer (clear) weighed 169 gram while the darX upper liquid
weighed 113 grams. (18 gram might have escaped ~1uring the
prolonged reflux period).
The 169 gram layer appears to be a solution of
dextrose in water, while the upper layer i5 mostly phenol.
After washing once with water, only 100 g dark liquid wzs
left. Since no directions were given on how to proceed in
the next step, and since the dark layer is obviously mostly
phenol, the experiment was not continued.
It will be apparent from the foregoing description
and examples that the present invention provides a simple
technique for the production of less expensive resol resins
as compared to the prior art. The resins produced in accor~
dance with the practice of this invention are particularly
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sui.table in applications where the adclition of a curing
agent to the resin (such as the hexameth~-lenetetramine
usually used with novolak resins) is dif-fi.cult~ as in ~he
manufacture of laminates, particle boarcl adhesives and the
like as described.
While the invention has been described in
connection with specific embodiments thereof, it will be
understood that it is capable of further modification, and
this application is intended to cover any variations, uses,
or adaptions of the invention following, in general, the
principles of the invention and including such departures
from the present disclosure as come within know~ or customary
practice in the art to which the invention pertains and as
may be applied to the essential features hereinbefore set
forth, as fall within the scope of the invention.
