An impact-resistant methacrylic resin composition comprising a multilayer structure methacrylic resin [II] is provided. The resin [II] is obtained by the following sequential four polymerization stages (i) through (iv): PA0 (i) forming 5-50 wt. parts of a hard crosslinked resin (A) containing at least 80 wt. % of methyl methacrylate units; PA0 (ii) obtaining 100 wt. parts of a multilayer structure acrylic elastomer [I] by forming on the periphery of resin (A) 95-50 wt. parts of a crosslinked acrylic acid ester copolymer (B) by polymerizing a monomer mixture comprising 69.9-89.9 wt. % of at least one alkyl (C.sub.1-8) acrylate, 10-30 wt. % of styrene or a mixture of styrene and a derivative thereof and 0.1-10 wt. % of ##STR1## (iii) forming on the periphery of elastomer [I] 5-100 wt. parts of a hard crosslinked resin (C) by polymerizing a crosslinkable monomer mixture comprising 80-99.9 wt. % of methyl methacrylate, 0-19.9 wt. % of at least one alkyl (C.sub.1-8) acrylate, 0-10 wt. % of other copolymerizable vinyl monomer and 0.1-10 wt. % of a copolymerizable polyfunctional monomer having at least two C--C double bonds in the molecule; and then PA0 (iv) forming on the periphery of resin (C) 5-1000 wt. parts of a hard non-crosslinked resin (D) by polymerizing a non-crosslinkable monomer or non-crosslinkable monomer mixture comprising 80-100 wt. % of methyl methacrylate, 0-20 wt. % of at least one alkyl (C.sub.1-8) acrylate and 0-10 wt. % of another copolymerizable vinyl monomer, the resin (D)/resin (C) weight ratio being from 0.5 to 200. The resin [II] may be blended with a methacrylic resin [III] formed by polymerizing 80-100 wt. % of methyl methacrylate and 0-20 wt. % of a vinyl or vinylidene monomer in such a proportion that the content of the acrylic elastomer [I] is 1-70 wt. % based on the total composition.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to an impact-resistant methacrylic resin composition 
excellent in surface appearance and transparency. 
(2) Description of the Prior Art 
A methacrylic polymer resin composed mainly of methyl methacrylate has such 
characteristics as a beautiful appearance, excellent transparency, high 
weather resistance and good fabricability and is widely used in various 
fields as cast sheets, extrusion-molded articles and injection-molded 
articles. However, this resin is hard and brittle. Several methods have 
heretofore been proposed to eliminate this defect, but no method for 
eliminating the brittleness without sacrificing the characteristics of the 
methacrylic resin has yet been realized. 
The most popular and effective method for overcoming the defect of 
brittleness of a methacrylic resin and imparting an impact resistance 
thereto comprises dispersing particles of an elastomer, which is rubbery 
at normal temperature, discontinuously in a continuous phase of a 
methacrylic resin. As the rubbery elastomer, there are used an unsaturated 
rubbery elastomer composed mainly of butadiene, and a saturated rubbery 
elastomer, such as an acrylic acid ester polymer, composed mainly of butyl 
acrylate, 2-ethylhexyl acrylate or other acrylates and an ethylene/vinyl 
acetate copolymer. An unsaturated rubber elastomer has the problem of poor 
weather resistance due to unsaturated double bonds present in the main 
polymer chain. A saturated rubbery elastomer has the problems of, for 
example, poor modulus of elasticity and elastic recovery of the rubber 
component per se and poor graft-polymerizability with a hard resin 
component, therefore insufficient impact resistance and degraded 
transparency and surface gloss. Furthermore, the surface appearance is not 
satisfactory because of flow mark. 
Important factors in preparing an impact-resistant resin composition of the 
above-mentioned two-component type comprising a discontinuous phase of 
rubbery elastomer particles homogeneously dispersed in a continuous phase 
of a hard resin such as a methacrylic resin are the particle size of the 
rubbery elastomer, the crosslinking degree of the rubber elastomer, the 
graft polymerizability of the hard resin phase to the rubber phase and the 
molecular weight of the hard resin phase. In fact, the relative 
superiority and balance of the resin characteristics are greatly 
influenced by these factors. Among these factors, the crosslinking degree 
of the rubber phase, the graft polymerizability of the hard resin to the 
rubber phase and the molecular weight of the hard resin phase are 
especially important. 
As the crosslinking degree of the rubbery elastomer is high, the surface 
appearance characteristics such as the surface gloss and prevention of 
flow marks are improved, but the impact resistance is degraded. 
The graft polymerizability of the hard resin phase to the rubber phase 
greatly influences the compatibility and dispersibility of the rubbery 
elastomer with the continuous resin phase. The impact resistance, 
transparency, stress-whitening resistance, surface gloss and flow 
processability are greatly influenced by this graft polymerizability. When 
a saturated rubbery elastomer is used, the graft polymerizability is 
ordinarily low, and special care should be taken. It has recently been 
proposed that a specific polyfunctional monomer called a "copolymerizable 
grafting monomer" be used in the polymerization for formation of an 
acrylic elastomer. This monomer, however, is used as a crosslinking agent 
in a broad sense and no complete improvement can be obtained. 
A higher molecular weight of the hard resin phase is effective for 
improving the impact resistance but causes degradation of surface 
appearance and fabricability. 
As is apparent from the foregoing description, the factors behave 
independently, and it is very difficult to set the general properties of 
an impact-resistant resin composition with a good balance. Thus, an 
impact-resistant methacrylic resin comparable to an unmodified methacrylic 
resin in transparency, surface appearance, and fabricability has not been 
developed. 
