Method of producing a naphthol-modified phenolic resin of highly increased molecular weight

A copolycondensation of a phenol, a naphthol and formaldehyde proceeds smoothly in the presence of an acid and a metallic element selected from the group consisting of transition metallic elements and metallic elements of Group IIa, Group IIIa, Group IVa, Group Va and Group VIa of the Periodic Table, and a naphthol-modified phenolic resin which has a large molecular weight and does not gel is obtained.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
The present invention relates to a method of producing a naphthol-modified 
phenolic resin which is excellent in heat resistance and insulating 
properties and is suitable for use as a molding material resin or a 
hardener for epoxy resins. 
(b) Description of the Related Art 
Phenolic resins are classified roughly into novolak phenolic resins and 
resol phenolic resins, both of which exhibit excellent properties as 
binders of organic or inorganic base materials. 
Recently, the requirement for the properties of phenolic resins has become 
strict, requiring higher heat resistance, higher strength and lower 
hygroscopicity. A possible means of improving these properties is 
introduction of comonomers having a fused ring structure, such as 
naphthols. However, naphthols have a larger reactivity than phenols, so 
that conventional catalysts for the synthesis of resol resins or novolak 
resins, such as acids, metal oxides, metal chlorides, metal hydroxides and 
amines cannot produce resins of high molecular weight. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a method of producing a 
naphthol-modified phenolic resin by which copolymerization proceeds so 
smoothly as to enable production of a resin having a highly increased 
molecular weight without causing gelation. 
The inventors studied the reaction between compounds having naphthalene 
structure, namely naphthols, and aldehydes, and they consequently 
completed the present invention. 
That is, the present invention provides a method of producing a 
naphthol-modified phenolic resin which method comprises allowing a phenol 
(P), a naphthol (N) and formaldehyde (F) to react in quantities which 
provide a mol % of the phenol ranging from 95 to 5 mol % and a mol % of 
the naphthol ranging from 5 to 95 mol %, each based on the total of the 
phenol and the naphthol, and a molar ratio of formaldehyde to the total of 
the phenol and the naphthol {F/(P+N)} ranging from 0.5 to 2.0, in the 
presence of metallic element selected from the group consisting of a 
transition metallic elements and metallic elements of Group IIa, Group 
IIIa, Group IVa, Group Va and Group VIa of the Periodic Table (1983) and 
in the presence of an acid. 
According to the present invention, an addition condensation of naphthols 
and phenols with formaldehyde is carried out by using specific metallic 
elements and acids as catalysts, thereby enabling control of the chemical 
structure, molecular weight and molecular weight distribution of obtained 
naphthol-modified phenolic resins. Also, according to the present 
invention, it is possible to produce naphthol-modified phenolic resins 
having a large molecular weight. The naphthol-modified phenolic resins 
produced by the method of the present invention are excellent in heat 
resistance and have low hygroscopicity. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to the present invention, a naphthol and a phenol are used in 
quantities which provide a mol % of the phenol ranging from 95 to 5 mol % 
and a mol % of the naphthol ranging from 5 to 95 mol %, each based on the 
total of the phenol and the naphthol. A ratio of the naphthol less than 
the above-described range hardly take the effects of 
naphthol-modification. The molar ratio of formaldehyde to the total of the 
phenol and the naphthol {F/(P+N)} ranges from 0.5 to 2.0, preferably from 
0.8 to 1.3. If the molar ratio of formaldehyde is less than 0.5, the 
molecular weight will be decreased, and if it is more than 2.0, gelation 
will occur. 
In order to provide formaldehyde for the addition condensation of the 
present invention, various kinds of formaldehyde-generating compounds may 
be used. The concentration of formaldehyde in formaldehyde-generating 
compounds is not particularly limited insofar as the 
formaldehyde-generating compounds are used in a quantity which provides 
the molar ratio {F/(P+N)} ranging from 0.15 to 2.0. Typical examples of 
the formaldehyde-generating compounds include formalin, paraformaldehyde 
and trioxymethylene. 
Phenols which may be used as the phenol in the present invention are not 
particularly limited, and those used for the synthesis of conventional 
phenolic resins, such as phenol, cresol, nonylphenol, tert-butylphenol and 
xylenol, may be used. 
Typical examples of the naphthol which may be used in the present invention 
include 1-naphthol and 2-naphthol. 
Metallic elements which may be used as the metallic element catalyst in the 
method of producing the naphthol-modified phenolic resin according to the 
present invention include transition metallic elements, such as chromium, 
manganese, nickel, cobalt, zinc, iron and copper, metallic elements of 
Group IIa of the Periodic Table, such as magnesium, metallic elements of 
Group IIIa of the Periodic Table, such as aluminum, gallium and indium, 
metallic elements of Group IVa of the Periodic Table, such as silicon, 
germanium, tin and lead, metallic elements of Group Va of the Periodic 
Table, such as phosphorus, arsenic and antimony, and metallic elements of 
Group VIa of the Periodic Table, such as sulfur, selenium and tellurium. 
Examples of the metallic elements which may be used in the present 
invention are not limited to those exemplified above, and other metallic 
elements of transition metallic elements and metallic elements of Groups 
IIa, IIIa, IVa, Va and VIa of the Periodic Table also may be used. These 
metallic elements may be used in the reaction system individually or as a 
mixture of two or more of them. The quantity of the metallic element to be 
used in the present invention is not particularly limited. Generally, the 
metallic element is used in a quantity of 0.0001 to 0.05 mol, preferably 
0.0005 to 0.002 mol, per one mol of the total of the phenol and the 
naphthol. 
The acid which may be used as an acid catalyst in the present invention is 
not particularly limited, and either of a weak acid and a strong acid may 
be used. Typical examples of the acid include oxalic acid, tartaric acid, 
succinic acid, citric acid, hydrochloric acid, sulfuric acid and 
p-toluenesulfonic acid. The quantity of the acid to be used as an acid 
catalyst is not particularly limited, and preferred quantity is 0.0001 to 
100 moles per one mol of the metallic element used. 
The reaction conditions for the production of the naphthol-modified 
phenolic resin are not particularly limited. When the phenol and naphthol 
are used in quantities which provide a mol % of the phenol ranging from 95 
to 20 mol % and a mol % of the naphthol ranging from 5 to 80 mol %, each 
based on the total of the phenol and the naphthol, the addition 
condensation of the phenol, the naphthol and formaldehyde proceeds easily 
in the absence of organic solvents. Herein, organic solvents means organic 
solvents other than those contained in the formaldehyde-generating 
compounds used for the addition condensation. In such a case, the addition 
condensation is generally carried out at a temperature ranging from 
100.degree. to 110.degree. C. under reflux. The reaction time under reflux 
depends on the kind and quantity of the catalyst used, and is generally 1 
to 50 hours. After completion of the reflux and addition condensation in a 
reaction vessel, thus obtained reaction product is dehydrated at a reduced 
pressure at a temperature of 230.degree. C. or lower until the reaction 
product has a desired softening point, and the resulting resin is then 
removed from the reaction vessel and cooled to obtain a desired novolak 
naphthol-modified phenolic resin. 
When the phenol and naphthol are used in quantities which provide a mol % 
of the phenol ranging from 20 to 5 mol % and a mol % of the naphthol 
ranging from 80 to 95 mol %, each based on the total of the phenol and the 
naphthol, it is preferable to carry out the addition condensation by a 
solution polymerization in the presence of a ketone solvent. In such a 
case, the addition condensation is carried out preferably at the boiling 
point of the ketone solvent used under reflux. The reaction time under 
reflux depends on the kind and quantity of the catalysts used, and it is 
generally 1 to 50 hours. 
The ketone solvent which may be used in the present invention is not 
particularly limited, and typical examples of the ketone solvent include 
acetone, methyl ethyl ketone, 2-pentanone, 2-hexanone, 
2-methyl-4-pentanone, 2-methyl-4-heptanone and cyclohexanone. The quantity 
of the ketone solvent is preferably 100 to 500 parts by weight per 100 
parts by weight of the total of the phenols and the naphthols used. 
Thus obtained novolak naphthol-modified phenolic resin are applicable to 
various uses, such as a molding material, a hardener for epoxy resins, a 
resin material for castings and a friction material.

Hereinafter, the present invention will be described in details referring 
to the following Examples, but the Examples do not limit the scope of the 
present invention. 
EXAMPLES 1 TO 10 AND COMATIVE EXAMPLES 1 TO 3 
EXAMPLE 1 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 72 g of 1-naphthol, 423 g of phenol, 323 g of 37% 
formaldehyde, 0.3 g of aluminum powder and 2.52 g of oxalic acid, and were 
then allowed to react for 4 hours under reflux. The reaction mixture was 
then dehydrated at a reduced pressure of 700 mmHg while the temperature 
was elevated up to 200.degree. C., to obtain 500 g of a solid resin. In 
the present invention, a high speed liquid chromatography L6000 (produced 
by Hitachi, Ltd.) and a data analyzer C-R4A (produced by Shimazu Corp.) 
were used as GPC apparatuses for the measurements of molecular weight and 
molecular weight distribution. Two KF-804L columns (produced by Showa 
Denko K. K.) were used as GPC columns. By using these apparatuses, the 
molecular weight Mn of the solid resin was measured to be 904, and the 
molecular weight distribution Mw/Mn was measured to be 3.3 (hereinafter, 
number average molecular weight will be called "Mn" for short, and weight 
average molecular weight "Mw"). 
EXAMPLE 2 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 215 g of 1-naphthol, 329 g of phenol, 162 g of 37% 
formaldehyde, 77 g of 86% paraformaldehyde, 0.3 g of gallium and 0.3 g of 
oxalic acid, and were then heated. After reaction was carried out for 36 
hours under reflux, the reaction mixture was then dehydrated at a reduced 
pressure of 700 mmHg while the temperature was elevated up to 200.degree. 
C., to obtain 510 g of a solid resin. Mn=776, Mw/Mn=3.1. 
EXAMPLE 3 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 215 g of 1-naphthol, 329 g of phenol, 162 g of 37% 
formaldehyde, 77 g of 86% paraformaldehyde, 0.3 g of aluminum powder and 
1.25 g of oxalic acid, and were then heated. After reaction was carried 
out for 5 hours under reflux, the reaction mixture was dehydrated at a 
reduced pressure of 700 mmHg while the temperature was elevated up to 
220.degree. C., to obtain 480 g of a solid resin. Mn=869, Mw/Mn=3.6. 
EXAMPLE 4 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 360 g of 1-naphthol, 235 g of phenol, 162 g of 37% 
formaldehyde, 77 g of 86% paraformaldehyde, 0.3 g of aluminum powder and 
1.5 g of succinic acid, and were then heated. Paraformaldehyde was 
dissolved gradually, and was dissolved completely in the vicinity of 
100.degree. C. After reaction was carried out for 5 hours under reflux, 
the reaction mixture was dehydrated at a reduced pressure of 700 mmHg 
while the temperature was elevated up to 220.degree. C., to obtain 510 g 
of a solid resin. Mn=968, Mw/Mn=6.2. 
EXAMPLE 5 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 360 g of 1-naphthol, 235 g of phenol, 162 g of 37% 
formaldehyde, 140 g of 86% paraformaldehyde, 0.3 g of aluminum powder and 
2.5 g of oxalic acid, and were then heated. After reaction was carried out 
for 3 hours under reflux, the reaction mixture was dehydrated at a reduced 
pressure of 700 mmHg while the temperature was elevated up to 200.degree. 
C., to obtain 500 g of a solid resin. Mn=982, Mw/Mn=4.0. 
EXAMPLE 6 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 215 g of 2-naphthol, 329 g of phenol, 122 g of 37% 
formaldehyde, 70 g of 86% paraformaldehyde, 0.3 g of aluminum powder and 
1.3 g of oxalic acid. Paraformaldehyde was dissolved gradually and was 
dissolved completely in the vicinity of 100.degree. C. After reaction was 
carried out for 5 hours under reflux, the reaction mixture was dehydrated 
at a reduced pressure of 700 mmHg while the temperature was elevated up to 
200.degree. C., to obtain 490 g of a solid resin. Mn=505, Mw/Mn=2.0. 
EXAMPLE 7 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 72 g of 2-naphthol, 423 g of phenol, 162 g of 37% 
formaldehyde, 77 g of 86% paraformaldehyde, 0.3 g of aluminum powder and 
1.25 g of oxalic acid, and were then heated. Paraformaldehyde was 
dissolved gradually, and was dissolved completely in the vicinity of 
100.degree. C. After reaction was carried out for 3 hours under reflux, 
the reaction mixture was dehydrated at a reduced pressure of 700 mmHg 
while the temperature was elevated up to 200.degree. C., to obtain 450 g 
of a solid resin Mn=635, Mw/Mn=2.6. 
EXAMPLE 8 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 72 g of 2-naphthol, 423 g of phenol, 162 g of 37% 
formaldehyde, 140 g of 86% paraformaldehyde, 0.5 g of gallium and 2 g of 
oxalic acid, and were then heated. Paraformaldehyde was dissolved 
gradually, and was dissolved completely in the vicinity of 100.degree. C. 
After reaction was carried out for 6 hours under reflux, the reaction 
mixture was dehydrated at a reduced pressure of 700 mmHg while the 
temperature was elevated up to 220.degree. C., to obtain 500 g of a solid 
resin. Mn=1400, Mw/Mn=5.4 
COMATIVE EXAMPLE 1 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 215 g of 1-naphthol, 215 g of phenol, 162 g of 37% 
formaldehyde, 140 g of 86% paraformaldehyde and 20 ml of 5-N hydrochloric 
acid, and were then heated. Paraformaldehyde was dissolved gradually, and 
was completely dissolved in the vicinity of 100.degree. C. After reaction 
was carried out for 3 hours under reflux, the reaction mixture was 
dehydrated at a reduced pressure of 700 mmHg while the temperature was 
elevated up to 180.degree. C., but the reaction mixture set to gel. 
COMATIVE EXAMPLE 2 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 72 g of 2-naphthol, 423 g of phenol, 162 g of 37% 
formaldehyde, 140 g of 86% paraformaldehyde and 5.5 g of aluminum oxalate, 
and were then heated. Paraformaldehyde was dissolved gradually, and was 
dissolved completely in the vicinity of 100.degree. C. After reaction was 
carried out for 6 hours under reflux, the reaction mixture was dehydrated 
at a reduced pressure of 700 mmHg while the temperature was elevated up to 
160.degree. C., but the reaction mixture set to gel. 
EXAMPLE 9 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 300 g of acetone, 144 g of 1-naphthol, 9.4 g of phenol, 40.5 g 
of 37% formaldehyde, 24 g of 86% paraformaldehyde, 0.15 g of manganese and 
0.3 g of oxalic acid, and were heated. After reaction was carried out for 
15 hours under reflux, the reaction mixture was reprecipitated in 
methanol, to obtain 160 g of a solid resin. Mn=806, Mw/Mn=2.2. 
EXAMPLE 10 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 400 g of 2-methyl-4-heptanone, 144 g of 1-naphthol, 15 g of 
phenol, 40.5 g of 37% formaldehyde, 27 g of 86% paraformaldehyde, 0.1 g of 
aluminum powder and 1.25 g of oxalic acid, and were then heated. After 
reaction was carried out for 10 hours under reflux, the reaction mixture 
was reprecipitated in methanol, to obtain 170 g of a solid resin. Mn=842, 
Mw/Mn=2.9. 
COMATIVE EXAMPLE 3 
Into a 2-liter flask equipped with a stirrer, a condenser and a thermometer 
placed were 144 g of 1-naphthol, 15 g of phenol, 40.5 g of 37% 
formaldehyde, 27 g of 86% paraformaldehyde and 20 ml of 2-N hydrochloric 
acid, and were then heated. Paraformaldehyde was dissolved gradually, and 
was dissolved completely in the vicinity of 100.degree. C. After reaction 
was carried out for 3 hours under reflux, the reaction mixture was 
dehydrated at a reduced pressure of 700 mmHg while the temperature was 
elevated up to 230.degree. C., but the reaction mixture set to gel.