U.S. patent application number 13/546065 was filed with the patent office on 2012-11-22 for reactive mixture for coating molded objects by means of reaction injection molding and coated molded object.
This patent application is currently assigned to Evonik Roehm GmbH. Invention is credited to Erwin Felger, Thorsten Goldacker, Elevtherios Gross, Werner Ho, Klaus Koralewski, Klaus SCHULTES, Ghirmay Seyoum.
Application Number | 20120296004 13/546065 |
Document ID | / |
Family ID | 39563532 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120296004 |
Kind Code |
A1 |
SCHULTES; Klaus ; et
al. |
November 22, 2012 |
REACTIVE MIXTURE FOR COATING MOLDED OBJECTS BY MEANS OF REACTION
INJECTION MOLDING AND COATED MOLDED OBJECT
Abstract
The invention relates to an injection moulding machine
containing a reactive mixture including at least 40% by weight of
(meth)acrylates having at least two double bonds, at least one
photoinitiator, and at least one thermal initiator.
Inventors: |
SCHULTES; Klaus; (Wiesbaden,
DE) ; Goldacker; Thorsten; (Rossdorf, DE) ;
Koralewski; Klaus; (Riedstadt, DE) ; Ho ; Werner;
(Shanghai, CN) ; Seyoum; Ghirmay; (Egelsbach,
DE) ; Gross; Elevtherios; (Frankfurt, DE) ;
Felger; Erwin; (Ober-Ramstadt, DE) |
Assignee: |
Evonik Roehm GmbH
Darmstadt
DE
|
Family ID: |
39563532 |
Appl. No.: |
13/546065 |
Filed: |
July 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12601852 |
Nov 25, 2009 |
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PCT/EP08/54678 |
Apr 17, 2008 |
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13546065 |
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Current U.S.
Class: |
522/183 |
Current CPC
Class: |
C08F 2/46 20130101; Y10T
428/263 20150115; B29C 45/0001 20130101; C09D 4/00 20130101; Y10T
428/264 20150115; B29C 45/1679 20130101; Y10T 428/31928 20150401;
Y10T 428/31913 20150401; Y10T 428/31721 20150401; C08F 4/32
20130101; Y10T 428/31924 20150401 |
Class at
Publication: |
522/183 |
International
Class: |
C08F 20/28 20060101
C08F020/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2007 |
DE |
10 2007 028 601.7 |
Claims
1-33. (canceled)
34. An injection moulding machine, wherein the machine comprises a
reactive mixture comprising at least 40% by weight of
(meth)acrylates having at least two double bonds, at least one
photoinitiator and at least one thermal initiator.
35. The machine of claim 34, wherein the reactive mixture comprises
at least 60% by weight of (meth)acrylates having at least two
double bonds.
36. The machine of claim 35, wherein the reactive mixture comprises
at least 90% by weight of (meth)acrylates having at least two
double bonds.
37. The machine of claim 34, wherein the reactive mixture comprises
at least one (meth)acrylate having three or more double bonds.
38. The machine of claim 37, wherein the proportion of
(meth)acrylates having three or more double bonds is at least 25%
by weight, based on the weight of the reactive mixture.
39. The machine of claim 38, wherein the proportion of
(meth)acrylates having three or more double bonds is at least 50%
by weight, based on the weight of the reactive mixture.
40. The machine of claim 34, wherein the reactive mixture comprises
not more than 75% by weight of monomers having two or less double
bonds.
41. The machine of claim 34, wherein the reactive mixture has a
dynamic viscosity in the range of 1 to 200 mPas at 25.degree.
C.
42. The machine of claim 34, wherein the reactive mixture comprises
0.01% by weight to 3% by weight of photoinitiator, based on the
weight of the reactive mixture.
43. The machine of claim 34, wherein the reactive mixture comprises
0.03% by weight to 5% by weight of thermal initiator, based on the
weight of the reactive mixture.
44. The machine of claim 34, wherein the weight ratio of
photoinitiator to thermal initiator is in the range of 20:1 to
1:5.
45. The machine of claim 34, wherein the reactive mixture comprises
1,6-hexanediol diacrylate, trimethylolpropane triacrylate and/or
pentaerythrityl tetraacrylate.
46. The machine of claim 45, wherein the reactive mixture comprises
trimethylolpropane triacrylate and 1,6-hexanediol diacrylate, the
weight ratio of trimethylolpropane triacrylate to 1,6-hexanediol
diacrylate being in the range of 5:1 to 1:5.
47. The machine of claim 45, wherein the reactive mixture comprises
trimethylolpropane triacrylate and pentaerythrityl tetraacrylate,
the weight ratio of trimethylolpropane triacrylate to
pentaerythrityl tetraacrylate being in the range of 5:1 to 1:5.
48. The machine of claim 45, wherein the reactive mixture comprises
pentaerythrityl tetraacrylate and 1,6-hexanediol diacrylate, the
weight ratio of pentaerythrityl tetraacrylate to 1,6-hexanediol
diacrylate being in the range of 5:1 to 1:5.
49. The machine of claim 34, wherein the reactive mixture comprises
a lubricant.
50. The machine of claim 34, wherein the reactive mixture comprises
colorants, metallic pigments, UV stabilizers, fillers or
nanomaterials.
Description
[0001] The present invention relates to a reactive mixture for
coating mouldings by means of reaction injection moulding.
Furthermore, the present invention describes a coated moulding.
[0002] Thermoplastic moulding materials which may be based, for
example, on polymethyl methacrylate (PMMA) are used for a very wide
range of applications. For this purpose, the materials are extruded
or injection moulded to give shaped articles.
[0003] The shaped articles are widely used nowadays for the
production of parts subjected to high stress, such as, for example,
displaceable parts (interior and exterior of automobiles, coverings
of electronic devices, such as mobile phone, computer, organizer,
MP3 player or television coverings), opaque coloured add-on parts
(e.g. in the automotive industry: exterior mirrors, pillar
claddings, mirror triangles) or opaque coloured commodity articles.
Owing to the high stress, the surface of the shaped articles thus
used tends to form scratches, which are often visually
unacceptable. Mouldings which were produced by injection moulding
are particularly scratch-sensitive in this respect. Furthermore,
from economic points of view, the colour of the mouldings produced
can be varied only with very great difficulty, in order thus to
permit simple colour matching of the add-on part with the
respective automobile, for example during production.
[0004] For improving the scratch resistance and for colour
matching, the mouldings described above can be provided with finish
coats. However, the classical application of reactive finishes is
relatively complicated and therefore expensive. These processes are
scarcely suitable for the production of mass-produced articles.
[0005] For this reason, processes by means of which a
scratch-resistant layer can be applied to the mouldings relatively
economically by means of injection moulding processes have already
been developed. For example, the publications JP 11300776 and JP
2005074896 describe injection moulding processes in which a
moulding having a scratch-resistant layer is obtained.
[0006] The publication JP 11300776 (Dainippon Toryo, 1998)
describes a two-stage RIM process. First, a moulding is obtained by
metathesis RIM of dicyclopentadiene. After the curing, the movable
part of the RIM mould is retracted so that a defined gap forms
between moulding and mould. A coating material which consists of
acrylate-functionalized urethane oligomers, styrene, diacrylate
crosslinking agents and optionally fillers and pigments (TiO.sub.2,
talc) and is cured by a free radical method at 95.degree. C. for 2
min is injected into this gap in a second RIM process.
[0007] The document JP 2005074896 (Toyota Motor Corp.; Dainippon
Toryo Co.) likewise describes an RIM process. In a first
conventional injection moulding step, a plastic, in particular
polycarbonate (PC), is processed to give a sheet-like shaped
article. The mould then opens to form a small gap and, within a few
seconds, a reactive solution of acrylate-functionalized urethane
oligomers, acrylate crosslinking agents, inhibitors and an organic
peroxide initiator is injected and cured. At 95.degree. C., the
curing is complete after a few seconds and the composite body is
removed from the mould after 90 s. It has good scratch resistance,
adhesion of the composite, thermal shock resistance and resistance
to warm water cycling. The presence of a urethane oligomer which is
composed of isophorone diisocyanate or
bis(isocyanocyclohexyl)methane building blocks is essential in all
claims.