In connection with an impact-resistant resin composition or 
impact-resistant methacrylic resin composition comprising an acrylic acid 
ester elastomer as the rubber phase, which is excellent in weather 
resistance, there has recently been proposed a method in which a hard 
resin is included in the interiors of rubber particles so as to improve 
the impact resistance-manifesting effect of the rubber phase, the 
transparency and stress-whitening resistance of the shaped article, and 
the pearl-like gloss due to deformation of the rubber particles (see 
Japanese Examined Patent Publication No. 52-30996, Japanese Unexamined 
Patent Publication No. 48-55233, U.S. Pat. No. 3,661,994 and U.S. Pat. No. 
3,793,402). Indeed, the intended effects can be attained to some extent 
according to this method, but the resulting resin composition is still 
inferior to an unmodified methacrylic resin in transparency and surface 
appearance. 
SUMMARY OF THE INVENTION 
Under the above-mentioned background, it is a primary object of the present 
invention to provide a methacrylic resin composition having a high impact 
resistance without impairing such inherent properties of the methacrylic 
resin as high transparency, excellent surface appearance and good weather 
resistance. 
This object can be attained when (i) a crosslinkable monomer having a 
special structure is used as a comonomer component at the polymerizing 
step for forming an acrylic acid ester elastomer containing in the 
interiors of particles thereof a hard crosslinked resin composed mainly of 
methyl methacrylate, (ii) at the step of grafting a hard resin composed 
mainly of methyl methacrylate to the resulting elastomer, the monomer 
component for this hard resin is divided into two portions, one portion 
initially polymerized while being crosslinked and the remaining portion 
being polymerized into a non-crosslinked hard resin, and (iii) the ratio 
of the crosslinked graft-polymerized portion to the non-crosslinked 
graft-polymerized portion is adjusted within a specific range. 
More specifically, in accordance with one aspect of the present invention, 
there is provided an impact-resistant methacrylic resin composition 
comprising a multilayer structure methacrylic resin composition [II] 
obtained by the following sequential four polymerization stages (i) 
through (iv): 
(i) the first stage of forming 5 to 50 parts by weight of a hard 
crosslinked resin (A) containing at least 80% by weight of methyl 
methacrylate units; 
(ii) the second stage of obtaining 100 parts by weight of a multilayer 
structure acrylic elastomer [I] by forming on the periphery of the hard 
crosslinked resin (A) 95 to 50 parts by weight of a layer of a crosslinked 
acrylic acid ester copolymer (B) by polymerizing a monomer mixture 
comprising 69.9 to 89.9% by weight of at least one alkyl acrylate having 1 
to 8 carbon atoms in the alkyl group, 10 to 30% by weight of styrene or a 
mixture of styrene and a derivative thereof and 0.1 to 10% by weight of at 
least one compound selected from the group consisting of a compound of the 
formula 
##STR2## 
and a compound of the formula 
##STR3## 
(iii) the third stage of forming on the periphery of the elastomer [I] 5 to 
10 parts by weight of a layer of a hard crosslinked resin (C) by 
polymerizing a crosslinkable monomer mixture comprising 80 to 99.9% by 
weight of methyl methacrylate, 0 to 19.9% by weight of at least one alkyl 
acrylate having 1 to 8 carbon atoms in the alkyl group, 0 to 10% by weight 
of an other copolymerizable vinyl monomer and 0.1 to 10% by weight of a 
copolymerizable polyfunctional monomer having at least two 
carbon-to-carbon unsaturated bonds in the molecule; and 
(iv) the fourth stages of forming on the periphery of the resin (C) 5 to 
1000 parts by weight of a layer of a hard non-cross-linked resin (D) by 
polymerizing a non-crosslinkable monomer or non-crosslinkable monomer 
mixture comprising 80 to 100% by weight of methyl methacrylate, 0 to 20% 
by weight of at least one alkyl acrylate having 1 to 8 carbon atoms in the 
alkyl group and 0 to 10% by weight of other copolymerizable vinyl, the 
resin (D)/resin (C) weight ratio being in the range of from 0.5 to 200. 
In accordance with another aspect of the present invention, there is 
provided an impact-resistant methacrylic resin composition comprising the 
above-mentioned multilayer structure methacrylic resin composition [II] 
and a methacrylic resin [III] formed by polymerizing 80 to 100% by weight 
of methyl methacrylate and 0 to 20% by weight of a vinyl or vinylidene 
monomer, wherein the content of the multilayer structure acrylic elastomer 
[I] is 1 to 70% by weight based on the total composition. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
One important feature of the present invention is that, as described 
hereinbefore, in the polymerization for forming a crosslinked acrylic acid 
ester copolymer having in the interior thereof a core of a hard 
crosslinked resin, a compound having a special structure defined by the 
formula (1) or (2) is used as a crosslinking agent and the polymerization 
is carried out in the specified sequential four stages to obtain a polymer 
having a multilayer structure. 
The process per se for the preparation of the resin composition of the 
present invention is not particularly critical, but it is preferable to 
adopt the emulsion polymerization process. 
In performing the preparation of the resin composition of the present 
invention, in order to impart a good transparency to the obtained resin 
composition, the refractive indexes of the resin phases obtained in the 
respective polymerization stages should be made equal or as close as 
possible to one another. 
