Methacrylate resin composition and process for its preparation

A methacrylate resin composition comprising a methacrylate resin containing methacrylimide units of the following formula: ##STR1## wherein R is a hydrogen atom or an aliphatic, alicyclic or aromatic hydrocarbon group having from 1 to 20 carbon atoms, and having a yellowness index (YIs) of at most 3 as measured in the form of a solution of the heated resin composition and a total light transmittance of from 89 to 95%.

The present invention relates to a composition of a methacrylate resin 
containing methacrylimide units, and a process for its preparation. 
Polymers composed of methacrylate esters such as methyl methacrylate 
(hereinafter referred to as methacrylate resins) are excellent not only in 
the transparency but also in the mechanical properties, weather 
resistance, etc. Therefore, they are used as high performance plastic 
optical fibers or decoration materials. In recent years, the optical 
fibers have been developed for applications in the fields of short 
distance optical communication, photosensors, etc. However, methacrylate 
resins do not have adequate heat resistance as is evident from the fact 
that the heat distortion temperature of polymethyl methacrylate is about 
100.degree. C. Therefore, the development for their applications has been 
restricted in many fields, and there has been a strong demand for 
improvement of the heat resistance. 
As a method for improving the heat resistance of a methacrylate resin, it 
has been proposed, for example, to react a polymer of methyl methacrylate 
with a primary amine (U.S. Pat. No. 2,146,209 and West German Patent Nos. 
1,077,872 and 1,242,369). 
Further, there have been proposed a method wherein a polymer of a 
methacrylate ester is reacted with a water-soluble ammonium salt or an 
N-alkyl ammonium salt (U.S. Pat. No. 3,244,679), and a method wherein a 
polymer obtained by using a methacrylate ester, is reacted with a primary 
amine in an aqueous system (U.S. Pat. No. 3,284,425). Furthermore, a 
method has been proposed wherein a polymer of a methacrylate ester and 
ammonia or a primary amine are reacted by using an extruder (U.S. Pat. No. 
4,246,374). 
Methacrylate resins containing methacrylimide units (hereinafter sometimes 
referred to as methacrylimide resins) obtained by the above methods and 
their compositions, have improved heat resistance. However, they are 
inferior in the mechanical properties, optical properties, yellowing 
resistance or moldability, since they are poor in the transparency, the 
molecular weight of the methacrylate resin is likely to be substantially 
lowered, or the imidization tends to be non-uniform. Thus, they are not 
practically useful. Particularly in the field where a high level of 
transparencey is required, it has been difficult to obtain a practically 
useful methacrylimide resin composition. 
For instance, in the process of U.S Pat. No. 2,146,209, the imidization is 
conducted in the presence of a single solvent or in the absence of any 
solvent. According to this process, it is possible to obtain a 
methacrylmide resin having improved heat resistance, but it is not 
possible to obtain a methacrylimide resin composition having excellent 
transparency and yellowing resistance (heat discoloration resistance). 
U.S. Pat. No. 4,246,374 discloses imidization of a molten methacrylate 
resin in an extruder by a gaseous low molecular weight imidizing agent 
such as ammonia or methylamine. However, in this process, a low viscosity 
or gaseous imidizing agent is added to a highly viscous molten system, 
whereby the imidization tends to be non-uniform. Besides, the time for the 
imidization tends to be insufficient becasue of the use of the extruder. 
There will be a further problem such that the molecular weight of the 
methacrylate resin tends to be lowered. If the imidization is non-uniform 
and the time for the imidization is insufficient, it is impossible to 
obtain a methacrylimide resin composition having excellent transparency 
and yellowing resistance. 
It is an object of the present invention to provide a methacrylimide resin 
composition having excellent heat resistance while maintaining the 
excellent optical properties, yellowing resistance, mechanical properties, 
weather resistance and moldability inherent to the methacrylate resin. 
The present invention provides a methacrylate resin composition comprising 
a methacrylate resin containing methacrylimide units of the following 
formula: 
##STR2## 
wherein R is a hydrogen atom or an aliphatic, alicyclic or aromatic 
hydrocarbon group having from 1 to 20 carbon atoms, and having a 
yellowness index (YIs) of at most 3 as measured in the form of a solution 
of the heated resin composition and a total light transmittance of from 89 
to 95%. 
Further, the present invention provides a process for preparing a 
methacrylate resin composition comprising a methacrylate resin containing 
methacrylimide units of the formula I, which comprises reacting a resin 
comprising methyl methacrylate units as the main constituent units and 
having a methyl methacrylate dimer content of not higher than 1,000 ppm, 
with an amine of the formula RNH.sub.2 wherein R is as defined above, 
under a condition such that said resin is dissolved in a solvent mixture 
for the resin. 
Now, the present invention will be described in detail with reference to 
the preferred embodiments.

As mentioned above, the methacrylimide resin composition of the present 
invention has a yellowness index (YIs) of at most 3, preferably from 0.1 
to 1, as measured in the form of a solution of the heated resin 
composition, a yellowness index (YIp) of preferably at most 2.7, more 
preferably from 0.2 to 1.5, as measured in the form of a molded plate, and 
a total light transmittance of from 89 to 95%, preferably from 92 to 94%. 