[0008] The mouldings described above already have good properties.
However, attempts are continuously being made to improve the
scratch resistance of mouldings thus obtained. Furthermore, the
production is time-consuming so that the overall process is
expensive. In addition, the stability of the mouldings to
weathering is in need of improvement. Premature polymerization of
the reactive mixture in the injection moulding apparatus presents a
further problem of the injection moulding process described in
publications JP 11300776 and JP 2005074896, so that short cycle
times are scarcely achievable by these processes in mass
production.
[0009] In view of the prior art, it was the object of the present
invention to provide a reactive mixture for coating mouldings by
means of a reaction injection moulding, which mixture leads to a
coating having particularly high scratch resistance and high
adhesive strength on a moulding.
[0010] A further object of the invention was to provide a reactive
mixture which can be completely cured particularly easily and in a
short time.
[0011] In addition, it was an object of the present invention to
provide processes for the production of coated mouldings which can
be carried out easily and economically. The moulding should be
obtained thereby with cycle times as short as possible and, as a
whole, with little energy consumption.
[0012] The provision of mouldings having outstanding mechanical
properties was furthermore an object of the present invention. In
particular, the mouldings should show a high scratch resistance and
great hardness. Moreover, the coated mouldings should have high
resistance to weathering and to chemicals.
[0013] These objects and further objects which are not explicitly
mentioned but can be derived or deduced directly from the
relationships discussed here at the outset are achieved by a
reactive mixture having all features of Patent Claim 1.
Modifications of the reactive mixture according to the invention
are protected in the dependent claims relating back to Claim 1.
With regard to the process and the moulding, Claims 18 and 27
provide achievements of the underlying object.
[0014] The present invention accordingly relates to a reactive
mixture for coating mouldings by means of reaction injection
moulding, comprising at least 40% by weight of (meth)acrylates
having at least two double bonds, which is characterized in that
the reactive mixture comprises at least one photoinitiator and at
least one thermal initiator.
[0015] It is possible thereby in an unforeseeable manner to provide
a coated moulding which has outstanding scratch resistance and can
be obtained very economically. Surprisingly, the coating shows a
very high adhesive strength in the moulding. In addition, the
coatings obtained with the reactive mixture according to the
invention show high stability to weathering. Furthermore, the
coated mouldings have good mechanical properties and may exhibit
both particularly great hardness and good impact strength.
[0016] Furthermore, the reactive mixture according to the invention
permits the production of a coating resistant to chemicals and to
heat on a moulding.
[0017] Moreover, the reactive mixture may have additives in order
to adapt the desired properties to specific requirements. Thus,
colour matching of the moulding may be effected in a simple
manner.
[0018] Furthermore, the process according to the invention can be
carried out easily and economically, it being possible to obtain
the moulding with surprisingly short cycle times and, as a whole,
with little energy consumption.
[0019] The reactive mixture according to the invention has at least
40% by weight, preferably at least 60% by weight and particularly
preferably at least 90% by weight of (meth)acrylates having at
least two double bonds, based on the total weight of the reactive
mixture. The term "double bond" designates in particular
carbon-carbon double bonds which are capable of free radical
polymerization. The expression "(meth)acrylate" represents
acrylate, methacrylate and mixtures of the two. (Meth)acrylates
having at least two double bonds are also known as crosslinking
monomers. These include in particular (meth)acrylates having two
double bonds such as, for example, (meth)acrylates which are
derived from unsaturated alcohols, such as, for example, 2-propynyl
(meth)acrylate, allyl (meth)acrylate or vinyl (meth)acrylate, and
(meth)acrylates which are derived from diols or higher hydric
alcohols, such as, for example, glycol di(meth)acrylates, such as
ethylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, triethylene glycol di(meth)acrylate, tetra- and
polyethylene glycol di(meth)acrylate, 1,3-butanediol (meth)
acrylate, 1,4-butanediol (meth) acrylate, 1,6-hexanediol
di(meth)acrylate, glyceryl di(meth)acrylate and diurethane
dimethacrylate; (meth)acrylates having three or more double bonds,
such as, for example, glyceryl tri(meth)acrylate,
trimethylolpropane tri(meth)acrylate, pentaerythrityl
tetra(meth)acrylate and dipentaerythrityl penta(meth)acrylate.
Particularly preferred (meth)acrylates having at least two double
bonds are in particular 1,6-hexanediol diacrylate,
trimethylolpropane triacrylate, pentaerythrityl tetraacrylate and
dipentaerythrityl pentaacrylate.
[0020] According to a particular modification, the reactive mixture
may comprise at least one (meth)acrylate having three or more
double bonds. Preferably, the proportion of (meth)acrylates having
three or more double bonds is at least 10% by weight, particularly
preferably at least 25% by weight, especially preferably at least
50% by weight and very particularly preferably at least 90% by
weight, based on the weight of the reactive mixture.
[0021] Reactive mixtures which comprise not more than 90% by
weight, particularly preferably not more than 75% by weight,
especially preferably not more than 50% by weight and very
particularly preferably not more than 7% by weight of monomers
having two or less double bonds are furthermore of particular
interest.
[0022] According to a particular embodiment, the reactive mixture
preferably comprise 1,6-hexanediol diacrylate, trimethylolpropane
triacrylate and/or pentaerythrityl tetraacrylate. In particular,
reactive mixtures which comprise trimethylolpropane triacrylate and
pentaerythrityl tetraacrylate are of particular interest, it being
possible for the weight ratio of trimethylolpropane triacrylate to
pentaerythrityl tetraacrylate to be preferably in the range of 10:1
to 1:10, preferably in the range of 5:1 to 1:5, particularly
preferably in the range of 3:1 to 1:3 and very particularly
preferably in the range of 2:1 to 1:2.
[0023] According to a further development, the reactive mixture
preferably comprises trimethylolpropane triacrylate and
1,6-hexanediol diacrylate, it being possible for the weight ratio
of trimethylolpropane triacrylate to 1,6-hexanediol diacrylate
preferably to be in the range of 10:1 to 1:10, preferably in the
range of 5:1 to 1:5, particularly preferably in the range of 3:1 to
1:3 and very particularly preferably in the range of 2:1 to
1:2.
[0024] Reactive mixtures which preferably comprise pentaerythrityl
tetraacrylate and 1,6-hexanediol diacrylate are furthermore of
particular interest. Expediently, the weight ratio of
pentaerythrityl tetraacrylate to 1,6-hexanediol diacrylate may be
in the range of 10:1 to 1:10, preferably in the range of 5:1 to
1:5, particularly preferably in the range of 3:1 to 1:3 and very
particularly preferably in the range of 2:1 to 1:2.
[0025] Reactive mixtures which comprise pentaerythrityl
tetraacrylate and/or trimethylolpropane triacrylate surprisingly
show particularly high scratch resistance which increases in
particular with the proportion of pentaerythrityl tetraacrylate.
Reactive mixtures which comprise 1,6-hexanediol diacrylate and/or
trimethylolpropane triacrylate show particularly high UV stability
which can be determined in particular by the xenon arc test. Thus,
mixtures having a high proportion of 1,6-hexanediol diacrylate
retain high scratch resistance according to the abrasive disc test
even after xenon arc exposure.
[0026] The scratch resistance of the coating is dependent, inter
alia, on the number of polymerizable double bonds, based on the
weight of the mixture. The higher this proportion, the higher is
the scratch resistance which the coating can achieve. Preferably,
the reactive mixture can accordingly have at least 1 mol of double
bond per 120 g of reactive mixture, particularly preferably at
least 1 mol of double bond per 105 g of reactive mixture. The
scratch resistance can be increased thereby, in particular by using
(meth)acrylates having three or more double bonds.
