Note: Descriptions are shown in the official language in which they were submitted.
:- 2~3~
RBP File No. 5788-2
Title: BINDE:R CONPOSITION FOR CHIP LIRE AND/OR FIBR~US llATERIAL -: .
FIE:I.D OF THE INVENTION
This invention relates to a novel binder
composition for chip like and/or fibrous material. More
specifically, this invention relates to a binder
composition comprising a waterglass, an isocyanate znd a
metal soap which may be mixed with chip like and/or
fibrous materials such as glass, asbestos, wood fibres and
cellulose to produce a variety of products including
chipboard, plywood, oriented strand board, fibreglass and
fibreboard ("fibrous boards").
BAC~GROUND TO THE INVENTION
', ~
Building material6 such as plywood, chipboard and
fibreboard are currently produced using aqueous adhesives
which are based upon phenol-formaldehyde resins or urea-
formaldehyde resins. During the hardening process,
volatile compounds present in the adhesive resins are
released. This creates two problems. First, part of the
20 adhesive is lost during the hardening process. Secondly, ;~;
the volatile components of the adhesive such as
formaldehyde comprise toxic components and/or carcinogens
the release of which is undesirable.
2 ~ $ 2
- 2 -
~ ''`According to the disclosure of United States
Patent No. 4,190,459, the combination of waterglass and
isocyanate as an adhesive is known. As disclosed in United
States Patent No. 4,190,459 at column 1, lines 53-58, ~the
simultaneous use of isocyanates with waterglass is of no
commercial value although the products may be used
alongside one another for bonding purposes, because the
quality of the bonds obtained is no better than in cases
where the two-components are used on their own".
United States Patent No. 4,190,459 discloses a
proces~ for the production of mineral fibre mats by
bonding mineral fibres with a binder comprising an
emul~ion of waterglass and isocyanate. The emulsion i~
prepared by mixing the isocyanate and the waterglass in
standard mixing units to obtain a stable emulsion. A
di~advantage of this emulsion is that the binder has a pot
life of a few minutes up to about 30 minutes. Due to the
short pot life, it is not economically viable to employ
the binder in a commercial process. If a binder having a
pot life of about 30 minutes or so is employed in a
commercial process, then when there is a breakdown in
machinery, the binder would commence to harden and block
the passageways in the machinery. This would require much
down time, and the possible replacement of parts, prior to
bringing the unit back on line. Even without such a
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breakdown, the binder would tend to harden due to its
short pot life and block the passageways in the machinery.
West German published Patent Application No. 37
18 297 discloses a chipboard which is manufactured by hot-
S pressing a mixture of wood chips and a binder. The bindercomprises waterglass, an alkanedioic dimethyl ester or
ethyl ester or a mixture of these esters and a
crosslinkable i~ocyanate resin. This binder composition
only has a pot life of about 1 hour.
10It is desirable to provide a binder composition
which ha~ an extended pot life. It is further desirable to
provide a binder composition of waterglass and isocyanate
which has a pot life sufficiently long to permit the
binder compoeition to be employed in a commercial process
for the manufacture of fibrous boards.
It is further desirable to provide a binder
material which does not contain any toxic or cancer
causing volatile compounds. It is also desirable to
,j j , provide a binder composition with which curing 'can be
precisely started and controlled.
:
SUMMARY OF TH~ INVFNTION
2 ~ ~ ~ 3 ~
_ 4 -
A binder composition having an extended pot life
may be prepared from a hardener and a waterglass. The `
hardener comprises a blocking amount of metal soap and
isocyanate. ~
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The metal soap preferably is a stearate and is
preferably oxylated or polyoxylated so that it is soluble.
The metal and the metal soap may be aluminum, titanium or
chrome and more preferably aluminum or titanium. ;
The isocyanate i8 preferably a crosslinking
isocyanate. The isocyanate may be a di- or poly-
isocyanate.
The waterglass is an aqueous solution of an
alkali metal silicate. Preferably, the waterglass
compri~es a sodium or potassium silicate. The waterglass
15 may contain from about 5 to about 50, more preferably from ;
about 30 to about 50 and most preferably about 40 weight
percent solids.