Such a methacrylimide resin composition can be obtained by a process 
characterized in that a methacrylate resin having a low methyl 
methacryalte dimer content is subjected to imidization in a mixture of 
solvents. 
The methyl methacrylate dimer in this invention is a compound derived from 
two molecules of a methyl methacrylate monomer, which is formed as a 
by-product during the preparation of a polymer comprising methyl 
methacrylate units as the main constituent units. The composition of a 
methacrylate resin containing at least 2% by weight, preferably at least 
10% by weight of methacrylimide units of the formula I, which is 
obtainable by reacting a methacrylate resin having such a methyl 
methacrylate dimer content of not higher than 1,000 ppm, preferably not 
higher than 250 ppm, with an amine of the formula RNH.sub.2 wherein R is 
as defined above, in a solvent mixture under a specific condition, is 
superior in the transparency, particularly in the heat discoloration 
resistance. 
If more than 1,000 ppm of the methyl methacrylate dimer is contained in the 
polymer comprising methyl methacrylate units as the main constituent 
units, this dimer reacts with the amine in the reaction step described 
hereinafter, to form a coloring substance made of a low molecular weight 
amide, and this coloring substance can hardly be separated from the 
methacrylimide resin in the step for separation of volatile substances. 
Accordingly, in order to obtain a methacrylimide resin composition having 
high transparency and minimun discoloration, intended by the present 
invention, it is important to minimize the content of the methyl 
methacrylate dimer in the methacrylate resin prior to the reaction with 
the amine. 
The methacrylimide resin composition of the present invention can be 
obtained, for example, by adding the above-mentioned amine (which may be 
of a single kind, or a mixture of two or more different kinds) to a 
solution obtained by dissolving from 5 to 80 parts by weight of the 
above-mentioned methacrylate resin in a solvent mixture comprising from 19 
to 94 parts by weight of an aromatic hydrocarbon and from 1 to 76 parts by 
weight of an aliphatic alcohol (the total amount of the methacrylic resin 
and the solvent mixture being 100 parts by weight), at a temperature of at 
least 100.degree. C. and lower than 350.degree. C., followed by stirring 
and mixing, and then separating volatile substances from the reaction 
product. If the solvent mixture is not used, it is impossible to obtain a 
methacrylimide resin composition having a low yellowness index as 
mentioned above. 
The methacrylate resin containing methacrylimide units, is meant for a 
polymer with methacrylimide segments introduced into polymer side chains 
of a methacrylate resin. 
The methacrylate resin to be empolyed in the present invention, includes a 
methyl methacrylate homopolymer or a copolymer of methyl methacrylate with 
other copolymerizable monomers such as acrylic esters, other methacrylate 
esters, acrylic acid, methacrylic acid, styrene or .alpha.-methyl styrene, 
which usually has an intrinsic viscosity of from 0.01 to 3.0 dl/g (at 
25.degree. C. in dimethylformamide). In such a case, other copolymerizable 
monomers are used in an amount of preferably not higher than 75% by weight 
based on the monomer mixture with methyl methacrylate. The acrylic esters 
include methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl 
acrylate, 2-ethylhexyl acrylate and benzyl acrylate, and the methacrylate 
esters include ethyl methacrylate, butyl methacrylate, cyclohexyl 
methacrylate and benzyl methacrylate. These momomers may be used alone or 
in a combination of two or more different kinds. 
The production of the methacrylimide resin composition of the present 
invention may be divided into two steps, i.e. the reaction step and the 
step for separating volatile substances, as mentioned above. The reaction 
step is a step wherein the methacrylate resin and the amine of the formula 
RNH.sub.2 are reacted under the specific condition to induce a 
condensation reaction among the polymer side chains of the methacrylate 
resin. The step for separating volatile substances is a step wherein 
volatile substances composed mainly of the solvent mixture, are separated 
from the reaction product containing the imidized methacrylate resin 
formed in the reaction step. In the reaction step, the amine of the 
formula RNH.sub.2 is dissolved into a solution of the methacrylate resin 
in the above-mentioned solvent mixture, and reacted with the resin. The 
solvents are required not to adversely affect the imidization which is a 
condensation reaction among the polymer side chains. They are also 
required not to affect methyl methacrylate or methacrylate ester segments 
in the case of a partial-imidization. 
As such solvents, there may be mentioned mixtures of at least two different 
types selected from the group consisting of alcohols, particularly 
aliphatic alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, 
isopropyl alcohol, butyl alcohol and isobutyl alcohol; aromatic 
hydrocarbons such as benzene, toluene, xylene; and ketone or ether 
compounds such as methyl ethyl ketone, tetrahydrofuran and dioxane. Among 
them, a mixture of benzene, toluene, xylene or a mixture thereof, and an 
aliphatic alcohol such as methyl alcohol, ethyl alcohol, propyl alcohol, 
isopropyl alcohol, butyl alcohol or isobutyl alcohol, is preferred. 
These solvents are used preferably after filtration by a porous membrane 
for purification, in order to obtain a methacrylimide resin composition 
having excellent transparency. 