[0027] The reactive mixture can be used in particular in reactive
injection moulding processes. Accordingly, the mixture has a
viscosity which permits such use. Preferably, the dynamic viscosity
of the reactive mixture is in the range of 1 to 200 mPas at
25.degree. C., particularly preferably in the range of 5 to 50 mPas
at 25.degree. C., it being possible to determine the dynamic
viscosity according to Brookfield (with UL adaptor).
[0028] For curing, the reactive mixture comprises at least one
initiator by means of which the monomers can be subjected to free
radical polymerization. Thermal initiators which form free radicals
by the action of heat or photoinitiators which initiate free
radical polymerization on irradiation with electromagnetic waves
can be used here. Surprisingly, particular advantages can be
achieved by using reactive mixtures which comprise both thermal
initiators and photo-initiators. These advantages include in
particular short cycle times in the production of the coated
mouldings, particularly high stability to weathering, scratch
resistance and adhesive strength of the coating.
[0029] Suitable thermal initiators are, inter alia, azo compounds,
peroxy compounds, persulphate compounds or azoamidines. Nonlimiting
examples are dibenzoyl peroxide, dicumene peroxide, cumene
hydroperoxide, diisopropyl peroxydicarbonate,
bis(4-tert-butylcyclohexyl) peroxydicarbonate, dipotassium
persulphate, ammonium peroxydisulphate,
2,2'-azobis(2-methylpropionitrile) (AIBN),
2,2'-azobis(isobutyramidine) hydrochloride, benzpinacol, dibenzyl
derivatives, methyl ethylene ketone peroxide,
1,1-azobiscyclohexanecarbonitrile, methyl ethyl ketone peroxide,
acetylacetone peroxide, dilauryl peroxide, didecanoyl peroxide,
tert-butyl per-2-ethylhexanoate, ketone peroxide, methyl isobutyl
ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide,
tert-butyl peroxybenzoate, tert-butyl peroxyisopropylcarbonate,
2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-butyl
peroxy-2-ethylhexanoate, tert-butyl
peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxyisobutyrate,
tert-butyl peroxyacetate, dicumyl peroxide,
1,1-bis(tert-butylperoxy)cyclohexane,
1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumyl
hydroperoxide, tert-butyl hydroperoxide,
bis(4-tert-butylcyclohexyl) peroxydicarbonate, and the free radical
formers obtainable from DuPont under the name .RTM.Vazo, for
example .RTM.Vazo V50 and .RTM.Vazo WS.
[0030] Expediently, the reactive mixture may comprise 0.01% by
weight to 3% by weight, preferably 0.1% by weight to 2.5% by weight
and particularly preferably 0.5% by weight to 1.5% by weight of
thermal initiator, based on the weight of the reactive mixture.
[0031] The preferred photoinitiators include, inter alia,
.alpha.,.alpha.-diethoxyacetophenone (DEAP, Upjohn Corp.),
n-butylbenzoin ether (.RTM.Triganol-14, AKZO) and
2,2-dimethoxy-2-phenylacetophenone (.RTM.Irgacure 651) and
1-benzoylcyclohexanol (.RTM.Irgacure 184),
bis(2,4,6-trimethylbenzoyl)-phenylphospine oxide (.RTM.Irgacure
819) and
1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-phenylpropan-1-one
(.RTM.Irgacure 2959), which in each case are commercially available
from Ciba Geigy Corp.
[0032] The proportion of photoinitiator is not critical per se.
Preferably, the reactive mixture has 0.01% by weight to 10% by
weight, particularly preferably 0.3% by weight to 5% by weight and
very particularly preferably 0.7% by weight to 2.3% by weight of
photoinitiator, based on the weight of the reactive mixture.
[0033] According to a preferred modification, the weight ratio of
photoinitiator to thermal initiator may be in the range of 20:1 to
1:5, preferably in the range 15:1 to 1:1 and particularly
preferably in the range 10:1 to 2:1.
[0034] In addition to the abovementioned constituents, the reactive
mixture may comprise a lubricant. Surprisingly, this makes it
possible to improve the demouldability of the coated moulding
without reducing the adhesive strength to critical values.
Accordingly, lubricants, for example selected from the group
consisting of the polysiloxanes, the saturated fatty acids having
less than C.sub.20, preferably C.sub.16 to C.sub.18, carbon atoms
or the saturated fatty alcohols having less than C.sub.20,
preferably C.sub.16 to C.sub.18 carbon atoms may be present as
auxiliaries. Small proportions of not more than 0.25, e.g. 0.05 to
0.2, % by weight, based on the weight of the reactive mixture, are
preferably present. For example, stearic acid, palmitic acid and
industrial mixtures of stearic and palmitic acid are suitable. In
addition, polysiloxanes which are acrylated, such as, for example,
13/6/.alpha..omega.2-hexylacryloylsiloxane are expedient, it being
possible to obtain this compound, for example, under the tradename
RC 725 from Goldschmidt GmbH. Polysiloxanes can also be used in
large amounts. For example, proportions of not more than 10% by
weight, preferably of not more than 1% by weight and very
particularly preferably of not more than 0.5% by weight are
expedient. For example, n-hexadecanol, n-octadecanol and industrial
mixtures of n-hexadecanol and n-octadecanol are furthermore
suitable. A particularly preferred lubricant or mould release agent
is stearyl alcohol.
[0035] Furthermore, the reactive mixture may comprise customary
additives, such as colorants, pigments, for example metallic
pigments, UV stabilizers, fillers or nanomaterials, in particular
ITO nanoparticles. The proportion of these additives is dependent
on the intended use and may therefore be within wide ranges. This
proportion, if additives are present, may preferably be 0 to 30% by
weight, particularly preferably 0.1 to 5% by weight.
[0036] The reactive mixture provided by the present invention can
be used in particular for coating mouldings by means of reaction
injection moulding. Accordingly, the present invention also relates
to processes for the production of coated mouldings.
[0037] Injection moulding processes have long been known and are
widely used. In general, the moulding material is injected into an
injection mould and cooled to give a moulding. The moulding thus
obtained can then be provided with a coating.
[0038] For example, the shaped article thus obtained can be finally
cooled and removed from the mould. In a second, downstream separate
injection moulding step, for example, this preform is then placed
in or transferred to another mould having a created cavity and the
reactive mixture is injected into the mould and thus injected onto
the preform. This process is known as the insert or transfer
process. For the subsequently achievable adhesion, it is
particularly advantageous if the preformed shaped article is
preheated.
[0039] According to a preferred embodiment, the coating is
advantageously effected in particular by changing the injection
mould, a space forming between that surface of the moulding which
is to be coated and the inner surface of the injection mould. The
resulting space can be filled with a reactive mixture by injection
moulding. The reactive mixture can preferably first be thermally
cured and, after the thermal curing, cured by irradiation.
[0040] By means of this procedure, it is possible to obtain in
particular coated mouldings having high scratch resistance, the
coating having particularly good adhesive strength. Moreover,
particularly short cycle times can also be achieved.
[0041] Plants which permit such a procedure are described, inter
alia, in the documents JP 11300776 and JP 2005074896 described
above.
[0042] Moulding materials for the production of the moulding to be
coated are known per se, these moulding materials containing
thermoplastically processable polymers as an obligatory component.
The preferred polymers include, for example, poly(meth)acrylates,
in particular polymethyl methacrylate (PMMA),
poly(meth)acrylamides, polyacrylonitriles, polystyrenes,
polyethers, polyesters, polycarbonates and polyvinyl chlorides.
Poly(meth)acrylates and poly(meth)acrylimides are preferred here.
These polymers can be used individually or as mixture. Furthermore,
these polymers may also be present in the form of copolymers.
Preferred copolymers are, inter alia, styrene-acrylonitrile
copolymers, styrene-maleic acid copolymers and polymethyl
methacrylate copolymers, in particular polymethyl
methacrylate-poly(meth)acrylimide copolymers.
