Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~C~69;~67
This invention concerns improvements in or relating to the
moulding of thermosetting moulding compositions.
An essential feature of the manufacture of thermosetting
moulding compositions has been the pre-mastication of the
thermosetting resinous material (used as curable matrix) with
the filler(s) so that the latter becomes fully compounded with,
impregnated by, and coated with, the resinous material. This
may be effected under either 'dry' conditions where the resinous
material is essentially solid and is melted or fluxed during
the mastication processing, or in the presence of a solvent
or other liquid medium optionally followed by drying. The
resultant moulding compound is subsequently converted, in a
separate stage, into cured artefacts by a moulding or
extrusion process.
U.S. Patent Specification No. 3746489 discloses a method
of manufacturing glass fibre-reinforced mouldings by mixing
the fibres and a liquid thermosetting resin material to form
a viscous dough-like mixture which is fed continuously for
direct transfer to an injection device having a nozzle through
which the mixture is injected into the cavity of a mould for
: reaction of the mixture to form cured mouldings. The objects
of this prior method are to facllitate handling of the glass
fibres, to ensure adequate dispersion of the fibres in the
resin material, and to maintain fibre leng-th so that no
significant loss of properties occurs. To meet these objects,
a special method of and apparatus for ? mixing the fibres with
the resin material are proposed. The dough-like material
fed directly from the mixing apparatus to the injection
device is, essentially, a homogeneous intimate mixture
of the fibres in the resin material, and, as is well
known in the art, the compounding action of the injection ~
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device must be minimized to pre~ent fibre degradation. We
have discovered that injection moulding machines and extruders
can be used to effect final compounding of rough blends of
fillers in thermosetting resin materials and to produce cured
arte~facts directly from such materials without previously
forming a homogeneous intimate dispersion of the filler in
the resin and withou~ using specially designed mixing apparatus.
In a homogenous dispersion, the filler (or
reinforcing material) particles are intimately mixed with
and impregnated or coated with the resin: in a non-homogenous
blend of the type used in our process, the filler is not
coated or impregnated to any great extent by the resin, but
becomes intimately compounded therewith only in the injection
or extruding machine. .
According to the present invention, we provide a
method of injection moulding artefacts from amino-formaldehyde
thermosetting material which comprises~
~ a) providing a dry thermosetting amino-formaldehyde material
which is partly condensed but essentially solid at ambient
temperatures,
(b) introducing said dry material with a filler separately :
or in a non-homogeneous blend directly into the barrel of an
injection moulding machine, said machine having a heated barrel ~.
and a rotary screw which is axially movable in said barrelr ::
(c) rotating said screw simultaneously to feed the material
and filler along the barrel, further condense the material, : -
plasticize said material and impregnate the filler with the
plasticized material to provide a homogeneous blend and effect ;~
transfer of homogeneous blend ahead of the screw by screw-back ~ -
of the screw,
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(d) injectin~ homogeneous blend from ahead of the screw
into a ~ould and
(e) curin~ the artefact in the mould.
The thermosetting material wi31 comprise a material
which is capable of condensing to form a cured matrix (hereafter
referred to as a thermosetting substance) in which may be
dispersed any of the usual additives such as catalyst,
lubricant, stabiliser, or plasticizer, and may be in granular
or powder form. The thermosetting substance preferably is
an essentially solid product of reaction between formaldehyde
and a precursor selected from ureas, and amino-s-triazines,
for example dimethylol urea, dimethylol melamine, or a
melamine-formaldehyde resin; a derivative thereof such as an
alkylated, hexamethylol melamine; or a mixtur~ or co-condensate
of any of these substances with each other or with another
thermosetting substance, such as a solid melamine unsaturated
polyester co-condensate. ~he thermosetting substance
preferably is a urea- or melamine-formaldehyde resin, optionally
mixed or co-condensed with other thermosetting material such
as an alkyd, diallyl phthalate or epoxy resin.
The thermosetting substance preferably is a thermo-
setting resin which is partly condensed but essentially solid
at ambient temperatures in the absence of solubilizing
quantities of water or other solvent. If a liquid plasticizer,
æuch as water or monocresylglyceryl ether, or other liquid `~
component is use~l, it ~hould be present in such an amount ~-~
that the thermosetting material is not liquid, nor ~preferably)
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~isibly wet. Preferably, not more than about 10% by weight
(of the weight of the thermosetting substance) will be
water or other solvent. Any volatile li~uid used initially
in the non-homogeneous blend, is preferably vented from
the barrel during compounding. Since the resins used; or
produced in the barrel, are of the condensation type, water
or other volatile substance may ble evolved during any con-
densation which may occur under the action of heat, as the
filler and thermosetting material are progressed through
the barrel. Thus the filler preferably is capable of
absorbing the volatile material, or the ~arrel may be vented.
