U.S. patent number 3,804,706 [Application Number 05/166,307] was granted by the patent office on 1974-04-16 for inorganic fiber board with binder of thermosetting resin and thermoplastic vinylic resin.
This patent grant is currently assigned to Kuraray Co., Ltd.. Invention is credited to Kiyonobu Fujii, Hirotoshi Kurashige.
United States Patent |
3,804,706 |
Kurashige , et al. |
April 16, 1974 |
INORGANIC FIBER BOARD WITH BINDER OF THERMOSETTING RESIN AND
THERMOPLASTIC VINYLIC RESIN
Abstract
An inorganic fiber board having improved high resistance to
splitting the board parallel to the plane of the board and an
apparent density of from about 0.3 g/cm.sup.3 to 1.0 g/cm.sup.3 is
produced by mixing 100 weight parts of an inorganic material
consisting of 40-98 weight parts rock wool or slag wool, 2-30
weight parts asbestos and 0-50 weight parts of an inorganic filler
with a binder of an aqueous emulsion of 3-25 weight parts (based on
100 weight parts of inorganic materials) of a thermosetting resin
and 0.3-10 weight parts of a thermoplastic vinyl resin to obtain a
slurry; dewatering the slurry on the screen to obtain a wet laid
mat; and then drying and curing the mat to convert the
thermosetting resin to an insoluble and infusible state. A surface
decorated board is obtained by mixing vermiculite particles in the
inorganic material. Another embodiment of a surface decorated board
having a fine uneven crepe like pattern is obtained by rubbing the
surface of a wet laid mat and applying suction to the other side of
the mat repeatedly.
Inventors: |
Kurashige; Hirotoshi
(Kurashiki, JA), Fujii; Kiyonobu (Kurashiki,
JA) |
Assignee: |
Kuraray Co., Ltd. (Kurashiki
City, JA)
|
Family
ID: |
13309459 |
Appl.
No.: |
05/166,307 |
Filed: |
July 26, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Jul 29, 1970 [JA] |
|
|
45-66218 |
|
Current U.S.
Class: |
162/109; 162/134;
162/152; 162/155; 162/162; 162/166; 162/168.7; 162/145; 162/153;
162/165; 162/168.1; 162/181.6 |
Current CPC
Class: |
C04B
24/26 (20130101); C04B 14/40 (20130101); C04B
14/202 (20130101); C04B 40/02 (20130101); C04B
14/46 (20130101); D21H 13/36 (20130101); C04B
26/12 (20130101); D21H 5/18 (20130101); D21H
13/42 (20130101); D21H 17/33 (20130101); D21H
17/49 (20130101); C04B 26/12 (20130101) |
Current International
Class: |
C04B
26/12 (20060101); C04B 26/00 (20060101); D21h
003/36 (); D21h 003/50 () |
Field of
Search: |
;162/145,152,155,162,165,168,111,164,225,222,305,362,210,205,109,134,153,181R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Tushin; Richard H.
Attorney, Agent or Firm: Stepno, Schwaab & Linn
Claims
1. An inorganic fiber board having an apparent density of about 0.5
g/cm.sup.3 to 1.0 g/cm.sup.3 and being highly resistant to
splitting in the plane of said board, one of the surfaces of said
board having a wrinkled surface, said board comprising:
i. 100 weight parts of inorganic materials comprising from 40 to 98
weight parts of rock wool or slag wool, from 2 to 30 weight parts
of asbestos, and from 0 to 50 weight parts of an inorganic filler,
and
ii. a binder consisting of from 3 to 25 weight parts, based on 100
weight parts of the inorganic materials, of a thermosetting resin,
and from 0.3 to 10 weight parts based on the 100 weight parts of
the inorganic materials, of a synthetic water-insoluble
thermoplastic vinylic polymer, said rock wool or slag wool forming
an interfelted web, said inorganic filler being dispersed in and
around the interfelted web, and said wool fibers being bound by the
cured thermosetting resin and the synthetic
2. An inorganic fiber board according to claim 1, wherein said
thermosetting resin is selected from the group consisting of
3. An inorganic fiber board according to claim 1, wherein said
synthetic water-insoluble thermoplastic vinyl polymer is
ethylene-vinyl acetate
4. An inorganic fiber board according to claim 1, wherein said
synthetic water-insoluble thermoplastic vinyl polymer is selected
from the group consisting of polyvinyl acetate, vinyl
acetate-ethylene copolymer, vinyl acetate-acrylonitrile copolymer,
vinyl acrylate copolymer, vinyl acetate-ethyl acrylate copolymer,
vinyl acetate-methylmethacrylate
5. An inorganic fiber board according to claim 1, further
comprising a minor amount of vermiculite particles randomly
dispersed throughout said
6. An inorganic fiber board according to claim 1, further
comprising a minor amount of a coloring agent and wherein said
coloring agent is concentrated in the crest portions of said
