U.S. patent application number 10/960671 was filed with the patent office on 2005-02-24 for plastic composites and process for their manufacture.
This patent application is currently assigned to ROEHM GBMH & CO. KG. Invention is credited to Benz, Volker, Rimpl, Manfred.
Application Number | 20050039850 10/960671 |
Document ID | / |
Family ID | 7634698 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050039850 |
Kind Code |
A1 |
Benz, Volker ; et
al. |
February 24, 2005 |
Plastic composites and process for their manufacture
Abstract
Flat composites of plastic are manufactured by thermal adhesive
bonding of at least two plastic parts which are heated at their
surfaces and which comprise a base material coated with a plastic
layer, wherein the Vicat softening point of the plastic of layer is
5 to 40.degree. C. lower than that of the base material, wherein
the base material has a thickness of 1 to 200 mm and the plastic
layer has a thickness of 5 to 400 .mu.m, and each of the parts is
heated on the surfaces coated with the plastic layer and then
welded under pressure.
Inventors: |
Benz, Volker; (Hoechst,
DE) ; Rimpl, Manfred; (Otzberg-Lengfeld, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ROEHM GBMH & CO. KG
Darmstadt
DE
|
Family ID: |
7634698 |
Appl. No.: |
10/960671 |
Filed: |
October 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10960671 |
Oct 8, 2004 |
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09793419 |
Feb 27, 2001 |
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6828009 |
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Current U.S.
Class: |
156/309.9 |
Current CPC
Class: |
B29C 66/71 20130101;
Y10T 428/23 20150115; B29C 66/71 20130101; C08J 5/128 20130101;
Y10T 156/1095 20150115; B29C 66/71 20130101; B29C 66/71 20130101;
B32B 37/04 20130101; B29C 66/71 20130101; B29C 66/0242 20130101;
B29C 65/08 20130101; Y10T 428/239 20150115; B29C 65/10 20130101;
Y10T 428/24479 20150115; B29C 66/7392 20130101; B29C 66/71
20130101; B29C 66/71 20130101; B29C 66/73115 20130101; B29K 2055/02
20130101; B29K 2033/12 20130101; B29K 2081/06 20130101; B29K
2067/00 20130101; B29K 2061/00 20130101; B29K 2001/08 20130101;
B29K 2027/06 20130101; B29K 2071/00 20130101; B29K 2025/06
20130101; B29C 65/1412 20130101; B29K 2069/00 20130101; Y10T
428/2495 20150115; B29C 65/02 20130101; B29C 66/71 20130101; B29C
66/71 20130101; B29C 66/71 20130101; B29C 66/71 20130101; B29C
66/723 20130101; Y10T 428/24868 20150115 |
Class at
Publication: |
156/309.9 |
International
Class: |
B32B 031/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2000 |
DE |
10012421.6 |
Claims
1. A process for manufacture of flat composites of plastic,
comprising: thermal adhesive bonding of at least two plastic parts
which each independently comprise a base material coated with a
plastic layer; wherein each of said plastic parts is heated on
their surfaces coated with said plastic layer, thereby providing
heated parts; wherein said heated parts are welded under pressure;
wherein a Vicat softening point of said plastic layer is 5 to
40.degree. C. lower than that of said base material; and wherein
said base material has a thickness of 1 to 200 mm and said plastic
layer has a thickness of 5 to 400 .mu.m.
2. The process according to claim 1, wherein said surfaces coated
with said plastic layer are heated to a temperature of 5 to
30.degree. C. above the Vicat softening point of said plastic
layer.
3. The process according to claim 1, wherein said heated parts are
joined by rolling.
4. The process according to claim 3, wherein said rolling is
performed between a pair of rolls, in which at least one roll, with
which the pressing force is exerted, is mounted movably; wherein
said rolling occurs at a feed speed of between 5 and 200 mm/s and
with a pressing force of between 10 and 500 N.
5. The process according to claim 1, wherein said plastic layer and
said base material of said plastic parts are manufactured by
coextrusion; and wherein said plastic parts are joined to one
another.