,: ~ i ~ , :''',
The binder composition contain~ at least about
0.5 weight percent isocyanate based upon the weight of the ;-~
binder composition. Further, the binder composition may
contain from about 1 to about 300 weight percent ~;~
isocyanate based upon the weight of the waterglass. The
2~lg~3~2
binder composition comprises from about 0.1 to about 50
weight percent metal soap based upon the weight of the
isocyanate and, more preferably from about 0.3 to about
10 weight percent metal soap based upon the weight of the
isocyanate. The balance of the composition comprises
waterglass. Preferably, the binder composition contains
from about 1 to about 20 weight percent waterglass based
upon the weight of the fibrous or chip like material with
which the binder composition is mixed.
" ~'"'
The fibrous or chip like material with which the
binder composition may be added may be any of those known
in the art which are used to prepare chipboard, plywood,
oriented strand board, fibre board, fibreglass and the
like. The fibrous or chip like material may contain from
about 8 to about 12 weight percent water.
The metal soap and the isocyanate are first
mixed to produce a ~olution. The metal soap is preferably
added to the isocyanate. These compounds are then
thoroughly mixed. Sub~equently, the waterglass, and the
mixture of isocyanate and metal soap may be mixed to form
an emulsion. The emulsion may then be applied as is known
in the art to suitable material to prepare plywood or
fibreglass. Alternately, in order to prepare particle
board, oriented strand board, chipboard or the like, the
mixture of isocyanate and metal soap and the waterglass
2~38~ ~
- 6 -
may each be individually added to the fibrous or chip like
material. The mixture of the fibrous or chip like
material and the binder composition may be pressed as is
known in the art. Preferably, the pressing occurs at from
about 180 to about 200C. Press time varies from about 7
to about 10 seconds per millimetre of pressed board. This
i~ approximately half the press time which is required
when utilizing binder compositions which are currently
u~ed in the art.
It has now been surprisingly found that by
incorporating a metal soap into a binder composition
compri~ing an isocyanate and waterglass that the pot life
of the binder composition may be extended for up to eight
hour~ or more. More surprisingly, by using such a
lS aomposition, it is in fact possible to control the curing
of the binder composition 80 that the hardening reaction
does not commence until the binder composition has been
applied to the selected fibrous or chip like material and
it is desired that the hardening process commence. By
utilizing the process of this invention, it is possible to
effectively delay the commencement of the hardening
reaction until the binder composition has in fact been
applied to the fibrous or chip like material and the
mixture of fibrous or chip like material and binder
compo ition has reached the stage in processing whereby it
is desired to commence the hardening reaction. This
,
',
20~3~ ~
provides the advantage that the hardening reaction can be
controlled to occur at the most opportune moment so that
the resultant fibrous board has the greatest possible
strength.
Further the use of a binder composition
according to the present invention avoids the release of
cancer causing compounds. Thus, the binder composition is
more environmentally friendly and less air treatment is
required of the air in a plant.
These and other advantages of the instant
invention may be more fully and clearly understood by the
following description of the preferred embodiment of the
invention.
DESCRIPTION OF TH~ INVENTION
The binder composition of the instant invention
comprises a waterglass, an isocyanate and a metal soap.
The waterglass used in the instant inventhon may
be any waterglass known in the art. In particular, those
disclosed in United States Patent No. 4,190,459 and
Canadian Patent No. 1,244,181 may be used in the binder
composition of the present invention.
3 ~ 2
- 8 -
The waterglass preferably comprises an aqueoussolution of alkali metal silicate. More preferably, the
silicate is sodium or potassium silicate and, most
preferably, the silicate is sodium silicate.
The water content of the waterglass is selected
to provide a binder composition having a viscosity of from
about 60 to about 70,000. Such binder compositions are
ea~ily workable and may be readily applied to fibrous or
chip like material as is known in the art.
:,' ~."'.,.
