Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE :INVENT_ON
1. Field of the Invention
This invention relates to a process for producing a
transparent molded article of a glass Eiber-reinforced resin
by using a resin syrup composed mainly of acrylic acid, an
acrylic acid ester, methacrylic acid, a methacrylic acid ester or
a mixture thereof, with methyl methacrylate being a typical
example thereof.
Molded articles of glass fiber-reinforced resins obtained
by impregnating glass fibers with a resin syrup composed mainly
of methyl methacrylate, and hardening the impregnated resin
syrup have frequently been utilized ~utdoors as sheet-lika molded
articles~ A technique is known to obtain a transparent molded
article of a glass fiber-reinforced resin by causing ~h~ refractive
index of the resin to correspond with that of the glass forming
the glass fibers. One method of this l:ype can be achieved by~
copolymerizing methyl methacrylate and a vinyl aromatic
hydrocarbon. A~ a result, the thus-obtained copolymer has a
refractive index ranging from 1.49 to 1~60~ and thus, it is
possible to adjust the refractive index of the copolymer to that
of the glass fibers, as described in, for example, R.B~ Beevers,
Trans. Faraday Soc., 58 1465 (1962). However, since the rate
of reaction of the vinyl aromatic hydrocarbon is slow, the
copolymerization of methyl methacrylate with the vinyl aromatic
hydrocarbon does not proceed easily, and a viscous solution for
glass fiber impregnation obtained by partially polymerizing
~hem (namely, a resin syrup) has a long hardening time. This
has been the defect in the method of producing glass fiber-
reinforced xesin products.
.,' ~
11 SUMMARY OF T~IE INVENTION
An object of this invention, therefore, is to provide
a process for producing glass fiber reinforced resin products
having superior mechanical properties within much shortened
periods of hardening without impairing the transparency o the
products.
Accordingly, thi~ invention provides a process for
producing a molded article of a glass fiber-reinforced resin,
which comprises dissolving about lO to about 50 parts by weight
of a copolymer of about lO to about 50% by weight of acrylo-
nitrile and about 90 to about 50% by weight of a vinyl aromatic
hydrocarbon in about 90 to about 50 parts by weight of a monomer -~:
.
selected from the group consisting of acrylic acid, acrylic
acid ester, methacrylic acid, methacrylic acid esters and mixtures
:
thereof to produce a resin syrup, impregnating glass fibers with
the rcsulting resin syrup, and thereafter hardening the
resin syrup with which the glass fibers have been impregnated.
DETAILED DESCRIPTIQN ~F THE INVENTION
According to the present invention, the correspondence
of the reEractive index of the resin with that of the glass
fibers can be achieved by use of the resin s~rup which is
obtained by dissol~ing a copolymer having a high refractive index
.
in a monomer selected fxom the group consisting of acrylic acid,
acrylic acid esters, methacrylic acid, methacrylic acid esters
and mixtures thereof. In addition; to harden -the resin syrup : ~:~
with which the glass fibers are impregnated within short periods ~ ;
of time, the process comprises using a so-called polymeric
syrup obtained by dissolving the copolymer in a monomer selected
from acrylic acid, acrylic acid esters~ methacrylic acid~
methacrylic acid esters and mixtures thereof. Since the copolymer
1 used at this time is an acrylonitrile-modified vinyl aromatic
hydrocarbon polymer of which a typical e~ample is an acrylonitrile/
styrene copolymer, the solubility parameter (calculated from the
small equation) of the polymer is made equal to, or larger than,
the soluhility parameter of the acrylic acid, the acrylic acid ester,
the methacrylic acid or the methacrylic acid ester. This
prevents a scattering of light caused by differences in the
refractive index due to a phase separation between the dissolved
polymer and the polymer obtained by polymerizing the monomer in
the resin syrup. Hence, transparent glass ~iber-reinforced resin
products can be obtained~
In order to produce resin molded products having
especially good transparency by the process of this invention,
it is necessary to use polymers having a calculated solubility
parameter, as described hereinabove r Of at least about 9.30.