In order to obtain a good balance among transparency, surface appearance 
and impact resistance-manifesting effect in the resin composition of the 
present invention, the particle size of the rubbery elastomer to be 
dispersed should be taken into consideration. In order to obtain a 
composition excellent in both transparency and impact resistance, the 
particle size of the rubbery elastome should be 0.13 to 0.45 .mu.m, 
preferably 0.2 to 0.35 .mu.m, when the polymerization for formation of the 
crosslinked acrylic acid ester copolymer (B) is substantially completed 
whereby the two-layer structure acrylic elastomer [I] is obtained. 
The multilayer structure acrylic elastomer [I] of the present invention has 
in the interiors of particles thereof a hard crosslinked resin (A) 
comprising at least 80% by weight of methyl methacrylate units and also 
has in the external layers of particles a crosslinked acrylic acid ester 
copolymer (B). 
The hard crosslinked resin (A) referred to in the present invention is a 
copolymer obtained by polymerizing a monomer mixture comprised of (i) 100 
parts by weight of methyl methacrylate or a monomer mixture comprising at 
least 80% by weight of methyl methacrylate and up to 20% by weight of 
other copolymerizable vinyl monomer and (ii) 0.1 to 10 parts by weight, 
preferably 0.5 to 5 parts by weight, of a crosslinking monomer. This hard 
crosslinked resin (A) occupies 5 to 50 parts by weight, preferably 10 to 
40 parts by weight, in 100 parts by weight of the multilayer structure 
acrylic elastomer [I]. If the amount of the hard crosslinked resin (A) is 
smaller than 5 parts by weight, the impact resistance-manifesting effect 
is poor and the transparency is degraded. In contrast, if the amount of 
the resin (A) exceeds 50 parts by weight, the surface gloss is reduced and 
the impact resistance is degraded. 
As the vinyl monomer copolymerizable with methyl methacrylate that is used 
for the formation of the hard crosslinked resin (A), styrene, 
acrylonitrile and alkyl acrylates having 1 to 8 carbon atoms in the alkyl 
group can be mentioned. 
Any crosslinking monomer copolymerizable with methyl methacrylate can be 
used for the formation of the hard crosslinked resin (A). For example, 
there can be mentioned bifunctional monomers such as ethylene glycol 
dimethacrylate, ethylene glycol diacrylate, 1,3-butylene dimethacrylate 
and tetraethylene glycol diacrylate; trifunctional monomers such as 
trimethylolpropane triacrylate, triallyl cyanurate and triallyl 
isocyanurate; and tetrafunctional monomers such as pentaerythritol 
tetraacrylate. These monomers may be used either alone or in combination. 
The crosslinked acrylic acid ester copolymer (B) is a copolymer obtained by 
polymerizing a monomer mixture comprising 69.9 to 89.9% by weight of at 
least one alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, 
preferably n-butyl acrylate or 2-ethylhexyl acrylate, 10 to 30% by weight 
of styrene or a mixture of styrene and a derivative thereof and 0.1 to 10% 
by weight of at least one member selected from a compound of the formula 
##STR4## 
(allyl sorbate; hereinafter referred to as "ASV") and a compound of the 
formula 
##STR5## 
(allyl cinnamate; hereinafter referred to as "ACM"). The monomer mixture 
is polymerized in an amount of 95 to 50 parts by weight in the presence of 
5 to 50 parts by weight of the hard crosslinked resin (A) to form an 
external layer on the resin (A). The proportions of the acrylic ester 
monomer and styrene or the mixture of styrene and a derivative thereof in 
the monomer mixture are important for imparting good transparency to the 
resulting resin composition. If the proportions are outside the above 
ranges, the transparency is degraded. The use of the compound of the 
formula (1) or (2) is one of most important factors in the present 
invention. If the compound of the formula (1) or (2) is not used, the 
intended object of the present invention cannot be attained. The function 
of the compound of the formula (1) or (2) cannot completely been 
elucidated, but it is construed that if the compound of the formula (1) or 
(2) is used, the crosslinking degree of the crosslinked acrylic acid ester 
copolymer and the grafting degree of methyl methacrylate are controlled 
with a good balance. The compound of the formula (1) or (2) is used in an 
amount of 0.1 to 10% by weight, preferably 0.3 to 5.0% by weight, though 
the appropriate amount varies depending upon whether these compounds of 
the formulae (1) and (2) are used in combination or alone. In addition to 
the compound of the formula (1) or (2), a conventional polyfunctional 
monomer can be used in an amount of up to 9% by weight. The type of the 
polyfunctional monomer is not particularly critical, but any customary 
polyfunctional monomer may be used. For example, ethylene glycol 
diacrylate, ethylene glycol dimethacrylate, 1,3-butylene diacrylate, 
1,3-butylene dimethacrylate, tetraethylene glycol diacrylate, 
tetraethylene glycol dimethacrylate and divinyl benzene can be mentioned. 
A crosslinkable monomer mixture is polymerized in the presence of the 
multilayer structure acrylic elastomer [I] to form the hard crosslinked 
resin (C). This crosslinkable monomer mixture comprises 80 to 99.9% by 
weight of methyl methacrylate, 0 to 19.9% by weight of at least one alkyl 
acrylate having 1 to 8 carbon atoms in the alkyl group, 0 to 10% by weight 
of other vinyl monomer copolymerizable with the monomers and 0.1 to 10% by 
weight of a copolymerizable polyfunctional monomer having at least two 
carbon-to-carbon double bonds in the molecule. 
If the content of methyl methacrylate in the monomer mixture is lower than 
80% by weight, the transparency, heat resistance and weather resistance 
are degraded. As the alkyl acrylate copolymerizable with methyl 
methacrylate, methyl acrylate, ethyl acrylate and butyl acrylate can be 
mentioned. As the other vinyl monomer that can be used as the comonomer, 
there can be mentioned styrene, acrylonitrile and methacrylic acid. 