[0043] Particularly preferred moulding materials have at least 15%
by weight, preferably at least 50% by weight and particularly
preferably at least 80% by weight of polymethyl methacrylate,
polymethylmethacrylimide and/or polymethyl methacrylate copolymers,
based on the total weight of the moulding material.
[0044] The moulding materials of the present invention can
preferably contain poly(meth)acrylates. The expression
(meth)acrylates comprises methacrylates and acrylates and mixtures
of the two.
[0045] Poly(meth)acrylates are polymers which are obtainable by
polymerization of a monomer mixture which has at least 60% by
weight, preferably at least 80% by weight, of (meth)acrylates,
based on the weight of the monomers. These monomers are widely
known among those skilled in the art and are commercially
available. They include, inter alia, (meth)acrylic acid and
(meth)acrylate which are derived from saturated alcohols, such as
methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,
butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate; (meth)acrylates
which are derived from unsaturated alcohols, such as, for example,
oleyl (meth)acrylate, 2-propynyl (meth)acrylate, allyl
(meth)acrylate, vinyl (meth) acrylate, etc; amides and nitriles of
(meth)acrylic acid, such as
N-(3-dimethylaminopropyl)(meth)acrylamide,
N-(diethylphosphono)(meth)acrylamide,
1-methacryloylamido-2-methyl-2-propanol; cycloalkyl
(meth)acrylates, such as 3-vinylcyclohexyl(meth) acrylate,
bornyl(meth)acrylate; hydroxyalkyl (meth)acrylates, such as
3-hydroxypropyl(meth) acrylate, 3,4-dihydroxybutyl(meth) acrylate,
2-hydroxyethyl(meth) acrylate, 2-hydroxypropyl (meth)acrylate;
glycol di(meth)acrylates, such as 1,4-butanediol (meth)acrylate,
(meth)acrylates of ethyl alcohols, such as tetrahydrofurfuryl
(meth)acrylate, vinyloxyethoxyethyl (meth)acrylate; and
polyfunctional (meth)acrylates, such as trimethylolpropane
tri(meth)acrylate.
[0046] In addition to the (meth)acrylates described above, further
unsaturated monomers which are copolymerizable with the
abovementioned methacrylates can also be used for the preparation
of the poly(meth)acrylates. In general, these compounds are used in
an amount of 0 to 40% by weight, preferably 0 to 20% by weight,
based on the weight of the monomers, it being possible to use the
comonomers individually or as a mixture. These include, inter alia,
1-alkenes, such as 1-hexene, 1-heptene; branched alkenes, such as,
for example, vinylcyclohexane, 3,3-dimethyl-1-propene,
3-methyl-1-diisobutylene, 4-methyl-1-pentene; vinyl esters, such as
vinyl acetate; styrene, substituted styrenes having an alkyl
substituent in the side chain, such as, for example,
.alpha.-methylstyrene and .alpha.-ethylstyrene, substituted
styrenes having an alkyl substituent on the ring, such as
vinyltoluene and p-methylstyrene, halogenated styrenes such as, for
example, monochlorostyrenes, dichlorostyrenes, tribromostyrenes and
tetrabromostyrenes; heterocyclic vinyl compounds, such as
2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine,
3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine,
vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole,
3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole,
2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone,
N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam,
N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene,
vinylthiolane, vinylthiazoles and hydrogenated vintylthiazoles,
vinyloxazoles and hydrogenated vinyloxazoles; vinyl and isoprenyl
ether; maleic acid derivatives, such as, for example, maleic
anhydride, methylmaleic anhydride, maleimide, methylmaleimide; and
dienes, such as, for example, divinylbenzene.
[0047] Preferred poly(meth)acrylates are obtainable by
polymerization of mixtures which have at least 20% by weight, in
particular at least 60% by weight and particularly preferably at
least 80% by weight, based in each case on the total weight of the
monomers to be polymerized, of methyl methacrylate. In the context
of the present invention, these polymers are referred to as
polymethyl methacrylates. Preferred moulding materials may contain
different poly(meth)acrylates which differ, for example, in the
molecular weight or in the monomer composition.
[0048] The preparation of the (meth)acrylate homo- and/or
copolymers from the monomers described above by the various free
radical polymerization processes is known per se. Thus, the
polymers can be prepared by mass, solution, suspension or emulsion
polymerization. The mass polymerization is described by way of
example in Houben-Weyl, volume E20, part 2 (1987), page 1145 et
seq. Information regarding the solution polymerization is also to
be found there on page 1156 et seq. Explanations of the suspension
polymerization technique are also to be found there on page 1149 et
seq., while the emulsion polymerization is also elaborated on and
explained there on page 1150 et seq.
[0049] Furthermore, preferred moulding materials may comprise
poly(meth)acrylimides. Poly(meth)acrylimides have repeating units
which can be represented by the formula (I)
##STR00001##
in which R.sup.1 and R.sup.2 are identical or different and denote
hydrogen or a methyl group and R.sup.3 denotes hydrogen or an alkyl
or aryl radical having up to 20 carbon atoms.
[0050] Units of the structure (I) preferably form more than 30% by
weight, particularly preferably more than 50% by weight and very
particularly preferably more than 80% by weight of the
poly(meth)acrylimide.
[0051] The preparation of poly(meth)acrylimides is known per se and
is disclosed, for example, in British Patent 1 078 425, British
Patent 1 045 229, German Patent 1 817 156 (=U.S. Pat. No.
3,627,711) or German Patent 27 26 259 (=U.S. Pat. No.
4,139,685).
[0052] In addition, these copolymers may contain further monomer
units which arise, for example, from esters of acrylic or
methacrylic acid, in particular with lower alcohols having 1-4
carbon atoms, styrene, maleic acid or the anhydride thereof,
itaconic acid or the anhydride thereof, vinylpyrrolidone, vinyl
chloride or vinylidene chloride. The proportion of the comonomers,
which cannot be cyclized or can be cyclized only with very great
difficulty, should not exceed 30% by weight, preferably 20% by
weight and particularly preferably 10% by weight, based on the
weight of the monomers.
[0053] Moulding materials which can preferably be used are those
which comprise poly(N-methylmethacrylimides) (PMMI) and/or
polymethyl methacrylates (PMMA). Poly(N-methylmethacrylimides)
(PMMI), polymethyl methacrylates (PMMA) and/or PMMI-PMMA copolymers
are preferably copolymers of PMMI and PMMA which are prepared by
partial cycloimidization of PMMA. (PMMI which is prepared by
partial imidization of PMMA is usually prepared in such a way that
not more than 83% of the PMMA used are imidized. The resulting
product is referred to as PMMI but strictly speaking is a PMMI-PMMA
copolymer.) Both PMMA and PMMI or PMMI-PMMA copolymers are
commercially available, for example under the brand name Pleximid
from Rohm. An exemplary copolymer (Pleximid 8803) has 33% of MMI
units, 54.4% of MMA units, 2.6% of methacrylic acid units and 1.2%
of anhydride units. The products and their preparation are known
(Hans R. Kricheldorf, Handbook of Polymer Synthesis, Part A,
published by Marcel Dekker Inc. New York--Basel--Hong Kong, page
223 et seq.; H. G. Elias, Makromoleku[Macromolecules], published by
Huthig and Wepf Basel--Heidelberg--New York; U.S. Pat. Nos.
2,146,209 and 4,246,374).
[0054] In addition, the moulding materials may comprise
styrene-acrylonitrile polymers (SAN). Particularly preferred
styrene-acrylonitrile polymers can be obtained by polymerization of
mixtures which consist of 70 to 92% by weight of styrene, 8 to 30%
by weight of acrylonitrile and 0 to 22% by weight of further
comonomers, based in each case on the total weight of the monomers
to be polymerized.