The smaller the amount of the solvent mixture, the better, from the 
viewpoint of the productivity. However, if the amount is too small, the 
effects of the solvent mixture as mentioned above tend to be low. 
Therefore, the amount of the solvent mixture is preferably within a range 
of from 20 to 80% by weight relative to the polymer concentration. 
In order to obtain a methacrylimide resin composition having excellent 
transparency and low yellowness indexes (YIs, YIp), the above-mentioned 
imidization has to be conducted in the presence of a solvent mixture 
capable of dissolving the above-mentioned mathacrylate resin starting 
material, the amine of the formula RNH.sub.2 and the formed methacrylimide 
resin. If the imidization is conducted in a non-dissolved condition or in 
the absence of a solvent, it is likely that a part of the methacrylate 
resin starting material is imidized, and the rest remains unimidized. 
Namely, the product will be a mixture of the methacrylate resin starting 
material and the methacrylimide resin, whereby it is impossible to obtain 
a resin composition having excellent transparency. 
If a solvent capable of dissolving only the methacrylate resin starting 
material, for example, an aromatic hydrocarbon such as benzene, toluene or 
xylene, is used alone, the resulting methacrylimide resin will not 
dissolve in such a solvent, whereby it is difficult to uniformly obtain a 
methacrylimide resin having a high imidization rate. Likewise, if a poor 
solvent to the methacrylate resin starting material, such as methanol, or 
an aliphatic alcohol which is poorer as a solvent than the aromatic 
hydrocarbon, is used alone as a solvent, the imidization will not proceed 
uniformly. Besides, the imidization will not be complete. Thus, a 
discolored methacrylimide resin composition having a high yellow index 
will be formed. 
Whereas, when a solvent mixture obtained by mixing at least two types of 
solvents is used as mentioned above, the above problems disappear, and it 
is possible to obtain a methacrylimide resin composition having high 
transparency and dicoloration resistance. Among the amines represented by 
the formula RNH.sub.2 used in the process of the present invention, those 
wherein R is an aliphatic hydrocarbon group, include methylamine, 
ethylamine and propylamine. However, it is also possible to use compounds 
capable of producing such amines under heating, such as 1,3-dimethylurea, 
1,3-diethylurea and 1,3-dipropylurea, or ammonia and urea. 
As amines wherein R is an aromatic hydrocarbon group, aniline, toluidine 
and trichloroaniline may be mentioned. As an amine wherein R is an 
alicyclic hydrocarbon group, cyclohexyl amine may be mentioned. 
These compounds are used in such an amount that the methacrylimide units of 
the formular I will be contained in an amount of at least 2% by weight. 
For instance, they may be employed within a range of from 0.01 to 20 mols 
relative to 1 mol of methyl methacrylate momomer units of the methacrylate 
resin. 
The reaction of the methacrylate resin with the amine in the reactor may be 
conducted at a temperature of at least 100.degree. C. and less than 
350.degree. C., preferably at least 150.degree. C. and less than 
300.degree. C. If the reaction temperature is lower than 100.degree. C., 
the imidization tends to be slow. If the temperature exceeds 350.degree. 
C., a decomposition reaction of the methacrylate resin starting material 
takes place concurrently. There is no particular restriction as to the 
reaction time. From the viewpoint of the productivity, the reaction time 
is preferably short, and is usually from 30 minutes to 5 hours. The 
reaction pressure is determined depending upon the type of the amine, the 
reaction temperature and the imidization rate. 
Any reactor may be employed for the preparation of the methacrylimide resin 
composition of the present invention so long as the object of the present 
invention can be accomplished without hindrance. However, in order to 
conduct the imidization uniformly and to obtain a uniform polymer 
containing mathacrylimide units, it is preferred to employ a tank-type 
reactor provided with an inlet, an outlet and a stirring device and 
adapted to provide a mixing function throughout the interior of the 
reactor. In the step for separating volatile substances, the majority of 
volatile substances will be separated and removed from the reaction 
product of the methacrylate resin and the imidizing agent. The content of 
the volatile substances remaining in the methacrylimide resin composition 
is finally reduced to a level of not higher than 1% by weight, preferably 
not higher than 0.1% by weight. The removal of the volatile substances can 
be conducted by using a usual vent extruder or devolatizer, or may be 
conducted by an another method such as a method wherein the reaction 
product is diluted with a solvent, and then precipitated in a large amount 
of a non-solvent, followed by the filtration and drying of the 
precipitates. 
In the process of the present invention, it is preferred to add a small 
amount of an antioxidant to prevent a decrease of the molecular weight due 
to the radical depolymerization of the methacrylate resin starting 
material under a high temperature reaction condition. The antioxidant for 
this purpose includes a phosphite type antioxidant such as tricresyl 
phosphite, cresylphenyl phosphite, trioctyl phosphite or tributoxyethyl 
phosphite, a hindered phenol type antioxidant such as hydroquinone, cresol 
or a phenol derivative, an amine type antioxidant such as naphthylamine, 
phenylenediamine or a hydroquinoline derivative, an alkylmercaptan and a 
dialkylsulfide derivative. 
Further, other additives such a plasticizer, lubricant, a ultraviolet 
absober, a coloring agent or pigment, may be incorporated to meet the 
requirments for the properties of the product. 