The more fully but not completely condensed material
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which issues from the downstream end of the barrel is moulded
immediately by direct injection into a mould (or by the so-
called injection-compression technique) and is thereby cured.
The non-homog$neous blend may be provided by one of several
alternative methods, e.g.:
~1) by roughly mixing the filler with the thermosetting
material in a mixer or blender and transferring
the rough mixture to the hopper of the injection
machine or extruder; or
(2) by introducing the filler and thermosetting material,
or the filler and the thermosetting substance and
additives, to the hopper and roughly mixing them
together in the hopper.
The separate feeding of the filler the thermosetting resin
may be achieved by providing the filler in one hopper, and
the thermosetting material in another hopper and feeding these
materials separately to the interior of the barrel so that
the non-hq~qgeneous blend is formed at the upstream end of
the barrel.
The thermosetting material may itself be partially filled -
prior to formation of the non- homogenequ$ blend with the filler
;~ referred to above.
The injection moulding machine preferably has a single
screw. It may be necessary to use a machine having a screw
housing (barrel) suitably grooved internally, depending on the
particle size of the filler or on the nature of the thermo-
setting material, particularly for thermosetting materials
in finely powdered form, to obtain the desired feed characteris-
tics.
Suitable fillers include powdered cellulose, woodflour, talc,
CaCO3, powdered glass, and the like, and the cured particulate `
aminoplast materials, described in our Belgian Patent
:
Specifications Number 796232 and 799052.
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The thermosetting materials ~ay also be filled or reinforced,
by means of the invention, with fibrous materials, such
as cellulose, glass fibres, asbestos fibres, or carbon
fibres, and may include any conventional additives or
processing aids such as plasticiæer, mould lubricant,
curing agent or pigment, Pigment may be incorporated,
in particular, by roughly blending it with the thermosetting
material at the same time as the particulate filler
is incorporate~.
10 ~ The following examples illustrate preferred embodiments
-of the invention.
Examples 1 and 2.
A BIPEL 155/50 injection moulding machine (BIPEL is
a Registered Trade llar~) was used, with t~vo modifications:-
(a) The standard barrel (screw housing) was replacedby one having longitudinal grooving, circumferentially
spaced around the interior wall of the barrel and
extending through substantially the whole length
of the barrel; and
(b) The feed hopper was provided ~vith an agitator to
eflect continuous agitation of the contents of the
hopper. ~ - -
~or both of the following formulations (Table 1), all
the ingredients were charged to a Baker-Perkins Z - blade
mixer, before blending commenced, and mixing was effected,
- from 10 to 30 minutes to produce a non-homogeneous blend
of the synthetic plastics material (BL35 - a spray-dried
melamine formaldehyde resin produced by our Chemicals
`Division), the filler, and the other ingredients. The - -
'rough' blend thus produced was fed to the hopper of
the machine, and the machine was operated to agitate
the contents o~ the hopper, feed them to the barrel, compound
the non-homogeneous blend in the barrel, and-to produce
test specimen rnouldings.
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The machine operating conditions and comments on the
results are presented in Table 2.
TABLE 1
Example Ingredients Parts by Weight
1. BL ~5 1956
MCGE(1) 148.5 Thermo-
~examine(2)14.9 settin~
Brooksite/~15 55.6 ~laterial
Lubricant 30.0
Woodflour10Q0 (Filler)
2. BL 352220 Thermo~
&lycerolsetting
monostearate10.8 ~laterial
Lubricant 9.0
Blue GLSR(3)22,0
Blue RS2(4) 9.0 Pigment
Black D.C.70(5) 1.5 -
White R~142(6) 1.2
Powdered
Cellulose 1000 (Filler)
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NOTES
(l) ~lonocresylglyceryl ether.
~ (2) Hexamethylene Tetramine ;- -
; ~ (3) Ciba Geigy (U.K.) Ltd.
(4) Reckitts Colours Ltd
(5) Blythe Colours Ltd.
, (6) TiO2-Laporte Industries Ltd
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In the following examples, thermosetting materials were
made from the thermosetting substances and additives as
dèfined and formed into non-homogenous blends with the
fillers, as defined, in a manner similar to that described
in Examples 1 and 2. All parts are weight. The non-
homogeneous blend was fed to the stirred hopper of a
BIPEL 70/31 screw injection moulding machine, and test
mouldings were made, the operating conditions of the
injection moulding machine being given in Table 3, and the
properties of the completed mouldings in Table 4.