[0055] For improving the impact strength values, silicone rubber
graft copolymers can be mixed with the moulding materials, which
graft copolymers are composed of 0.05 to 95% by weight, based on
the total weight of the copolymer, of a core a) of an organosilicon
polymer which corresponds to the general formula
(R.sub.2SiO.sub.2/2).sub.x.(RSiO.sub.3/2).sub.y.(SiO.sub.4/2).sub.z
where x=0 to 99.5 mol %, y=0.5 to 100 mol % and z=0 to 50 mol %, R
denoting identical or different alkyl or alkenyl radicals having to
6 carbon atoms, aryl radicals or substituted hydrocarbon
radicals,
[0056] 0 to 94.5% by weight, based on the total weight of the
copolymer, of a polydialkylsiloxane layer b) and
[0057] 5 to 95% by weight, based on the total weight of the
copolymer, of a shell c) of organic polymer, the core a) comprising
vinyl groups prior to grafting and the shell c) being obtainable by
free radical polymerization of a mixture which comprises acrylates
and methacrylates.
[0058] The moulding materials according to the invention can
furthermore contain acrylate rubber modifiers. Surprisingly,
outstanding impact strength behaviour of the mouldings at room
temperature (about 23.degree. C.) which were produced from the
moulding materials can be achieved thereby. What is particularly
important is that the mechanical and thermal properties, such as,
for example, the modulus of elasticity or the Vicat softening
temperature, are maintained at a very high level. If an attempt is
made to achieve similar notched impact strength behaviour at room
temperature only by the use of acrylate rubber modifier or silicone
rubber graft copolymer, these values decrease substantially.
[0059] Such acrylate rubber modifiers are known per se. They are
copolymers which have a core-shell structure, the core and the
shell having a high proportion of the (meth)acrylates described
above.
[0060] Preferred acrylate rubber modifiers here have a structure
comprising two shells which differ in their composition.
[0061] Particularly preferred acrylate rubber modifiers have, inter
alia, the following composition:
[0062] Core: Polymer having a proportion of methyl methacrylate of
at least 90% by weight, based on the weight of the core.
[0063] Shell 1: Polymer having a proportion of butyl acrylate of at
least 80% by weight, based on the weight of the first shell.
[0064] Shell 2: Polymer having a proportion of methyl methacrylate
of at least 90% by weight, based on the weight of the second
shell.
[0065] For example, a preferred acrylate rubber modifier may have
the following composition:
[0066] Core: Copolymer of methyl methacrylate (95.7% by weight),
ethyl acrylate (4% by weight) and allyl methacrylate (0.3% by
weight)
[0067] S1: Copolymer of butyl acrylate (81.2% by weight), styrene
(17.5% by weight) and allyl methacrylate (1.3% by weight)
[0068] S2: Copolymer of methyl methacrylate (96% by weight) and
ethyl acrylate (4% by weight)
[0069] The ratio of core to shell(s) of the acrylate rubber
modifier may vary within wide ranges. Preferably, the weight ratio
of core to shell C/S is in the range of 20:80 to 80:20, preferably
of 30:70 to 70:30, in the case of modifiers having one shell or the
ratio of core to shell 1 to shell 2 C/S1/S2 is in the range of
10:80:10 to 40:20:40, particularly preferably of 20:60:20 to
30:40:30, in the case of modifiers having two shells.
[0070] The particle size of the acrylate rubber modifiers is
usually in the range of 50 to 1000 nm, preferably 100 to 500 nm and
particularly preferably 150 to 450 nm, without any limitation being
intended thereby.
[0071] According to a particular aspect of the present invention,
the weight ratio of silicone rubber graft copolymer to acrylate
rubber modifier is in the range of 1:10 to 10:1, preferably of 4:6
to 6:4.
[0072] Particular moulding materials consist of
[0073] f1) 20 to 95% by weight of poly(meth)acrylates,
[0074] f2) 0 to 45% by weight of styrene-acrylonitrile
polymers,
[0075] f3) 5 to 60% by weight of silicone rubber graft
copolymers
[0076] f4) 0 to 60% by weight of impact modifiers based on acrylate
rubber,
[0077] based in each case on the weight of the components f1 to
f4,
[0078] and customary additives and compounding materials.
[0079] In addition, the compositions to be polymerized, the
moulding materials according to the invention or the mouldings
obtainable therefrom may contain further widely known additives.
These additives include, inter alia, molecular weight regulators,
release agents, antistatic agents, antioxidants, demoulding agents,
flameproofing agents, lubricants, dyes, flow improvers, fillers,
light stabilizers, pigments, antiweathering agents and
plasticizers.
[0080] The additives are used in customary amounts, i.e. up to 80%
by weight, preferably up to 30% by weight, based on the total mass.
If the amount is greater than 80% by weight, based on the total
mass, properties of the plastics, such as, for example, the
processability, may be disturbed.
[0081] The weight average molecular weight M.sub.w of the homo-
and/or copolymers to be used according to the invention as matrix
polymers may vary within wide ranges, the molecular weight usually
being tailored to the intended use and the method of processing of
the moulding material. In general, however, it is in the range
between 20 000 and 1 000 000 g/mol, preferably 50 000 to 500 000
g/mol and particularly preferably 80 000 to 300 000 g/mol, without
any limitation being intended thereby.
[0082] The thickness of the coating is often dependent on the type
of reactive mixture and the moulding. The production of very thin
coatings is often technically very demanding. On the other hand,
very thick coatings frequently have a strong tendency to cracking,
the adhesive strength decreasing in some cases. Coated mouldings
whose coating preferably has a thickness in the range of 1 .mu.m to
100 .mu.m, preferably 5 .mu.m to 75 .mu.m, particularly preferably
8 .mu.m to 50 .mu.m, especially preferably 10 .mu.m to 40 .mu.m and
very particularly preferably 15 .mu.m to 30 .mu.m are therefore of
particular interest. The thickness of the coating can be adjusted
via the size of the space between that surface of the moulding
which is to be coated and the inner surface of the injection
mould.
[0083] The temperature at which the moulding material is injected
into the injection mould depends in particular on the type of
polymer and of the additives. These processing temperatures are
known to the person skilled in the art. In general, the moulding
material is injected into the injection mould at a temperature in
the range of 150 to 350.degree. C., preferably 220 to 330.degree.
C.
[0084] The temperature of the mould can also be adjusted to the
temperature customary for the respective moulding material. The
moulding material can preferably be cooled to a temperature in the
range of 40 to 160.degree. C., particularly preferably 70 to
150.degree. C. and very particularly preferably 60 to 80.degree. C.
before the reactive mixture is injected into the space.
[0085] The temperature at which the thermal curing of the reactive
mixture is effected is dependent on the type of thermal initiator.
In particular, processes in which the thermal curing is preferably
effected at a temperature in the range of 70 to 160.degree. C.,
preferably 80 to 130.degree. C., particularly preferably in the
range 85 to 120.degree. C. and very particularly preferably in the
range 90 to 110.degree. C. in the injection mould are of particular
interest. If the temperature during the thermal curing is too high,
the formation of cracks may occur after UV irradiation. In the case
of temperatures which are too low, the coating often shows an
excessively high adhesion to the metal of the injection mould, it
also being possible in some cases to improve the scratch resistance
by a higher temperature during the thermal curing. The ranges
described above have proved to be particularly expedient, without
any limitation intended thereby.
[0086] According to a particular embodiment, the reactive mixture
can be effected, for example, at a temperature in the range of 70
to 85.degree. C., preferably in the range of to 80.degree. C. This
embodiment is particularly advantageous if the reactive mixture
comprises a particularly high proportion of compounds having at
least four double bonds, for example of pentaerythrityl
tetra(meth)acrylate. According to a further development of the
process according to the invention, the reactive mixture can be
cured at a temperature in the range of 85.degree. C. to 120.degree.
C., preferably in the range of 90.degree. C. to 110.degree. C. This
embodiment is particularly advantageous if the reactive mixture
comprises a particularly high proportion of compounds having two or
three double bonds, such as, for example, 1,6-hexanediol
di(meth)acrylate.