Now, a typical apparatus to be used for the production of the 
methacrylimide resin composition of the present invention, will be 
described with reference to FIG. 1. 
An inert solvent mixture from a solvent reservoir 1 passes through a line 
2, and is sent to a solvent supply tank 4 by a pump 3. An antioxidant 
which may be added as the case requires, is supplied from an antioxidant 
reservoir 5 via a line 6 to the solvent supply tank 4 and dissolved in the 
solvent mixture, which is then sent to a resin dissolving tank 10. On the 
other hand, the resin is supplied from a pellet reservior 8 via a line 9 
to the resin dissolvi,ng tank 10. The resin dissolving tank 10 is provided 
with a stirrer 11 and a jacket 12. In the jacket, a heating medium is 
circulated through openings 13 and 14. The dissolved resin in the resin 
dissolving tank 10 is supplied via a line 15, a pump 16 and a line 17, to 
a reaction tank 20, and reacted therein with an imidizing agent supplied 
from an imidizing agent reservoir 18 via a line 19. The reaction tank 20 
is provided with a spiral ribbon type stirrer 21 and jacket 22. In the 
jacket, a heating medium is circulated through openings 23 and 24. The 
reaction product in the reactor 20 is sent via a discharge line 25, a pump 
26 and a line 27, to a volatile substance separator 28, wherein a volatile 
component is removed, and the polymer composition is discharged from a 
polymer outlet 29. The volatile substance separator 28 is provided with a 
screw 30, a vent 31 and a heating means 32. 
Now, the present invention will be described in detail with reference to 
Examples and Reference Examples. However, it should be understood that the 
present invention is by no means restricted to these specific Examples. In 
the following description, "parts" and "%" mean "parts by weight" and "% 
by weight" respectively, except for the case of the total light 
transmittance. The apparatus in FIG. 1 had the following specification. 
Resin dissolving tank: 500 liters 
Reaction tank: 40 liters 
Volatile substance separator: 
Single screw vented extruder 
Screw: 30 mm in diameter.times.720 mm in length 
Length of the vent: 60 mm 
In the Examples, the properties of the polymer starting materials and the 
resulting resin compositions, were measured by the following methods. 
(1) The infrared absorption spectrum was measured by a KBr disk method by 
means of an infrared spectrophotometer (285 Model, Manufactured by 
Hitachi, Limited). 
(2) The intrinsic viscosity of the polymer was determined by measuring the 
flow time (ts) of a dimethylformamide solution containing 0.5% by weight 
of the tested polymer and the flow time (to) of the dimethylformamide at a 
temperature of 25+0.degree. C. by means of Deereax-Bishoff viscometer, 
then obtaining the relative viscosity .eta. rel of the polymer from the 
ts/to value and then calculating the intrinsic viscosity by the following 
equation: 
##EQU1## 
wherein C is the amount of the polymer by grams per 100 ml of the solvent. 
(3) The heat distortion temperature was measured in accordance with ASTM 
D648. 
(4) The melt index of a polymer was obtained in accordance with ASTM D1238 
(grams for 10 min. at 230.degree. C. under a load of 3.8 kg). 
(5) The imidization rate (%) of the polymer was determined from the 
nitrogen content obtained from the elemental analysis (measuring device: 
CHN coder (MT-3), manufactured by Yanagimoto Seisakusho K.K.) and from the 
measurement by a proton NMR JNM-FX-100 (JEOL) spectrometer 100 MHz, 
whereby the weight of the imide ring units relative to the total amount of 
the imide ring units and the methyl methacrylate units, was shown by "%". 
(6) The transparency was measured in accordance with ASTM D1003-61 after 
the obtained resin composition was molded by heat-pressing to have a 
thickness of 2 mm. 
(7) The yellowness index (YIs) as measured in the form of a solution of the 
heated resin composition, was obtained in accordance with JIS K-7103. 
Namely, pellets of the obtained methacrylimide resin composition was 
heated in air at 150.degree. C. for 15 days, and then dissolved to obtain 
a 15 wt % methylene chloride solution, and then the yellowness index (YIs) 
was measured with a transmitted light in accordance with the above method 
and represented as the yellowness index under heating. YIs is calculated 
by the following equation. 
##EQU2## 
X, Y and Z: tristimulus values of a test sample or a test piece with 
standard lights. 
Further, by using the same molded plate as obtained in (6), the molded 
plate was heated in the same manner as mentioned above to 150.degree. C. 
for 15 days, whereupon the discoloration of the molded plate by heating 
was visually evaluated. 
No substantial change: O 
Slightly yellowed: .DELTA. 
Yellowed: X 
(8) The yellowness index (YIp) of a molded plate was determined by molding 
the obtained polymer pellets into a flat plate having a thickness of 2 mm 
and a size of 80.times.80 mm by means of a 5 ounce injection molding 
machine (SAV-30, manufactured by Meiki Seisakusho K.K.), and then 
measuring the yellowness index by the transmitted light of the flat plate. 
Molding condition: 
Cylinder temperature: 290.degree. C. 
Molding cycle: 60 sec. 
YIp was calculated by the following equation. 
