Note: Descriptions are shown in the official language in which they were submitted.
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MOLDED ARTICLE OF METHACRYLIC RESIN
AND METHOD FOR PRODUCTION THEREOF
BACKGROUND OF TH~ INVENTION
Field of the Invention:
This invention relates to a molded article of
methacrylic resin excelling in transparency, weatherability,
and abrasion resistance and possessing high heat resistance
and to a method for the production thereof.
Description of the Prior Art:
Methacrylic resins excel in appearance,
transparency, and weatherability and, therefore, find
extensive utility in indoor and outdoor applications to
glazings, lampshades, decorations, etc. They, however, are
inferior in heat resistance to inorganic glass and are
further deficient in scratchproofness. When they have these
qualities improved, they can be expected to attain further
growth in utility. Various studies are now under way in
search of means of mending such drawbacks as mentioned
above. Generally, there prevails a practice of forming
synthetic resin molding materials by the use of various
molding machines such as press molding machine, injection
molding machine, extrusion molding machine, and vacuum
molding machine or by the polymerization and formation in
casting dies and then applying abrasion resistant
film-forming materials on the surface of the resulting
molded articles by the technique of spraying or dipping and
polymerizing and hardening the applied layers of the
film-forming materials by means of electron beam or heat
thereby covering the molded articles with abrasion resistant
thin films. The problem encountered by this method resides
in the fact that since the step of polymerization for the
formation of the abrasion resistant thin film is carried out
subsequent to the step of molding, such expensive facilities
as those for coating, curing, and dust removing must be
disposed separately of those used for the molding and the
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operation of this method entails complica-te management such
as of the viscosity of the film-forming materials, for
example.
As means of improving the method just described,
Japanese Patent Publication SHO 54(1979)-14,617 and SHO
54(1979)-14,618 disclose a method for producing a molded
article of synthetic resin possessing an abrasion resistant
surface, which comprises applying an abrasion resistant
film-forming material on a mold, polymerizing the material
as covered with a synthetic resin film or kept under an
atmosphere of inert gas, relieving the material being
polymerized of the film or the inert gas after the gel
content has reached a level in the range of about 40 to 95~,
post-curing the polymerized material generally until the gel
content reaches a level not lower than 85% thereby allowing
the material to assume a state neither swelled nor dissolved
by the basic resin material to be poured therein afterward,
pouring the basic resin material into the mold, and
polymerizing and forming the resin material. This method,
however, entails inevitable complication of process because
the impartation of abrasion resistance to the required two
steps of polymerization, i.e. prior polymerization and post
polymerization. In this case, when the prior polymerization
is exclusively used, the produced molded article acquires a
defective appearance because the surface thereof has craters
and cracks, shows uneven abrasion resistance, and fails to
exhibit ample abrasion resistance.
As a second problem, insufficient adhesiveness
between the basic resin and the abrasion resistant thin film
can be cited. As means of solving this problem, there
exists a method which resorts to interposing between the
abrasion resistant thin film and the basic resin a layer
capable of adhering to both the outer layers. This method
suffers from poor productivity because it requires the step
of application and the step of plolymerizing the applied
layer to be repeated at least twice. The molded article
~ S'7~
obtained by this method has a disadvantage that since
pinholes due to the contamination of dust existing in the
abrasion resistant film is inevitable and tends to allow the
adhesive layer to be dissolved at those points, the parts of
the coat centering around the pinholes as the cores suffer
from notable impairment of the resistance to solvent.
Japanese Patent Publication SHO 53(1978)-9,876
discloses a method which effects improvement of adhesiveness
by exposing the surface of a molded article to ultraviolet
light and applying a abrasion resistant thin film on this
surface of the molded article. This method, however, is
complicate in process because it requires both the molded
article and the film formed thereon to be separately exposed
to ultraviolet light. The abrasion resistant thin film
formed by this method on the molded article has been
demonstrated by a Q W weathering test to have not served the
purpose of improving the abrasion resistance of the molded
àrticle. There also prevails a practice of adding to the
raw material for the abrasion resistant thin film a good
solvent for the basic molding resin. If this power is too
high, this practice has the dissibility of inflicting cracks
on the surface of the molded article or impairing the
smoothness of the surface. co`nversely, if the power is
weak, the desired tight adhesion is not obtained. Thus,
this practice entails complication in the formulation of the
solvent and, at the same time, requires installation of
facilities exclusively for disposal of the waste gas
resulting from the vaporization of the solvent, for example.
Methacrylic resins using methyl methacrylate as a
main component possess excellent weatherability and
outstanding transparency and, therefore, have found utility
in applications to lampshades and automobile parts. These
methacrylic resins, however, are linear polymers and,
therefore, do not suit applications which demand relatively
high heat resistance, resistance to solvents, resistance to
shocks, and surface hardness. In terms of heat resistance,
~7~5~;~3
they cannot be used in applications requiring protracted
exposure to elevated temperatures exceeding 100C, such as
those to head lamp lens for automobiles, covers for solar
heat warmers, etc.
Heretofore, for the purpose of improving heat
resistance of methacrylic resins, there have been introduced
numerous methods such as, for example, a method which relies
on copolymerization to methyl methacrylate with ~ -methyl
styrene (US Patent No. 3,135,723), a method which resorts to
copolymerization of methyl methacrylate with ~ - methyl
styrene and maleic anhydride (Japanese Patent Publication
SHO 45(1970)-31,953 and Japanese Patent Publication SHO
49(1974)-10,156), and a method which adopts copolymerization
of methyl methacrylate with ~ - methyl styrene and maleimide
(Japanese Patent Laid-Open SHO 48(1973)-95,490).
Although these methods are invariably capable of
improving heat resistance, some of them suffer from notably
low rates of polymerization and fail to attain high ratios
of polymerization and some others, though capable of
producing polymers efficiently in relatively short spans of
time, suffer the produced polymers to assume colors strongly
and degrade in transparency, weatherability, surface
hardness, mechanical strength, etc.
It has been separately proposed to produce a
molded article using a gel polymer which is obtained by
partially cross-linking an alkyl methacrylate homopolymer or
syrup with a cross-linking agent (Japanese Patent Laid-Open
SHO 60(1985)-212,128). This method is capable of producing
a cross-linked molded article excelling in transparency and
heat resistance. When an abrasion resistant thin film is
applied on this molded article, there ensues a disadvantage
that this molded articles exhibits poor adhesiveness to the
abrasion resistant thin film. For effective application of
this film on the surface of the molded article, it becomes
necessary to enhance the adhesiveness of the film by
subjecting this molded articles to a complicated preparatory
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treatment as mentioned above.