wrinkles thereby producing
7. A process for producing an inorganic fiber board which
comprises:
i. mixing 100 weight parts of an inorganic material comprising from
40 to 98 weight parts of rock wool or slag wool, from 2 to 30
weight parts of asbestos, and from 0 to 50 weight parts of an
inorganic filler, with an aqueous emulsion of from 3 to 25 weight
parts, based on 100 weight parts of the inorganic materials, of a
thermosetting resin, and from 0.3 to 10 weight parts, based on 100
weight parts of the inorganic materials, of a synthetic
water-insoluble thermoplastic vinylic polymer to produce a
slurry;
ii. dewatering said slurry to produce a wet laid mat;
iii. repeatedly rubbing one face of the wet laid mat with a roll
and applying a vacuum to the opposite surface of the mat; and
iv. drying said mat and then curing the thermosetting resin in the
mat to an insoluble and infusible state, whereby there is produced
an inorganic fiber board having high resistance to splitting
parallel to the plane of
8. The process for producing an inorganic fiber board according to
claim 7, further comprising adding a minor amount of coloring agent
into step (i), whereby there is produced an inorganic fiber board
having a wrinkled surface wherein said coloring agent is
concentrated in the crest portions of said wrinkled surface
producing crest parts of the wrinkles and
9. The process for producing an inorganic fiber board according to
claim 7, wherein said thermosetting resin is selected from the
group consisting of
10. The process for producing an inorganic fiber board according to
claim 7, wherein said synthetic water-insoluble thermoplastic
vinylic polymer is ethylene-vinyl acetate copolymer.
Description
This invention relates to an inorganic fiber board containing slag
wool or rock wool, and to a wet process of producing the same.
The object of the present invention is to provide an inorganic
fiber board which possesses high resistance to split out parallel
to the plane of the board.
One of the objects of the present invention is to provide an
inorganic fiber board useful for a wall board.
A further object of the present invention is to provide a
decorative inorganic fiber board which has particles of vermiculite
on the surface of the board.
Another object of the present invention is to furnish a decorative
inorganic fiber board which has a crepe like patterned surface on
the board.
An inorganic fiber board comprising a mineral wool, such as rock
wool or slag wool, bound said fibers with a thermosetting resins,
such as urea-formaldehyde resin, phenol-formaldehyde resin or
malamine-formaldehyde resin is disclosed in U.S. Pat. No.
2,633,433. A wet process of producing such a board is disclosed in
U.S. Pat. No. 2,732,295.
These inorganic fiber boards have relatively low density, i.e., an
apparent density of about 0.1 to 0.4 g/cm.sup.3, relatively high
flexural strength, water proof, fire proof and high electrical and
thermal insulating properties. Therefore these boards are used as
acoustical panels or sheets in ceilings.
But as these boards are formed from a water suspension of the
mineral wool and the binder, the major proportion of the fibers
therein are oriented in a plane substantially parallel to the plane
of the board. Therefore, the layer of these boards are readily
split out parallel to the plane of the board by a weak force.
This defect is caused by the migration of binder resin to the outer
surface during the drying cycle of the wet sheet, and this
migration results in a product that has a strong outer crust but a
weak inner core. This phenomenon is considerably reduced by
including a natural clay, such as bentonite and kaolin in the fiber
board. But this method does not entirely prevent this phenomenon,
therefore, these boards are limited to use as acoustical ceiling
panels.
On the other hand, it is also known to make inorganic fiber boards
comprising a mineral wool, such as rock wool or slag wool with such
fibers bound with starch, such as gelatinized starch. These boards
are also used principally for acoustical ceiling panels, but these
panels have a tendancy to sag in a high humid atmosphere.
The present invention relates to an improved inorganic fiber board
having resistance to split out parallel to the plane of the board
and resistance to sag in a high humid atmosphere. Therefore, the
board of the present invention is useful not only as a ceiling
panel but also as a wall board in a room.