[0087] The reactive mixture can be cured at the same temperature at
which the injection moulding is cooled in the mould. The beginning
and the rate of the polymerization (curing) of the reactive mixture
can be adjusted thereby by the choice of the type and of the
proportion of thermal initiator and by the choice of the mould
temperature. In addition, the beginning of curing can be controlled
by the choice of the polyfunctional (meth)acrylates present in the
reactive mixture.
[0088] After the thermal curing, the precured reactive mixture can
be cured by irradiation at a temperature in the range of 0.degree.
C. to 120.degree. C., preferably 10.degree. C. to 40.degree. C.
Customary radiation sources can be used for this purpose, depending
on the type of initiator. The curing can preferably be effected in
particular by UV radiation, it being possible for the wavelength of
the radiation source used to be in particular in the range of 100
nm to 500 nm, preferably 200 to 400 nm.
[0089] The present invention provides in particular novel coated
mouldings which have an outstanding property profile and can
therefore be used for a variety of applications. The present
invention accordingly furthermore relates to coated mouldings
comprising a moulding which is obtainable by injection moulding
processes and comprises at least one polymer selected from the
group consisting of polymethyl methacrylate,
polymethylmethacrylimide, styrene-acrylonitrile copolymer,
styrene-maleic acid copolymer and polymethyl methacrylate
copolymers and a coating which is obtainable by polymerization of
(meth)acrylates having at least two double bonds.
[0090] The moulding is distinguished in particular by high scratch
resistance, which can be determined, for example, by an abrasive
disc test. Especially coated, transparent mouldings whose haze
value after a scratch resistance test according to ASTM 1044
(12/05) (applied weight 500 g, number of cycles =100) increases by
not more than 10%, particularly preferably by not more than 6% and
very particularly preferably by not more than 3% are of particular
interest. The scratch resistance according to ASTM 1044 (12/05)
(applied weight 500 g, number of cycles=100) can moreover be
measured by the decrease in gloss at 20.degree.. Here, preferred
coated mouldings show a decrease of gloss at 20.degree. after a
scratch resistance test according to ASTM 1044 (12/05) (applied
weight 500 g, number of cycles=100) of not more than 10%,
particularly preferably by not more than 6% and very particularly
preferably by not more than 3%. The decrease in gloss at 20.degree.
C. can be determined according to DIN EN ISO 2813. By determining a
change of gloss, for example, the scratch resistance of coloured
mouldings or of coloured coatings can be measured.
[0091] In addition, the mouldings according to the invention show
outstanding adhesive strength of the coating which can be
investigated according to the cross hatch test. For this purpose,
the coating is scored crosswise and thus divided into
chessboard-like individual segments. In general, at least 20
individual segments, preferably at least 25 individual segments,
are formed thereby. Here, the spacing between the lines is about 1
mm. A 25 mm wide adhesive tape is then stuck on and peeled off
again. The force required to release the adhesive tape per
cm.sup.2, measured according to DIN EN ISO 2409, is about 10 N per
25 mm width. For carrying out the test, for example, an adhesive
tape which is obtainable under the trade name type 4104 from Tesa
can be used. The coated mouldings preferably achieve a rating
according to the cross hatch test of not more than 1, particularly
preferably of 0. The coated mouldings achieve a rating of 1 if not
substantially more than 5% of the individual segments are detached.
If none of the individual segments (0%) is detached, the coated
mouldings achieve a rating of 0.
[0092] In addition, preferred coatings are free of cracks and show
high resistance to chemicals. Thus, the coatings resist in
particular ethanol, ethanol/water (70/30), petrol, pancreatin and
sulphuric acid (1% strength), no stress cracks being formed through
contact with these compounds.
[0093] Preferred mouldings may have a modulus of elasticity greater
than or equal to 1200 MPa, preferably greater than or equal to 1600
MPa, according to ISO 527 (at 1 mm/min). Furthermore, mouldings
according to the invention may exhibit a Charpy impact strength
greater than or equal to 10 kJ/m.sup.2, preferably greater than or
equal to 15 kJ/m.sup.2, according to IS0179.
[0094] In addition, plastics having tensile strengths greater than
or equal to 55, preferably greater than or equal to 60, according
to DIN 53 455-1-3 (at 1 mm/min), can be produced, which plastics
have excellent scratch resistance.
[0095] It is particularly surprising that this scratch-resistant
moulding may have a transmittance .tau..sub.D65.gtoreq.88%,
preferably.gtoreq.90%, according to DIN 5036 Part 3. No limitation
of the invention is intended by the abovementioned mechanical
and/or optical properties of the moulding. Rather, these data serve
for illustrating the particularly outstanding properties of the
moulding which can be achieved in combination with good scratch
resistance.
[0096] Furthermore, the mouldings of the present invention may show
excellent stability to weathering. Thus, the stability to
weathering according to the xenon arc test is preferably at least
1000 hours, particularly preferably at least 2000 hours. This
stability can be determined, for example, by a slight decrease of
the transmittance or by a slight decrease of the scratch
resistance. Especially coated mouldings whose transmittance after
exposure to a xenon arc for 2000 hours decreases by not more than
10%, particularly preferably by not more than 5%, based on the
transmittance value at the beginning of the irradiation, are of
particular interest. In addition, preferred mouldings may show an
increase in the haze value after a scratch resistance test
according to ASTM 1044 (12/05) (applied weight 500 g, number of
cycles =100) to not more than 25%, particularly preferably to not
more than 15%, after exposure to a xenon arc for 2000 hours.
Furthermore, the determination of the scratch resistance after
exposure to a xenon arc is also possible via the decrease in the
gloss. Here, preferred coated mouldings show a decrease in the
gloss at 20.degree. after a scratch resistance test according to
ASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) of
not more than 25%, particularly preferably by not more than 20% and
very particularly preferably by not more than 15% after exposure to
a xenon arc for 2000 hours.
[0097] In addition, preferred coatings which were obtained using a
coating material according to the invention show high resistance in
an alternating climate test, only slight cracking occurring in
spite of deformation of the base body. The loading programme shown
in FIG. 1 can preferably be used for carrying out the alternating
climate test (BMW PR 303--part d).
[0098] Below, the present invention is to be explained with
reference to examples and comparative examples without any
limitation being intended thereby.
COMPARATIVE EXAMPLE 1
[0099] In a small-scale experiment, the efficiency of the present
reactive mixtures was investigated. For this purpose, an injection
moulding (200.times.100.times.3 mm) was first produced from a PMMA
moulding material (8N, commercially available from Rohm GmbH) and
preheated to 85.degree. C. For the preheating, the injection
moulding was placed between two metal cylinders (having high
gloss), the lower cylinder having a diameter of 150 mm and the
upper metal cylinder a diameter of 120 mm. In order to prevent
excessive cooling of the upper metal cylinder, the latter, was
taken down after thermostating of the injection moulding for about
5 minutes, placed alongside the hotplate and further heated
(thermostated at 85.degree. C.). In the meantime, the injection
moulding remained lying flat on the large metal cylinder and was
further heated again for 5 minutes without weighting.
[0100] Thereafter (after thermostating of the injection moulding
for 10 minutes), 1.5 g of reactive mixture which comprised 68.60%
by weight of 1,6-hexanediol diacrylate, 29.40% by weight of
trimethylolpropane triacrylate, 1% by weight of
bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator)
and 1% by weight of 1-benzoylcyclohexanol (.RTM.Irgacure 184) was
added to the injection moulding and the reaction solution was
weighted (pressed) immediately with a small metal cylinder at
85.degree. C. The coating was then allowed to cure for 60 sec, the
reaction beginning about 15 seconds after the small metal cylinder
had been placed on top. This could be measured on the basis of
emerging reaction solution. A crack-free coating was obtained.
[0101] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, a scale of 0 (very high scratch
resistance) to 7 (very low scratch resistance) being used. The
coating thus obtained achieved a scratch resistance of 6 (low
scratch resistance).
EXAMPLE 1
[0102] Comparative Example 1 was substantially repeated, but curing
was effected by UV irradiation after the thermal curing of the
coated injection moulding. The coating remained free of cracks. The
scratch resistance of the coating was investigated in a small-scale
test using steel wool, the coating thus obtained achieving a
scratch resistance of 3 (good scratch resistance).