An object of an aspect of this invention, therefore, is to
provide a molded article of methacrylic resin excelling in both abrasion
resistance and heat resistance, and more particularly a molded article
of methacrylic resin haviny a abrasion resistant thin film adhere fast
~ereto and enjoying high heat resistance.
An object of an aspect of this invention is to provide a
method for easy production of a molded article of the foreyoing description.
SUMMARY OF THE INVENTION
The objects described above are accomplished by a
molded article of methacrylic resin formed of a cross-linked
polymer having at least part of the surface thereof coated
with an abrasion resistant layer, produced by placing (A) an
abrasion resistant layer-forming material selected from the
group consisting of ta) cross-linked polymerizing compounds
having a molecular weight of not less than 150 and
containing at least two (meth)acryloyloxy groups per
molecule, (b) mixtures of at least 30~ by weight of the
cross-linked polymerizing compounds with other copoly-
merizable monomers, and (c) partial polymerization productsthereof, and possessed of a composition such that the
number, x, of the (meth)acryloyloxy groups of the cross-
linked polymerizing compound and the ratio of polymerization
y (~), of the abrasion resistant layer-forming material
satisfy the follwoing formula I or II:
y < 70 (2 ~ x < 3.5) (I)
Y <_7.SX2 + 52x - 18 (3.5 < x ~ 6) (II)
in contact with (B) a basic molding material made of an
acrylic partially cross-linked gel obtained by partially
polymerizing a mixture of (i) a resin material selected from
the group consisting of alkyl methacrylate monomers,
mixtures of alkyl methacrylates as main components with~ ,~
-ethylenically unsaturated monomers, and syrups containing
polymers thereof with (ii) 3 to 30 parts by weight, based on
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100 parts by weight of the resin material, of a cross-
linking agent and stopping the partial polymerization when
the gel content of the partial polymer reaches a level in
the range of 15 to 95% thereby allowing the gel consequently
produced to possess the property of retaining the
polymerization in a stopped state, and simultaneously
polymerizing the two materials held in mutual contact under
a condition capable of imparting a desired shape to the
combined materials.
These objects are further accomplished by a method
for the production of a molded article of methacrylic resin
formed of a cross-linked polymer having at least part of the
surface thereof coated with an abrasion resistant layer,
which method comprises placing (A) an abrasion resistant
layer-forming material selected from the group consisting of
(a) crosslinked polymerizing compounds having a molecular
weight of not less than 150 and containing at least two
(meth)acryloyoxy groups per molecule, (b) mixtures of at
least 30~ by weight of the cross-linked polymerizing
compounds with other copolymerizable monomers, and (c)
partial polymerization products thereof, and possessed of a
composition such that the number, x, of the (meth)-
acryloxyloxy groups of the cross~linked polymerizing
compound and the ratio of polymerization, y, (%), of the
abrasion resistant layer-forming material satisfy the
following formula (I) or (II):
Y ~ 70 (2 ~ x < 3-5) (I)
Y ~_7.5X2 + 52x - 18 (3.5 ~ x <6) (II)
in contact with (B) a basic molding material made of an
acrylic partially cross-linked gel obtained by partially
polymerizing a mixture of (i) a resin material selected form
the group consisting of alkyl methacrylate monomers,
mixtures of alkyl methacrylates as main components with ~ ,~
-ethylenically unsaturated monomers, and syrups containing
polymers thereof with (ii) 3 to 30 parts by weight, based on
100 parts by weight of the resin material, of a
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cross-linking agent and stopping the partial polymerization
when the gel content of the partial polymer reaches a level
in the range of 15 to 95% thereby allowing the gel
consequently produced to possess the property of retaining
the polymerization in a stopped state, and simultaneously
polymerizing the two materials held in mutual contact under
a condition capable of imparting a desired shape to the
combined materials.
B~IEF DESCRIP~ION OF THE DRAWING
The drawing is a graph showing the relation
between the time of exposure to ultraviolet light and the
difference of haze by the steel wool test, obtained by
molded articles produced in accordance with this invention,
articles produced by forming an abrasion resistant thin film
on the molded articles, and a commercially available
abrasion resistant plate.
DESCRIPTION OF PREFERRED EMBODIMENT
In the molding material (B) formed of an acrylic
partially cross-linked gel of the present invention, the
monomer to be used as the resin material (i) is an alkyl
methacrylate monomer or a mixture of an alkyl methacrylate
as a main component with a copolymerizable ~ , ~
-ethylenically unsaturated monomer. In the monomer mixture,
the proportion of alkyl methacrylate is not less than 50
mol%, preferably not less than 60 mol%. Typical examples of
alkyl methacrylate include methyl methacrylate, ethyl
methacrylate, n-propyl methacrylate, isopropyl methacrylate,
n-butyl methacrylate, sec-butyl methacrylate, tert-butyl
methacrylate, lauryl methacrylate, and cyclohexyl
methacrylate. One member or a mixtrue of a plurality of
members selected from the group mentioned can be used.
Among other alkyl methacrylates enumerated above, lower
alkyl methacrylates, particularly methyl methacrylate, prove
to be particularly desirable.
Example of the copolymerizable monomer include
alkyl acrylates such as methyl acrylate, ethyl acrylate,
~ ~7~573
propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate,
and lauryl acrylate, cyclohexyl acrylate, hydroxyalkyl
acrylates such as 2-hydroxyethyl acrylate, and hydroxyalkyl
methacrylates such as 2-hydroxyethyl methacrylate,
3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate,
and 2-hydroxy-3-chloropropyl methacrylate.
The aforementioned syrup containing the polymer of
an alkyl methacrylate or a monomer mixture having an alkyl
methacrylate as a main component thereof is a monomer which
possesses a viscosity in the range of 1 to 20,000 cps at
25C and contains 3 to 40% by weight, preferably 6 to 20~ by
weight, of the polymer.
The cross-linking agent (ii) to be used in the
present invention is desired to possess at least two (meth)-
acryloyl groups per molecule and contain not more than 10
atoms as interposed between the aforementioned (meth)-
acryloyl groups. Specifically, it is one of the compounds
represented by the following formulas III through V.
MA-O ~CH2 ~ O-MA (III)
wherein n stands for an integer of the value of 3 to 6 and
MA for a methacryloyl group.
Il 13
(M)A-O-CH2-C ~ CH- O-(M)A (IV)
wherein Rl stands for H, CH3, C2H5, or CH2OH, R2 for H, CH3,
R4
CH2OCOC = CH2 (wherein R4 stands for H or CH3), or CH2OH, R3
for H or CH3, providing that Rl, R2, and R3 do not
simultaneously stand for hydrogen, and (M)A stands for a
methacryloyl group or an acryloyl group, and
(M)AC--~CH2CH2Otn (M)A (V)
wherein n stands for an integer of the value of 1 or 2 and
~'~7~573
(M)A for a methacyloyl group or an acryloyl group.