It ha~ been confirmed, however, that a transparency of a degree
as is required for use in plastic panels used in green-houses
can be achieved also by polymers having a calculated solubility
parameter of about 9.25. The upper limit for the calculated
solubility parameker is not particularly limited, but when the
chain length of the acylonitxile unit in the copolymer is too
long, an intramolecular cyclization takes place in the hardeniny
step, which leads to problems in particle use.
The calculated solubility parameter of an acrylonitrile/
styrene copolymer, which is a typical example of the
acrylonitrile/vinyl aromatic hydrocarbon copolymer used in
this invention, is 9.25, 9.35 and 9 63, respectively, when the
acrylonitrile content therein is 10, 20 and 30% by weight. Thus,
the solubility parameter of the copolymer tends to increase as
the content of acrylonitrile increases.. A feasible transparency
can be sufficiently achieved when the acrylonitrile content is
about 10~ by weiyht.
-- 3 --
1 If the acrylonitrile content of the copolymer exceeds
about 50% by weight, the sequence of the chain length of the
acrylonitrile unit increases, and intramolecular cyclization occurs
in the harde~ing step performed after impregnating the glass
fibers with the resin syrup, thus impairing the transparency of
the final product. Moreover, the styrene content o~ the copol~mer
naturally decreases, and the refractive index of the polymer can
be adjusted only within a narrow range. Thus, it is dif~icult to
adjust the refractive index of the polymer when more than about 50%
10 hy weight acrylonitrile i5 used.
If the concentration of the acrylonitrile/vinyl aromatic
hydrocarbon copolymer in the resin syrup used in this invention -
is more than about 50~ by weight, the viscosity Qf the resin
syrup is high and the syrup is di~ficult to handle. Preparatlon
of a resin syrup which has too high a concentration should,
therefore, be avoided. In order, however, to adjust the
refractive index of the hardened resin product to near the
refractive index tl.51 to l.55) of the glass fibers and to~avoid
non-transparent glass fiber-reinforced resin products caused by
the difference between the refractive index of the glass fibers ànd
that of the resin impregnated therein9 the vinyl aromatic
hydrocarbon adde~ to àdjus~ the refractive index of the resin
syrup ~obtained by~dissolving an acrylonitrile/vinyl aromatic
hydrocarbon copolymer in acrylic acld, an acrylic acid ester~
methacrylic acid, a methacrylic acid ester or a mixture thereof)~
must be present in an amount of at least about 5~ by weight in the
resin syrup. It has been ascertained that in view of the amount
of the vinyl aromatic hydrocarbon required, the concentration of
the acrylonitrile/vinyl aromatic hydrocarbon copolymer in the
resin syrup should be at least about 10% by weight. It has been
found that, for example, a resin syrup obtained by dissolving an
acrylonitrile/styrene (50:50 monomer ratio by weight) copolymer
in a concentration o~ about 10% (the concentration of styrene
being about 5~ by weight~ in me-thyl methacrylate has a refractive
index of about 1.505, and that a gla5s fiber-reinforced resin
product obtained by using such a resin syrup has a transparency
which is feasible for practical applications such as for use as
plastic panels in greenhouses.
A xesin syrup of a 50% by weight solution (the highest
viscosity from the standpoint of handling the resin syrup, with
a suitable viscosity ranging from about 3 to about 7 poises at the
temperature of impregnation) of an acrylonitrile/styrene
(10:90 monomer ratio by weight) copolymer has a refractive index
of about 1.535, and a resin syrup composed of a 50% by weight
solution of an acrylonitrile/styrene ~50:50 monomer ratio by
weight) copolymer has a refractive index of about 1.516. Since
glass fibers having a relatively low refractive index near 10510
are used in the art as reinforcing materials for molded articles of
this kind, hardened resin products of a high refractive index of
the degree intended by the pre~ent invelltion can be obtained,
even i the amount of the vinyl aromatic hydrocarbon is confined
within a range where the handling of ~he resin syrup is easy,
namely even if the concentratlon of the acrylonitrile/vinyl ~ :-
aromatic hydrocarbon copolymer in the resin syrup is limited to .:
not more than about 50% by weight.