If the amount of the acrylic acid ester in the crosslinkable monomer 
mixture is larger than 19.9% by weight, the heat resistance and 
transparency of the final composition are poor. If the amount of the other 
copolymerizable vinyl monomer is larger than 10% by weight, the 
transparency, weather resistance and water resistance are degraded. 
The copolymerizable polyfunctional monomers having at least two 
carbon-to-carbon double bonds in the molecule, which are an indispensible 
component of the crosslinkable monomer mixture, include, for example, 
ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-butylene 
dimethacrylate, tetraethylene glycol diacrylate, trimethylolpropane 
triacrylate, triallyl cyanurate, triallyl isocyanurate and pentaerythritol 
tetraacrylate. These polyfunctional monomers may be used either alone or 
in combination. If the amount of the polyfunctional monomer used is 
smaller than 0.1% by weight, the stress-whitening resistance and surface 
appearance are degraded. If the amount of the polyfunctional monomer used 
is larger than 10% by weight, the impact resistance-manifesting effect is 
reduced. 
The amount of the hard crosslinked resin (C) used is 5 to 100 parts by 
weight, preferably 5 to 50 parts by weight, per 100 parts by weight of the 
two-layer structure acrylic elastomer [I]. If the amount of the hard 
crosslinked resin (C) is smaller than 5 parts by weight, no substantial 
improvement of the surface appearance or processability can be attained. 
If the amount of the resin (A) exceeds 100 parts by weight, reduction of 
the surface appearance and processability is observed and the impact 
resistance is degraded. 
In the present invention, at the time when polymerization of the 
crosslinkable monomer mixture is substantially completed, a 
non-crosslinkable monomer or non-crosslinkable monomer mixture comprising 
80 to 100% by weight of methyl methacrylate, 0 to 20% by weight of at 
least one alkyl acrylate having 1 to 8 carbon atoms in the alkyl group and 
0 to 10% by weight of other vinyl monomer copolymerizable with the 
monomers is polymerized in an amount of 5 to 100 parts by weight, 
preferably 10 to 700 parts by weight, per 100 parts by weight of the 
two-layer structure acrylic elastomer [I] to form a hard non-crosslinked 
resin (D). In this polymerization stage, the resin (D)/resin (C) weight 
ratio should be in the range of from 0.5 to 200. If the amount of the hard 
non-crosslinked resin (D) is smaller than 5 parts by weight per 100 parts 
by weight of the two-layer structure acrylic elastomer [I], the impact 
resistance is reduced. If the amount of the resin (D) is larger than 1000 
parts by weight, the productivity is reduced. If the weight ratio of the 
hard non-crosslinked resin (D) to the hard crosslinked resin (C) obtained 
in the preceding stage, that is, the resin (D)/resin (C) weight ratio, is 
lower than 0.5, the surface appearance, transparency, flowability and 
impact resistance are reduced. If the resin (D)/resin (C) weight ratio is 
higher than 200, the productivity is reduced. If the amount of methyl 
methacrylate in the non-crosslinkable monomer mixture is smaller than 80% 
by weight, the transparency and heat resistance are degraded. 
As the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group that is 
copolymerized with methyl methacrylate, methyl acrylate, ethyl acrylate 
and butyl acrylate can be used in an amount of up to 20% by weight. If the 
amount of the alkyl acrylate is larger than 20% by weight, the heat 
resistance and transparency are degraded. As the other copolymerizable 
vinyl monomer, for example, styrene, acrylonitrile and methacrylic acid 
can be used in an amount of up to 10% by weight. If the amount of the 
vinyl monomer exceeds 10% by weight, the transparency, weather resistance 
and water resistance are degraded. 
In the present invention, a polymerization degree modifier such as a 
mercaptan compound may be added to the non-crosslinkable monomer or 
non-crosslinkable monomer mixture so as to control the molecular weight, 
if desired. As the polymerization degree modifier, alkyl mercaptans, 
thioglycolic acid, esters thereof and aromatic mercaptane such as 
thiophenol and thiocresol can be mentioned. It is preferable to use the 
polymerization degree modifier in an amount of 0.01 to 5.0% by weight. 
The multilayer structure methacrylic resin composition [II] obtained 
through the series of the above-mentioned polymerization processes can be 
used as it is. If desired, it may be used after it has been mixed with 
other thermoplastic resins, preferably a methyl methacrylate resin formed 
by polymerizing 80 to 100% by weight of methyl methacrylate and 0 to 20% 
by weight of another vinyl monomer, for example, an alkyl acrylate having 
1 to 4 carbon atoms in the alkyl group, so that the content of the 
two-layer structure acrylic elastomer [I] is 1 to 70% by weight based on 
the total resin composition. 
The process per se for the preparation of the multilayer structure 
methacrylic resin composition of the present invention is not particularly 
critical, but it is preferable to adopt an emulsion polymerization 
process. Accordingly, an embodiment of the preparation of the multilayer 
structure methacrylic resin composition of the present invention according 
to the emulsion polymerization will now be described. 
A reaction vessel is charged with deionized water and, if necessary, an 
emulsifier. Then, a monomer mixture forming the hard crosslinked resin (A) 
is charged and polymerized. Thereafter, a monomer mixture forming the 
crosslinked acrylic acid ester copolymer (B) is polymerized to obtain the 
multilayer structure acrylic elastomer [I]. Then, a crosslinkable monomer 
mixture (C) is polymerized and subsequently a non-crosslinkable monomer or 
non-crosslinkable monomer mixture (D) is polymerized. 
