Apparatus for injecting additives into a flow of a highly viscous liquid

The apparatus for injecting one or more additives (4) into a flow (5) of a highly viscous liquid into which the additives are to be admixed comprises a supply member (3) for each additive. This supply member is releasably connected to a tube section (2) conducting the flow. Each of the supply members has a supply channel (30) for the additive which stands transversely to the direction of flow. The additives temporarily form separate phases which coexist with the phase of the highly viscous liquid after having been fed in. A wall section (1) which is oriented in the direction of flow and can be flowed about on both sides by the highly viscous liquid is associated in each case with at least some of the injection members. Its inner side (10), that lying nearer the center of the tube, spans a surface on which the exit opening (35) of the supply member at least approximately lies. The wall section is provided downstream from the discharge opening as a spreading means (11) for the additive supplied.

BACKGROUND OF THE INVENTION 
The invention relates to an apparatus for injecting additives into a 
product flow formed by a highly viscous liquid. The invention also relates 
to a plant with an apparatus of this kind as well as to a method or 
process which can be performed using the plant. 
The highly viscous liquid envisaged is in particular a polymer melt; the 
additives are low viscosity liquids, in particular lubricants (namely 
stearates, alcohols, paraffin oils, softeners) which are to be worked into 
the polymer melts. The difference in viscosities between the melts and the 
additives is as a rule very large; the viscosities can differ by a factor 
on the order of magnitude of two or more powers of ten. 
When mixing lubricants into a polymer melt, the former must eventually 
enter homogeneously distributed into solution. As a rule a proportion of 
about 0.1 to 6% of dissolved lubricants is provided. A lubricant acts as a 
partition agent, for example during the injection molding of polymers, 
which develops its action when the products are being demolded, i.e. 
removed from the injection tool or mold. The admixing is preferably 
performed by means of static mixers. A plant is known from JP-A 07 100 825 
(see PATENT

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The components of the section of the apparatus in accordance with the 
invention shown in FIG. 1 are as follows: A wall section 1 for the 
preliminary distribution of a supplied additive in a flow of a highly 
viscous liquid; a tube section 2 conducting the flow; and a connection 
piece 12 by means of which the wall section 1 is fastened to the tube 
section 2. A supply member 3 for the additive 4--see FIGS. 2 and 3--is 
missing in FIG. 1. The wall section 1 has a bore 13 for the mouth 31 of 
the supply member 3. An aperture 23 is arranged in the tube section 2 for 
the injection member 3 into which the member 3 can be releasably inserted. 
FIG. 2 shows the supply of the additive 4, with the flow of the highly 
viscous liquid not being shown. The supply channel 30 of the supply member 
3 stands transversely to the direction of flow. The wall section 1 is 
oriented in the direction of flow and the highly viscous liquid flows 
about both sides of the wall section. The inner side 10 of the wall 
section 1 spans a surface on which the exit opening 35 of the supply 
channel 30 lies. Under the hydrodynamic influence of the flow the additive 
spreads out downstream on the wall section 1 and in particular along the 
tail edge 11 and is subsequently embedded, for example as a trail (or in 
the form of droplets), into the liquid flow, in which it finally passes 
into solution through diffusion and under the action of non-illustrated 
static mixers. 
The supply member 3 can, as is shown in FIG. 3, be screwed into the tube 
section 2. Further, not yet named components are: a sealing ring 33 and a 
needle 32 by means of which the injection of the additive 4 can be 
regulated (regulatory movement indicated as a double arrow 32'). The flow 
of the highly viscous liquid 5 is indicated by long arrows, the flow of 
the additive 4 by short arrows. 
FIG. 4a shows a section of an apparatus in accordance with the invention in 
which a wall section 1 is fastened at its sides 12' to the tube wall 2. 
The part of the wall section 1 lying downstream is made in the shape of a 
trapezoid so that the tail edge 11 does not lead the additive up to the 
tube wall 2 and the trail 40 flowing away remains restricted to an inner 
region of the liquid flow. 
The wall section 1 can be straight, as shown in FIGS. 1 to 4a, or curved. A 
ring-shaped wall section 1' is illustrated in FIG. 4b with which three 
injection members--indicated in chain dotted lines 3'--are associated. The 
ring 1' is fastened to the non-illustrated tube section 2 by three 
connecting pieces 12. 
The longitudinal section of FIG. 5 shows three ring-shaped wall sections 
1.sup.1, 1.sup.2, 1.sup.3 which are arranged concentrically, with a wall 
section 1.sup.1 or 1.sup.2 that lies closer to the center of the tube 
lying upstream ahead of the adjacent wall section 1.sup.2 or 1.sup.3 
respectively that lies further outwardly. The wall sections 1.sup.1, 
1.sup.2 and 1.sup.3 can also be arranged at the same level. A static mixer 
can also be arranged in the open inner space of the wall section 1.sup.3, 
for example. 
FIG. 6 shows a cross-section through the tube section 2 with a plan view of 
four wall sections 1 with four associated supply members 3. In this 
exemplary embodiment the wall sections 1 are built up of plates in such a 
manner that parts of these plates produce the firm connections to the tube 
section 2. The two wall sections 1 fastened to the tube wall 2 are 
advantageously shaped as in the example shown in FIG. 4a. 
The wall sections 1 of the apparatus in accordance with the invention have 
a further advantageous effect. They support the head 31 of the supply 
members 3 so that the latter need not be constructed very massively in 
order to be able to counteract a deformation through the pressure forces 
arising in the flowing liquid. 
FIG. 7 shows a plant with an apparatus 2' in accordance with the invention 
which is arranged in a bypass line 7. A pump 70 forwards a small portion 
of the highly viscous liquid to be treated out of a main line 6 to the 
apparatus 2'. Subsequently a line section with a static mixer 71 (or 
static mixers 71a, 71b) produces a connection to the main line 6, with the 
bypass line 7 discharging into the main line 6 ahead of a static mixer 61. 
The additives are fed in from reservoirs 44 through lines 43 by means of 
metering devices 34 and into the apparatus 2' through the supply members 
3.