As typical examples of the compounds, there can be
cited 1,3-propylene glyciol dimethacrylate, 1,4-butylene
glycol dimethacrylate, 1,6-hexanediol dimethacrylate,
1,3-butylene glycol dimethacrylate, dimethylol ethane
diemthacrylate, 1,1-dimethylol propane dimeth~crylate,
2,2-dimethy]ol propane dimethacrylate trimethylol ethane
tri(meth)acrylate, trimethylol propane tri(meth)acrylate,
tetramethylol methane tri(meth)acrylate, tetramethylol
methane dimethacrylate, ethylene glycol di(meth)acrylate,
and diethylene glycol glycol di(meth)acrylate.
The amount of the cross-linking agent to be
incorporated is in the range of 3 to 30 parts by weight,
prererable 10 to 25 parts by weight,based on 100 parts by
weight of the aforementioned resin material (i). If this
amount is less than 3 parts by weight, the heat resistance
is not sufficient. If the amount exceeds 30 parts by
weight, the polymrization disadvantageously is required to
be carried out for a long time and in addition say the
product shows inferior weatherability.
In the present invention, a polymerization
initiator is used when the partially cross-linked gel is
prepared and when the gel and the abrasion resistant layer-
forming material are brought into mutual contact and
subjected to poymerization in situ. This polymerization
initiator can be one member or a mixture of a plurality of
members selected from the group consisting of low
temperature-active polymerization initiators and high
temperature-active polymerization initiators. Generally, a
low temprature-active polymerization initiator is suitable
for the preparation of the partially cross-linked gel.
Among other low temperature-active polymerization
initiators, those whose decomposition temperatures for
obtaining a half-value period of 10 hours fall below 50C,
preferably in the range of 26 to 45C prove to be
particularly desirable. Radical polymerization initiators
_g _
. =
~L~ 7~ rj 73
of peroxides and azo compounds whose decomposition
temperatures fall in the range of 26 to 41C are preferred
selections.
The amount of the polymerization initiator to be
used is in the range of 0.002 to 1% by weight, preferably
0.005 to 0.1% by weight, based on the total amount of the
resin material (i) and the cross-linking agent(ii).
Examples of the low temperautre-active polymeriza-
tion initiator advantageously usable herein include (I)
acetylcyclohexylsulfonyl peroxide, isobutyryl peroxide,
cumyl peroxy-neodecanoate, diisopropyl peroxydicarbonate,
dimyristyl peroxydicarbonate, and 2,2'-azobis (4-methoxy-2,-
4-dimethyl valeronitrile), (II) di(2-ethoxyethyl)
peroxydicarbonate, di(methoxyisopropyl)peroxy dicarbonate,
and di(2-ethylhexyl) peroxydicarbonate, and (III)
di(3-methyl-3-methoxybutyl)peroxy dicarbonate, t-butyl-
peroxydecanoate, and 2,2'-azobis (2,4-dimethylvaleronitrile-
). In the low temperature-actlve polymerization initiators
enumerated above, the compounds belonging to the groups (I)
and (II) prove to be desirable and those belonging to the
group (I) prove to be particularly desirable.
High temperature-active polymerization initiators
are suitable for the polymerization to be carried out in the
present invention under molding conditions and, therefore,
are desired to possess decomposition temperatures in the
range of 60 to 220C, preferably 70 to 170C. The amount
of the high temperature-active polymerization initiator to
be used is desired to fall in the range of 0.02 to 5.0% by
weight, preferably 0.05 to 4% by weight, based on the total
amount of the resin material (i) and the cross-linking agent
(ii) .
Example of the high temperature-active polymeriza-
tion initiator advantageously usable herein include (IV)
t-butylcumyl peroxide, diisopropyl benzene hydroperoxide,
di-t-butyl peroxide, p-methane hydroperoxide, 1,1,3.3-
tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-
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dihydroperoxide, cumene hydroperoxide, t-butyl-hydroper-
oxide, and 1,1,2,2tetraphenyl-1,2-ethanediol, (V) l,l-bis
(t butylperoxyl)3,3,5-trimethyl cyclohexane, t-butyl-
peroxylaurate, cyclohexanone peroxide, t-butylperoxy-
isopropyl carbonate, 2,5-bis(t-butylperoxy)octane,
t-butylperoxy acetate, 2,2-bis (t-bitylperoxy)butane,
t-butylperoxy benzoate, di-t-butyldiperoxy isophthalate,
and methylethyl ketone peroxyde, and ~ , ~ '-bis(t-butyl-
peroxyisopropyl)-benzene, dicumylperoxide, and (VI) t-butyl
hydroperoxide, m-toluoyl peroxide, benzoyl peroxide,
t-butylperoxy isobutyrate, octanoyl peroxide, lawroyl
peroxide, succinic acid peroxide, acetyl peroxide, and
l,l'-azobis(cyclohexane-l-carbonitrile). In the high
temperature-active polymerization initiators enumerated
above, the compounds belonging to the groups IV and V prove
to be desirable and those belonging to the group IV prove to
be particularly desirable.
In the present invention, the partially cross-
linked gel is prepared by heating the mixture of the resin
material ~i) with the cross-linking agent (ii) in the
presence of the polymerization initiator thereby causing
polymerization thereof. This reaction of polymerization is
carried out at a temperature in the range of 10 to 80c,
preferably 35 to 65C, for a period in the range of 10 to
200 minutes, preferably 20 to 150 minutes. When the low
temperature active-polymerization initiator and the high
temperature-active polymerization initiator are used
simultaneously herein, the prior polymerization initiator is
consumed substantially wholly and the post polymerization
initiator remains in its undissolved state at the
aforementioned reaction temperature and, afterward, allowed
to function as a polymerization initiator under the
conditions of the subsequent molding operation.
The gel content of the partially cross-linked gel
is desried to be in the range of 15 to 95%, preferably 15 to
75%. If the gel content is less than 15%, the mixture being
t7X573
molded is liable to foam and the produced molded article to
sustain cracks or undergo deformation. If the gel content
exceeds 95%, the mixture being polymerized fails to show
good flowability.
The partially cross-linked gel having a desired
ratio of polymerization can be obtained by stopping the
reaction of polymerization by suddenly cooling the reaction
system undergoing the polymerization or by suitably
selecting the amount of the low temperature-active
polymerization initiator, the temperature of polymerization,
and the time of polymerization. This is accomplished more
readily by adding a specific regulating agent in a specific
amount to the mixture of the resin material (i) with the
cross-linking agent (ii) when it is to be thermally
polymerized in the presence of the aforementioned
polymerization initiator.