The polymerization temperature is 30.degree. to 120.degree. C., preferably 
50.degree. to 120.degree. C. In each of the polymerization stages (A), 
(B), (C) and (D), the polymerization time is ordinarily 0.5 to 7 hours, 
though the polymerization time varies depending upon the kinds and amounts 
of the polymerization initiator and emulsifier and the polymerization 
temperature. 
It is preferred that the monomer/water ratio be in the range of from 1/20 
to 1/1. The polymerization initiator and emulsifier may be added to either 
or both of the aqueous phase and monomer phase. 
In each of the polymerization stages (A), (B), (C) and (D), the monomers 
may be added at once or by lots. However, in view of the generation of 
polymerization heat, it is preferred that the monomers be added by lots. 
Any conventional emulsifier can be used. For example, a long-chain alkyl 
carboxylic acid salt, a sulfosuccinic acid alkyl ester salt, an 
alkylbenzenesulfonic acid salt and an N-acyl sarcosinic acid salt may be 
used as the emulsifier. 
The type of the polymerization initiator is not particularly critical. For 
example, a conventional inorganic initiator such as a water-soluble 
persulfate or perborate may be used either alone or in combination with a 
sulfite or thiosulfate as a redox type initiator. Furthermore, a redox 
type initiator such as organic hydroperoxide-sodium formaldehyde 
sulfoxylate or an organic initiator such as benzoyl peroxide or 
azobisisobutyronitrile can be used. 
A polymer latex obtained by the emulsion polymerization is coagulated and 
dried according to known procedures. 
In the case where the obtained multilayer structure methacrylic resin 
composition is incorporated with a methyl methacrylate resin, a 
melt-mixing method is preferably employed. If desired, additives such as a 
stabilizer, a lubricant, a plasticizer, a dye, a pigment, and a filler may 
be added in appropriate amounts to the resin composition prior to the 
melt-mixing. Then, the mixture is blended by a V-blender or Henschel mixer 
and melt-kneaded by a mixing roller or screw type extruder. 
The obtained resin composition is molded by an extrusion molding machine or 
injection molding machine, whereby molded articles excellent in 
transparency and surface appearance as well as impact resistance can be 
obtained.

The present invention will now be described in detail with reference to the 
following examples. In these examples, all of "parts" and "%" are by 
weight. 
EXAMPLE 1 
(1) Preparation of Hard Crosslinked Resin (A) 
A stainless steel reaction vessel having an inner capacity of 50 l was 
charged with a starting material (a) having the composition described 
below. Nitrogen was blown into the vessel with stirring so that there was 
no substantial influence of oxygen. Thereafter, the temperature was 
elevated to 70.degree. C. and then a starting material (b) having the 
composition described below was added. Polymerization was carried out for 
2 hours to obtain a latex of a hard crosslinked resin (A). 
______________________________________ 
Starting Material (a) 
Deionized water 20 kg 
Sarcosinate LN (S-LN) (N--acyl 
9.6 g 
sarcosinic acid salt supplied 
by Nikko Chemicals) 
Boric acid 40 g 
Sodium carbonate 4 g 
Monomer mixture comprising 97% of 
1.2 kg 
methyl methacrylate (MMA), 1% of 
ethyl acrylate (EA) and 2% of 
1,3-butylene dimethacrylate (BDMA) 
Cumene hydroperoxide (CHP) 
6 g 
Starting Material (b) 
Deionized water 400 g 
Sodium formaldehyde sulfoxylate (SFS) 
24 g 
______________________________________ 
The conversion of MMA in this latex was 98.5%, and the particle size was 
0.16 .mu.m. 
(2) Preparation of Two-layer Structure Acrylic Elastomer [I] by Formation 
of Crosslinked Acrylic Acid Ester Copolymer (B) 
431 g of an aqueous solution containing 14 g of sodium formaldehyde 
sulfoxylate (hereinafter referred to as "SFS") and 16.8 g of S-LN was 
charged into the reaction vessel containing therein the hard crosslinked 
resin latex in an amount corresponding to 1.2 kg of the solids. The 
temperature was elevated to 80.degree. C., and then an acrylic acid ester 
monomer mixture having the composition described below was continuously 
added over a priod of 150 minutes. After completion of the addition, 
polymerization was conducted for 3 hours to obtain a latex of a two-layer 
structure acrylic elastomer containing in the interiors of particles 
thereof the hard crosslinked resin (A) and also having a crosslinked 
acrylic acid ester type copolymer (B) in the external layer portions of 
the particles. 
______________________________________ 
Acrylic acid ester monomer mixture 
Monomer mixture comprising 80% of 
2.8 kg 
butyl acrylate (BA), 18.5% of 
styrene (ST) and 1.5% of ACM 
CHP 14 g 
______________________________________ 
The conversion of BA was 97%, the conversion of ST was more than 99.5%, and 
the particle size of the obtained latex was 0.28 .mu.m. 
(3) Preparation of Multilayer Structure Methacrylic Resin Composition [II] 
To the reaction vessel containing the latex obtained in (2) above in an 
amount corresponding to 100 parts of the solids of the two-layer structure 
acrylic elastomer [I], 1.2 parts of S-LN and 10 parts of deionized water 
were added, while being stirred. Then, a crosslinkable monomer mixture (C) 
having the composition described below was continuously added over a 
period of 45 minutes. Polymerization was conducted for 1 hour. Then, a 
non-crosslinkable monomer mixture (D) having the composition described 
below was continuously added into the reaction vessel over a period of 400 
minutes. Polymerization was conducted for 1 hour to obtain a latex of a 
multilayer structure methacrylic resin composition [II]. The conversion of 
the monomer mixtures (C) and (D) were more than 99.5% and 99.5%, 
respectively. 