6. The process according to claim 1, wherein said base material and
said plastic layer comprise independently a polymethyl methacrylate
plastic or a polycarbonate plastic.
7. The process according to claim 1, wherein said plastic layer is
applied to the base material in the form of a lacquer or by
coextrusion with the base material.
8-27. (Cancelled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a process for manufacture of flat
composites of plastic and to the resulting plastic composites.
[0003] 2. Discussion of the Background
[0004] European Patent Application EP 584593 describes plastic
composites in which at least one part of the composite comprises
acrylic glass and at least one acrylic-glass joint is formed by
welding. Joining by thermal welding is achieved in the presence of
an intermediate layer having a thickness of 0.01 to several mm and
comprising polymers formed substantially from methyl methacrylate.
The shaped parts of acrylic glass can be joined in the presence of
the thin intermediate layers of polymethyl methacrylate with shaped
parts made of plastics, such as PVC, cellulose ethers, polystyrene,
ABS plastics and polycarbonate, especially polycarbonate of
bisphenol A.
[0005] If the prescribed temperature program is not exactly
followed, inclusions of air or monomeric decomposition products
occasionally occur during this process in the composite.
[0006] European Patent Application EP 710549 describes a process
for the manufacture of flat composites from polymethyl methacrylate
plastic by thermal adhesive bonding of at least two parts of
polymethyl methacrylate plastic heated at their surfaces. The parts
of polymethyl methacrylate plastic, which are preheated on the
adhesive side to surface temperatures of 130 to 200.degree. C.
while retaining their original shape during the preheating phase,
are pressed together between a pair of rolls with a feed velocity
of between 5 and 200 mm/s and with a pressing force of between 10
and 500 N. At least one roll, with which the pressing force is
applied, is mounted movably. European Patent Application EP 710548
describes the same process for thermoplastic compositions in
general.
[0007] Although these processes have been proven in principle,
problems occur occasionally when the prescribed temperature program
is not exactly followed. Optical distortions, warping and adhesion
problems can then occur. In particular, the handling of parts with
small thickness has proved to be very difficult. The handling of
parts of very different thicknesses with correspondingly different
heat-absorption capacities also frequently causes problems in
practice.
SUMMARY OF THE INVENTION
[0008] It was an object of the present invention to develop a
process for the manufacture of flat composites of plastic by
thermal adhesive bonding that results in composites that do not
have the above mentioned problems and wherein the process and the
properties of the resulting flat composites are less dependent on
temperature fluctuations. In particular, it was an object to
develop a process for the manufacture of flat composites of plastic
by thermal adhesive bonding wherein the thermal joining of thin
parts and parts of different thicknesses, asymmetric joining, with
very different heat-absorption capacity is possible. In addition,
it was an object to obtain plastic composites having unimpaired
strength.
[0009] These and other objects have been achieved according to the
present invention, the first embodiment of which includes a process
for manufacture of flat composites of plastic, comprising:
[0010] thermal adhesive bonding of at least two plastic parts which
each independently comprise a base material coated with a plastic
layer;
[0011] wherein each of said plastic parts is heated on their
surfaces coated with said plastic layer, thereby providing heated
parts;
[0012] wherein said heated parts are welded under pressure;
[0013] wherein a Vicat softening point of said plastic layer is 5
to 40.degree. C. lower than that of said base material; and
[0014] wherein said base material has a thickness of 1 to 200 mm
and said plastic layer has a thickness of 5 to 400 .mu.m.
[0015] In another embodiment the present invention includes a
plastic composite obtained according to the above process.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention provides for a process for the
manufacture of flat composites of plastic by thermal adhesive
bonding of at least two plastic parts which are heated at their
surfaces and which comprise a base material (B) coated with a layer
(S), wherein the Vicat softening point (VST) of the plastic of
layer (S) is 5 to 40.degree. C. lower than that of base material
(B), base material (B) has a thickness of 1 to 200 mm and layer (S)
has a thickness of 5 to 400 .mu.m, and each of the parts is heated
on the surfaces coated with layer (S) and then welded under
pressure.