Under the investigation of the present inventors, it was found that
these defects of the prior art can be prevented combining a water
insoluble thermoplastic vinyl polymer resin with a thermosetting
resin as the binder for the mineral wool fibers. In the practice of
the present invention, the thermosetting resins are usually
dissolved or dispersed in a water suspension of mineral wool, and
the water insoluble vinyl polymer resins are dispersed in the water
suspension of mineral wool.
The inorganic fiber board of the present invention consists of the
following ingredients:
(1) Inorganic materials 100 weight parts rock wool or slag wool 40
- 98 weight parts asbestos 2 - 30 weight parts inorganic filler 0 -
50 weight parts (2) Binder resins a thermosetting resin 3 to 25
weight parts (water-soluble or water-insoluble) a thermoplastic
vinyl polymer resin 0.3 -10 weight parts (water-insoluble)
The apparent density of the inorganic fiber board of the present
invention may be regulated in the range of about 0.3 g/cm.sup.3 to
1.0 g/cm.sup.3. A board having a density of about 0.5 to 1.0
g/cm.sup.3 is preferred for use as a wall board, since this board
has improved impact strength and high bend modulus.
The mineral wool used in the present invention may be rock wool or
slag wool, either long-fibre or loose wool, or what is known in the
trade as granulated or nodulized wool.
As the asbestos used in the present invention, asbestos fibers
known as chrysotile in the range of 5 to 7D may be used.
The effect of the blend of asbestos in the mineral wool is not only
to produce inorganic fiber board with improved tensile strength and
impact strength but also to promote the dispersion of the inorganic
filler in the present inorganic fiber board. This effect is
obtained by the adsorption force of asbestos to the inorganic
filler and the filtering of the inorganic filler with asbestos in
the step of dewatering the aqueous suspension. Therefore, the
amount of asbestos must be regulated with the amount of the
inorganic filler. The amount of asbestos in the practice of this
invention may be in the range of about 2 to 30 parts by weight. If
the amount of asbestos is increased to more than 30 parts,
dewatering of the mineral fiber suspension on the screen is more
difficult.
The inorganic filler used in the present invention may be powders
of calcium carbonate, plaster and gypsum, slag, fly-ash, silica,
sericite, natural clay, such as kaolin, bentonite or acid clay, or
calcium silicate.
In the preferred embodiment of the invention, calcium carbonate,
plaster and gypsum, slag, fly-ash, silica or sericite is employed
so that the inorganic fiber board will have high impact strength.
Heavy calcium carbonate or precipitated calcium carbonate is
especially preferred. But in the present invention, portland cement
or diatom aceous earth is not preferable as the inorganic
filler.
The presence of the inorganic filler in the finished mineral wool
board, which filler is dispersed among the mineral wool, serves to
enlarge the contact points or surfaces of the binder resin with the
mineral wool fibers. Accordingly, the strength of the finished
mineral wool fiber board is improved.
Therefore, there may be obtained a relatively thin board having a
thickness of about 4 to 8 mm with relatively high flexural strength
and impact strength. But when the amount of the inorganic filler in
the finished product is in excess of 50 parts by weight, the
density of the product is too large for a wall board or ceiling
board and the impact strength of the product is decreased.
In the practice of the present invention, if desired, a minor
amount of glass fibers may be used. The fiber length of the glass
fibers is in the range of about 3 to 13 mm and the amount of the
glass fibers in the board may be in the range of 0.5 to 30 weight
parts.
As the thermosetting resin used in the invention, urea-formaldehyde
resin, phenol formaldehyde resin, or melamineformaldehyde resin may
be used. These thermosetting resins are in the initial stage of
polymerization, and are curable by heat to insoluble and infusible
resins.
As the water-insoluble thermoplastic vinyl polymers used in the
invention, polyvinyl acetate, vinyl acetate-ethylene copolymer,
vinyl acetate-acrylonitrile copolymer, vinyl acrylate copolymer,
vinyl acetate-ethyl acrylate copolymer, vinyl
acetate-methylmethacrylate copolymer, and acrylic polymers may be
used.
The thermosetting resin is the predominant ingredient of the
binder. This resin serves to improve the tensile strength, flexural
strength, rigidness, hardness, and water-resistance and high
humidity-resistance properties of the finished board. But when only
this resin is used as the binder, the finished board is readily
split or peeled out parallel to the plane of the board by even a
weak force.
To prevent this phenomenon, it is necessary to use a minor amount
of the water insoluble vinyl polymer resin with the thermosetting
resin. These water insoluble vinyl polymer resins are usually
available as an aqueous emulsion.
