Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ LD O~ INVB~TION
;? The present invention relates to a triple-wall
tubular element made of thermoplastic material utilizing
mainly recycled plastic materials. More particularly,
the invention pertains to the use of thermoplastic
~J recycled material for the making of tubular elements,
such as tubes and pipes, while retaining the physical
properties required for such products.
;-J BACRGROUND OF ~ INV~N~ION
The use of recycled plastic material for the
making of tubes and pipes is well known. Also well known
is the knowledge that with the use of recycled waste
material, there results an alteration of the mechanical
properties of the products either due to contamination of
the waste material or to a successive degradation of the
products being used.
There exists various methods for making triple-
wall tubular elements, such as described in U.S. patent
No. 4,731,002 issued March 15, 1988 to Spence et al.,
wherein the intermediate layer is composed of foam
plastic. However, it has been noted that this method as
well as other proc~sses contribute to decrease the
properties of the pipes thus made, mainly with respect to
impact resistance.
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Hence, it is necessary to provide an element of
the type described wherein recycled plastic material is
used without altering the properties of the product made.
OBJECq! AND 8TATBME:}~T OF ~ DIYEN~!IO~
It is therefore an object of the present
invention to provide a triple--wall tubular element which
overcomes the above-described problems and wherein a
major part of the finished product is composed of
recycled plastic materialO
The invention therefore relates to a triple-
wall tubular element which comprises:
- a thin outer layer composed of non-recycled
thermoplastic material, the outer layer having
a thickness in the neighborhood of 10% of the
wall tAickness of the tubular element;
- a thin inner layer composed of non-recycled
thermoplastic material, the inner layer having
a thickness in the neighborhood of 5% of the
wall thickness of the tubular element; and
- a thick intermediate layer sandwiched
between the inner and outer layers, the
intermediate layer being composed of recycled
thermoplastic material.
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q In one preferred form of the invention, khe
outer layer includes ultraviolet protection means as well
as impact modifier means.
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In another preferred form of the invention, the
thermoplastic material of the intermediate layer is
similar to or compatible with the thermoplastic material
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of the inner and outer layers of the tubular element.
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~ Other objects and further scope of
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applicability of the present invention will become
apparent from the detailed description given hereinafter.
It should be understood, however, that this detailed
description, while indicating preferred embodiments of
the invention, is given by way of illustration only,
since various changes and modifier within the spirit and
scope of the invention will become apparent to those
skilled in the art.
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B~IE~ DEæC~IPTION O~ T~E DRaWINGS
- Figure 1 is a perspective view of a tripl~-wall
tubular element made in accordance with the present
invention; and
Figure 2 is a cross-sectional view of the wall
of the tubular element taken along line 2-2 of figure 1.
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DE~CRIPTION OF PREFERRBD E~BODIMEN~
Referring to figures 1 and 2, the tubular
element or pipe 10 consists of a body formed of three
layers 12, 14 and 16.
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~l 5The outer layer 12 is composed of a non-
recycled thermoplastic material which includes protective
agents against ultraviolet rays and impact modifiers.
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The intermediate layer 14 is composed of
recycled thermoplastic material which has been obtained
10from plastic material pulverized in powder form to
provide homogeneity to the product.
The inner layer 16 is composed of non-recycled
thermoplastic material.
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It has been found that it is possible to make
15a pipe or tube of thermoplastic material containing at
least 80% of recycled plastic material without altering
the physical mechanical properties of the product. This
has been achieved by applying on both faces of the
recycled thermoplastic material an inner layer and an
20outer layer of non-recycled material.
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The outer layer must include a matrix with
ultraviolet protection, such as titanium dioxide or
carbon black, in order to protect this thin outer layer
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from sun exposure. The outer layer 12 should also
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contain impact modfiers of the acrylic type or of the
chlorinat~d polyethylene type in order to avoid the
breaking of this thin outer layer when subjected to
impact. It has been determined that the outer layer
should preferably constitute about 10% of the total
thickness of the tubular element. This thickness enables
an adequate protection to ultraviolet rays while
permitting also to maintain the needed rigidity for the
tube or pipe.
The intermediate layer 14 must be constituted
of thermoplastic material which has been prior pulverized
at 20 mesh so as to be in powder form thus enabling
adequate homogeneity of the mixture and ensuring
sufficient compactness during the extrusion process of
the tubular element. Preferably, this extrusion must be
accomplished with a thermoplastic material which is
chemically similar to or at least compatible with the
thermoplastic material of the inner and outer layers in
order to provide an intimate connection with these
layers. It has been found that polyvinyl chloride
obtained from vinyl sidings, from window frames, from PVC
bottles, from plastic credit cards, from blister packs
and from vertical blinds provide satisfactory results.
Also, it has been noted that wastes originating from
acrylonitrite butadiene styrene, styrene-base polymers,
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acrylic base polymers and certain polyolefins provide
satisfactory results.
A further importance of the present invention
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is that the inner layer, which must constitute a
thickness in the neighbourhood of 5% of the tokal
thickness of the tubular element, should be made of a
polymer, preferably identical to that of the outer layer.
The inner layer 16 enables to maintain intact the flowing
properties of the pipe or tubular element and, also, to
retain the impact resistance of the entire assembly.
In order to make this multi-layer tubular
~; element, it is necessary to utilize an apparatus having
two or three extruders. It is also necessary to use a
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temperature differential of at least 30F between the
internal temperature, the external temperature and the
temperature of the central part. This differential
enables the non-recycled thermoplastic material to join
adequately with the recycled thermoplastic material and
to make up for its defects.
Xa~PLE -;~
A resin of polyvinyl chloride having a K value
of 60-70 (in the present case 66 of Esso chemical) to
which was added 2 phr of impact modifier of the
chlorinated polyethylene type, such as CPE 3615 sold by
Dow Chemicals, was added to 1 phr of titanium oxide,
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Titanox RCR-40O A mixture of lubricant composed of
parafin wax, calcium stearate and polyethylene wax wa5
"i also used. This matrix served for ~orming the inner and
, outer layers. Waste from vinyl sidings, window frames
,j 5 and plastic credit cards were pulverized at 20 mesh and
mixed together. This mixture was extrudea3 by means of a
~' conventional extruder, Krauss Maf~ei KMD 90 twin screw.
The non-recycled material was extruded by means of a twin
screw extruder American Maplan DSK 52.
A conventional coextruder block equipped with
two flow control valves ~or the inner and outer layers
was used, to which was fixed an extruder head for the
tubular elements. This assembly was used to produce
pipes of 4" (100 mm) DR~35 and of 6" (150 mm) such as
described in the standard ASTM D-3034. Also produced
were pipes having a thickness DR 28 in accordance with
the standard NQ 3624-130. The melt temperature was
maintained at 400F for the non-recycled material and
between 365F and 370F for the recycled material.
The produced tubular element was cooled, cut
and belled such as is conventionally done with standard3
equipment. The results of crushing tests and rigidity
tests were comparable to the results obtained with
conventional pipes. The impact resistance at room
temperature has indicated an increased resistance
compared to a conventional extruded pipe. At 0C, the
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results were satisfactory with respect to standard
~L',: re~uirements, such as 95 joules for the 100 mm and 150
joules for the 150 mm. In these tests, a delamination oP
the layers was not observed.
Although the invention has been described above
with respect with one specific form, it will be evident
to a person skilled in the art that it may be modified
and refined in various ways. It is therefore wished to
have it understood that the present invention should not
be limited in scope, except by the terms of the ~ollowing
claims.
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