[0017] Plastic parts are used for the process according to the
present invention, especially plastic plates which comprise a base
material (B) coated with a layer (S).
[0018] Base material (B) has a thickness in the range of standard
plate thicknesses of 1 to 100 mm, preferably 1 to 50 mm, more
preferably 2 to 20 mm and most preferably 2 to 10 mm. Extruded base
materials (B) are preferred.
[0019] The area of base material (B) can range, for example, from
0.01 to 10 m.sup.2 with plate widths of between 0.1 and 2 m and
plate lengths of between 0.1 and 5 m.
[0020] The area of base material (B) includes all values and
subvalues therebetween, especially including 0.05, 0.1, 0.5, 1,
1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 and
9.5 m.sup.2. The plate width includes all values and subvalues
therebetween, especially including 0.5, 1 and 1.5 m. The length of
the plate includes all values and subvalues therebetween,
especially including 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 and 4.5 m.
[0021] Layer (S) can be applied in the form of a lacquer or, for
example, by doctoring or, in a preferred embodiment, can be applied
by coextrusion with the base material in the case of
thermoplastically processable plastics. Layer (S) has a thickness
of 5 to 400 .mu.m, preferably 10 to 200 .mu.m, especially
preferably 20 to 80 .mu.m.
[0022] The thickness of layers (S) includes all values and
subvalues therebetween, especially including 10, 50, 100, 150, 200,
250, 300 and 350 .mu.m.
[0023] Base material (B) and layer (S) comprise at least one
thermoelastic or thermoplastic plastic. Preferably they are
thermoplastically processable, more preferably they are compatible
with one another and adhere well to one another.
[0024] Examples of suitable thermoplastic plastics or plastic types
are polymethyl methacrylates, polyvinyl chloride (PVC), cellulose
esters, polystryrene, ABS plastics, polycarbonates, polyesters,
polyethers, polyketones, polysulfones or copolymers thereof.
Preferred are polymethyl methacrylate and polycarbonate plastics,
especially bisphenol A polycarbonates.
[0025] Base material (B) and layer (S) preferably comprise the same
plastic type. In this case base material (B) and layer (S) differ
in their monomer composition, insofar as the Vicat softening point
VST (according to ISO 306 Part B 50) of the plastic of layer (S) is
5 to 40, preferably 10 to 30.degree. C. lower than that of base
material (B).
[0026] Thus, base material (B) can comprise, for example, a
polycarbonate with high Vicat softening point VST, and layer (S)
can comprise a polycarbonate with appropriately lower VST.
[0027] Methyl methacrylate accounts for 50 to 100 wt % of the
structure of polymethyl methacrylates. The most common comonomers
are alkyl esters of acrylic acid with 1 to 4 carbon atoms in the
alkyl group, as well as acrylonitrile and/or methacrylonitrile,
styrene or maleic anhydride. Thermoplastically and
thermoelastically deformable acrylic plastics are preferred. Their
coefficient of viscosity according to DIN 53727 and DIN 51562 Part
1 usually ranges from 20 to 1500 ml/g. The coefficient of viscosity
includes all values and subvalues therebetween, especially
including 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000,
1100, 1200, 1300 and 1400 ml/g.
[0028] Polymethyl methacrylates with very high molecular weights
such as about 10.sup.6 g/mol and higher exhibit thermoelastic
behavior as cast acrylic glasses. They are not accessible to
thermoplastic processing. Nevertheless, cast polymethyl
methacrylate is suitable, for example, as base material, on which
layer (S) comprising a thermoplastic polymethyl methacrylate, for
example, is applied in the form of a lacquer.
[0029] Thermoplastically processable polymethyl methacrylate
molding compounds for injection molding usually have molecular
weights (weight-average molecular weight, Mw) of 50,000 to 150,000
g/mol, for example about 120,000 g/mol, and such compounds for
extrusion have a molecular weight of above 150,000 to 250,000
g/mol, for example about 180,000 g/mol.