##EQU3## 
X, Y and Z: tristimulus values of a test sample or a test piece with 
standard lights 
(9) Method for measuring a methyl methacrylate dimer 
The methacrylate resin comprising methyl methacrylate as the main 
component, was dissolved in an acetone solvent, and the dimer was measured 
by gas chromatography. 
The temperature of the column during the measurment was 150.degree. C. 
REFERENCE EXAMPLE 
Preparation of a methacrylate resin containing methyl methacrylate dimer 
A typical apparatus to be used for the preparation of various methyl 
methacrylate polymers, will be described with reference to FIG. 2. 
A mixture comprising 100 parts of a methyl methacrylate monomer, 0.0017 
part of di-tert-butylperoxide as the polymerization initiator, 0.25 part 
of dodecylmercaptan and from 0 to 50 parts of a non-polymerizable solvent 
(such as toluene), is charged to a reservoir 40, and supplied via a line 
41 by a pump 42 at a flow rate of 3 kg/hr (as the monomer content) to a 
polymerization reaction tank 43. If necessary, an additive such as an 
antioxidant may be supplied from an additive reservoir 44 via a line 45 to 
the reaction tank 43. The reaction tank 43 is provided with a spriral 
ribbon-type stirrer 46 and a jacket 47. In the jacket, a heating medium is 
circulated through openings 48 and 49. This reaction tank has an internal 
capacity of 25 liters, and the polymerization reaction temperature is 
variable within a range of from 60.degree. to 190.degree. C. The 
conversion (monomer to polymer) in this polymerization is variable within 
a range of from 40 to 70%. The methyl methacrylate polymer syrup formed in 
the polymerization reaction tank 43 is passed through a line 50, a pump 
51, a line 52 and a syrup heater 53, whereby the syrup is heated to a 
temperature of from 200.degree. to 240.degree. C. Then, the syrup is sent 
via a line 54 to a volatile substance separator 55. Here, volatile 
substances such as an unreacted methyl methacrylate monomer and in some 
cases a non-polymerizable solvent such as toluene or the methyl 
methacrylate dimer are partially removed at a vent portion temperature of 
from 190.degree. to 250.degree. C. under a reduced pressure of from 3 to 
500 mm Hg. The methyl methacrylate dimer here is meant for a by-product 
formed in the polymerization reaction tank 43 or in the syrup heater 53. 
The formed methyl methacrylate polymer is discharged from the polymer 
outlet 59 in the form of a strand, and processed into pellets by e.g. a 
cutting machine. The volatile substance separater 55 is provided with a 
screw 56, a vent 57 and a heating means 58. 
The volatile substance separater here had the following specification. 
Single screw vented extruder 
Screw: 30 mm in diameter and 720 mm in length 
Length of the vent: 60 mm 
In the methacrylate resin thus obtained, a methyl methacrylate dimer is 
contained. The amount of such dimer is variable depending upon the 
polymerization condition (such as the amount of the solvent used, the 
polymerization temperature and the conversion) and the syrup heating 
temperature and the volatile substance separating ability. In the 
following Examples and Comparative Examples, analytical values wil be used 
as the contents of the methyl methacrylate dimer. 
EXAMPLE 1 
Into a 500 liter dissolving tank, 100 parts of an adequately dried methyl 
mathacrylate polymer (methyl methacrylate dimer: 30 ppm, intrinsic 
viscosity: 0.51 dl/g) was introduced together with 90 parts of toluene 
dried and purified by filtration with a 0.1 .mu.m fluoropore (manufactured 
by Sumitomo Denki Kogyo K.K.) and 10 parts of methanol dried and purified 
with a 0.1 .mu.m fluoropore, and the polymer was dissolved at 200.degree. 
C. under stirring. 
Then, this solution was continuously supplied to the reaction tank at a 
supply rate of 5 kg/hr (as resin content), and the internal temperature of 
the tank was adjusted to 230.degree. C. while thoroughly mixing the 
solution under stirring at a rotational speed of 90 rpm. Then, dried 
methylamine was purified by filtration with a 0.1 .mu.m fluoropore and 
continuously supplied to the reaction tank at a rate of 20 mol/hr, 
whereupon the internal pressure was adjusted to 45 kg/cm.sup.2 (gauge 
pressure). The temperature in the reaction tank was maintained at 
230.degree. C. during the reaction, and an average retention time was 4.5 
hours. The reaction product withdrawn from this reaction tank, was 
introduced into a 20 liter aging tank (not shown in FIG. 1), and aged 
under thorough stirring at a temperature in the aging tank of 230.degree. 
C. for an average retention time of 2.0 hours. The aged product was 
continuously supplid to a vented extruder, and the volatile substances 
were separated. The temperature of the vented extruder was adjusted to 
230.degree. C. at the vent portion and to 230.degree. C. at the extrusion 
portion, and the vacuum at the vent portion was adjusted to 9 mmHg abs'. 
A strand extruded from the die was cooled with water and then cut to obtain 
a resin composition in the form of pellets having excellent transparency. 
On the other hand, toluene, methanol and the unreacted amine discharged 
from the vent portion, were cooled and recovered. The infrared absorption 
spectrum of the resin composition thus obtained, was measured, whereby 
absorption specific to a methyl methacrylimide polymer was observed at 
wave numbers of 1720 cm.sup.-1, 1663 cm-1 and 750 cm.sup.-1. 