The amount of solids present in the waterglass
may vary within fairly broad ranges. The amount of solids
may be selected in part ba~ed upon the desired moisture
content of the finished fibrous board. The greater the
solid content, the less the amount of water which is
incorporated into the final product board. The water
content of fibrous boards made from chip like or fibrous
material i~ known to those skilled in the art. These
values are designed to avoid the board swelling or
shrinking when in use. For example, th~ moisture content
20l of fibroufi boards for use in a house varies from about 8
to about 12 weight percent. Accordingly, in the
. ~ ,.
preparation of plywood or particle board for use in a
house, it is desired to have a moisture content in the
finished board of from about 8 to about 12 weight percent.
If the amount of solids in the waterglass is lowered, then
2 ~ 2
g
an increased amount of water will be added to the binder
composition and thus to the final product board. If
additional water is required to obtain the desired
moisture content in the final product, additional water
may be added by a separate stream or any other source
which is used in industry.
Preferably, the waterglass contains from about
to about 50 weight percent solids in water. Nore
preferably, the waterglass contains from about 30 to about
50 weight percent solids in water and, most preferably,
the waterglass contains about 40 weight percent solids in
water.
The amount of waterglass which may be employed
in the binder composition of the present invention varies
between fairly broad ranges. The amount of waterglass
employed may vary from about 1 weight percent to about 20
weight percent, based upon the weight of fibrous or chip
like material to be bonded. More preferably, with respect
to the production of chipboards, from about 0.5 to about
10 weight percent waterglass based upon the weight of the
wood particles may be employed. With respect to plywood,
from about 1 to about 40 weight percent waterglass, based -
on the weight of the binder composition and, more
25 preferably, about 10 weight percent waterglass may be ~
employed. With respect to oriented strand board, from ;
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-- 10 -- ::
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about 0.3 to about 20 weight percent and, more preferably
from about 0.3 to about 4 weight percent waterglass, based
upon the weight of the wood particles may be employed. For -~
the production of fibreglass , about 10 weight percent ;~
waterglass, based upon the weight of fibreglass may be
used. With respect to the production of medium density
fibreboard, from about 1 to about 25 weight percent
waterglass and, more preferably, from about 1 to about 10
weight percent waterglass, based upon the weight of
fibreglass may be employed.
'. ' ~'"
The isocyanates which may be employed in a
binder composition of waterglass and isocyanates are known
to those skilled in the art. Suitable isocyanates are
di~clo~ed in United States Patent No. 4,190,459. The
isocyanate which is employed i~ preferably a crosslinking
isocyanate. Preferably, the isocyanate is a di-isocyanate;
however, polyisocyanates may also be employed.
.,, ~ .
Examples of isocyanates which may be employed
include methyl-4,4'-diisocyanate and diphenyl methyl-
4,4'-diisocyanate.
The amount of isocyanate which may be employed
in the proce~s of the present invention may vary between
fairly broad ranges. Generally, a sufficient amount of
isocyanate to react with the waterglass must be provided
-- 11 -- ! 2 ~ 3L 9 3 ~ 2
so that suitable bonding characteristics are obtained.
Generally, at least about 0.5 weight percent isocyanate,
based upon the total weight of the binder compositions ic
employed to ensure that the hardened binder composition
has sufficient strength. In general, by increasing the
amount of isocyanate present in the binder composition,
the adhesive stxength of the bonding composition and the
water stability of the bonded product are increased.
However, as the isocyanate is relatively expensive, an
increase in the amount of isocyanate results in an
increase in the cost of the final binder composition. The
~pecific amount of isocyanate which must be employed will
thus vary depending upon such factors a~ the degree of
water resistance in the desired product, the adhesive
strength which is required and the target cost of the
bonded material. These factors will vary depending whether
it is desirous to produce chipboard, oriented strand
board, medium density fibreboard, plywood, fibreglass or
some other related material. ;
'''''~'"'';'
Preferably, from about 1 to about 300 weight
percent, more preferably from about 150 to about 250
weight percent and, most preferably from about 180 to
about 220 weight percent isocyanate, based upon the weight
of waterglass, is employed. If the binder composition is
to be employed in the production of chipboard, oriented
strand board or medium density fibreboard, from about 100
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2~3~2 ~: ~
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to about 300 weight percent, more preferably from about
150 to about 250 weight percent and most preferably from
about 180 to about 220 weight percent isocyanate based
upon the weight of the waterglass may be employed. In the
. . .