[0030] Base material (B) can be made, for example, from a
thermoplastic polymethyl methacrylate plastic comprising 95 to 100
wt % of methyl methacrylate and up to 5 wt % of methacrylate units
with a Vicat softening point VST ranging from 100 to 120.degree.
C., preferably 102 to 110.degree. C.
[0031] Layer (S) can be made, for example, from a thermoplastic
polymethyl methacrylate plastic comprising 80 to 95 wt % of methyl
methacrylate and correspondingly 20 to 5 wt % of methacrylate units
with a Vicat softening point VST ranging from 65 to 100.degree. C.,
preferably 70 to 90.degree. C.
[0032] Layer (S) can also be made from a polymethyl methacrylate
modified to acquire impact strength and obtained by mixing an
elastomer phase such as a bead or emulsion polymerization having a
two-shell or three-shell structure with a polymethyl methacrylate
matrix. Appropriate impact-strength-modifying agents for
polymethacrylate plastics have long been known. The manufacture and
structure are described, for example, in European Patent
Applications EP 0113924, EP 0522351, EP 0465049 and EP 0683028. The
Vicat softening points VST range from 60 to 80.degree. C. due to
mixing with the soft elastomer phase.
[0033] Layer (S) can also be made from a polyurethane plastic,
preferably in combination with a base layer (B) of
polycarbonate.
[0034] The thermal energy necessary for welding can be applied to
the parts to be joined by several methods, such as infrared
radiation. In addition, the thermal energy can be applied with
hot-air blowers or even with indirect physical methods such as
exposure to high-frequency or ultrasonic fields. In the process,
the surfaces coated with layer (S) are preferably heated to a
temperature of 5 to 30.degree. C. above the Vicat softening point
VST of the plastic of layer (S) and then directly pressed together
under pressure.
[0035] For this purpose the pressure is expediently applied by
rolling between a pair of rolls, in which at least one roll with
which the pressing force is exerted, is mounted movably. The parts
are pressed together with a feed speed of between 5 and 200 mm/s
and a pressing force of between 10 and 500 N. The speed feed
includes all values and subvalues therebetween, especially
including 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130,
140, 150, 160, 170, 180 and 190 mm/s. The pressing force includes
all values and subvalues therebetween, especially including 50,
100, 150, 200, 250, 300, 350, 400 and 450 N.
[0036] The pressing force exerted with the upper roll on the
polymethacrylate parts and on the composite being formed from
polymethacrylate parts can, for example, be generated pneumatically
or hydraulically with simple lever-type apparatuses. In general,
the pressing force is constant during the entire pressing process,
wherein pressing forces of between 10 and 500 N, preferably between
25 and 400 N are applied. Corresponding processes are described in
European Patent Applications EP 710548 and EP 710549.
[0037] The parts to be welded to one another can be the same or
different in regard to the plastics used for base material (B) and
layer (S) and in regard to the thicknesses of base material (B) and
layer (S). Preferably the parts to be welded to one another have
the same chemical structure, in which base material (B) and layer
(S) comprise at least the same plastic type or identical plastics.
Plastic types within the context of the present invention are for
example polymethyl methacrylates, polyvinyl chloride (PVC),
cellulose esters, polystryrene, ABS plastics, polycarbonates,
polyesters, polyethers, polyketones, polysulfones or copolymers
thereof. Further, its is advantageous if the thicknesses of layer
(S) do not differ by more than a factor of two or preferably are
equally thick.
[0038] The plastic composites obtained from two parts comprise base
material (B) externally and two layers (S) fused or welded to one
another internally. Correspondingly, it is possible, for example,
to provide a base material (B) with a layer (S) on both sides and
to weld it to two parts coated on one side to obtain a plastic
composite comprising three parts. By proceeding according to this
principle, it is also possible to produce plastic composites
comprising more than three parts. Preferred are plastic composites
comprising two parts.
[0039] The composites according to the present invention can be
manufactured with acrylic-glass parts in the form of plates or any
other desired shape. However, the site participating in the joint
is preferably a plane face.