Suitable vinyl aromatic hydrocarbons which can be used
- in this invention are aromatic hydrocarbons in which one vinyl
group is directly bonded to the aromatic ring, and which is
copolymerizable with acrylonitrile. Suitable vinyl aromatic
3~ hydrocarbolls which can be used in -this invention include styrene,
vinyltoluene, Yinylxylene, ~-methylstyrene and the like.
-- 5 --
1 The monomer for dissolving the acrylonitrile/vi.nyl
aromatic hydrocarbon copolymer includes acrylic acid, ethyl
acrylate, hydroxyethyl acrylate~ methacrylic acid, butyl metha-
crylate and methyl methacrylate. These monomers can be used
either individually or as admixtures of two or more thereof. Of
these, methyl methacrylate is most suitable for practical
application.
As described above, according to this invention, glass
fibers are impregnated with a resin syrup obtained by dissolving
1~ about 10 to about 50 parts by weight of an acrylonitrile/vinyl
aromatic hydrocarbon copolymer of about lO to about 50~ by weigh-t
of acrylonitrile and about 90 -to about 50% by weight o a vinyl ~ -~
aromatic hydrocarbon in about 90 to about 50 parts of acrylic :: -
acid, acrylic acid esters, methacrylic acid, methacrylic acid
esters or a mixture thereof. Thus, the impregnated resin
includes the vinyl aromatic hydrocarbon in polymeric state, which
does not retard the ha.rdening of the resin syrup. Hencei the
rate of hardening of the resin syrup after the impregnation ca~ be
sùfficiently decreased as compared with the case of using a
conventional monomer-prepolymerized resin syrup. This greatly
increases the productivity o the process in commercial ~ ~
operations. . .:
Suitable glass fibers which can be used in this invention
are those of the so-called "chemical glass" including a
substantial amount of alkali metal oxides wi~h a relatively
low refractive index near 1.510. The strand of the glass fibers
which is used in this invention conkains about 200 filaments
having a fiber diameter of about 4.5 ~um and is cut into a size
of 2 inches for ease of handling.
The hardening time for the resin syrup with which the
~8~7~
glass fibers are lmpregnat~d can, of course, be shortened further
by using means generally used for promoting the hardening of
resins, for example, by increasing the reactivity of the resin
by adding a catalys-t such as benzoyl peroxide, acetyl peroxide and
t-butylperoxypivalate, which can be employed in a small amoun-t
to harden the resin syrup, to the composition or raising the
temperature to about 50 to about 80C, or by using a chain
transfer agent. The chain transfer agent used herein can reduce
the molecular weight of the resulting polymer, and as a result,
the viscosity of the resin syrup does not increase. Thus, it
is possible to prepare a syrup having a relatively low viscosity
which contains a high content of polymer. The hardening time can
be decreased still further by using a polyfunctional monomer
in combination therewith to promote a gel effect r and positively
perfoxming a three-dimensional cross-linking reaction. A
shorter hardening time is preferred.
Useful chain transfer agents which can be used in general
include alkyl mercaptans such as n-dodecyl mercaptan,
isopropyl mercaptan and n-butyl mercaptan, aryl mercaptans such
as thiophenol, thiocresol and thionaphtol and sulfur compounds
containing an active hydrogen such as thioglycolic acid and the
esters thereof. The effective amount of the chain transfer agent
is about 0.1 to 1.0 part by weight per 100 parts by weight of
monomer.
Examples of suitable polyfunctional monomers which
can be employed include ethylene glycol dimethacrylate, diethylene
glycol dimethacrylate, trimethylolpropane tri-methacrylate,
ethylene dimethacrylate, ethylene glycol diacrylate,
trimethylolethane triacrylate, 1,3-butylene dimethacrylate,
glycidyl methacrylate, tetrahydrofurEuryl methacrylate,
8~75
l divinylben2ene, -triallyl cyanurate and triallyl isocyanurate.
Of these compounds, 1,3-bu-tylene dimethacrylate, ethylene dimeth-
acrylate and trimethylol propane trimethacrylate are especially
effective. However, the use of such a polyfunctional monomer
as a cross-linking agent is not essential.