The amount of the thermosetting resin used in the binder may be in
the range of about 3 to 25 weights parts by weight based on the
inorganic material, which is the total weight of the mineral wool,
asbestos and the inorganic filler. If the amount of the
thermosetting resin is in excess of 25 parts, the fire resistance
of the board decreases and the excess of the resin does not act to
promote the binding effect of the mineral wool.
The amount of the water insoluble vinyl polymer resin used in the
binder may be in the range of about 0.3 to 10 weight parts based on
the weight of the inorganic materials.
In this invention, known binders used for the production of mineral
wool boards may be used as a supplemental ingredient of the binder
of the invention. These supplemental binder ingredients include,
for example, polyvinyl alcohol, polyethylene oxide, carboxymethyl
cellulose, hydroxyethyl cellulose, polyacrylamide, the salts of
polyacrylic acid, water soluble starch, starch, gum arabic,
gelatine, glue and casein. These water soluble ingredients act as
thickeners or protective colloids. The amount of these ingredients
used is below about 4 weight parts based on the inorganic
material.
The product of the present invention may be prepared by any process
in which a thermosetting resin and a thermoplastic vinyl polymer in
the presence of an aqueous medium is incorporated with inorganic
fibrous material, the fibers of which are interfelted in an aqueous
suspension thereof and in which the resin after its association in
the interfelted web is converted by heat to the infusible,
insoluble stage.
In the preferred process of the invention, the board, which is
subjected to heat to convert the thermosetting resin, is formed
from an aqueous suspension of the inorganic fibrous material by the
use of a screen to remove water therefrom. Preferably, the
inorganic fibrous materials are mixed with an aqueous medium
containing a dissolved thermosetting resin and a dispersed
thermoplastic vinyl polymer or a synthetic rubber polymer. The
mixing may be accomplished, for example, in a beater or a mixing or
agitating tank or a head box, and the aqueous suspension containing
the inorganic fibrous material and resinous binders is dewatered by
the use of a screen. The resulting suspension may then be deposited
either continuously on a conveying system or batchwise into the wet
laid mat.
One of the surface decorated inorganic fiber boards of the present
invention may be prepared by adding and dispersing vermiculite
particles in the aqueous suspension of inorganic fibrous materials
and the resinous binders, and treating said aqueous suspension by
the above noted process. As the vermiculite particles are a mixture
of various colored particles such as gold, silver, black brown and
yellow ocher, the product board has various colored dots randomly
disposed on a white gray surface background.
The particle size of vermiculite used in the present invention are
in the range of passing 5 mesh sieve but being retained on 80 mesh
sieve, especially in the range of passing 10 mesh but retaining 50
mesh sieve. Particles below 80 mesh are not suitable to prepare the
decorated board having the colored dots. The content of vermiculite
particles in the board may be in the range of about 0.5 to 15
weight parts based on the total weight of the inorganic materials.
When the content of vermiculite particles is more than about 15
weight parts, the appearance of the board surface is too loud and
the mechanical strength of the board has a tendency to
decrease.
Another embodiment of a surface decorated inorganic fiber board of
the present invention may be prepared by the combination of the
steps of sucking by a reduced pressure the water involved in the
wet laid mat and rubbing the surface of the wet laid mat with the
surface of the roll repeatedly.
By repeating the above noted combination of steps, for example,
from two times to six times, the surface of the board has uneven
wrinkles resembling the surface of "crepe" fabrics, such as crepe
de Chine, sakker or voile.
When a minor amount of coloring agent such as a lake or pigment is
added during the production of this board, most of the coloring
agent migrates on to the hills of the wrinkles and the valleys of
the wrinkle lack the coloring agent. Therefore, the surface of the
board has colored hill parts of the wrinkles and non-colored (white
gray) valley parts of the wrinkles. The product board, thus
obtained, has a good appearance and is useful for a decorative wall
board.
The present invention is illustrated by the following examples in
which, unless otherwise specified, all parts are by weight.
EXAMPLE I
One hundred parts of inorganic material consisting of 53 parts of
slag wool, 17 parts of asbestos (10 parts of chrysotile 7 D and 7
parts of chrysotile 6 D) and 33 parts of precipitated calcium
carbonate powder were mixed into 1,150 parts of water containing 13
parts of urea-formaldehyde resin, 0.9 parts of vinyl
acetate-ethylene copolymer (ethylene content: 30 mol percent) and
0.6 parts of polyvinyl alcohol having a polymerization degree of
1,700 to produce a mineral wool suspension.