Examples of this specific regulating agent include
1,4~8)-p-menthadiene, 2,6-dimethyl-2,4,6-octatriene,
1,4-p-menthadiene, 1,4-cyclohexadiene, and ~ -methylstyrene
dimer.
The regulating agent of the foregoing description
can be used in an amount in the range of 0.0001 to 0.5~ by
weight, desirably 0.001 to 0.2% by weight, and most
desirably 0.005 to 0.1% by weight, based on the total amount
of the aforementioned resin mateial (i) and the cross-linked
polymerizing compound. If the amount of the regulating
agent to be added is less than 0.0001% by weight, the
desired effect of regulation cannot be manifested. If the
amount exceeds 0.5% by weight, the desired gel content of
the polymer cannot be attained.
Since the basic molding material is not viscous
and possesses the property of retaining the shape intact, it
can be handled in any desired form such as, for example,
sheet, rod, block, and pellets.
For the convenience of molding, for example, the
basic molding material may be dispersed or kneaded or, when
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necessary, may incorporate therein a coloring agent or some
other additive prior to being molded.
The abrasion resistant layer-forming material is a
cross-linked polymerizing compound possessing a molecular
weight exceeding 150, desirably falling in the range of 200
to 2,000, preferably in the range of 200 to 1,200 and
containing at least two acryloyloxy groups or methacryloy-
loxy groups, a mixture of not less than 30% by weight of the
compound with other copolymerizable monomer, or a partial
polymerization product thereof. The average number of
(meth)acryloyloxy groups in the cross-linked polymerizing
compound or the mixture thereof is desired to fall in the
range of 2.0 to 6.0, preferably 2.5 to 5.5. If this number
is less than 27 no sufficient abrasion resistance is
obtained. If the number exceeds 6.0, the reaction
sufficiently proceeds with difficulty and the product of the
polymerization possesses poor weatherability such as to
induce defective phenomena as yellowing and cracking.
The cross-linked polymerizing compound is such
that the residue linked to the acryloyloxy group or
methacryloyloxy group thereof is a hydrocarbon or a
derivative thereof. This compound may contain in the
molecular unit thereof an ether bond, a thioether bond, an
ester bond, an amide bond, or an urethane bond or may
possess an isocyanuric acid skeleton or a melamine skeleton.
Examples of the compound usable advantageously
herein include trimethylol propane triacrylate, 1,6-
hexanediol diacrylate, neopentyl glycol diacrylate, hydroxy-
bivalic acid neopentyl glycol diacrylate, dipentaerythritol
hexaacrylate, caprolactammodified dipentaerythritol
hexaacrylate, urethane acrylate, trisacryloxyl cyanurate,
(meth)acryloxy compounds possessing an isocyanuric acid
backbone, epoxyacrylate, and polyester acrylate.
As examples of the compounds, there can be cited
trimethylol propane triacrylate, 1,6-hexandiol diacrylate,
neopentilglycol diacrylate, hydroxy neopentilglycol
-13-
diacrylate pibariate, dipentaerythritol hexaacrylate,
caprolactam-mo-dified dipentaerythritol hexaacrylate,
urethaneacrylate, tris-acryloyl cyanurate, epoxyacrylate and
polyeter-acrylate.
As examples of the copolymerizable monomer usable
advantageously herein as mixed with the aforementioned
partialy cross-linked polymerizing compound, there may be
cited methyl methacrylate, tetrahydrofurfuryl acrylate,
ethylcarbitol acrylate, phenylcarbitol acrylate, hydroxy-
ethyl acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.
The abrasion resistant layer-forming material is
required to be such that the number, x, of the (meth)-
acryloyloxy group and the ratio of polymerization, y (~),
will satisfy the following formula I or II.
Y < 70 (2 < x < 3.5) (I)
y <_7~5X2 ~ 52x - 1~ (3.5 < x < 6) (II)
When this compound satisfies the condition, it
acquires sufficient adhesiveness relative to the basic
molding material.
This ratio of polymerization, y, is determined by
calculating the residual double bond content in percentage
from the peak height of the absorption band due to C=C
appearing near 4620 nm and then subtracting this percentage
from 100%.
Adjustment of this ratio of polymerization may be
effected by applying the abrasion resistant layer-forming
material on the mold and subjected in situ to polymerization
through the agency of heat or a photopolymerization
initiator before the basic molding material is introduced
into the mold or it may be polymerized in advance on the
surface of a plastic film.
In the present invention, the abrasion resistant
layer-forming material and the basic molding material formed
of the partially cross-linked gel are simultaneously
polymerized as held in a state of mutual contact. To be
more specific, the abrasion resistant layer-forming material
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~'~ 7 ~ 5~ 3
and the basic molding material are subjected to simultaneous
polymerization with at least part of the surface of the
latter material in contact with the former material so that
at least part of the surface of the molded article formed of
the cross-linked polymer produced from the basic molding
material will be coated with the polymer layer formed of the
abrasion resistant layer-forming material. This polymeriza-
tion is carried out under the conditions capable of
producing the molded article in a desired shape.
The molding can be carried out by (1) a method
which comprises applying the abrasion resistant layer-
forming material by suitable means such as spraying or
rolling on the mold of a press molding machine or an
injection molding machine heated to a temperature in the
range of 80 to 160C in advance, polymerizing the applied
layer of the material under the conditions falling in the
aforementioned ranges, then introducing the basic molding
material into the mold, and subjecting the introduced
material to polymerization in situ or (2) a method which
comprises applying the abrasion resistant layer-forming
material by suitable means such as spraying or rolling on
the surface of the basic molding material, introducing the
coated basic molding material into the mold of a press
molding machine heated to a temperature in the range of 80
to 160C in advance, and subjecting the introduced material
to molding in situ. If the ratio of elongation in this case
exceeds 72~, the molded article may possibly have both the
portion containing the abrasion resistant layer and the
portion containing no abrasion resistant layer.
Alternatively, the molding may be effected by (3)
a method which comprises applying the abrasion resistant
layerforming material on a film such as of synthetic resin,
polymerizing this material through the agency of ultraviolet
light or heat until a desired ratio of polymerization,
superposing the basic molding material on the partially
polymerized material, introducing the combined materials
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into the mold heated to a temperature in the range of 80 to
160C in advance, and subjecting them to molding in situ or
(4) a method which comprises introducing the basic molding
material into the mold heated to a temperature in the range
of 80 to 160C in advance, allowing this material to be
polymerized in situ partially to a prescribed ratio, opening
the mold, applying the abrasion resistant layer~forming
material by suitable means such as spraying on the surface
of the mold or on the surface of the partially polymerized
layer of the molding material or injecting the abrasion
resistant layer-forming material between the mold and the
partially polymerized layer of the molding material, then
closing the mold, and subjecting the combined materials to
molding in situ.