[0040] Base material (B) and layers (S) can be transparent, colored
translucent, or pigmented. Particular color effects can be
incorporated in the composite. A coating of layers (S) that acts as
a joint only at rim locations of the base materials (B) to be
joined leads to a composite with an internal cavity, which can be,
for example, rectangular and which can be used to accommodate
information, such as sealed-in pictures or similar items.
[0041] The selection of layer (S) from compatible thermoplastic
plastics, wherein the Vicat softening point VST of the plastic of
layer (S) is 5 to 40.degree. C. lower than that of base material
(B), in combination with a smaller thickness of layer (S) of from 5
to 400 .mu.m, offers the advantage that, for preparation of the
bonding points, only a relatively small quantity of heat, which is
just sufficient to soften layer (S), needs to be applied. Since the
quantity of heat can be supplied independently of the thickness and
condition of the base material, the risk of underheating or
overheating is reduced. The tolerance range is broader. In
addition, the energy consumption is correspondingly smaller.
[0042] There are obtained optically good joint sites, especially in
the case of clear, transparent materials. Such clear joints are not
achieved with adhesive bonds. Since layer (S) and base material (B)
comprise plastics already joined firmly to one another before
heating, no disadvantages result in regard to the strength of the
obtained plastic composite. The strength of the resulting plastic
composite is just as high as in the known processes with optimal
temperature programs. The parts welded together adhere so strongly
that, in attempts to destroy the joint by force, it is often not
the seam but the composite material itself that breaks.
[0043] The welding of relatively thin parts, having thicknesses
ranging from 1 to 6 mm, for example, and of such thin parts with
thicker parts is possible with high reliability in regard to an
optically flawless result.
[0044] Numerous further embodiments, known from European Patent
Applications EP 710548 and EP 710549, are accessible in
particularly high optical quality via the process according to the
present invention. Due to the relatively high tolerances for
heating of layers (S), production with relatively low failure rate
is possible, especially in the case of thin parts having
thicknesses ranging from 1 to 6 mm and of the combination of thin
parts with thicker parts.
[0045] Composites can also be manufactured from plastic parts with
flat rims, such as cupola roofs, barrel vaults or shells, by
selectively heating the rims and joining them together by the
process according to the present invention.
[0046] In further embodiments of the invention, it is possible to
laminate flat or elongated objects between the adhesive sides of
the plates or films. The prerequisite for optically flawless
lamination of such objects, or in other words for avoiding air
inclusions or streaking, is that the thickness of the objects be at
most 50%, and preferably at most 25% of the thickness of the plates
or films. Examples of flat objects that can be laminated between
layers (S) of the plates or films are photographs, prints, colored
films, pigment papers or films of thermoplastic elastomers, the
last-mentioned of which can be used to obtain safety-glass
composites. The laminated objects are permitted to occupy at most
90%, preferably at most 80% and more preferably at most 70% of the
area of the adhesive sides. Examples of elongated objects that can
be laminated between plates or films are narrow plastic bands,
which may be colored wires, steel spirals, material ribbons, paper
strips or preferably threads, most preferably plastic threads with
high elasticity and high modulus, such as polyester or nylon
threads, the lamination of which leads to composites with
particularly good impact strength.
[0047] The plates or films can be provided with engraved or
embossed patterns which have depths of at least 0.2 mm, preferably
at least 1 mm, and which are disposed either on the outside or on
the adhesive side of the plates or films. If the engraved or
embossed patterns are disposed on the adhesive side,
three-dimensional inclusions of well-defined geometry can be
produced in the composite. Preferably such three-dimensional
inclusions are produced by adhesively bonding at least two plates,
in which each plate is provided on the adhesive side with engraved
or embossed patterns, which can be joined together in mirror-image
relationship. The condition for manufacture of such
three-dimensional inclusions is that the engraved or embossed
patterns remain dimensionally stable during heating of the surfaces
of the adhesive side.
[0048] The priority document of the present application, German
patent application 100 12 421.6, filed Mar. 15, 2000, is
incorporated herein by reference.
[0049] Obviously, numerous modifications and variations on the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *