U.S. patent application number 11/579329 was filed with the patent office on 2007-09-27 for moulding compound for mouldings with high weather resistance.
This patent application is currently assigned to ROEHM GMBH. Invention is credited to Klaus Albrecht, Werner Hoess, Martin Mohrmann, Klaus Schultes, Michael Wicker.
Application Number | 20070222117 11/579329 |
Document ID | / |
Family ID | 34963017 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070222117 |
Kind Code |
A1 |
Hoess; Werner ; et
al. |
September 27, 2007 |
Moulding Compound for Mouldings with High Weather Resistance
Abstract
A moulding compound comprises a copolymer (I)a), produced by
polymerisation of 90-100% by weight methylmethacrylate, styrene and
malic acid anhydride, and optionally 0-10% by weight additional
monomers which can be copolymerised with methylmethacrylate, a
(co)polymer (II)b), produced by polymerisation of 80-100% by weight
methylmethacrylate and optionally 0-20% by weight additional
monomers which can be copolymerised with methylmethacrylate, and
has a solution viscosity in chloroform at 25.degree. C. (ISO 1628
Part 6) of 50 to 55 ml/g, as well as c) optional conventional
additives, auxiliary agents and/or fillers. The moulding compound
is characterised in that the copolymer (I) has a solution viscosity
in chloroform at 25.degree. C. (ISO 1628 Part) of 55 ml/g or less.
Also disclosed are mouldings produced by thermoplastic processing
of the moulding compound and their uses.
Inventors: |
Hoess; Werner; (Shanghai,
CN) ; Wicker; Michael; (Seeheim-Jugenheim, DE)
; Schultes; Klaus; (Wiesbaden, DE) ; Albrecht;
Klaus; (Mainz, DE) ; Mohrmann; Martin;
(Weiterstadt, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ROEHM GMBH
Kirschenallee
Darmstadt
DE
64293
|
Family ID: |
34963017 |
Appl. No.: |
11/579329 |
Filed: |
April 7, 2005 |
PCT Filed: |
April 7, 2005 |
PCT NO: |
PCT/EP05/03652 |
371 Date: |
November 1, 2006 |
Current U.S.
Class: |
264/328.1 ;
106/287.24; 524/523 |
Current CPC
Class: |
Y10T 428/24322 20150115;
C08L 33/04 20130101; C08L 33/12 20130101; C08L 2205/02 20130101;
C08L 33/04 20130101; Y10T 428/31909 20150401; Y10T 428/24273
20150115; C08L 2666/04 20130101; C08L 2666/04 20130101; Y10T
428/24694 20150115; C08L 33/12 20130101 |
Class at
Publication: |
264/328.1 ;
106/287.24; 524/523 |
International
Class: |
C08L 33/12 20060101
C08L033/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 5, 2004 |
DE |
10 2004 022 540.0 |
Claims
1. A molding composition, encompassing the following components a)
a copolymer (I), polymerized to an extent of from 90 to 100% by
weight from methyl methacrylate, styrene, and maleic anhydride,
and, optionally, from 0 to 10% by weight of other monomers
copolymerizable with methyl methacrylate, b) a (co)polymer (II),
polymerized from from 80 to 100% by weight of methyl methacrylate
and, if appropriate, from from 0 to 20% by weight of other monomers
copolymerizable with methyl methacrylate, whose solution viscosity
in chloroform at 25.degree. C. (ISO 1628-Part 6) is from 50 to 55
ml/g, and c) optionally conventional additives, auxiliaries, and/or
fillers characterized in that the solution viscosity of the
copolymer (I) in chloroform at 25.degree. C. (ISO 1628-Part 6) is
less than or equal to 55 ml/g.