Thereafter, the molded article formed consequently
is subjected to post-polymerization at at temperature in the
range of 120 to 140C for a period of 3 to 12 hours for the
purpose of improving the heat resistance of the basic
molding material in the molded article.
As the initiator for the polymerization of the
abrasion resistant layer-forming material, the same low
temperature-active polymerization initiator and high
temperature-active polymerization initiator as used during
the preparation of the partially cross-linked gelled polymer
can be used. Alternatively, a photopolymerization initiator
may be used. Examples of the photopolymerization initiator
include l-hydroxycyclohexylphenyl ketone, benzyl dimethyl
ketal, benzophenone, Michler's ketone, benzoin, aceto-
phenone, 2-hydroxy2-methylphenyl-propane-1-on, 2,4-
diethlthioxanthone, and 4-chlorothioxanthone.
The amount of the low temperature-active
polymerization initiator to be incorporated is desired to
fall in the range of 0.5 to 3% by weight, preferably 1 to 2%
by weight, based on the amount of the cross-linked
polymerizing compound or the mixture thereof with a
copolymerizable monomer. If this amount is less than 0.5
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by weight, the polymerization of the abrasion resistant
layer is retarded and the abrasion resistant effect is not
obtained sufficiently. If the amount exceeds 3% by weight,
the abrasion resistant layer-forming material is set
polymerizing before it is uniformly applied on the mold and,
as the result, the layer consequently formed fails to
acquire smooth surface.
The amount of the high temperature-active
polymerization initiator -to be incorporated is desired to
fall in the range of 0.5 to 5% by weight, preferably 2 to 4%
by weight. If this amount is less than 0.5% by weight, the
polymerization is not sufficiently effec-ted within the
period of the molding and the formed abrasion resistant
layer exhibits the abrasion resistant property insufficient-
ly. If the amount exceeds 5% by weight, the formed abrasion
resistant layer is set too quickly to estabilish sufficient
adhesion between the basic molding material and the abrasion
resistant layer.
In the methods cited previously as available for
simultanesouly effecting the molding of the basic molding
material and the formation of the abrasion resistant layer,
the photopolymerization initiator is desired to be used in
the method of (l) or the method of (3) for the purpose of
reducing the time required for the molding. The amount of
this initiator to be incorporated is desired to be in the
range of 0.2 to 1.0% by weight, preEerably 0.3 to 0.6~ by
weight, though variable by the output of the lamp to be
adopted for the generation of ultraiolet light. If this
amount is less than 0.2% by weight, the formed layer fails
to acquire a smooth surface because of occurrence of fine
irregularities. If this amount exceeds 1.0% by weight, the
formed layer is set too quic~ly to establish sufficient
adhesion between this layer and the molding material.
For the purpose of coloring the molded article,
either the basic molding material may incorporate therein a
coloring material or the abrasion resistant layer-forming
-17-
~ X7~
material may inocorporate therein the coloring material.
Optionally, the abrasion resistant layer-forming
material may incorporate therein a leveling agent, an
ultraviolet absorbent, an antioxidant or other suitable
agent proof against degradation.
By the method of this invention, there can be
easily produced an acrylic resin product which excels in
wea-therability and heat resistance and possesses an abrasion
resistant layer enjoying highly satisfactory rigidity and
abrasion resistance and exhibiting very high adhesiveness to
acryl.
Now, the present invention will be described more
specifically below with reference to working examples.
Examples 1-3 and Control l
A mixture prepared by dissolving 0.08 g of 1,4(8)-
p-menthadiene, 0.05 g of cumylperoxy neodecanoate, and 2 g
of di-t-butyl peroxide each per kg in 80 parts by weight of
methyl methacrylate syrup containing 8% by weight of
polymethyl methacryalte having an average polymerization
degree of about 8,000 and 20 parts by weight of 2,2-
dimethylol propane dimethacryalte was poured into a cell
which had been formed by opposing two plate glasses 6 mm in
wall thickness and 450 x 350 mm in area across an
intervening space 10 mm in thicknèss and sealing the
intervening space with a gasket of vinyl chloride resinO
The cell thus filled to capacity with the mixture was
immersed in a constant temperature water bath heated in
advance to 50C and left standing therein for a varying
length of time, to obtain a partially cross-linked gel being
a mixture of monomer, homopolymer, crosslinking oligomer,
and crosslinking polymer, and possessing a varying
prescribed gel content. The gel content of the polymer was
determined by keeping a prescribed amount (10 to 15 g) of
the polymer in a finely cut form standing for 6 hours in
acetone for extraction and then vacuum drying the insoluble
residue of the extraction at 50C for 12 hours, finding the
-18-
-
~.~7~573
ratio of the weight of the insoluble residue to the weight
of the polymer before the test, and reporting this ratio in
percentage. From the partially cross-linked gel, a portion
200 x 180 mm in area was cut off. On the surface of the cut
portion of the polymer, an abrasion resistant layer-forming
material consisting of 70 parts by weight of
dipentaerysritol hexaacrylate, 15 parts by weight of
1,6-hexanediol diacryalte, 15 parts by weight of
tris-acryloyl cyanurate, and 10 parts by weight of methyl
methacryalte plus 2~ by weight of cumylperoxy neodecanoate
and 3% by weight of di-t-butylperoxy-hexahydroterephthalate
and having an average number of acryloyloxy groups of about
4.3 was applied bY spraying. The coated polymer was
immediately introduced in a positive mold 200 x 180 mm in
area heated to 130C and kept pressed therein for 10
minutes. Thus, the mold was opened and the molded product
was removed there form. In a hot air circulation drier,
this molded product was left polymerizing at 130C for 10
hours. It was then tested for tightness of adhesion, pencil
hardness, and taber abrasion respectively in accordance with
JIS Z 1522, JIS K 5400, and ASTM D 1044. Then, by the use
of a scratch tester made by Toyo Seiki Seisakusho, a wad of
steel wool, #000, pressed against the surface of the
abrasion resistant thin film of the molded product with
pressure of 100 g/cm2 was reciprocated 100 times at a
lateral speed of 16 mm/sec. In accordance with JIS K 7105,
the cloud value, i.e. the ratio of the diffuse transmittance
to the total light transmittance, was determined of the
surface before and after the scratch test and the difference
between the two haze values so obtained was reported as the
scratching ability of the steel wool relative to the
surface. The results of these tests were as shown in Table
1.