S case of the production of the plywood or fibreglass, from
about 45 to about 75, weight percent isocyanate based upon
the weight of the waterglass may be u~ed.
The third ingredient used in the binder
composition of the present invention is a metal soap.
Preferably, the metal soap is solubilized so that it may
be readily mixed with the isocyanate. Accordingly, the
metal soap may be oxylated or polyoxylated as described
hereinafter. Metal soaps which are oxylated or
polyoxylated are not in a powder or water based paste.
Preferably, the metal soap is dissolved in an alcohol or
an aromatic solvent. More preferably, the metal soap is
di~solved in a higher aromatic compound. Most preferably,
the metal soap is dissolved in xylene, toluene or white
spirit.
The metal in the metal soap may be any of those
known in the art. Preferably, the metal is aluminium,
titanium or chrome and, most preferably, the metal is
aluminium or titanium.
2 0 1 9 3 ~ 2
_ 13
The fatty acid used in the production of the
metal soap may be saturated or unsaturated. Preferably,
the fatty acid used in the production of the metal soap
may contain about 18 carbon atoms. Most preferably, the
metal soap i8 a stearate. Quite surprisingly, the results
obtained using stearates are greatly improved over those
obtained using metal soaps made from fatty acids having
greater than or less than 18 carbon atoms.
''.''~ ~ ,;
The amount of the metal soap which is employed
varies between fairly broad ranges. If the amount of
metal ~oap used is too little, then the reaction will
commence more or less immediately upon contacting the
waterglass with the isocyanate. In general, the greater
the amount of metal soap which is used, the more
pronounced i8 the effectivene~s of the stearate in
delaying the reaction between the isocyanate and the
waterglass. Further, the use of greater amounts of the
metal soap alleviate the problem of the fibrous board
sticking to the press, a problem which is known to the
industry. For example, if greater than about 10 weight
! I : I percent stearate is used, based upon the weight of the
isocyanate, then the resultant board does not stick to the
press. Without meaning to be limited to any extent by
theory, it iB believed that when the metal soap is mixed
with the isocyanate, the metal soap acts as a blocking
agent isolating the isocyanate from the waterglass thus
201~38~ ~-
- 14
delaying the reaction between the waterglass and the
isocyanate. Accordingly, the longer the pot life which is
required, the greater the amount of metal soap which must
be employed. Accordingly, it is preferred to employ a
blocking amount of metal soap; namely, a sufficient amount
to delay the hardening reaction between the isocyanate and
the waterglass for a preselected time. Preferably, from
about 0.1 to about 50 weight percent metal soap, based
upon the weight of the isocyanate may be used and, more
preferably, from about 0.3 to about 10 weight percent.
According to the process of the instant
invention, the isocyanate is contacted with the metal soap
prior to contacting the isocyanate with the waterglass.
The mixture of the metal soap and the isocyanate may be
stored for up to 8 hours or more prior to their use. The
isocyanate and the metal soap may be added in any order to
a suitable mixing vessel. Preferably, the metal soap is
added to the isocyanate. The two compounds are then mixed
to form a solution of isocyanate and metal soap. This
solution comprises the hardener for the binder
composition. Preferably, the mixing occurs rapidly and
with high energy input such as is obtained with a
dissolver mixer or a blender operating at about 500 to 800
rpm. The Dixing may be conducted ~t room temperature.
'
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2~ ~3~
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The binder composition and the fibrous or chip
like material may be contacted and processed into a
fibrous board according to means known in the art. The
binder compo~ition may be mixed with the fibrous or chip
like material as is known in the art. Any standard
additives known in the art may also be added. The mixture
of binder composition and chip like or fibrous material
may then be placed in a mold and pressed.
In particular, as will be explained in more
detail hereinafter, the subsequent processing steps will
vary dèpending upon the product which is to be obtained.