Further, from the NMR spectrum, a signal corresponding to this structure 
was shown. The elemental analysis also indicated a nitrogen content of 
8.3% (imidization rate=100%), thus indicating that the product was almost 
completely a N-methyl methacrylimide polymer. From the evaluation of the 
physical properties of the obtained resin (composition), the following 
properties were obtained. 
Intrinsic viscosity: 0.48 
Melt index: 1.5 
Heat distortion temperature: 175.degree. C. 
Refractive index .eta..sup.D 25: 1.530 (as measured by Abbe refractometer) 
By using the pelletized resin composition thus obtained, a flat plate 
having a thickness of 2 mm and a size of 80.times.80 mm was molded by a 5 
ounce injection molding machine (SAV-30, manufactured by Meiki Seisakusho 
K.K.), and the transparency was measured. 
Total light transmittance: 94% 
Parallel light transmittance: 93% 
Haze: 1.0% 
The pelletized resin composition was heated at 150.degree. C. for 15 days 
in an atmosphere of air, and the yellowness index (YIs) was measured. The 
following initial value YI was obtained by measuring the yellowness index 
in the same manner except that the pelletized resin composition was not 
heated before dissolving it to form a 15 wt % methylene chloride solution. 
Initial value YI=0.15 
Heat discoloration degree of the molded plate: O 
After heating YIs=0.4 
Molded plate YIp=0.6 
From the above measurements, it is evident that the methacrylimide resin 
composition in this Example has excellent transparency, and the change 
with time under heating is very small. 
EXAMPLES 2 to 29 
Various methacrylimide resin compositions were prepared in the same manner 
as in Example 1 by using methacrylate resins and amines as identified in 
Table 1. 
The internal pressure of the reaction tank was maintained at a level of 
from 20 to 80 kg/cm.sup.2 (gauge pressure). The reaction conditions and 
the properties of the resin compositions obtained are shown in Table 1. 
In the Tables, the supply rate of the resin solution is shown as resin 
content. 
TABLE 1 
__________________________________________________________________________ 
Resin Imidizing 
solution agent Transparency 
Methyl Solvents Supply Supply 
(total light 
Methacrylate 
metharylate 
(weight rate rate transmittance) 
resin dimer (ppm) 
ratio) 
Concentration 
(kg/hr) 
Type (mol/hr) 
(%) 
__________________________________________________________________________ 
Example 2 
MMA polymer 
50 Toluene/ 
30 2.7 Methyl 20 94 
*1 methanol amine 
(90/10) 
Example 3 
MMA-MAA 950 Toluene/ 
20 " Methyl " 93 
copolymer *2 methanol amine 
(90/10) 
Example 4 
MMA-MA 600 Toluene/ 
20 " Methyl " 93 
copolymer *3 methanol amine 
(90/10) 
Example 5 
MMA-AA 350 Toluene/ 
30 " Methyl " 93 
copolymer *4 methanol amine 
(90/10) 
Example 6 
MMA-BA 750 Toluene/ 
30 " Methyl " 93 
copolymer *5 methanol amine 
(90/10) 
Example 7 
MMA-BMA-MAA 
250 Toluene/ 
20 " Methyl " 93 
copolymer *6 methanol amine 
(90/10) 
Example 8 
MMA-t-BA- 370 Toluene/ 
30 " Methyl " 93 
t-BMA methanol amine 
copolymer *7 (90/10) 
Example 9 
MMA-t-BA 130 Toluene/ 
30 " Methyl " 93 
copolymer *8 methanol amine 
(90/10) 
Example 10 
MMA-ST 30 Toluene/ 
30 " Methyl " 93 
copolymer *9 methanol amine 
(90/10) 
Example 11 
MMA-BZMA 50 Toluene/ 
30 2.7 Methyl 20 93 
copolymer methanol amine 
*10 (90/10) 
Example 12 
MMA-CHMA 70 Toluene/ 
30 " Methyl " 93 
copolymer methanol amine 
*11 (90/10) 
Example 13 
MMA 30 Toluene/ 
50 2.0 Methyl 0.15 
94 
polymer methanol amine 
*12 (90/10) 
Example 14 
MMA " Toluene/ 
50 " Methyl 1.0 94 
polymer methanol amine 
*12 (90/10) 
Example 15 
MMA " Toluene/ 
50 " Methyl 5.0 94 
polymer methanol amine 
*12 (90/10) 
Example 16 
MMA " Toluene/ 
50 " Methyl 10 94 
polymer methanol amine 
*12 (90/10) 
Example 17 
MMA " Toluene/ 
50 " Methyl 25 94 
polymer methanol amine 
*12 (90/10) 
Example 18 
MMA " Toluene/ 
" " Methyl 30 94 
polymer methanol amine 
*12 (90/10) 
Example 19 
MMA " Toluene/ 
" " Dodecyl 
20 94 
polymer methanol amine 
*12 (90/10) 
Example 20 
MMA " Toluene/ 
" " Cyclo " 94 
polymer methanol hexyl 
*12 (90/10) amine 
Example 21 
MMA polymer 
" Toluene/ 
" " N--butyl 
" 94 
methanol amine 
(90/10) 
Example 22 
" " Toluene/ 
" " N--propyl 
" 94 
methanol amine 
(90/10) 
Example 23 
" " Toluene/ 
" " Ammonia 
0.15 
93 
methanol 
(90/10) 
Example 24 
" " Toluene/ 
" " " 1.0 93 
methanol 
(90/10) 
Example 25 
" " Toluene/ 
" " " 5.0 93 
methanol 
(90/10) 
Example 26 
" " Toluene/ 
50 " " 10 93 
methanol 
(90/10) 
Example 27 
" " Toluene/ 
" " " 25 93 
methanol 
(90/10) 
Example 28 
" " Toluene/ 
" " " 30 93 
methanol 
(90/10) 
Example 29 
" " Toluene/ 
" " " 20 93 
methanol 
(90/10) 
__________________________________________________________________________ 
Heat Yellowness 
yellowness 
index of 
Heat 
index molded 
distortion 
Visual 
plate temperature 
Imidization 
YIs 
evaluation 
YIp (.degree.C.) 