Example 3
BL 352220 parts Thermosetting
Lubricant20 parts material
Catalyst3.2 parts
Powdered Cellulose 900 parts Filler
BaS04 100 parts
Example 4
Thermosetting material
; as in Ex.. 3 2543.2 parts
Powdered cellulose 700 parts
1/8" glass fibres 300 parts Filler :
BaS04 100 parts
:~ Example 5 ~ ~
Urea-formaldehyde ~ :
resin1400 parts Thermo- :
Lubricant10 parts setting
Plast:icizer40 parts ~laterial
catalyst 1.4 parts
-- Powdered cellulose 4.76 parts Filler
BaS04 133 parts
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The urea-formaldehyde resin was produced by reacting
dimethylol urea and urea in a ~eight ratio of 10:1.
Example 6
Melamine-urea-formaldehyde
resin 1600 parts Thermo-
Stabilizer 67 parts setting
Lubricant 27 parts l!aterial
: Woodflour (filler) 1070 parts
. The melamine-urea-formaldehyde resin was.made by blending:
' '- '
Melamine-formaldehyde
resin 100 parts
Urea-formaldehyde resin 200 parts
~ormaldehyde 165 parts
plasticizer 40 parts
- 15 Example 7
Solid alkyd as incorporated .
:- in BEETLE 4128 polyester
resin* 1000 parts . .:~. - BL 35 - 1000 parts Thermo-
Diallyl phthalate 100 -setting
. Tertiary butyl peroxide 50 ~ Material - ~ . -
` - .Silar.e coupling agent 13 . . :~
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- ~ . Lubricant - ~ 70
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~ Powdered cellulose .1200 :. :
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~- :25 "Millicarb" CaC031000 Filler ` . ....
China Clay 780
*BEETLE is a Registered Trade ~lark. The alkyd and melamine - .
formaldehyde re~in crosslink to produce a mixed resin
-system in the cured articles. .
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Example 8
BL 351400 parts
Phenolic resin 700 parts Thermo-
Lubricant20 parts setting
Catalyst2 parts material
WoodIlour1000 parts Filler
BaSO4150 parts .-
.
TABLE 3
EXA~LE 3 4 5 6 7 8
lO Barrel Temp ~ 95 95 90 9 50 100
Mould Te~p C 165 165 150 150 165 165
Injection
Pressure(p.s.i) 1750 1750 1750 1750 1750 1750 : ;
Hold-on
Pressure (p.s.i) 700 ~700 700 700 700 700 ~ .
lnjection
: Times (secs) 10 10 10 10 10 10
Total cycle ~ .
time (secs) 40 40 20 20 40 40 ~ -
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TA~LE 4
Example
Property 3 4 5 6 7 8
~le~ural Strength
`(~'/m ) 77 66 87 95 48 84 59
Flexural Modulus
(G~/m ) 4.8 6.0 4,.8 5.5 4.5 5.4
Engergy to
- Break (KJ/m2) 618 363 788 820 256 654
tO De~lection at
.break (mm) 1.6 1.1 1.8 1.7 1.1 1.6
- Boiling Water
. - . absorption
g/g) ~2 23 25 50 10 17
Insulation
resistance .
(101ohms) 1.3 3.3 27 1.6 43 40~: .
.
In each of Examples 3 to 8, the mouldings produced were
in the form o~ pin-gated bars. These showed acceptable
:: 20 surface finish, mechanical strength and physical properties.
The operating conditions of the injection moulding machine
- - (or of an extruder) can be selected readily by those skilled
.in the-art. ~or machines of the general type used--as
- described above, preferred conditions are~
: - : Barrel temperature 80 to 110C ` - . ~ `
ould:temperature 140 to 170C
' ~ Injection pressure up to 20000 p.s.i. ~ . .`
: Total cycle time 15 to 130 seconds. ~ .
`: : These may be ~aried at ~Yill depending on the materials
. being used and the type of mouldings to be produced.
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~(369Z67
Heretofore, it has been necessary for trade moulders to
order from manufacturers moulding compositions containing
a suitable amount and type of Eiller for the particular
application which the moulder has în hand accordingly
it has often been necessary for the moulding composition
: manufacturers to hold stocks of different moulding comp-
ositions, based on the same resinous material but incorp~
orating differ~nt amounts and/or types of homogeneously
dispersed filler, hence space which could be put to
better use is often required for storage of such stocks.
by virture of the present invention, it is no~ possible
for the moulding composition manufacturer to produce
only unfilled or partially filled synthetic thermosetting
materials for supply to trade moulders who themselves,
without much effort or capital expenditure, can roughly
mix the thermosetting material with the desired amount
and type of filler to produce the non-Xomogeneousblend
referred to above.
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