In the present invention, in dissolving the monomer
in the resin syrup of the above-described composition can be
partially polymerized by adding a small amount of a catalyst
such as benzoyl peroxide, azobisisobutyronitrile, etc~ The
polyfunctional monomer can be employed with equal results be~ore
or after the partial polymerization of the resin syrup.
When the amount of the polyfunctional monomer is up
to about 5% by weight, such promotes a shortening of the hardening
time depending on the amount thereof, and does not adversely
affect the mechanical characteristics of the hardened product.
If the amount of the polyfunctional monomer exceeds about 5~ ~ ;
by weight, the hardened product becomes brittle. Hence, it is
neaessary to restrict the amount of the polyfunctional monomer
within about S~ by weight based on the monomer used. Generally,
2~ when such a cross~linking agent is emp:Loyed in an amount of
about 5% by weight, the hardening time for the monomer-pre
pol~merized resin syrup, which is generally about 30 minutes in
the absence of such a cross-linking agent r can be shortened to ~ ,
about 20 to 22 minutes. It has been confirmed that the
hardening time for the polymeric syrup used in this invention,
under the same conditions, can be shortened to about 8 to lO `
minutes from about 16 minutes by using the polyfunctional monomer.
To obtain good mechanical strength in a glass fiber-
reinforced plastic panel produced in accordance with this
3~ invention, the glass fibers are generally employed in an amount
~r~2~5
1 of about 20 to 30 parts by weight based on 100 parts by weight of
the resin syrup.
The following experimental examples and comparative
~xperimental examples are given to illustrate in detail the
synthesis of the resin syrup which forms a basis for the dis-
covery of the process for producing glass fiber~reinforced resin
products in accordance with this invention, and the various
properties of the hardened products obtained by using 1 part by
weight of t-butylperoxypivalate~ as a polymerization
initiator, per 100 parts by weight of the resin syrup in com-
parison with the synthesis of a resin syrup using a conventional
method and the properties of the hardened product obtained by
curing the resin syrup. Unless otherwise indicated herein,
all parts, percents, ratios and the like are by weight.
In the experimental examples; comparative experimental
examples, example and comparative example given hereinafter,
the various properties described were measured using the
following methods.
Viscosity Averaqe Molecular Weiqht o ;~y~
Measured using an Ostwald capillary viscometer using
benzene (25C) as a solvent for the methyl methacrylate/styrenesystem and dimethyl formamide ~25C) as a solvent for the
methyl methacrylate/styrene/acrylonitrile system.
Polymerization Conversion
Measured by a precipitation method using acetone (good
solvent)-methanol (poor solvent).
Viscosity
Measured with a BM-type standard viscometer (a product
of Tokyo Keiki K.K.) using a No. 2 rotor at a speed of 30 rpm.
32~
1 Hardening Time -- -
, ~
The time required to harden ~cure) a mixture of 100 parts
of each of the resin syrups and 1 part of t-butylperoxy~ ~ -
pivalate was measured using a differential scanning calorimeter
(DSC, a product of Perkin-Elmer Company) at 65 C.
Transparenc~
Evaluated by visual observation with the naked eye.
Light Transmittance
1~ Transmittance of light at a wavelength of 350 m~ which
was measured using a double-beam spectrophotometer (a product
of Shimadzu Seisakusho K.K.).
Refractive Index
Measured at 25C using an Abbe refractometer (a product
of Shimadzu SeisàXusho K.K.).
Flexural Stren ~ ~ -
Measured with a tensile tester ~"Tènsilon", a product
of Toyo Baldwin Co., Ltd.) using a test piece having a width
2~ of 20 mm, a span of 50 mm and a thickness of 1 mm.
Tensile Stren~th
Measured with a tensile tester ("Tensilon") using a
dumbbell-shaped test piece having a width of 5 mm ~central
width of 3 mm), a length of 100 mm and a thickness of 1 mm.
Weatherability
A test sample was exposed to a weather-ometer (a product
of Suga Tester Co., Ltd.) for 400 hours, and then the change in
the colour of the sample was visually observed.