rate 
__________________________________________________________________________ 
(%) 
Example 2 
0.7 
O 1.0 177 98.5 
Example 3 
2.7 
O 2.6 175 98.5 
Example 4 
1.9 
O 2.0 173 97.0 
Example 5 
0.8 
O 1.7 175 97.0 
Example 6 
2.3 
O 2.5 159 73.0 
Example 7 
1.0 
O 1.5 160 77.0 
Example 8 
1.2 
O 1.7 163 78.0 
Example 9 
1.0 
O 1.3 159 77 
Example 10 
0.5 
O 0.9 155 70 
Example 11 
0.4 
O 1.1 175 97 
Example 12 
0.6 
O 1.2 173 96 
Example 13 
0.4 
O 0.8 115 12 
Example 14 
0.3 
O 0.8 135 45 
Example 15 
0.5 
O 0.8 155 65 
Example 16 
0.5 
O 0.8 165 75 
Example 17 
0.5 
O 0.9 179 98 
Example 18 
0.4 
O 1.0 187 100 
Example 19 
0.5 
O 0.7 135 100 
Example 20 
0.5 
O 0.7 137 100 
Example 21 
0.5 
O 0.7 145 100 
Example 22 
0.4 
O 0.7 163 100 
Example 23 
0.3 
O 0.9 121 11 
Example 24 
0.3 
O 0.9 135 25 
Example 25 
0.4 
O 1.0 197 75 
Example 26 
0.4 
O 1.1 215 88 
Example 27 
0.5 
O 1.1 215 90 
Example 28 
0.5 
O 1.1 225 92 
Example 29 
0.5 
O 1.1 217 90 
__________________________________________________________________________ 
*1: Methyl methacrylate polymer (intrinsic viscosity = 0.56) 
*2: Methyl methacrylatemethacrylic acid copolymer (weight ratio = 95/5, 
intrinsic viscosity = 0.7) 
*3: Methyl methacrylatemethylacrylate copolymer (weight ratio = 95/5, 
intrinsic viscosity = 0.35) 
*4: Methyl methacryalteacrylic acid copolymer (weight ratio = 95/5, 
intrinsic viscosity = 0.6) 
*5: Methyl methacrylatebutylacrylate copolymer (weight ratio = 90/10, 
intrinsic viscosity = 1.0) 
*6: Methyl methacryaltebutyl methacrylatemethacrylic acid copolymer 
(weight ratio = 90/5/5, intrinsic viscosity = 0.65) 
*7: Methyl methacrylatetert-butylacrylate-tert-butyl methacrylate 
copolymer (weight ratio = 90/5/5, intrinsic viscosity = 1.05) 
*8: Methyl methacrylatetert-butylacrylate copolymer (weight ratio = 95/5, 
intrinsic viscosity = 0.55) 
*9: Methyl methacrylatestyrene copolymer (weight ratio = 80/20, intrinsic 
viscosity = 0.6) 
*10: Methyl methacrylatebenzyl methacrylate copolymer (weight ratio = 
90/10, intrinsic viscosity = 0.55) 
*11: Methyl methacrylatecyclohexyl methacylate copolymer (weight ratio = 
90/10, intrinsic viscosity = 0.6) 
*12: Same as used in Example 1. 
EXAMPLES 30 to 34 
Various methacrylimide resin compositions were prepared in the same manner 
as in Example 1 by using methacrylate resins, amines and solvents as 
identified in Table 2. 