The suspension was mixed with a beater to produce a homogenized
slurry. The slurry was dewatered on a screen of 80 mesh size to
produce a wet laid mat. This mat was further dewatered with a press
roll and suction to a water content of about 100 weight per cent
based on the solid ingredients. The mat was dried at 60.degree. C
and then cured with heat under a pressure of 0.1 kg/cm.sup.3 and a
temperature of 160.degree. C for 7 minutes.
In the process of producing the board, 10 per cent of calcium
carbonate and a minor amount of vinyl acetate-ethylene copolymer
were lost by dewatering.
The board, thus obtained, was a light gray colored rigid board and
has a thickness of about 7 mm., an apparent density of about 0.6
g/cm.sup.3, bend break strength of about 26 kg., bend modulus of
about 80 kg/cm.sup.2, tensile strength of about 40 kg/cm.sup.2, and
an impact strength of 0.20 ft. lb/in.
The board possesses high tenacities compared with the usual rock
wool board. Therefore, this board can be used as a wall board, and
this board better permits the making of large panel board units of
dry board by cutting the board into the panels, such as 3 x 6 foot
size.
On the other hand, a rock wool board produced by the usual known
method compensates for low bend modulus and tensile strength by
increasing the thickness of the board up to about 9 to 18 mm. But
these thickened boards usually possess only a bend modulus below 40
kg/cm.sup.2 (most of them below 30 kg/cm.sup.2) and tensile
strength of 20 kg/cm.sup.2 (most of them below 10 kg/cm.sup.2).
The bend breaking strength and the bend modulus were measured by
the test of "The method of bending test for building boards"
JIS-A-108 (1964) which is investigated by Japanese Industrial
Standards Committee.
EXAMPLE II
One hundred parts of inorganic material consisting 55 parts of slag
wool, 15 parts of asbestos (chrysotile 7 D) and 30 parts of heavy
calcium carbonate fine powder were mixed into 1500 parts of water
to obtain a mineral wool suspension. Fourteen parts of
urea-formaldehyde resin were dissolved into said suspension, and
then four parts of ethylene-vinyl acetate resin (Trade name:
PANFLEX OM-4000) were added into said suspension to prepare the
slurry.
The slurry was dewatered on a screen of 50 mesh size to prepare the
wet laid mat. The mat was further dewatered with suction under a
reduced atmosphere and pressed with rolls to a water content of
about 80 weight per cent. The mat was dried at 90.degree. C and
cured at 170.degree. C for 25 minutes.
The board, thus obtained, has a crepe like patterned surface and an
apparent density of about 0.65 g/cm.sup.3.
The tearing strength parallel to the plane of the board of this
example was 2.8 kg/cm.sup.2. On the other hand, the tearing
strength of a comparison board which was produced by the same
process but without adding the ethylene-vinyl acetate copolymer
resin was only 0.4 kg/cm.sup.2.
As seen from the above comparison, ethylene-vinyl acetate
copolymer, which is one of the water-insoluble vinyl resins,
remarkably increased the tearing strength parallel to the plane of
the board.
EXAMPLE III
70 parts of slag wool, 30 parts of asbestos and 18 parts of
powdered aluminum oxide (Trade name: almina white, made by Daimei
Chemical Company) were mixed into 1,000 parts of water. The mixture
was homogenized with a beater to obtain a suspension. 23 parts of
phenol-formaldehyde resin (novolak type aqueous emulsion) and 5
parts of ethylene-vinyl acetate copolymer were dispersed in the
suspension to obtain the slurry. The slurry was dewatered on a 50
mesh screen to prepare the wet laid mat. The mat was further
dewatered with suction under a reduced pressure and lightly pressed
with rubber rolls to a water content of 120 weight per cent. The
mat on the screen was dried at a temperature of 90.degree. C and
removed from the screen. The dried mat was then cured at
145.degree. C for 20 minutes.
The resulting board had the following properties: Thickness 16 mm
Apparent density 0.39 g/cm.sup.3 Bend strength 50 kg Wet bend
strength 46 kg (After 24 hours in 20.degree.C water) The content of
the phenol-formaldehyde resin in the board 11 weight per cent
EXAMPLE IV
55 parts of slag wool, 15 parts of asbestos (chrysotile 7 D), 7
parts of vermiculite (particle size 10 - 30 mesh) and 23 parts of
calcium carbonate were dispersed in 1,150 parts of white water
containing 14 per cent of urea-formaldehyde resin, 1 per cent of
polyvinyl alcohol (polymerization degree 1700), and 1 per cent of
ethylene-vinyl acetate copolymer (ethylene content 30 mol per
cent), and beaten to obtain a homogeneous slurry.