-- 10 --
7~i
1 Experimental Exam~le 1
In accordance with Run No. 1 shown in Table 1 below,
a monomeric mi~ture of 10 parts by weight of acrylonitrile
and 90 parts by weight of styrene, 0.1 part by weight of t-
butylperoxypivalate as a polymerization initiator and 0.6 part
by weight of n-dodecyl mercaptan as a chain transfer agen~ were
charged into a reactor, and reacted at 60C to product a pre-
copolymer of acrylonitrile and styrene having a viscosity
average molecular weight of 70,000.
To 25 parts by weight of the resulting prepolymer were
added 75 parts by weight of methyl methacrylate and 0.05
part by weight of azobisisobutyronitrile as a polymerization
initiator, and these materials were reacted in a reactor to
produce a resin syrup having a polymerization conversion of 31
to 33~ and a viscosity of 5.5 poises ~25C) for use in this
invention.
Then, t-butylperoxypivalate was added in an amount of
1 part hy weight per 1~0 parts by weight of the resin syrup~
The mixture was poured into a mold having the shape o~a flat
~ plate, and heated at about 65C;for 16 minutes to produce a
resin hardened produ~t having a thic]cness of about 1 mm.
Repetition of these procedures confirmed that the
curing of the resin syrup en~ed in 15 to 17 minutes.
The resulting resin hardened products were semi-
;
transparent but sufficiently transparent that they could beused as transparent plates in practical application. The product
had a light transmittance at 350 my o~ 82 to 83~, a refractive
index of 1.513, a flexural strength of 10 to 12 kg/mm~, and a
tensile strength of 5 to 7 k.g~mm .
The propOrtlonS of the monomers used to form resin syrups,
2~5
1 and the characteristics of the resin :hardened products in the
a~ove and subsequent experimental examples are summarized in
the following Table 1.
iO ~ .
:~0:
::
: ' ~ :
3~
- 12 -
7~ o
u~ o , , , o , o , ~ o o
~: :~, o ~ ~`1 1 1 1 o I I . o
U) ~o o ~ o ~ o o
a) a) ~ ~ ~ O
~: ~ ~ ~ o ~ ~ , , , 00 ~ O i ~D o o
,1 X O O ~ o ~1 o o , ~ o
~, W P~ X
~ a) 5~ o
a) P~ ~ I I o I o o I ~ o
.~ X ~ ~o a~ O I O ~
~ r~
5~
Q ~ o
~ Q) S~
c) ~ a) E~-- ' o
C~ ~ . ~ U~ o U~ o
E~ o - ~ I c~ I o o o ~ ~ o o
~ ~ ~ ~ ~; - I ~ I ~ ~7 I CO,~
~ ~0 ~o o o o
a~
,_, a~ U~ O
~ ~ O O ~ D o
W ~0 ~ O O O
. I ~ :
a)
''I ~ ~ ~ æ ~ O Z ~ o ~ o O
rrl a~
m ~ ~ ~0 U~~ O
o ~ :
^ ~ ~ ~ ~ I 1 r. II o I t9 o
~ 0
a) ~ a) a~ o
~ v ~ ~ N o o ~ 00 1 1 0 o~ O - ~ ~
~X ~ ~
a~ ~I s, ',3 : ,
~ ' O
t ~ o I I ~ D o o ~ '
O ~0 ~ '11'1 -1 I I C~l I I O C~
r ~ , 0
P
3 0 Q, ~ o ~ O
h N g ~ ~ h ~ r~ ~ o
~rl r{ ~ ~ ~ O C) -1 ~ O O ~rl
~ O o ~ ~ P ~ æ ~ ~ ~ ~ P 3
-- 13 --
r~ ~
.~ ~ ~ ~ o o c~o ~r Ll^) r-¦ ~-¦ .r ,q
,a)
r I ~ O O
.,, a)
,~ a) s:: ,i O ~ ~ N ~
X ~ ~ O 0~
C)
~er Ln In I O ~ r'~
l 1~ ~ I~ O I CO C;~
~i a)
~ r~ ~ ~ ~
E~ ~ ~C u~ o ~ I ~
20 ~ D
x
~i ~ r~ o I oo o h~ ri
,~, . '
~ ,, ` ~ 5 co 3 o r i B
bl 0~~ d~ In tq '
~ ~
i ~ ~ n~
~ ~ ~1 ~ 1
P. :~ O ~ U~ 1~
~, t, ~, v a) P:; o o E~
3 0 I:L td ~ ~ ~o ,~ E~ o ~ t:n
O >~ tD O ,i t S.l ri ri ri u~ tD @ o~O
,i ~ ,~ ,~ tn ~ ~1 ~ g,, O V ~ ~ ~ .~
C) tl) ~ Q O ~ ~ O O t~ Q
-- 14 --
r~
X I I Ci~ Lf)
'.