The waterglass, isocyanate and metal soap may be mixed and
sprayed on to the fibrous or chip like material.
Alternately, the waterglass and the mixture of the
isocyanate and the metal soap may each be separately
sprayed onto the fibrous or chip like material which are
in a mixer. By way of example, if plywood or fibreglass is
to be prepared, the waterglass and the mixture of
isocyanate and metal soap may be blended to form àn
emulsion. The fibrous or chip like material is coated with
this emulsion and the coated material is subsequently
processed to obtain the desired product. Alternately, if
it iB desired to prepare particle board, chipboard or
oriented strand board, the mixture of isocyanate and metal
soap may be sprayed onto the fibrous or chip like material
from one nozzle and the waterglass (possibly blended with
. ~' .
20~382
- 16
additional water and or a parafin wax as described
hereinafter) may be sprayed onto the fibrous or chip like
material from a second nozzle. The material is then
processed as is known in the art.
The binder composition of the present invention
may be used as a binder for known fibrous or chip like
material including glass, asbestos, wood and cellulose
chips and fibres and related chip and fibrous material.
Accordingly, the binder composition is suitable for use in
10 the preparation of numerous building materials such as
particle board, plywood, oriented strand board, chipboard,
fibreglass, fibreboards including medium density
fibreboards and other related materials.
Typically, in the production of particle board
¦ 15 and the like, standard production methods known in the art
require that the particles be dried to about 3% humidity.
If the wood fibres contain a higher percent water, then
the resultant board will split. By employing the binding
composition of the present invention, it is possible to
20l prepare particle board and the like wherein the particles,
before addition of the binder composition, have a water
content of up to about 12 weight percent water. The
~ ability to use fibrous or chip like material having
3 increased amounts of water present therein provides
¦ 25 various advantages. First of all, as particles having an
.~ , .
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201~382 :
- 17
increased amount of water may be used, less energy is
required in obtaining particles having the required degree
of dryness. This decreases the energy which must be input
to obtain the drier particles. Further, this results in a
relatively substantial cost savings and increases the
flexibility of the proces~ since a greater range of
starting material may be employed.
As i8 apparent from the forgoing, the mixture of
the isocyanate and the metal soap, namely the hardener,
may be mixed with the waterglass in any order or
~eparately applied to the chip like or fibrous material.
Once mixed to form the binder composition, the binder
composition has a pot life of about 8 hours or more at
room temperature, particularly if the metal soap i8 a
~tearate. This provides sufficient time for utilizing the
binder composition in a commercial manufacturing process.
The curing of the binder composition to form a
hard silicate adhe~ive commences fairly rapidly upon the
addition of heat. Accordingly, the binder composition and
the fibrous or chip like material may be mixed and`placed
in a mold at room temperature. Pursuant to these
processing steps, substantially no curing of the binder
composition occurs. Once the mixture of the binder
composition and the fibrous or chip like material is in
the mold and ready to be pressed, heat may be applied. In
: '
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~- ?~3~
_ 18
this manner, the commencement of the curing of the binder
composition may be precisely controlled to commence at the
most opportune time in the process. As the curing
reaction is exothermic, part of the heat needed to
complete reaction is provided by the curing reaction
itself.
The curing reaction is relatively rapid. In the
industry, pre6sing is normally conducted from about 180 to
about 200C. These temperatures may be used in preparing
boards incorporating the binder composition of the present
invention. This simplifies replacing the binder
composition presently used in the industry with the binder
composition of the present invention. In comparison with
boards bonded by phenol resins which are currently used by
industry, when using the binder composition of the present
invention, the press time is approximately half of that
required when using phenol resins. For example, phenol
formaldehyde resins require a press time of between about
14 to about 16 seconds for each one millimetre of board
thickness. In comparison, the binder composition of the
present invention requires only from about 7 to about 10
second of press time for each millimetre of board
thickness.
The binder composition of the present invention
may be used to replace the binder composition presently
: .. . . ~ . .