Examples 4-7 and Controls 2-3
A mixture prepared by dissolving 0.08 g of
1,4(8)-p-menthadiene, 0.05 g of cumyl peroxy neodecanoate,
--19--
~27~573
and 3 g of di-t-butyl peroxide each per kg in 80 parts by
weight of methyl methacryLate syrup containing 8% by weight
of polymethyl methacrylate having an average polymerization
degree of about 8,000 and 20 parts by weight of
2,2-diemthylolpropane dimethacrylate was poured into a cell
which was formed by opposing two plate glasses 6 mm in wall
thickness and 450 x 350 mm in area across an intervening
space 5 mm in thickness and sealing the intervening space
with a gasket of vinyl chloride resin. The cell thus filled
to capacity with the mixture was immersed in a constant
temperature water bath heated in advance to 50C and left
standing therein for 2.5 hours for polymerization of the
contained mixture and, then, removed from the bath. The
partially cross-linked gel consequently formed was subjected
to extraction in acetone and then tested for the gel content
by following the procedure of Examples 1-3. Thus, the gel
content was found to be 28~. From this partially
cross-linked gel, a portion of the same size as in Examples
1-3 was cut off. This portion of the polymer was placed in
the same mold heated in advance to 120C as in Examples 1-3.
AEtr a varying length of polymerization time, i.e. 0.5
minute, 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5
minutes, the mold was opened. The same abrasion resistant
layer-forming material as used in Examples 1-3 was applied
by spraying on the surface of the basic molding material in
process of polymerization and the mold was immediately
closed. The combined materials were kept pressed in the
mold for 20 minutes. Then, the molded product consequently
produced was removed from the mold. In a hot air
circulation drier, this molded product was left polymerizing
at 130C for 10 hours and then tested for scratching
property and tightness of adhesion by following the
procedure of Examples 1-3. The results were as shown in
Table 1. For the determination of the gel content of the
basic molding material, the portion of the partially cross-
linked gel remaining in the same cell was treated under the
-20-
~
~72573
same conditions in the same mold as those of the molding,
removed from the mold after a varying length of time, i.e.
0.5 minute, 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5
minute, and immediately immersed in liquefied nitrogen for
sudden cooling. A prescribed amount (10 to 15 g) of the
cooled polymer was subjected to acetone extraction by
following the procedure of Examples 1-3.
Examples 8-11 and Control ~
A mixture prepared by dissolving 0.08 g of 1,4(8)-
p-menthadiene, 0.03 g of 2,2'-azobis (4-methoxy-2,4-dimethyl
valeronitrile), 0.05 g of di-t-butyl peroxy-hexahydro-
terephthalate, 1 g of 2,2-bis(t-butylperoxy)butane, and 3 g
of di-t-butyl peroxide each per kg in 80 parts by weight of
methyl methacrylate syrup containing 4% by weight of
polymerthyl methacrylate having an average polymerization
degree of about 12,000 and 20 parts by weight of
2,2-dimethylolpropane dimethacrylate was poured into the
same cell as used in Examples 1-3. The cell thus filled to
capacity with the mixture was immersed in a constant
temperature water bath heated in advance to 50C and left
standing therein for 2.5 hours for polymerization of the
contained mixture. When the partially cross-linked gel
consequently obtained was subjected to acetone extraction by
~ollowing the procedure of Examples 1-3, the gel content
thereof was found to be 36~. Then, the abrasion resistant
layer-forming material of the same formula as used in
Example 1 was applied by spraying on the inner surface of
the cavity of the same mold as used in Example 1 heated in
advance to 130C and heated for polymerization for a varying
length of time, i.e. 0.5 minute, 1 minute, 5 minutes, 7
minutes, and 10 minutes. Then, on the partially polymerized
abrasion resistant material, the aforementioned partially
cross-linked gel was superposed. The mold was closed and
the combined materials were kept pressued for 10 minutes.
The molded product consequently obtained was removed from
the mold and subjected to post-polymerization at 130C for
~;~7~5t73
hours. The molded article was tested for abrasion
resistance and tightness of adhesion by following the
procedure of Example 1. The results were as shown in Table
1. For the determination of the ratio of polymerization of
the abrasion resistant layer, the abrasion resistant layer-
forming material was applied by the use of an applicator in
the same thickness, Ieft s-tanding for a varying length of
time, i.e. 0.5 minute, 1 minute, 5 minutes, 7 minutes, and
minutes, removed and suddenly cooled. The residual
double bond content of the resulting polymer was calculated
by the infrared ray method based on the peak height of the
absorption band due to C=C appearing near 1620 mm and
expressed in percentage. The ratio of polymerization was
then found by subtracting this percentage from 100%. The
results of these tests were as shown in Table 1. In the
same table, the results separately obtained by the same
extraction method as used in Examples 1-3 mere additionally
shown for comparison.
Examples 12-13
A mixture prepared by dissolving 0.04 g of
cumylperoxy neodecanoate and 2 g of di-t-butyl peroxide each
per kg in 80 parts by weight of methyl methacrylate
containing 4% by weight of polymethyl methacrylate having an
average polymerization degree of about 12,000 and 20 parts
by weight of 2,2-dimethylol propane dimethacrylate was
poured into the same cell as used in Example 4 and then
polymerized in a constant temperature water bath at 50C for
2 hours. The partially cross-linked gel consequently
obtained had a gel content of 74%. Then, by following the
procedure of Example 8, the abrasion resistant layer-forming
material of the same formula was applied on the inner
surface of the mold cavity and then left polymerizing for a
varying length of time, i.e. 1 minute and 7 minutes. A
portion 200 x 180 mm in area cut from the aforementioned
partially cross-linked gel was superposed on the consequent-
ly formed layer of the abrasion resistant material and
~ 7~
subjected to molding. Then, the molded product consequently
obtained was subjected to after-polymerization at 130C for
10 hours and tested for abrasion resistance and tightness of
adhesion by following the procedure of Example 1. The
results were as shown ln Table 1.
Example 14-15
An abrasion resistant layer-forming material of
the same formula as used in Example 1 was polymerized for a
varying length of time, i.e. 1 minute and 7 minutes by
following the procedure of Example 12. A portion 200 x 180
mm in area was cut from the partially cross-linked gel of
Example 1 was superposed on the partially polymerized
abrasion resistant material and kept pressed for 20 minutes,
to obtain a molded product. This molded product was
subjected to after-polymerization at 130C for 10 hours and
then tested for scratching property by following the
procedure of Example 1. The results were as shown in Table
1.