COMPARATIVE EXAMPLE 2
[0103] Comparative Example 1 was substantially repeated, but a
reactive mixture which comprised 67.90% by weight of 1,6-hexanediol
diacrylate, 29.10% by weight of trimethylolpropane triacrylate, 1%
by weight of bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal
initiator) and 2% by weight of benzoylcyclohexanol (.RTM.Irgacure
184) was used.
[0104] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained
achieving a scratch resistance of 6 (low scratch resistance).
EXAMPLE 2
[0105] Comparative Example 2 was substantially repeated, but curing
by UV irradiation was effected after the thermal curing of the
coated injection moulding. The coating remained free of cracks. The
scratch resistance of the coating was investigated in a small-scale
test using steel wool, the coating thus obtained achieving a
scratch resistance of 3 (good scratch resistance).
EXAMPLE 3
[0106] Example 1 was substantially repeated, but a reactive mixture
which comprised 97.75% by weight of trimethylolpropane triacrylate,
0.25% by weight of bis(4-tert-butylcyclohexyl) peroxydicarbonate
(thermal initiator) and 2% by weight of 1-benzoylcyclohexanol
(.RTM.Irgacure 184) was used.
[0107] The thermal curing reaction began after about 15 seconds.
After the UV curing, a crack-free coating which had a thickness of
about 20 .mu.m (average value of four individual measurements) was
obtained.
[0108] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained
achieving a scratch resistance of 1 (very good scratch
resistance).
EXAMPLE 4
[0109] Example 3 was substantially repeated, but the reaction
temperature was reduced from 85.degree. C. to 80.degree. C.
[0110] The thermal curing reaction began after about 25 seconds.
After the UV curing, a crack-free coating which had a thickness of
about 25 .mu.m (average value of four individual measurements) was
obtained.
[0111] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained
achieving a scratch resistance of 1 (very good scratch
resistance).
EXAMPLE 5
[0112] Example 4 was substantially repeated, but a reactive mixture
which comprised 97.50% by weight of trimethylolpropane triacrylate,
0.50% by weight of bis(4-tert-butylcyclohexyl) peroxydicarbonate
(thermal initiator) and 2% by weight of 1-benzoylcyclohexanol
(.RTM.Irgacure 184) was used.
[0113] The thermal curing reaction began after about 15 seconds.
After the UV curing, a crack-free coating which had a thickness of
about 12 .mu.m (average value of four individual measurements) was
obtained.
[0114] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained having
a scratch resistance of 1 (very good scratch resistance).
EXAMPLE 6
[0115] Example 4 was substantially repeated, but a reactive mixture
which comprised 97.00% by weight of trimethylolpropane triacrylate,
1.00% by weight of bis(4-tert-butylcyclohexyl) peroxydicarbonate
(thermal initiator) and 2% by weight of 1-benzoylcyclohexanol
(.RTM.Irgacure 184) was used.
[0116] The thermal curing reaction began after about 8 seconds.
After the UV curing, a crack-free coating which had a thickness of
about 13 .mu.m (average value of four individual measurements) was
obtained.
[0117] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained having
a scratch resistance of 1 (very good scratch resistance).
EXAMPLE 7
[0118] Example 4 was substantially repeated, but a reactive mixture
which comprised 9 g of trimethylolpropane triacrylate, 1 g of
pentaerythrityl tetraacrylate, 0.05 g of
bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator)
and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184) was
used.
[0119] After the UV curing, a crack-free coating which had a
thickness of about 27 .mu.m (average value of four individual
measurements) was obtained.
[0120] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained having
a scratch resistance of about 0.5 (very good scratch
resistance).
EXAMPLE 8
[0121] Example 7 was substantially repeated, but a reactive mixture
which comprised 8 g of trimethylolpropane triacrylate, 2 g of
pentaerythrityl tetraacrylate, 0.05 g of
bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator)
and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184) was
used.
[0122] After the UV curing, a crack-free coating which had a
thickness of about 14 .mu.m (average value of four individual
measurements) was obtained.
[0123] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained having
a scratch resistance of about 0 (excellent scratch resistance; no
scratches could be produced by muscle power).
EXAMPLE 9
[0124] Example 7 was substantially repeated, but a reactive mixture
which comprised 5 g of trimethylolpropane triacrylate, 5 g of
pentaerythrityl tetraacrylate, 0.05 g of
bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator)
and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184) was
used.
[0125] After the UV curing, a crack-free coating which had a
thickness of about 16 4m (average value of four individual
measurements) was obtained.
[0126] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained having
a scratch resistance of 0 (excellent scratch resistance; no
scratches could be produced by muscle power).
EXAMPLE 10
[0127] Example 7 was substantially repeated, but a reactive mixture
which comprised 3 g of trimethylolpropane triacrylate, 7 g of
pentaerythrityl tetraacrylate, 0.025 g of
bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator)
and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184) was
used.
[0128] The thermal curing was effected at 85.degree. C., a curing
time of about 30 seconds being sufficient. After the UV curing, a
crack-free coating was obtained.
[0129] The scratch resistance of the coating was investigated in a
small-scale test using steel wool, the coating thus obtained
achieving a scratch resistance of 0 (excellent scratch
resistance).
EXAMPLE 11
[0130] In a small-scale experiment, the efficiency of the present
reactive mixtures was investigated. For this purpose, an injection
moulding (200.times.100.times.3 mm) was first produced from a PMMA
moulding material (8N, commercially available from Rohm GmbH) and
preheated to 85.degree. C. For the preheating, the injection
moulding was placed between two metal cylinders (having high
gloss), the lower cylinder having a diameter of 150 mm and the
upper metal cylinder a diameter of 120 mm. In order to prevent
excessive cooling of the upper metal cylinder, the latter, was
taken down after thermostating of the injection moulding for about
5 minutes, placed alongside the hotplate and further heated
(thermostated at 85.degree. C.). In the meantime, the injection
moulding remained lying flat on the large metal cylinder and was
further heated again for 5 minutes without weighting.
[0131] Thereafter (after thermostating the injection moulding for
10 minutes), 1.5 g of a reactive mixture which comprised 5 g of
trimethylolpropane triacrylate, 5 g of pentaerythrityl
tetraacrylate, 0.025 g of bis(4-tertbutylcyclohexyl)
peroxydicarbonate (thermal initiator) and 0.20 g of
1-benzoylcyclohexanol (.RTM.Irgacure 184) was added to the
injection moulding and the reaction solution was immediately
weighted (pressed) with a small metal cylinder at 85.degree. C. and
a metal block weighing 3 kg. The coating was then allowed to cure
for 30 seconds. A crack-free coating was obtained.
[0132] After the thermal curing, the coated injection moulding was
cured by UV irradiation. Here, the cooled coating was exposed to UV
light for about 1 minute without nitrogen. A crack-free, 20 .mu.m
thick coating was obtained. The scratch resistance of the coating
was investigated in a small-scale test using steel wool, the
coating thus obtained achieving a scratch resistance of 0
(excellent scratch resistance).
EXAMPLE 12
[0133] Example 11 was substantially repeated, but a layer thickness
of 80 .mu.m was produced. For this purpose, the injection moulding
was covered with a polyester film which had been cut out in annular
form and had a thickness of about 80 .mu.m.
[0134] After the thermal curing, an initially crack-free coating
was obtained. As a result of exposure to UV light, however,
substantial cracking occurred. The scratch resistance of the
coating was investigated in a small-scale test using steel wool,
the coating thus obtained having a scratch resistance of 0
(excellent scratch resistance).