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2 0 ~ 9 3 8 2
19 - . ;: '.
used in the industry. Accordingly, the binder composition
of the present invention may be readily adopted by
industry. Further, due to the decreased pressing time, the
amount of product produced by an existing plant may be
~ubstantially increased, thus reducing the cost of the
fibrous board. Further, as the binder composition of the
present invention does not result in the release of toxic
compounds during the pre~sing of the boards, the binder
composition of the present invention is more ;;
environmentally friendly and results in further cost
savings in the production of boards. Further, boards `~
prepared using the binder composition of the present
invention may be treated in the same manner as boards` ;~
processed from phenol resins and similar materials.
Accordingly, the boards made by the binder composition of
the present invention may be laminated like known boards.
.. ,: . ,.
The binder composition of the present invention
may optionally include additives which are currently used
in the production of chipboard, oriented strand board,
20 plywood, fibreglass, fibreboard and related materials. As `~ i
! 1 1 is known in the art, the resultant board may be
waterproofed by the addition of a parafin wax emulsion,
preferably having 50 to 60 percent solids, or a dimer
alkyl ketene to the binder composition. The emulsion or
~ .....
ketene is preferably added to the mixture of the
isocyanate and the waterglass. According to normal
.. ...
" ,...
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1. ., .,,.",
~ 20~382
_ 20
production methods using conventional binder compositions,from about 0.6 to about 2.4 percent of this wax emulsion
i8 added to the binder composition based upon the dry wood
weight. This results in an increase in the two hour swell
of wood as measured by British Standard. When used with
the binder composition of the present invention, the 2 -
24 hour water swell is improved by using only about 0.6percent of the emulsion.
The invention will be further understood by the
following examples which are not to be construed as a
limitation on the invention. Those skilled in the art
will appreciate that other and further embodiments are
obviou~ and within the spirit and scope of this invention
from the teachings of the present examples taken with the
accompanying specification.
Example 1 - Preparation of Particle Board
1 gram oxylated aluminum stearate were added to
grama of diphenylmethyl-4,4'-diisocyanate ("MDI").
These compounds were mixed to form 51 grams of a hardener
for the binder composition. This hardener and 25 grams of
an aqueous solution of sodium silicate (40 percent solids)
were sprayed from separate nozzles onto 1,000 grams of
particles abs.dry. The particles, silicate and hardener
were mixed and placed in a mold 16 mm thick. The
. ,.. , . , . .. , . . ~ ". ~
2~193~2 ; ~
- 21
composition was pressed at 200C for 160 seconds. The
resultant particle board could be cut, used for screws and
otherwise handled as a particle board made from a phenol
resin from the same particles.
ExamPle 2 - Production of Particle Board
The method of Example 1 was repeated except
prior to spraying the silicate on the particles, 10 grams
of dimer alkyl ketene 60~ were mixed with the sodium
silicate. The mixture of the sodium silicate and ketene
and the mixture of the isocyanate and stearate were each
separately sprayed onto 1,000 grams of wood particles abs
dry. The resultant particle board could also be cut, used
for screws and otherwise handled as a particle board
prepared from a phenol resin made from the same particles.
': ,,, .,'
The particle board had a swelling property of
2.22 percent a~ measured by British Standard with a water
absorption of 11.4 percent. After 24 hours, the swelling
was 8.1 percent with a water absorption of 27.5 percent.
,," ,~, ,,
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Example 3 - Water Resistant PlYwood of Narine QualitY
: ,:
A binder composition was prepared from the `
following constituents:
~' ~
2~9382
- 22
100 grams water
5 grams carboxyl methyl cellulose 4,000
1,000 gram~ silicate of sodium, 50 baume
100 grams dimer alkyl ketene
5500 grams MDI
5 grams Al stearate
The compounds were mixed in the following order.
The stearate and the isocyanate were placed in a mixer and
mixed. This mixture was then set aside. The water and
cellulose was added to a mixer and mixed for 5 minutes.
The silicate and ketene were added and mixing continued
for 5 minutes. The MDI/stearate mixture was added and
mixing continued for 5 minutes.
The constituents were mixed in a dissolver mixer
at 1,500 to 2,000 rpm to prepare the final emulsion. The
emulsion was pumped to spreading (distributing) machines.