Example 16-19 and Control 5
An abrasion resistant layer-forming material
having an average number of acryloyloxy groups of about 3.3
was obtained by dissolving 2~ by weight of cumylperoxy
neodecanoate and 0.2% by weight of di-t-butylperoxyhexa-
hydrophthalate in 15 parts by weight of dipentacerythri-tol
hexaacrylate, 10 parts by weight of 1,6-hexanediol
diacrylate, 22.5 parts by weight of tris-acryloyl cyanurate,
and 5 parts by weight of methyl methacrylate. This abrasion
resistant layerforming material was applied in a thickness
of 45 to 50 ~ m on the surface of the same mold as used in
Example 1 heated in advance to 130C, then left standing in
situ for a varying length of time, i.e. 1 minute, 5 minutes,
10 minutes, 15 minutes, and 20 minutes. Then, the same
partially cross-linked gel as used in Example 8 and
thermally molded for 10 minutes. The resultant molded sheet
was subjected to 10 hours after polymerization at 130C and
tested for abrasion resistant by following the procedrue of
-23-
~ ~7~j73
Example 1. The results were as shown in Table 1.
Example 20-21 and Control 6
An abrasion resistant layer-forming material
prepared by dissolving 2% by weight of cumylperoxy
neodecanoate and 0.3~ by weight of di-t-butylperoxy-hexa-
hydroterephthalate in 100 parts by weight of dipentaery-
thritol hexaacrylate and having an average number of
acryloyloxy groups of 5.5 was applied by spraying in a
thickness of 45 to 50 ~m on the surface of the same mold as
used in Example 1 and heated in advance to 130C and left
standing thereon for a varying length of time, i.e. 0.5
minute, 1 minute, and 2 minutes. Then, the same partially
cross-linked gelled polymer as used in Example 8 was
superposed on the formed layer and su~jected to thermal
molding for 10 minutes. The molded product consequently
obtained was subjected to 10 hours' post-polymerization at
130C and tested for abrasion resistant by following the
procedure of Example 1. The results were as shown in Table
1.
Examples 22-23, and Control 7
On a polyethylene terephthalate film, an
ultraviolet light curring abrasion resistant layer-forming
material (produced by General Aniline and Film Company and
marketed under trademark designation of !lGAFGuADE-233ll) was
applied in a thickness of 45 to 50 ~ m with an applicator.
The coated surface of the film was irradaited for a varying
length of time, i.e. 6 minutes, 8 minutes, and 10 minutes,
with the light from two 50-W chemical lamps aprallelly
disposed at a height of 5 cm. The film and the same
partially crosslinked gel as obtained in Example 1 brought
into contact with the coated surface of the film were placed
in the same mold as used in Example 1, left setting under
pressure at 120C for 20 minutes, and subjected to 10 hours'
postpolymerization at 130C, and tested for abrasion
resistance by following the procedure of Example 1. The
results were as shown in Table 1.
:;
-24-
:: : ,
~ . ,
573
Control 8
A portion 200 x 180 mm in area cut fro~ the same
partially cross-linked gel as used in Example 8 was placed
in the same mold as used in Example l, kept pressed therein
for lO minutes, removed from the mold, and subjected to 10
hours' post-polymerization at 130C. The molded product
consequently obtained was tested for abrasion resistance by
following the procedure of Example 1. The results were as
shown in Table l.
Example 24
An abrasion resistant layer-forming material was
obtained by adding 0.5% by weight of 2-hydroxy-2-methyl-
phenylpropan-l-one to 75 parts by weight of dipentaery-
thritol hexaacrylate, 10 parts by weight of tris-acryloyl
cyanurate, 15 parts by weight of 1,6-hexanediol diacrylate,
and 5 parts by weight of methyl methacrylate. This abrasion
resistant layerforming material was applied by spraying in a
thickness of 25 to 30 ~ m on the inner surface of the same
mold as used in Example l heated in advance to 130C, and
irradiated with the light rom a high-pressure mercury-vapor
lamp having an output of 80 W/cm for five seconds. Then,
the basic molding material was superposed on the formed
layer and kept pressed for 10 minutes. The molded product
consequently obtained was removed from the mold and
subjected to lO hours' postpolymerization at 130C and
tested for abrasion resistance by following the procedure of
Example 1. The results were as shown in Table 1.
Example 25
~ mixture prepared by dissolving 0.1 g/kg of
1,~(8)p-menthadiene, 0.03 g/kg of 2,2'-azobis (4-methoxy-
2,4-dimethyl valeronitrile, 0.5 g/kg of di-t-butylperoxy-
hexahydroterephthalate, and 3 g/kg of di-t-butyl peroxide in
90 parts by weight of methyl methacrylate containing 8% by
weight of polymethyl methacrylate having an average
polymerization degree of about 20,000 and lO parts by weight
of 2,2-diemthylol propane dimethacrylate was polymerized by
-25-
~ ~ 7~ ~ ~3
following the procedure of Example 1 to obtain a partially
cross-linked gel having a gel content of 36%. Then, on the
same mold as used in Example l and heated in advance to
135C, an abrasion resistant layer-forming material prepared
by dissolving 1.0% by weight of benzoyl peroxide and 4.0 %
by weight of t-butylperoxyisopropyl carbonate in 40 parts by
weight of a caprolactam-modified dipentaerythritol
hexaacylate (produced by Nippon Kayaku Co., Ltd. and
marketed under product code of "DPCA-20"), 40 parts by
weight of tris-acryloyl cyanurate, 20 parts by weight of
1.6-hexanediol diacrylate, and 20 parts by weight of methyl
methacrylate was applied by spraying and thermally
polymerized for 45 seconds. The~, the aforementioned
partially cross-linked gel was superposed on the formed
layer and kept pressed for lO minutes. Then, the molded
product consequently obtained was removed from the mold and
subjected to lO hours' post-polymerization in a hot air
circulation drier at 120C. It was tested for abrasion
resistance and tightness of adhesion by following the
procedure of Exmaple 8. The results were as shown in Table
1.
Example 26
A mixture prepared by dissolving 0.08 g/kg of
1,4(8)-p-menthadiene, 0.05 g/kg of cumyl peroxy decanoate,
0.5 g of dibutylperoxyhexahydroterephthalate, l.0 g/kg of
2,2-bis~t-butylperoxy)butane and 3 g/kg of di-t-butyl
peroxide in 95 parts by weight of methyl methacrylate
containing 8% by weight of polymethyl methacrylate having an
average polymerization degree of about 20,000 and 5 parts by
weight of 2,2-diemthylol propane dimethacrylate was
polymerized for 2.5 hours by following the procedure of
Example l to obtain a partially cross-linked gel having a
gel content of 25~. Then, on the same mold as used in
Example 1 and heated in advance to 135C, an abrasion
resistant layer-forming material having the same formulation
as that of Example 25 was applied by spraying and thermally
-26-
~.~7~5'7;3
polymerized for 45 seconds. Then, the aforementioned
partially cross-linked gel was superposed on the formed
layer and kept pressed for 10 minutes, and the temperature
of the mold was decreased to 100C. Then, the molded
product consequently obtained was subjected to 10 hours'
post-polymerization in a hot air circulation drier at 115C.