a)
Q~ I r-l
E~ I r~l 1
,~ ~ ~r l I
11~ X o~Lt')
~ r~
r r_
a) Q~ r~
Ql E~ Is ) r~
X ~ ~) ~ I
~ r~
r~
1~ r-~
5~ ~ r~
Q ~ O u~
C) ~ ,~ ~1 '
r-l c~3
r-l r-l rl
11~ O L l
r-l r l
~ a)
O r-¦ G~ t~
~: ~ O r~
C~) ~i r~
r~l r-l r-l ¦
1~ ~ ~) ~ r~
~ .~D ~1
~, a~
2 0 r j r J t~--
1~1 Id ~Y Il~ I I
X ~ r~
~ ~I r-l
rl
~ rl u7 1
X oIf'l
~--I r-l
X
a
rc~
a~
H ~1 a~
o ~ U~
3 0 aU~ .,~ ,~ . '.
t) ~ r~l
~rl
~1 0 S-l X Ul
a) ~ 4~ a) ~:
r,~ ~L) rl a)
~ O
.' P~ P~
- 15 -
1 Experimen-tal Examples 2 to 4
In Run Nos. 2 to 4 ln Table 1, a monomeric mixture
of acrylonitrile and styrene in the proportion indicated in
Table 1, 0~1 part by weight of t-butylperoxypivalate as a poly-
merization initiator and optionally 0.6 part by weight of n-
dodecyl mercaptan as a chain transfer agent were charged in-to a
reactor, and reacted at 60C to produce a pre-copolymer of
acrylonitrile/styrene.
To 25 parts by weight of the prepolymer were added
75 parts by weight of methyl methacrylate and optionally 0.05
part by weight of azobisisobutyronitrile as a polymerization
initiator~ These materials were reacted in a reactor, or allowed
to stand as a mixture. Resin syrups having the polymerization
conversions and viscosities shown in Table 1 were obtained.
Then, t-bu-tylperoxypivalate was added in an amount
of 1 part by weight per 100 parts by weight of the resin syrup,
and the mixture was poured into a mold having the shape of a
f1at plate, and heated at about 65C for each of the periods
indicated in Table 1 below to produce resin hardened products
having a thickness of a~sut 1 mm and very good transparency. -
In these examples, the use o~ a polyfunctional monomeras a cross-linking agent capable of shortening the hardening
time ~or resin syrups was omit-ted. ~owever,as described
hereinabove r the joint use of a suitable amount of a poly- -
functional monomer can reduce the hardening time (16 to 19
minutes) for the resin syrups to about 8 to 10 minutes.
Table 1 shows that the mechanical strength character-
istics of the hardened products obtained from the resin syrups
used in this invention are somewhat better than those of
hardened products obtained in the comparative experimental
- 16 -
~ 9
1 examples (conventional method) to be given hereinbelow, and
that whe~ the hardened products are in the form o a plate, the
plates are flexible and thus pliable when bent. Because of this
characteristic, plastic panels for greenhouses, which are one
important use of plate-like products of this kind outdoors, can
be designed with a curvature, and the insertion or fitting
operation of the plate-like product by bending the product is
made possible. Accordingly, the glass fiber-reinforced resin
products obtained by the present invention have very good utility
10 in commercial applications.