______________________________________ 
Crosslinkable Monomer Mixture (C) 
Mixture comprising 92.5% of MMA, 
800 g 
6% of EA and 1.5% of BDMA 
CHP 2.4 g 
Non-Crosslinkable Monomer Mixture (D) 
Mixture comprising 94% of MMA and 
11.2 g 
6% of EA 
n-octylmercaptan (n-C.sub.8 SH) 
39.2 g 
CHP 44.8 g 
______________________________________ 
The monomer mixture (D)/monomer mixture (C) weight ratio was 14. 
According to the procedure described below, the so-obtained latex was 
coagulated, washed and then dried to obtain a powder of the multilayer 
structure methacrylic resin composition [II]. 
A stainles steel vessel was charged with 14 kg of an aqueous 1.0% sulfuric 
acid solution. The temperature was elevated to 80.degree. C. with 
stirring. Then, 7 kg of above-mentioned latex was continuously added over 
a period of 20 minutes. The inner temperature was elevated to 95.degree. 
C. and this temperature was maintained for 5 minutes. Then, the 
temperature was lowered to room temperature. The polymer was recovered by 
filtration and then washed with deionized water to obtain a white creamy 
polymer. The polymer was dried at 70.degree. C. for 24 hours to obtain a 
white powdery polymer. 
The powder was melt-kneaded and pelletized by using a screw extruder having 
an outer diameter of 40 mm (Model P-40-26 AB-V supplied by Nippon 
Seikosho; L/D=26) at a cylinder temperature of 200.degree. to 260.degree. 
C. and a die temperature of 250.degree. C. to obtain an impact-resistant 
methacrylic resin composition [II] containing 25% of the two-layer 
structure acrylic elastomer [I]. 
The resin composition was injection-molded under conditions described 
below. Physical properties of the obtained test pieces were tested. The 
results are shown in Table 1. 
______________________________________ 
Injection molding machine: 
Screw type automatic 
injection molding 
machine Model V-17-65 
supplied by Nippon 
Seikosho 
Injection molding Cylinder temperature of 
conditions: 250.degree. C. and injection 
pressure of 700 kg/cm.sup.2 
Size of test piece: 
110 mm .times. 110 mm .times. 2 mm 
(thickness) or 
70 mm .times. 12.5 mm .times. 6.2 mm 
(thickness) 
______________________________________ 
TABLE 1 
__________________________________________________________________________ 
Total 
Izod Dynstat 
MI Value.sup.6 
Defects 
Glossiness.sup.1 (%) 
trans- 
impact impact (g/10 min, 
Tensile 
on surface 
(incident 
Haze.sup.2 
mission.sup.3 
strength.sup.4 
strength.sup.5 
260.degree. C. .times. 
strength.sup.7 
of molded 
angle of 60.degree.) 
(%) (%) (kg .multidot. cm/cm) 
(kg .multidot. cm/cm.sup.2) 
6 kg) (kg/cm.sup.2) 
plate 
__________________________________________________________________________ 
99.5 1.9 92.1 5.1 23.0 21.4 400 None 
__________________________________________________________________________ 
Note 
.sup.1 ASTM D673-44 
.sup.2 and .sup.3 ASTM D1003-52 
.sup.4 ASTM D256-54T 
.sup.5 BS 1330 
.sup.6 ASTM D1238-52T 
.sup.7 ASTM D638-56T 
EXAMPLE 2 AND COMATIVE EXAMPLES 1 THROUGH 6 
An impact-resistant methyacrylic resin composition was prepared in the same 
manner as described in Example 1 except that the composition of the 
monomer mixture for formation of the cross-linked acrylic ester type 
copolymer (B) was changed as shown in Table 2. The results of the tests 
made on the composition are shown in Table 3. 
TABLE 2 
__________________________________________________________________________ 
Composition (%) of Crosslinked Acrylic Acid Ester Type Copolymer 
BA ST ASV 
SVA.sup.1 
MSV.sup.2 
BDMA EDMA.sup.3 
DVB.sup.4 
AMA.sup.5 
__________________________________________________________________________ 
Example 2 
80 18.5 
1.5 
-- -- -- -- -- -- 
Comparative 
80 18.5 
-- 1.5 -- -- -- -- -- 
Example 1 
Comparative 
80 18.5 
-- -- 1.5 -- -- -- -- 
Example 2 
Comparative 
80 18.5 
-- -- -- 1.5 -- -- -- 
Example 3 
Comparative 
80 18.5 
-- -- -- -- 1.5 -- -- 
Example 4 
Comparative 
80 18.5 
-- -- -- -- -- 1.5 -- 
Example 5 
Comparative 
80 18.5 
-- -- -- -- -- -- 1.5 
Example 6 
__________________________________________________________________________ 
Note 
.sup.1 Sorbic acid 
.sup.2 Methyl sorbate 
.sup.3 Ethylene glycol dimethacrylate 
.sup.4 Divinyl benzene 
.sup.5 Allyl methacrylate 
TABLE 3 
__________________________________________________________________________ 
Glossiness (%) Izod impact 
Dynstat impact 
Tensile 
Defects on 
(incident angle 
Total trans- 
strength 
strength strength 
surface of 
of 60.degree.) 