2. The molding composition as claimed in claim 1, characterized in
that the molding composition or a test specimen produced from the
molding composition has the following properties simultaneously: a
Vicat softening temperature VST (ISO 306-B50) of at least
109.degree. C., a melt index MVR (ISO 1133, 230.degree. C./3.8 kg)
of at least from 2.5 to 5.0 cm.sup.3/10 min. Xenotest weathering
resistance (DIN EN ISO 4893, Part 2) after 10 000 hours
characterized via a yellowness index (DIN 6167) of less than or
equal to 2.0.
3. The molding composition as claimed in claim 1, characterized in
that the increase in the yellowness index (DIN 6167) of a test
specimen produced from the molding composition is not more than 1.5
units after Xenotest weathering (DIN EN ISO 4893, Part 2) for 10
000 hours.
4. The molding composition as claimed in claim 1, characterized in
that when the Taber 203 scratch hardness of a test specimen
produced from the molding composition is determined using an
applied force of 3.0 N the value obtained is not more than 3
.mu.m.
5. The molding composition as claimed in claim 1, characterized in
that the copolymer (I) and the (co)polymer (II) are present in a
ratio of from 95 to 5 to 5 to 95 parts by weight.
6. The molding composition as claimed in claim 1, characterized in
that the copolymer (I) has been polymerized from from 50 to 90% by
weight of methyl methacrylate, from 10 to 20% by weight of styrene,
and from 5 to 15% by weight of maleic anhydride.
7. The molding composition as claimed in claim 1, characterized in
that the copolymer (II) is a polymer composed of from 95 to 99.5%
by weight of methyl methacrylate and from 0.5 to 5% by weight of
methyl acrylate.
8. The molding composition as claimed in claim 1, characterized in
that the proportion of the conventional additives, auxiliaries,
and/or fillers is not more than 10% by weight.
9. The molding composition as claimed in claim 1, characterized in
that a lubricant is present as auxiliary.
10. The molding composition as claimed in claim 1, characterized in
that the mold-release agent stearyl alcohol is present as
auxiliary.
11. Molded parts, producedentirely or to some extent from a molding
composition as claimed in claim 1 via thermoplastic processing, in
particular injection molding or extrusion, or via coextrusion,
lamination, or lacquering.
12. Extruded parts as claimed in claim 11, characterized in that
the materials are solid sheets, corrugated sheets, panels having
cavities, selected from multiple-web sandwich panels, twin-web
sandwich panels, triple-web sandwich panels, or quadruple-web
sandwich panels, or sandwich panels with lattice geometry, or other
sandwich panels.
13. Molded parts as claimed in claim 11, characterized in that the
materials are parts of household devices, of communications
devices, of equipment for hobbies or for sports, or are bodywork
parts, or are parts of bodywork parts in automobile construction,
in shipbuilding, or in aircraft construction, lamp covers,
instrument covers, tachometer covers, panels, or decorative
strips.
14. Molded parts as claimed in claim 11, characterized in that it
has at least one coextruded, laminated, or lacquered layer composed
of the parts
15. The method of using the molding composition as claimed in claim
1 for production of molded parts or of parts thereof via
thermoplastic processing, selected from injection molding or
extrusion, or via coextrusion, lamination, or lacquering.
16. The method of using the molding composition as claimed in claim
1 for the coating of surfaces or for the impregnation of wood.
Description
[0001] The invention relates to a molding composition for molded
parts with high weathering resistance.
PRIOR ART
[0002] EP 0 113 105 A1 describes heat-resistant methacrylate
plastic mixtures composed of two copolymers. Copolymer I is
obtained via polymerization of methyl methacrylate, of an aromatic
vinyl component, and of maleic anhydride, and copolymer II is a
polymer composed of from 80 to 100% by weight of methyl
methacrylate and of from 0 to 20% by weight of other
copolymerizable ethylenic monomers.
[0003] In particular, the copolymer I can be composed of from 50 to
98% by weight of methyl methacrylate, from 1 to 25% by weight of
styrene, and from 1 to 25% by weight of maleic anhydride. The
preparation process is described as non-critical. By way of
example, a specific proposal converts the monomers mentioned via
partial polymerization to give a prepolymer in the presence of
2,2'-azobis(2,4-dimethylvaleronitrile) as initiator and of
tert-dodecyl mercaptan as molecular-weight regulator. The
prepolymer is then polymerized first for 30 minutes at 80.degree.
C. and then again for 2 hours at 130.degree. C. in the presence of
lauryl 2,2'-peroxide as initiator and tert-dodecyl mercaptan in a
polymerization cell to give a sheet. The polymer sheet is then
comminuted to give pellets. Nothing is said about the molecular
weight of the polymer, but a factor deserving attention is that the
preparation process necessarily has to lead to comparatively high
molecular weights, attended by solution viscosities in chloroform
of more than 60 ml/g at 25.degree. C. (ISO 1628-Part 6).
[0004] In EP 0 113 105 A1, various mixtures of the copolymer I with
a commercially available polymethyl methacrylate molding
composition as copolymer II are prepared and their properties are
studied. The product is plastics mixtures with high transparency,
with no detectable tendency toward yellowing in the case of
injection-molded parts, and with high weathering resistance after
exposure for 1100 hours.
OBJECT AND SOLUTION OF OBJECT
[0005] Starting from EP 0 113 105 A1, the intention was to provide
a molding composition whose weathering resistance has been further
improved and whose MVR flowability (230.degree. C./3.8 kg) in
particular in the region advantageous for injection molding is from
2.5 to 5.0 cm.sup.3/10 min. In particular, the intention is that
the surface of specimens subjected to long-term weathering exhibit
only very slight or no cracking. The intention was that, when
comparison is made with EP 0 113 105 A1, there is to be no or only
very slight impairment of the Vicat softening temperature VST (ISO
306-B50), and that this is to achieve a value of 109.degree. C.
[0006] The object is achieved via a molding composition,
encompassing the following components [0007] a) a copolymer (I),
polymerized to an extent of from 90 to 100% by weight from methyl
methacrylate, styrene, and maleic anhydride, and, if appropriate,
from 0 to 10% by weight of other monomers copolymerizable with
methyl methacrylate, characterized via a solution viscosity in
chloroform at 25.degree. C. (ISO 1628-Part 6) of less than or equal
to 55 ml/g [0008] b) a (co)polymer (II), polymerized from from 80
to 100% by weight of methyl methacrylate and, if appropriate, from
from 0 to 20% by weight of other monomers copolymerizable with
methyl methacrylate whose solution viscosity in chloroform at
25.degree. C. (ISO 1628-Part 6) is from 50 to 55 ml/g, and [0009]
c) optionally conventional additives, auxiliaries, and/or fillers,
characterized in that the solution viscosity of the copolymer (I)
in chloroform at 25.degree. C. (ISO 1628-Part 6) is less than or
equal to 55 ml/g.
BRIEF DESCRIPTION OF THE INVENTION
[0010] The inventive molding composition encompasses or is composed
of the following components [0011] a. a copolymer (I), polymerized
to an extent of from 90 to 100% by weight from methyl methacrylate,
styrene, and maleic anhydride, and, if appropriate, from 0 to 10%
by weight of other monomers copolymerizable with methyl
methacrylate, characterized via a solution viscosity in chloroform
at 25.degree. C. (ISO 1628-Part 6) of less than or equal to 55 ml/g
[0012] b. a (co)polymer (II), polymerized from from 80 to 100% by
weight of methyl methacrylate and, if appropriate, from from 0 to
20% by weight of other monomers copolymerizable with methyl
methacrylate whose solution viscosity in chloroform at 25.degree.
C. (ISO 1628-Part 6) is from 50 to 55 ml/g, and [0013] c.
optionally conventional additives, auxiliaries, and/or fillers
[0014] The advantageous properties of the inventive molding
composition are substantially based on the mixture of copolymer (I)
with the (co)polymer (II). A decisive factor for the properties
improved in comparison with EP 0 113 105 A1 is the low molecular
weight of the copolymer (I), characterized via a solution viscosity
in chloroform at 25.degree. C. (ISO 1628-Part 6) of less than or
equal to 55 ml/g. It is self-evident that the molding composition
can in many instances comprise not only the copolymer (I) and the
(co)polymer (II) but also conventional additives, auxiliaries,
and/or fillers, examples being colorants, pigments, or organic
dyes, in the case of colored injection-molded parts.
[0015] A test specimen produced, for example via injection molding,
from the inventive molding composition can have the following
properties simultaneously. [0016] a Vicat softening temperature VST
(ISO 306-B50) of at least 108.degree.0 C., preferably of
110-115.degree. C., [0017] a melt index MVR (ISO 1133, 230.degree.
C./3.8 kg) of at least from 2.5 to 5.0, preferably from 2.8 to 4.9,
cm.sup.3/10 min. [0018] Xenotest weathering resistance (DIN EN ISO
4893, Part 2) after 10 000 hours characterized via a yellowness
index (DIN 6167) of less than or equal to 2.0.
[0019] The Xenotest to DIN EN ISO 4892, Part 2 (artificial
weathering or irradiation in devices--filtered xenon arc
irradiation) can be carried out by the person skilled in the art,
for example using the following parameters: Beta LM Xenotest
device; lower wavelength threshold lambda G=300 nm (Xenochrom 300
filter); black standard temperature=65 +/-3.degree. C.; water
spray/drying cycle: 18 min of water spray, 102 min of drying time;
relative humidity during drying=65%; constant conditions=continuous
irradiation of specimens; irradiation intensity=standard method A
(artificial weathering); test device: Xenosensitiv (lambda from 300
to 400 nm), controllable from 45 to 120 W/m.sup.2, normal
specification 60 W/m.sup.2.
[0020] The molding composition is further characterized in that the
increase in yellowness index (DIN 6167, D65/10.degree. illuminant,
3 mm) of a test specimen produced from the molding composition is
not more than 1.5 units, preferably not more than 1.0 unit, after
Xenotest weathering (DIN EN ISO 4893, Part 2) for 10 000 hours.
[0021] The molding composition is characterized in that a test
specimen produced from the molding composition has no cracking
visible to the naked eye after Xenotest weathering (DIN EN ISO
4893, Part 2) for 5000 hours, indeed even after 10 000 hours.
[0022] The molding composition is characterized in that when the
Taber 203 scratch hardness of a test specimen produced from the
molding composition is determined using an applied force of 3.0 N
the value obtained is not more than 3 .mu.m crack depth, in
particular not more than 2.8 .mu.m crack depth.
[0023] Copolymer (I)
[0024] The (co)polymer (II) is composed of from 80 to 100% by
weight, preferably from 90 to 100% by weight, in particular from 99
to 100% by weight, of methyl methacrylate, styrene, and maleic
anhydride. If appropriate, from 0 to 20% by weight, preferably from
0 to 10% by weight, in particular from 0 to 1% by weight, of other
comonomers capable of free-radical polymerization can also be
present, examples being .alpha.-methylstyrene or C1-C4-alkyl
(meth)acrylates, in particular methyl acrylate, ethyl acrylate, or
butyl acrylate, in particular n-butyl acrylate.
[0025] The copolymer (I) is particularly preferably composed only
of units capable of free-radical polymerization and composed of
methyl methacrylate, styrene, and maleic anhydride.
[0026] Examples of suitable quantitative proportions can be: [0027]
from 50 to 90% by weight, preferably from 70 to 80% by weight, of
methyl methacrylate, [0028] from 10 to 20% by weight, preferably
from 12 to 18% by weight, of styrene, and [0029] from 5 to 15% by
weight, preferably from 8 to 12% by weight, of maleic
anhydride.
[0030] The solution viscosity of the copolymer (I) in chloroform at
25.degree. C. (ISO 1628-Part 6) is less than or equal to 55 ml/g,
preferably less than or equal to 50 ml/g, in particular from 40 to
55 ml/g, particularly preferably from 43 to 50 ml/g.
[0031] This can correspond to a molar mass M.sub.w (weight-average)
of 95 000 g/mol (M.sub.w determination by means of gel permeation
chromatography based on polymethyl methacrylate as calibration
standard). By way of example, molecular weight M.sub.w can be
determined by gel permeation chromatography or by a
light-scattering method (see, for example, H. F. Mark et al.,
Encyclopedia of Polymer Science and Engineering, 2nd Edition, Vol.
10, pages 1 ff., J. Wiley, 1989).
[0032] Corresponding copolymers can be obtained in a manner known
per se via free-radical polymerization. EP-A 264 590 describes by
way of example a process for preparation of a molding composition
composed of a monomer mixture composed of methyl methacrylate, of a
vinylaromatic compound, and of maleic anhydride, and, if
appropriate, of a lower alkyl acrylate, where the polymerization is
carried out to 50% conversion in the presence or absence of a
non-polymerizable organic solvent, and where, starting at
conversion of at least 50%, the polymerization is continued in the
temperature range from 75 to 150.degree. C. in the presence of an
organic solvent as far as at least 80% conversion, and then the
low-molecular-weight volatile constituents are evaporated.
[0033] JP-A 60 147 417 describes a process for preparation of a
highly heat-resistant polymethacrylate molding composition in which
a monomer mixture composed of methyl methacrylate and of maleic
anhydride, and of at least one vinylaromatic compound is fed to a
polymerization reactor suitable for solution polymerization or bulk
polymerization at a temperature from 100 to 180.degree. C. and is
polymerized. DE-A 44 40 219 describes another preparation
process.
[0034] By way of example, the copolymer (I) can be prepared by
taking a monomer mixture composed of, for example, 6355 g of methyl
methacrylate, 1271 g of styrene, and 847 g of maleic anhydride, and
admixing 1.9 g of tert-butyl perneodecanoate and 0.85 g of
tert-butyl 3,5,5-trimethylperoxyhexanoate as polymerization
initiator and 19.6 g of 2-mercaptoethanol as molecular weight
regulator, and 4.3 g of palmitic acid. The resultant mixture can be
charged to a polymerization cell and, for example, devolatilized
for 10 minutes. The mixture can then be polymerized in a water
bath, for example for 6 hours at 60.degree. C., and then for 30
hours at 55.degree. C. water bath temperature. After about 30
hours, the polymerization mixture reaches its maximum temperature:
about 126.degree. C. Once the polymerization cell has been removed
from the water bath, the polymer corresponding to component a) is
further heat-conditioned in the polymerization cell for about 7
hours, for example at 117.degree. C., in an oven under air.
[0035] (Co)polymer (II)
[0036] The copolymer (II) is a (meth)acrylate (co)polymer whose
solution viscosity in chloroform at 25.degree. C. (ISO 1628-Part 6)
is from 50 to 55 ml/g, preferably from 52 to 54 ml/g.
[0037] This can correspond to a molar mass M.sub.w (weight-average)
in the range from 80 000 to 200 000 g/mol, preferably from 100 000
to 150 000 g/mol. By way of example, molecular weight M.sub.w can
be determined by gel permeation chromatography or by a
light-scattering method (see, for example, H. F. Mark et al.,
Encyclopedia of Polymer Science and Engineering, 2nd Edition, Vol.
10, pages 1 ff., J. Wiley, 1989).
[0038] The (co)polymer (II) is a homopolymer or copolymer composed
of at least 80% by weight of methyl methacrylate and, if
appropriate, up to 20% by weight of other monomers copolymerizable
with methyl methacrylate. The (co)polymer (II) is composed of from
80 to 100% by weight, preferably from 90 to 99.5% by weight, of
methyl methacrylate units polymerized by a free-radical route and,
if appropriate, of from 0 to 20% by weight, preferably from 0.5 to
10% by weight, of other comonomers capable of free-radical
polymerization, e.g. C1-C4-alkyl (meth)acrylates, in particular
methyl acrylate, ethyl acrylate, or butyl acrylate, preferably
n-butyl acrylate. The average molar mass M.sub.w of the copolymer
(II) is preferably in the range from 90 000 g/mol to 200 000 g/mol,
in particular from 100 000 g/mol to 150 000 g/mol.
[0039] By way of example, the (co)polymer II can have been
polymerized from from 95 to 99.5% by weight of methyl methacrylate
and from 0.5 to 5% by weight, preferably from 1 to 4% by weight, of
methyl acrylate.
[0040] The Vicat softening temperature VST (ISO 306-B50) of the
(co)polymer (II) can be at least 107.degree. C., preferably from
108 to 114.degree. C. The melt index MVR (ISO 1133, 230.degree.
C./3.8 kg) can, for example, be in the range greater than or equal
to 2.5 cm.sup.3/10 min.
[0041] Conventional Additives, Auxiliaries, and/or Fillers
[0042] The molding composition can also comprise, alongside the
polymer mixture composed of the copolymer (I) and of the
(co)polymer (II), in a manner known per se, conventional additives,
auxilaries, and/or fillers, examples being heat stabilizers, UV
stabilizers, UV absorbers, antioxidants, and/or colorants,
pigments, or organic dyes. It is preferable that the amount of
conventional additives, auxiliaries, and/or fillers present is not
more than 10% by weight, particularly preferably not more than 5%
by weight, in particular not more than 2% by weight. The molding
composition can, if appropriate, also comprise absolutely no
additives, auxiliaries, and/or fillers.
[0043] For the injection-molding process, lubricants or
mold-release agents are particularly important, and can reduce the
level of, or entirely prevent, possible adhesion of the polymer
mixture to the injection mold. Furthermore, many moldings in
particular, particularly injection-molded parts, are
non-transparent but have a color, therefore comprising colorants,
pigments, or organic dyes, as additives. Parts for outdoor uses
generally comprise UV stabilizers, UV absorbers, or antioxidants
for additional protection from weathering.
[0044] Lubricants can therefore be used as auxiliaries, examples
being those selected from the group of the saturated fatty acids
whose number of carbon atoms is less than C.sub.20, preferably from
C.sub.16 to C.sub.18, or from the saturated fatty alcohols whose
number of carbon atoms is less than C.sub.20, preferably from
C.sub.16 to C.sub.18. Quantitative proportions present are
preferably very small, at most 0.25% by weight, for example from
0.05 to 0.2% by weight, based on the polymer mixture.
[0045] Examples of suitable materials are stearic acid, palmitic
acid, industrial mixtures composed of stearic and palmitic acid.
Examples of other suitable materials are n-hexadecanol,
n-octadecanol, and industrial mixtures composed of n-hexadecanol
and n-octadecanol.
[0046] Stearyl alcohol is a particularly preferred lubricant or
mold-release agent.
[0047] Preparation of the Molding Composition
[0048] The molding composition or polymer mixture can be prepared
via dry blending of components a) and b), which may take the form
of powder, beads, or preferably pellets.
[0049] It is preferable that the copolymers (I) and the (co)polymer
(II) are present 5in a ratio of copolymers (I) to (co)polymer (II)
which is from 95 to 5 to 5 to 95, preferably from 20 to 80 to 80 to
20, in particular from 20 to 60 to 80 to 40, in each case based on
parts by weight.
[0050] The polymer mixture can also be processed via melting and
mixing of the individual components in the melt, or via melting of
dry premixes of the individual components, to give a ready-to-use
molding composition. This can take place by way of example in
single- or twin-screw extruders. The resultant extrudate can then
be pelletized. Conventional additives, auxiliaries, and/or fillers
c) can be directly admixed or can be added as required subsequently
by the further processor.
[0051] Uses of the Molding Composition/Moldings
[0052] The inventive molding composition can be used in a manner
known per se to produce molded parts, entirely or to some extent
via thermoplastic processing, in particular injection molding or
extrusion, or via coextrusion or lamination, or else via
lacquering. A feature of the inventive moldings, due to the
inventive molding composition present, is high weathering
resistance, very little tendency toward yellowing, and very little
tendency toward cracking. The surface is also highly
scratch-resistant.
[0053] The moldings are composed entirely or to some extent of the
inventive molding composition, which is preferably composed to an
extent of from 90 to 100% by weight of the copolymer (I) and of the
(co)polymer (II), and, if appropriate, to an extent of from 0 to
10% by weight of conventional additives, auxiliaries, and/or
fillers.
[0054] Examples of extruded moldings can be solid sheets,
corrugated sheets, panels having cavities, in particular
multiple-web sandwich panels, twin-web sandwich panels, triple-web
sandwich panels, or quadruple-web sandwich panels, or sandwich
panels with lattice geometry, or other sandwich panels.
[0055] Injection molded parts can by way of example be parts of
household devices, of communications devices, of equipment for
hobbies or for sports, or are bodywork parts, or are parts of
bodywork parts in automobile construction, in shipbuilding, or in
aircraft construction, examples being lamp covers, instrument
covers, tachometer covers, displays, panels, or decorative strips.
Parts of moldings, e.g. bodywork parts in automobile construction,
in shipbuilding, or in aircraft construction, can be parts with a
layer structure, where the inventive molding composition is used by
way of example as external clear-lacquer layer and/or as internal
layer provided with a colorant.
[0056] Typical examples of bodywork parts or parts of bodywork
parts of automobiles are lamp covers, instrument covers, tachometer
covers, panels, decorative strips, spoilers, roof modules, or
exterior-mirror housings.
[0057] The inventive molding composition can be particularly
advantageously used for the coating of surfaces or for the
impregnation of wood, because it has high weathering
resistance.
[0058] A possible method of application introduces the molding
composition into an organic solvent or a solvent mixture and then
processes it as a lacquer.
[0059] As an alternative, wood can be coated by the
injection-molding process, by injecting a melt of the inventive
molding composition over an article composed of wood, e.g. a
control knob or a panel, in an injection mold.
EXAMPLES
A) Preparation of a Copolymer (I)
[0060] The copolymer (I) is a copolymer composed of 75% by weight
of methyl methacrylate, 15% by weight of styrene, and 10% by weight
of maleic anhydride.
[0061] The procedure takes a monomer mixture composed of 6355 g of
methyl methacrylate, 1271 g of styrene, and 847 g of maleic
anhydride, and admixes this with 1.9 g of tert-butyl
perneodecanoate and 0.85 g of tert-butyl
3,5,5-trimethylperoxyhexanoate as polymerization initiator, and
19.6 g of 2-mercaptoethanol as molecular weight regulator, and with
4.3 g of palmitic acid.
[0062] The resultant mixture is charged to a polymerization cell
and devolatilized for 10 minutes. The mixture can then be
polymerized in a water bath, for example for 6 hours at 60.degree.
C., and then for 30 hours at 55.degree. C. water bath temperature.
After about 30 hours, the polymerization mixture reaches its
maximum temperature: 126.degree. C.
[0063] Once the polymerization cell has been removed from the water
bath, the polymer is further heat-conditioned in the polymerization
cell for 7 hours, at 117.degree. C., in an oven under air.
[0064] The resultant copolymer (I) is clear and almost colorless,
and its V.N. (solution viscosity number to ISO 1628-6, 25.degree.
C., chloroform) is 48.7 ml/g. The flowability of the copolymer was
determined as MVR=3.27 cm.sup.3/10 min to ISO 1133 at 230.degree.
C., using 3.8 kg.
B) (Co)polymer (II)
[0065] The (co)polymer (II) used comprised: a commercially
available copolymer composed of 99% by weight of methyl
methacrylate and 1% by weight of methyl acrylate whose solution
viscosity in chloroform at 25.degree. C. (ISO 1628-Part 6) was
about 53 ml/g.