The internal pressure of the reaction tank was maintained at a level of 
from 40 to 80 kg/cm.sup.2 (gauge pressure), and the purification of the 
solvents was conducted in the same manner as in Example 1. The reaction 
conditions and the properties of the resin compositions thus obtained, are 
shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Resin Imidizing 
solution agent Transparency 
Methyl Solvents Supply Supply 
(total light 
Methacrylate 
metharylate 
(weight rate rate transmittance) 
resin dimer (ppm) 
ratio) 
Concentration 
(kg/hr) 
Type (mol/hr) 
(%) 
__________________________________________________________________________ 
Example 30 
MMA polymer 
30 Xylene/ 
50 2.0 Methyl 5.0 94 
*13 methanol amine 
(80/20) 
Example 31 
MMA polymer 
" Toluene/ 
" " Methyl " 94 
*13 ethanol amine 
(90/10) 
Example 32 
MMA polymer 
" Xylene/ 
" " Methyl " 94 
*13 ethanol amine 
(80/20) 
Example 33 
MMA polymer 
" Xylene/ 
" " Methyl " 94 
*13 iso- amine 
propanol 
(80/20) 
Example 34 
MMA polymer 
" Toluene/ 
" " Methyl " 94 
*13 iso- amine 
butanol 
(70/30) 
__________________________________________________________________________ 
Heat Yellowness 
yellowness 
index of 
Heat 
index molded 
distortion 
Visual 
plate temperature 
Imidization 
YIs 
evaluation 
YIp (.degree.C.) 
rate 
__________________________________________________________________________ 
(%) 
Example 30 
0.6 
O 0.9 153 63 
Example 31 
0.5 
O 0.8 155 65 
Example 32 
0.6 
O 0.9 156 66 
Example 33 
0.5 
O 0.8 156 66 
Example 34 
0.5 
O 0.8 156 66 
__________________________________________________________________________ 
*13 Same as used in Example 1 
COMATIVE EXAMPLES 1 to 11 
The same operation as in Example 1 was repeated except that the content of 
the methyl methacrylate dimer in the methacrylate resin and the solvent 
were changed as identified in Table 3. The properties of the 
methacrylimide resin compositions thus obtained are shown in Table 3. When 
the methyl methacryalte dimer was present in a large amount and when a 
single solvent was used, the discoloration of the resin composition under 
heating was substantial. 
TABLE 3 
__________________________________________________________________________ 
Resin Imidizing 
solution agent Transparency 
Methyl Solvents Supply Supply 
(total light 
Comparative 
Methacrylate 
metharylate 
(weight rate rate transmittance) 
Example 
resin dimer (ppm) 
ratio) 
Concentration 
(kg/hr) 
Type (mol/hr) 
(%) 
__________________________________________________________________________ 
1 MMA polymer 
2,500 Toluene/ 
30 2.7 Methyl 20 89 
*14 methanol amine 
(90/10) 
2 MMA polymer 
1,900 Toluene/ 
" " Methyl " 90 
*14 methanol amine 
(90/10) 
3 MMA polymer 
1,730 Toluene/ 
" " Methyl " 90 
*14 methanol amine 
(90/10) 
4 MMA polymer 
1,030 Toluene/ 
" " Methyl " 90 
*14 methanol amine 
(90/10) 
5 MMA 1,500 Toluene/ 
50 2.0 Methyl 0.15 
90 
polymer methanol amine 
*15 (90/10) 
6 MMA 1,500 Toluene/ 
" " Methyl 1.0 90 
polymer methanol amine 
*15 (90/10) 
7 MMA 1,500 Toluene/ 
" " Methyl 5.0 90 
polymer methanol amine 
*15 (90/10) 
8 MMA 1,500 Toluene/ 
" " Methyl 10 90 
polymer methanol amine 
*15 (90/10) 
9 MMA 30 Toluene 
" " Methyl 5.0 91 
polymer amine 
*16 
10 MMA " Xylene 
" " Methyl " 89 
polymer amine 
*16 
11 MMA " Methanol 
" " Methyl " 88 
polymer amine 
*16 
__________________________________________________________________________ 
Heat Yellowness 
yellowness 
index of 
Heat 
index molded 
distortion 
Comparative 
Visual 
plate temperature 
Imidization 
Example 
YIs 
evaluation 
YIp (.degree.C.) 
rate 
__________________________________________________________________________ 
(%) 
1 10.0 
X 6.5 175 97 
2 7.0 
X 4.5 176 98 
3 6.0 
X 6.2 176 98 
4 3.4 
.DELTA. 
4.4 176 98 
5 5.0 
X 4.5 114 11 
6 5.1 
X 5.5 135 46 
7 5.2 
X 5.7 154 64 
8 5.3 
X 6.0 163 73 
9 8.8 
X 12.1 143 64 
10 9.7 
X 13.9 140 63 
11 10.3 
X 15.0 139 60 
__________________________________________________________________________ 
*14: Methyl methacrylate polymer (intrinsic viscosity: 0.56 dl/g) 
*15: Methyl methacrylate polymer (intrinsic viscosity: 0.51 dl/g) 
*16: Same as used in Example 1 
According to the process of the present invention, the imidizing reaction 
can easily be controlled, and it is thereby possible to industrially 
advantageouly produce a methacrylimide resin composition having excellent 
quality. Further, the methacrylimide resin composition thereby obtained is 
superior in the transparency, heat resistance and heat discoloration 
resistance. Therefore, it is useful in a wide range of fields wherein such 
properties are required, for example, in the fields of CRT filters, TV 
filters, fluorecent tube filters, liquid crystal filters, meters, display 
devices such as digital display boards, illumination and optics, head 
light cover electric parts for atomobiles or for core or sheath materials 
for optical fibers.