Haze (%) 
mission (%) 
(kg .multidot. cm/cm) 
(kg .multidot. cm/cm.sup.2) 
(kg/cm.sup.2) 
molded 
__________________________________________________________________________ 
plate 
Example 2 99.2 1.8 92.0 4.7 22 410 None 
Comparative Example 1 
34.0 30.5 83.0 2.5 10.0 320 Poor gloss, 
- flow 
marks 
observed 
Comparative Example 2 
47.5 25.6 85.1 2.4 11.3 340 Poor gloss, 
flow marks 
observed 
Comparative Example 3 
88.8 2.7 91.5 2.2 9.6 380 None 
Comparative Example 4 
89.5 2.9 91.4 1.9 10.4 360 None 
Comparative Example 5 
89.2 2.8 91.0 2.0 10.0 370 None 
Comparative Example 6 
89.8 3.8 91.4 3.6 15.4 390 Flow marks 
observed 
__________________________________________________________________________ 
EXAMPLES 3 AND 4 COMATIVE EXAMPLES 7 THROUGH 10 
(1) Preparation of Hard Crosslinked Resin (A) 
A stainless steel reaction vessel having an inner capacity of 50 l was 
charged with a starting material (a) having the composition described 
below and 3 g of tertiary butyl hydroperoxide (t-BH). Nitrogen was blown 
into the reaction vessel so that there was no substantial oxygen present. 
The temperature was elevated with stirring. When the inner temperature 
reached 70.degree. C., 500 g of an aqueous 5% SFS solution was added. 
Polymerization was conducted for 1 hour while controlling the inner 
temperature to 80.degree. C. Then, 500 g of an aqueous 3% S-LN solution 
was added and then a starting material (b) having the composition 
described below, which contained 3 g of t-BH dissolved therein, was added. 
Polymerization was conducted for 1 hour to obtain a latex of a hard 
crosslinked resin (A). 
______________________________________ 
Starting Material (a) 
Deionized water 19.5 kg 
S-LN 10 g 
Boric acid 100 g 
Sodium carbonate 10 g 
Ferrous sulfate 0.04 g 
Disodium ethylenediamine- 
0.12 g 
tetraacetate 
Mixture comprising 96% of MMA, 
1000 g 
1% of BA and 3% of BDMA 
Starting Material (b) 
Mixture comprising 96% of MMA, 
1000 g 
1% of BA and 3% of BDMA 
______________________________________ 
The conversion MMA in this latex was 98.5%. 
(2) Preparation of Two-Layer Structure Acrylic Elastomer [I] 
To the reaction vessel containing the latex of the hard crosslinked resin 
(A) obtained by the polymerization in (1) above, 500 g of an aqueous 7% 
SFS solution and 500 g of an aqueous 6% S-LN solution were added. Then, 
8.04 kg of an acrylic acid ester monomer mixture having the composition 
shown in Table 4 and containing 40 g of t-BH dissolved therein was 
continuously added at a rate of 3.2 per kg hour while controlling the 
inner temperature to 80.degree. C. After completion of the addition, 
polymerization was conducted for 3 hours to form a crosslinked acrylic 
acid ester copolymer (B), whereby a latex of a two-layer structure acrylic 
elastomer [I] containing the hard crosslinked resin in the interiors of 
particles was obtained. 
TABLE 4 
______________________________________ 
Monomer Composition (%) of Cross-linked Acrylic 
Acid Ester Copolymer (B) 
BA ST ACM ASV BDMA AMA.sup.1 
______________________________________ 
Example 3 80 18.0 1.0 1.0 -- -- 
Example 4 80 18.0 1.2 -- 0.8 -- 
Comparative 
80 20 -- -- -- -- 
Example 7 
Comparative 
68 17 -- 15 -- -- 
Example 8 
Comparative 
80 19.95 -- 0.05 -- -- 
Example 9 
Comparative 
80 18.0 -- -- -- 2.0 
Example 10 
______________________________________ 
Note 
.sup.1 Allyl methacrylate 
In each run, the conversion of each of BA and ST was higher than 98%, and 
the particle size of the obtained latex was 0.25 to 0.28 .mu.m. 
(3) Preparation of Multilayer Structure Methacrylic Resin Composition [II] 
To the vessel containing the two-layer structure acrylic elastomer [I] 
obtained in (2) above, 500 g of an aqueous 1% S-LN solution was added. 
Thereafter, a crosslinkable monomer mixture (C) having the composition 
shown below and containing 3 g of t-BH was continuously added over a 
period of 1 hour while controlling the inner temperature to 80.degree. C. 
Polymerization was then conducted for 1 hour. Then, 500 g of an aqueous 7% 
SFS solution and 500 g of an aqueous 6% S-LN solution were added. Then, a 
non-crosslinkable monomer mixture (D) having the composition shown below 
and containing 22 g of t-BH and 8.2 g of n-C.sub.8 SH was continuously 
added at a rate of 3700 g per hour. After completion of the addition, 
polymerization was conducted for 90 minutes to obtain a latex of a 
multilayer structure methacrylic resin composition [II]. In each run, the 
conversion of each of the monomer mixtures (C) and (D) was higher than 
99.0%. 
______________________________________ 
Crosslinkable Monomer Mixture (C): 
Mixture comprising 98.5% of MMA, 
1000 g 
1.0% of BA, and 0.5% of BDMA 
Non-crosslinkable Monomer Mixture (D): 
Mixture comprising 99% of MMA and 
6000 g 
1.0% of BA 
______________________________________ 
The monomer mixture (D)/monomer mixture (C) weight ratio was 6.0. 