C) Copolymer (III)
[0066] The material used for comparison comprised: [0067] A
commercially available copolymer (copolymer II) composed of 75% by
weight of methyl methacrylate, 15% by weight of styrene, and 10% by
weight of maleic anhydride whose solution viscosity to ISO 1628-6,
25.degree. C., chloroform, was 68 ml/g. Copolymer (III) therefore
differs from copolymer (I) only in the higher molecular weight. D)
Preparation of Molding Compositions A to D
[0068] Molding compositions A to D were prepared via mixing of the
copolymers I, II, and, respectively, III.
[0069] Once the individual components had been weighed out into a
10 l mixing drum, a homogeneous pellet mixture was prepared via
mixing for 5 minutes on a tumbling mixer. The mixture was placed in
the hopper of a single-screw extruder with 35 mm screw diameter and
extruded at 230.degree. C. melt temperature. Extrudates were drawn
from the extruder die head and were chopped by means of a
pelletizer to give pellets after cooling in a water bath and then
in an air-cooling section. This procedure was used to prepare
mixtures composed of copolymer I and copolymer II, and also
mixtures composed of copolymer II and copolymer III.
[0070] For testing of Theological properties, a sample amount of
the pellets was used to carry out the tests. From the pellets
obtained, sheets of dimensions 110.times.110.times.3 mm were also
injection-molded for determination of scratch hardness, as also
were test specimens with dimensions 65.times.40.times.3 for the
weathering tests and the optical measurements.
[0071] An injection-molding machine from Demag; Schwaig DEMAG D150
was used for this purpose. The injection-molding parameters set
were as follows: [0072] melt temperature 250.degree. C., mold
temperature 70.degree. C., injection pressure: from 120 to 160 bar,
hold pressure: from 80 to 75 bar).
[0073] The following table includes the constitutions of the
products, the tests carried out, and also the test results
obtained.
[0074] Table: Constitution, tests, and test results for various
polymer mixtures. Examples A and B are inventive, and examples C
and D are non-inventive TABLE-US-00001 Solution viscosity Example
number ISO 1628-6, C D 25.degree. C., chloroform [ml/g] A B (comp.)
(comp.) Copolymer (I) 48.7 25 50 -- -- (Co)polymer (II) 53 75 50 75
50 Copolymer (III) 68 -- -- 25 50 Xenotest (DIN EN ISO 4892, Part
2) Optical assessment of surface quality Cracking after 1000 h none
none none none Cracking after 5000 h none none little little
Cracking after 10 000 h none none much much Taber 203 scratch
hardness [.mu.m] with applied force of 1.0 N 0.17 0.10 1.5 N 0.70
0.21 2.0 N 1.20 0.75 3.0 N 2.50 2.10 MVR (ISO 1133, 3.4 4.3 2.4 2.0
230.degree. C./3.8 kg) [cm.sup.3/10 min] VST (ISO 306 B) [.degree.
C.] 112.5 114.5 111.0 114.0 Yellowness index to DIN 6167
(D65/10.degree. illuminant, 3 mm) after 0 h 0.5 0.3 1.5 1.0 after
10 000 h 1.0 0.8 4.0 3.5
[0075] The Xenotest to DIN EN ISO 4892, Part 2 (artificial
weathering or irradiation in devices--filtered xenon arc
irradiation) was carried out with a Beta LM Xenotest device. The
lower wavelength threshold lambda G=300 nm; black standard
temperature=65 +/-3.degree. C.; water spray/drying cycle: 18 min of
water spray, 102 min of drying time; relative humidity during
drying=65%; constant conditions=continuous irradiation of
specimens; irradiation intensity=standard method A (artificial
weathering); test device: Xenosensitiv (lambda from 300 to 400 nm),
controllable from 45 to 120 W/m.sup.2, the standard specification
value of 60 W/m.sup.2 being used for testing.
* * * * *