EXAMPLE 13
[0135] In a small-scale experiment, the efficiency of the present
reactive mixtures was investigated. For this purpose, an injection
moulding (200.times.100.times.3 mm) was first produced from a PMMA
moulding material (8N, commercially available from Rohm GmbH) and
preheated to 85.degree. C. For the preheating, the injection
moulding was placed between two metal blocks (having high gloss),
which had a size of 17017027 mm. In order to prevent excessive
cooling of the upper metal block, the latter, was taken down after
thermostating of the injection moulding for about 5 minutes, placed
alongside the hotplate and further heated (thermostated at
85.degree. C.). In the meantime, the injection moulding remained
lying flat on the lower metal block and was further heated again
for 5 minutes without weighting.
[0136] Thereafter (after thermostating the injection moulding for
10 minutes), 1.5 g of a reactive mixture which comprised 5 g of
trimethylolpropane triacrylate, 5 g of pentaerythrityl
tetraacrylate, 0.05 g of bis(4-tertbutylcyclohexyl)
peroxydicarbonate (thermal initiator) and 0.20 g of
1-benzoylcyclohexanol (.RTM.Irgacure 184) was added to the
injection moulding and the reaction solution was immediately
pressed with the upper metal block at 85.degree. C. The coating was
then allowed to cure for 60 seconds. A crack-free coating was
obtained.
[0137] After the thermal curing, the coated injection moulding was
cured by UV irradiation. Here, the cooled coating was exposed to UV
light for about 1 minute without nitrogen. A crack-free coating was
obtained.
[0138] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles=100). The haze of the moulding increased to
2.8% thereby. Furthermore, the adhesive strength of the coating was
determined by means of a cross hatch test. For this purpose, the
coating was scored crosswise and thus divided into chessboard-like
individual segments. The spacing between the lines is about 1 mm
here. An adhesive tape is then stuck on and peeled off again. For
carrying out the test, an adhesive tape which is available under
the tradename Type 4104 from Tesa was used. The adhesive strength
of the coating was so high that no individual segment was
detached.
EXAMPLE 14
[0139] Example 13 was substantially repeated, but a reactive
mixture which comprised 10 g of trimethylolpropane triacrylate,
0.05 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal
initiator) and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184)
was used.
[0140] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles=100). The haze of the moulding increased to
5.4% thereby. Furthermore, the adhesive strength of the coating was
determined by means of a cross hatch test. For this purpose, the
coating was scored crosswise and thus divided into chessboard-like
individual segments. The spacing between the lines is about 1 mm
here. An adhesive tape is then stuck on and peeled off again. For
carrying out the test, an adhesive tape which is available under
the tradename Type 4104 from Tesa was used. The adhesive strength
of the coating was so high that no individual segment was
detached.
[0141] Furthermore, a moulding thus produced was subjected to an
alternating climate test according to (BMW PR 303--part d), the
loading programme being shown in FIG. 1. The moulding was greatly
deformed by this test, but the coating showed only very slight
cracking.
[0142] In addition, a moulding thus produced was irradiated with
xenon arc light for 2000 hours (according to DIN EN ISO 4892, part
2, xenon arc tester: Atlas/Heraeus type 1200), with the result that
the transmittance decreased only from 91.8% to 91.1%. The scratch
resistance of the coating was likewise slightly adversely affected
by the xenon arc test. The haze of the moulding increased from 5.4%
to 22.3%.
EXAMPLE 15
[0143] Example 13 was substantially repeated, but a reactive
mixture which comprised 5 g of trimethylolpropane triacrylate, 5 g
of 1,6-hexanediol diacrylate, 0.05 g of bis(4-tert-butylcyclohexyl)
peroxydicarbonate (thermal initiator) and 0.20 g of
1-benzoylcyclohexanol (.RTM.Irgacure 184) was used.
[0144] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles=100). The haze of the moulding increased to
5.8% thereby. Furthermore, the adhesive strength of the coating was
determined by means of a cross hatch test. For this purpose, the
coating was scored crosswise and thus divided into chessboard-like
individual segments. The spacing between the lines is about 1 mm
here. An adhesive tape is then stuck on and peeled off again. For
carrying out the test, an adhesive tape which is available under
the tradename Type 4104 from Tesa was used. The adhesive strength
of the coating was so high that no individual segment was
detached.
[0145] Furthermore, a moulding thus produced was subjected to an
alternating climate test according to (BMW PR 303--part d), the
loading programme being shown in FIG. 1. The moulding was greatly
deformed by this test, but the coating showed no cracking.
[0146] In addition, a moulding thus produced was irradiated with
xenon arc light for 2000 hours (according to DIN EN ISO 4892, part
2, xenon arc tester: Atlas/Heraeus type 1200), with the result that
the transmittance decreased only from 91.4% to 91.1%. The scratch
resistance of the coating was likewise slightly adversely affected
by the xenon arc test. The haze of the moulding increased from 5.8%
to 13.5%.
EXAMPLE 16
[0147] Example 13 was substantially repeated, but a reactive
mixture which comprised 7.2 g of trimethylolpropane triacrylate,
1.8 g of 1,6-hexanediol diacrylate, 1.0 g of polysiloxane
(lubricant; RC 725, commercially available from Goldschmidt GmbH),
0.1 g of bis(4-tertbutylcyclohexyl) peroxydicarbonate (thermal
initiator) and 0.20 g of 1-benzoylcyclohexanol (.RTM.Irgacure 184)
was used. In addition, a PMMA moulding material coloured black (8N
black 90084, commercially available from Rohm GmbH) was used.
[0148] The thermal curing was effected at 90.degree. C., a curing
time of about 60 seconds being sufficient. After the UV curing, a
crack-free coating was obtained.
[0149] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05), (applied weight
500 g, number of cycles=100). A decrease in the gloss at 20.degree.
according to DIN EN ISO 2813 of 6.8% was obtained thereby.
EXAMPLE 17
[0150] Example 16 was substantially repeated, but the reaction
temperature was increased from 90.degree. C. to 95.degree. C.
[0151] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles =100). A decrease in the gloss at
20.degree. according to DIN EN ISO 2813 of 5.3% was obtained
thereby.
EXAMPLE 18
[0152] Example 15 was substantially repeated, but a reactive
mixture which comprised 5 g of trimethylolpropane triacrylate, 5 g
of 1,6-hexanediol diacrylate, 0.1 g of bis(4-tert-butylcyclohexyl)
peroxydicarbonate (thermal initiator) and 0.20 g of
1-benzoylcyclohexanol (.RTM.Irgacure 184) was used. In addition, a
PMMA moulding material coloured black (8N black 90084, commercially
available from Rohm GmbH) was used.
[0153] The thermal curing was effected at 90.degree. C., a curing
time of about 30 seconds being sufficient. After the UV curing, a
crack-free coating was obtained.
[0154] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles=100). A decrease in the gloss at 20.degree.
according to DIN EN ISO 2813 of 4.7% was obtained thereby.
[0155] Furthermore, a moulding thus produced was subjected to an
alternating climate test according to (BMW PR 303--part d), the
loading programme being shown in FIG. 1. The moulding was greatly
deformed by this test, but the coating showed no cracking.
EXAMPLE 19
[0156] Example 18 was substantially repeated, but a reactive
mixture which comprised 7 g of trimethylolpropane triacrylate, 3 g
of 1,6-hexanediol diacrylate, 0.1 g of bis(4-tert-butylcyclohexyl)
peroxydicarbonate (thermal initiator) and 0.20 g of
1-benzoylcyclohexanol (.RTM.Irgacure 184) was used.
[0157] The thermal curing was effected at 90.degree. C., a curing
time of about 60 seconds being sufficient. After the UV curing, a
crack-free coating was obtained.
[0158] The scratch resistance of the coating was investigated by an
abrasive disc test according to ASTM 1044 (12/05) (applied weight
500 g, number of cycles=100). A decrease in the gloss at 20.degree.
according to DIN EN ISO 2813 of 1.8% was obtained thereby.
[0159] Furthermore, a moulding thus produced was subjected to an
alternating climate test according to (BMW PR 303--part d), the
loading programme being shown in FIG. 1. The moulding was greatly
deformed by this test, but the coating showed no cracking.
* * * * *