A white powdery polymer was prepared from the so-obtained latex under the 
same conditions according to the same procedures as in Example 1. 
Then, 3.4 kg of the powdery multilayer structure methacrylic resin 
composition was mixed with 6.6 kg of Acripet VH (methacrylic resin 
material supplied by Mitsubishi Rayon Co.) by a Henschel mixer. The 
mixture was melt-kneaded and pelletized in the same screw extruder as used 
in Example 1 at a cylinder temperature of 200.degree. to 270.degree. C. 
and a die temperature of 260.degree. C. to obtain an impact-resistant 
methacrylic resin composition containing 20% by weight of the two-layer 
structure acrylic elastomer [I]. 
The resin composition was injection-molded under the same conditions as 
described in Example 1, and the obtained test pieces were tested. The 
results are shown in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Dynstat 
Glossiness (%) Izod impact 
impact Tensile 
(incident angle 
Total trans- 
strength 
strength 
strength 
Defects on surface 
of 60.degree.) 
Haze (%) 
mission (%) 
(kg cm/cm) 
(kg cm/cm.sup.2) 
(kg/cm.sup.2) 
of molded 
__________________________________________________________________________ 
plate 
Example 3 
99.0 1.9 92.0 4.3 18.4 470 None 
Example 4 
99.4 1.7 92.1 4.4 19.2 455 None 
Comparative 
48.0 26.0 80.0 2.2 9.0 330 Poor gloss, flow marks 
Example 7 observed 
Comparative 
82.0 17.6 88.0 1.9 7.5 385 Flow marks observed 
Example 8 
Comparative 
60.5 11.5 82.0 2.1 10.8 345 Poor gloss, flow marks 
Example 9 observed 
Comparative 
78.8 6.5 90.2 2.6 11.2 395 Poor gloss, flow marks 
Example 10 observed 
__________________________________________________________________________ 
EXAMPLE 5 AND COMATIVE EXAMPLES 11 AND 12 
An impact-resistant methacrylic resin composition [II] was prepared 
according to the same procedures as described in (1) through (3) of 
Example 3 except that the composition of the monomer mixture used for 
formation of the hard crosslinked resin (A) was changed as shown in Table 
6. The properties were evaluated in the same manner as in Example 3. The 
results are shown in Table 7. 
TABLE 6 
______________________________________ 
Tetraethylene 
Methyl glycol 
MMA acrylate diacrylate 
(%) (MA) (%) (C.sub.4 --DA) (%) 
ST (%) 
______________________________________ 
Example 5 
97 1 2 -- 
Comparative 
99 1 -- -- 
Example 11 
Comparative 
30 -- 2 68 
Example 12 
______________________________________ 
TABLE 7 
______________________________________ 
Izod impact 
Defects on 
Haze Total trans- 
strength surface of 
(%) mission (%) 
(kg .multidot. cm/cm) 
molded plate 
______________________________________ 
Example 5 
1.8 92.0 4.2 None 
Comparative 
1.8 92.0 2.9 None 
Example 11 
Comparative 
27.0 79.0 4.0 Poor trans- 
Example 12 parency 
______________________________________ 
EXAMPLES 6 AND 7 AND COMATIVE EXAMPLES 13 THROUGH 15 
A methacrylic resin composition was prepared in the same manner as 
described in Example 3 except that the monomers and additives of the 
crosslinkable monomer mixture (C) and non-crosslinkable monomer mixture 
and the (D)/(C) weight ratio were changed as shown in Table 8. The 
properties were evaluated in the same manner as in Example 3. The results 
are shown in Table 9. 
TABLE 8 
__________________________________________________________________________ 
Amount (g) 
Amounts (g) Composition (%) of Composition (%) of 
of crosslink- 
of non-cross- 
(D)/(C) 
cross-linkable non-cross-linkable 
able monomer 
linkable monomer 
weight 
monomer mixture (C) 
monomer mixture (D) 
mixture (C) 
mixture (D) 
ratio MMA EA BDMA TMP-3A.sup.1 
MMA EA n-C.sub.8 SH 
__________________________________________________________________________ 
(g) 
Example 6 
700 6300 9 96 1 3 -- 97 3 9.5 
Example 7 
1000 6000 6 96 2.5 
-- 0.5 97 3 9.0 
Comparative 
6000 1000 0.167 96 2.5 
-- 0.5 97 3 1.5 
Example 13 
Comparative 
1000 6000 6 84 1 -- 15 97 3 9.0 
Example 14 
Comparative 
-- 7000 -- -- -- -- -- 97 3 -- 
Example 15 
__________________________________________________________________________ 
Note 
.sup.1 Trimethylolpropane triacrylate 
TABLE 9 
__________________________________________________________________________ 
Glossiness (%) 
Izod imapct 
M.I. value 
(incident angle 
strength 
(g/10 min, 
Defects of surface 
of 60.degree.) 
Haze (%) 
(kg.cm/cm) 
260.degree. C. .times. 6 kg) 
molded plate 
__________________________________________________________________________ 
Example 6 
99.6 1.9 4.6 21.3 None 
Example 7 
99.2 1.8 4.2 22.1 None 
Comparative 
85.1 7.6 2.3 13.6 Uneven gloss, flow marks 
Example 13 observed 
Comparative 
95.2 2.9 2.4 10.2 flow marks observed 
Example 14 
Comparative 
87.8 4.3 4.1 9.7 Poor gloss, flow marks 
Example 15 observed 
__________________________________________________________________________