Comparative Experimental Examples 1 to 3
In Run Nos. 5 to 7 shown in Table l, ~ monomeric :
mixture of methyl methacrylate and each of the vinyl aromatic
hydrocarbons indicated in Table l, in the proportions .
indicated, 0.05 part by weight of azobisisobutyronitrile as a
polymerization initiator and 0.6 part by weight o n-dodecyl
mercaptan as a chain transfer agent were charged into a reactor,
and reacted at 80& to produce a monomeric syrup having a
viscosity average molecular weight of 50,000.
Then, t~butylperoxypivalate was added in an amount
of l part by weight per lO0 part3 by weight o~ the monomex-
prepolymerized resin syrup. The mixture was poured into a mold
having the shape of a flat plate in the same manner as in
Experimental Examples l to 4, and heated at about 65C to
produce resin hardened products having a thickness of about 1 mm.
As indicated in Table l below, the required hardening time was
more than 30 minutes in all of the runs. The flexural strengths
and tensile strengths of these products were inferior to those
of the products obtained in Experimental Examples l to 4.
- 17 -
1 Comparative Experimental Examples 4 and 5
In Run Nos. 8 and 9 in Table 1, a prepolymer of
styrene was prepared, and mixed with methyl methacrylate in
the proportions shown in Table 1 . The mixture was
optionally heated in a reactor and resin syrups were obtained.
Then, t-butylperoxypivalate was added in an amount of 1 part
by weight per 100 parts by weight of each resin syrup. The
mixture was poured into a mold having the shape of a flat
plate, and heated at about 65C to produce resin hardened
products having a thickness of about 1 mm.
As can be seen from the results in Table 1, the required
hardening time could be shortened to about 15 to 20 minutes.
However, the resulting resin hardened products all had white
cloudy areas therein, and the transparent products intended by
the invention could not be formed.
Glass fibers were impregnated with the same resin
syrups as produced in Experimental Example 2 and Comparative
Experimental Example 1 to obtain resin hardened products.
The time re~uired to cure the resin syrup and the properties of
the resulting glass fiber-reinforced resin products are
described in the following examples.
~ E_e
1 part by weight of t-butylperoxypivalate was added
to 100 parts by weight o~ the same resin s~rup as obtained in
Experimental Example 2 (MMA 75 : ST 20 : AN 5). After thorough
mixing, the mixture was used to impregnate a 2-inch chopped
strand of chemical glass fibers having a refractive index of
1.517 with the weight ratio o~ the glass to the resin syrup
being maintained at 1 : 4. By using a spacer to obtain a plastic
plate having a uniform thickness of 1 mm, the impregnated glass
- 18 -
7~;i
1 fibers were heated at 65C for 17 minu-tes to cure the resin.
Post-curing was subsequently performed at 120C for 5 minutes
to produce a glass fiber-reinforced resin plate.
The characteristics of the resulting resin plate
are shown in Table 2.
Comparative Example
1 part by weight of t-butylperoxypivalate was added
to 100 parts by weight of the same monomeric syrup (MMA 80 ~ 5T
20j as obtained in Comparative Experimental Example 1, and the
materials were thoroughly mixed. The mixture was used to
impregnate a 2-inch chopped stra~d of chemical glass fibers
with the weight ratio o~ the glass to ~he resin syrup being
maintained at 1 : 4. While bein~ pressed with a spacer
having a thickness of 1 mm, the impregnated glass fibers were
~eated at 65C. More than about 34 minutes were required to
cure the resin. Post-curing was performed at 120C for 5 minutes
to produce a glass ~iber-reinforced resin plate having the
characteristics shown in Table 2 below.
T~BLE 2
Molded Plate
Characteristics of Comparative
Molded Plate Exam~l~ Example
Transparency Excellent Excellent
Light Transmittance82-83 82-83
at 350 m~
WeatherabilityNo discolourationNo discolouration
Flexural Strength
(kg/mm2) 13-15 12-14
Tens~le Strength 8-9 7-9
(kg/mm )
-- 19 --
-
32~i
While the invention has been described in detail and
with reference to specific embodiments thereof, it will be
apparent to one skilled in the art that various changes and
modifications can be made therein without departing from:the ,-
spirit and scope thereof.
1~ '
3~
20 -