Then, the slurry was dewatered on a screen having the 80 mesh size
to make a wet laid mat. The wet laid mat was dewatered and pressed
by sucking and pressing. The sheet material was removed from the
screen and dried at 70.degree. C and further cured at low pressure
and 160.degree. C. The obtained board had a thickness of about 7
mm, and an apparent density of 0.5 g/cm.sup.3. The surfaces of this
board was decorated with vermiculite particles having various
colors, such as gold, silver-like, black and brown which are
scattered on a gray-white board.
The strength of this board was enhanced by adding only 3 to 4 parts
of glass fibers to the slurry without changing the decorative
appearance of the board.
Embossing may be applied to the wet laid mat and the thus obtained
board has decorative embossing and the pattern of the vermiculite
particles.
EXAMPLE V
80 parts of slag wool, 10 parts of chrysotile 6 D asbestos and 10
parts of vermiculite were mixed into 1,150 parts of water having 10
parts of urea-formaldehyde resin, 0.8 parts of vinyl
acetate-ethylene copolymer (ethylene content: 33 mol per cent) and
0.8 parts of polyvinyl alcohol to produce a slurry.
This mixture was beaten with a beater to obtain a homogeneous
slurry. This slurry was dewatered on a screen of 80 mesh size to
produce a wet laid felt, and then this wet laid mat was dewatered
by suction and by press-roll. This mat was dried at 60.degree. C
and the urea-formaldehyde resin in the mat was cured under a
pressure of 1 kg/cm.sup.2 and a temperature of 160.degree. C for 10
minutes.
The surfaces of the board were decorated with vermiculite particles
forming golden, silver-like, black and brown dots on the white
surfaces.
EXAMPLE VI
55 parts of slag wool, 15 parts of asbestos (chrysotile 7 D) and 30
parts of heavy calcium carbonate fine powder were mixed in white
water containing 180 parts of urea-formaldehyde resin, 5 parts of
ethylene-vinyl acetate copolymer (ethylene content: 30 mol per
cent) 0.3 part of powdered aluminum metal (coloring agent, particle
size 1 - 10 .mu.) and 1,150 parts of water, and beaten to provide a
homogeneous slurry.
The slurry was filtered on a 80 mesh screen to remove water in
order to make a wet laid mat.
After the upper surface of the mat was smoothened with a rubber
roll four times, the mat was sucked from the screen side to remove
the water contained in the mat and the water content in the mat was
regulated to about 100 weight per cent based on the total weight of
slag wool, asbestos and calcium carbonate.
Then the mat was removed from the screen and dried at 80.degree. C
and further heated at 150.degree. C for 15 minutes to cure the
urea-formaldehyde resin.
The board, thus obtained, had a thickness of 7.0 mm., an apparent
density of 0.65 g/cm.sup.3, and a decorative surface like a crepe
de Chine pattern. The convex parts of the said pattern were colored
gray with powdered aluminum metal and the valley parts of the said
pattern were colored white gray. This board is useful for a
decorative wall board.
EXAMPLE VII
54 parts of slag wool (granulated wool), 16 parts of asbestos
(chrysotile 7 D), 28 parts of heavy calcium carbonate fine powder
and 2 parts of glass fibers (fiber length: 6 mm) were mixed into an
aqueous emulsion containing 160 parts of urea-formaldehyde resin, 4
parts of ethylene-vinyl acetate copolymer (ethylene content: 40 mol
per cent), 0.10 part of inorganic pigment (brown), 0.025 part of
inorganic pigment (black) and 1,150 parts of water, and made into a
slurry by the same process described in Example VI.
A wet laid mat was produced from a slurry by the same process
described in Example VI.
The steps of rubbing the surface of the wet mat with the surface of
the roll and sucking and dewatering the wet mat were repeated for
three times, respectively. Then the mat was removed from the screen
and dried at 70.degree. C and cured at 150.degree. C for 15
minutes.
The surface of the board had a fine uneven pattern like the surface
of crepe de Chine fabrics.
EXAMPLE VIII
A board was produced by the same process described in Example VII
from inorganic materials consisting of 77 parts of rock wool
(granulated white wool), 20 parts of asbestos (the same as in
Example VII) and 3 parts of vermiculite particles.
The surfaces of this board had a fine uneven pattern like the crepe
de Chine fabrics and vermiculite particles are dispersed on the
surfaces.
* * * * *