Cut wood plies were covered with this emulsion, sandwiched
with crossing direction fibres and pre-pressed at room
temperature for 10 minutes. Subsequently, the plywood was
processed in a hot press (180 C) for 2 minutes and 40
seconds to obtain 16 mm plywood.
Example 4 - ChiPboard
'~.
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- 23
A hardener composition was prepared by adding 1
gram of Al stearate to 50 grams of NDI and mixing for 5
minutes in a dissolver mixer at 1,500 rpm. Twenty-five
grams of sodium silicate (40 percent solids) and 10 grams
of dimer alkyl ketene were mixed to form a second
solution.
One thousand grams of planing chips were placed
in a compulsory mixer. Two spray nozzles were focused on
the chips. Mixing was commenced and the chips were
sprayed with the hardener composition from one nozzle and
the silicate mixture from a second nozzle. The mixing
continued for 5 minutes. Subsequently, the mixture was
... . ~
placed in a press and pressed at 200C for 2 minutes and : -
.' "J
40 seconds to form chipboard 16 mm thick. ;;~
:'., ~" ,'' '
ExamPle 5
' '' ,': :.,.
An emulsion was prepared according to the
.. ... ..
process of Example 3 from 1,000 gram~ water, 1,000 grams -~
sodium silicate 50 baume, 200 grams MDI and 10 grams al
~tearate. The resultant mixture was sprayed~onto 33 kg
of wood fibres and pressed at 200C for 2 minutes and 40
seconds to obtain board 16 mm thick.
, '~ ,;
ExamPle 6 - Preparation of Construction Grade 3/8" Plywood
Havinq 14 Percent Wood Moisture Content
;~ ' '
20~3~2
- 24
A hardener composition was prepared as follows.
One hundred kg of isocyanate was added to an 80 horsepower
dissolver/mixer. The di6solver mixer was started and 50
kg of aluminum stearate in white spirit was added. Mixing
continued for 5 minutes. This mixture was set aside.
Six hundred and seventy kg of water were placed
in an 80 horsepower dissolver/mixer. The mixer was
operated at 1500 rpm. One kg of tylose (10,000 yp) was
added to the mixer. Mixing continued for 2 minutes.
Subsequently, one kg of 30 percent ammonia solution was
added to the mixer and mixing continued for one minute.
One hundred and thirty kg of waterglass (36 percent
solids) were added. Subsequent to the addition of
waterglass, 40 kg of wheat flour were added slowly in a
number of part~. Mixing continued for approximately 2
minutes until the lumps disappeared. Thirty kg of COCOB
were ~lowly added while mixing continued. Mixing
continued until the lumps disappeared. At this time, 60
kg of the isocyanate/stearate mixture, which had been
previously prepared, was added to the mixer. IMixing
continued for 5 minutes until a medium viscosity was
obtained.
201~3~2 :
- 25
'', ,:, ,: '
The resulting emulsion was applied by
mechanical rollers onto plywood veneers at a rate of about ,
200 grams of binder composition per square metre of
plywood. The plywood was placed in a press and pressed at
a rate of 10 seconds per millimetre of pressed wood at
200C.
' ' ,.'~'~:
A similar process could be used to prepare
fibreglass insulation.
~ ' ':':
Example 7
'" ': " '
The hardener composition was prepared as set out
in Example 6. A waterglass mixture was prepared by
placing 135 kg of water, 100 kg of parafin mobilcer (60
percent solids) and 50 kg of sodium silicate (50 percent
solids) in a dissolver/mixer and mixing at 1,500 rpm for
5 minutes.
One thousand kg of wood wafers (9 percent
, moisture content) were placed in a blender/mixer. The
mixer was started and the wood was sprayed with 28.5 kg
waterglass mixture from one nozzle and 10 kg of the
hardener from a second nozzle.
-1 2~3~
_ 26
The mixture of wood chips and binder composition
was placed in a press and pressed at 200C for 10 seconds
of press time per millimetre of board thickness at 35 bars
of pressure. A similar process can be used to prepare
wafer boards and chipboards.
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