It was tested for abrasion resistance and tightness of
adhesion by following the procedure of Example 8. The
results were as shown in Table 1.
Example 27
A mixture prepared by dissolving 0.1 g of 1,4(8)-
p-menthadiene, 0.03 g of 2,2'-azobis(~-methoxy-2,4dimethyl
valeronitrile), 0.5 g of di-t-butylperoxy-hexahydro-
terephthalate, 1 g of 2,2-bis (t butylperGxy)butane, and 3
g of di-t-butyl peroxide each pel kg in 75 parts by weight
of methyl methacrylate syrup containing 8% by weight of
polymethyl metahcrylate having an average polymerization
degree of about 20,000 and 25 parts by weight of
2,2-diemthylol propane dimethacrylate was polymerized by
following the procedure of Example 1 to obtain a partially
cross-linked gel having a gel content of 34~. Then, on the
same mold as used in Example 1 and heated in advance to 135
C, the same abrasion resistant layer-forming material as
used in Example 25 was applied by spraying and subjected to
thermal polymerization for 43 seconds. The molded product
consequently obtained was removed from the mold and
subjected to 10 hours' post-polymerization at 130C and
tested for abrasion resistance and tightness of adhesion by
following the procedure of Example 1. The polymerization
ratio o~ the abrasion layer-forming material was determined
by following the procedure of Example 8. The results were
as shown in Table 1.
Example 28
A portion having an area equal to the projected
surface area of the mold was cut from the partially cross-
linked gel obtained in Example 25 and having a gel content
-27-
~7~ra7~
of 36%, placed in the same mold as used in Example 1 heated
in advance to 130C, and kept pressed therein for 80
seconds. On the surface of the partially polymerized
material removed from the mold, the same abrasion resistant
layer-forming material as used in Example 25 was applied by
spraying. The mold was closed immediately on the combined
materials to keep them pressed for 10 minutes. The molded
product consequently formed therein was removed from the
mold and subjected to 10 hours' post-polymerization at 130C
in a hot air circulation drier. It was tested for abrasion
resistant and tightness of adhesion by following the
procedrue of Example 1. The gel content of the basic
molding material was determined by following the procedrue
of Example 4. The results were as shown in Table 1.
Control 9
The same partially cross-linked gel as obtained in
Example 8 was placed in the cavity of the same mold as used
in Example 1 and heated in advance to 130C and kept pressed
for 10 minutes in the closed mold. The molded polymer was
removed from the mold and irradiated with the light from a
high-pressure mercury vapor lamp (main wavelength 365 nm
having an output of 80 W/cm to a total dosage of 8.5 x 104
(wat.sec./m2) for the purpose of conferring adhesiveness
upon the molded polymer relative to the abrasion resistant
layer-forming material. Then, on the treated surface of the
polymer, the same abrasion resistant layer-forming material
as used in Example 1 was applied in a thickness of 10 to 20
~m by spraying and subjected to 10 hours' post-polymerization
at 130C to be simultaneously polymerized and solidified,
giving rise to an abrasion resistant layer. The results of
the tests conducted on the molded product were as shown in
Table 1.
Example 29
The shaped articles obtained in Example 21,
Example 9, and Control 9 and commercially available abrasion
; resistant plate were subjected to an ultraviolet light
-28-
~7'~5~3
acceleratd exposure test with a QUV weathering tester
produced by Toyo Seiki Seisakusho and marketed under
TM
produce code of " WCON") under the conditions of W 70C 8
hours 50C condensnation cycle. Then, the difference of
haze was found by the same steel wool test as used in
Example 1. By plotting the time of ultraviolet light
accelerated exposure vs. the difference of haze, there is
obtained a curve shown in the diagram.
-29-
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~:7~5~7~3
From the working examples cited above, Table 1
given above, and the drawing attached hereto, it is noted
that this invention permits production of molded articles
possessing highly desirable adhesiveness and abrasion
resistance and enjoying highly satisfactory heat resistance
thermal stability. To be more specific:
(1) Examples 1-7 and 28 and Controls 1-3 which regard
the gel content of basic molding material demonstrate that
the molded articles using molding materials whose gel
contents were less than 10~ and not less than 96~ suffered
from deformation and poor adhesion of coat, whereas the
other molded articles acquired highly satisfactory
adhesiveness and abrasion resistance on being molded.
(2) Examples ~-27 and Controls 4-7 which regard the
number, x, of acryloyl groups and the ratio of polymeriza-
tion of abrasion resistant layer-forming material
demonstrate -that when monomers having as a main component
thereof a crosslinked polymerizing compound containing at
least two acryloyloxy groups in the molecular unit or
partial polymers of such monomers were used and they had
compositions such that the numbers, x, of acryloyloxy groups
and the ratios of polymerization, y(%), of abrasion
resistant layer-forming materials satisfied the formula I or
formula II, the molded products consequently formed enjoyed
highly satisfactory adhesiveness and abrasion resistance on
being molded.
(3) As concerns the abrasion resistance to be
exhibited after the weatherability tes-t for determination of
durability, Fig. 1 shows that, in the molded articles of
working examples of this invention, the degradation in the
abrasion resistance as the function of time of exposure to
ultraviolet light were half of those observed in the
commercially available abrasion resistant plate and the
shaped article of control which was obtained by applying an
abrasion resistant thin film on a separately finished molded
article.
As described above, the present invention uses the
-32-
~ ~7;~5'7~
abrasion resistant layer-forming material which is made of a
monomer having as a main component thereof a cross-linked
polymerizing compound possessing a molecular weight of not
less than 150 and containing at least two (meth)acryloyloxy
groups per molecule or a partial polymer of the aforemen-
tioned monomer, possesses a composition such that the
number, x, of (meth)acryloyloxy groups and the ratio of
polymerization, y(%), satisfy the formula I or formula II,
and is capable of forming on the surface of a basic molding
material of excellent heat resistance, simultaneously with
the formation of the molding material in a prescribed shape,
an abrasion resistant layer. It, therefore, permits
production of a molded article of methacrylic resin which
enjoys highly satisfactory adhesiveness of the molding
material to the abrasion resistant layer and exhibits
outstanding abrasion resistance and possesses high heat
resistant such that the abrasion resistance is minimally
affected by exposure to natural conditions. Further, this
invention offers an advantage that the process of production
is simple because of simultaneous molding.
The molded articles obtained by this invention,
therefore, find utility in applications demanding weather-
ability, abrasion resistance, and heat resistance such as,
Eor example, in applications to head lamp lens and lamp
covers in automobiles, mèter covers in two-wheelers, and
covers for solar heat water warmers.
-33-
..
