U.S. patent application number 09/809520 was filed with the patent office on 2001-08-16 for method of producing thermotropic liquid crystalline copolyester, thermotropic liquid crystalline copolyester composition obtained by the same method, and molding made of the same composition.
This patent application is currently assigned to NIPPON PETROCHEMICAL CO., LTD.. Invention is credited to Kobayashi, Toshitaka, Murouchi, Satoshi, Yamada, Yoshikuni.
Application Number | 20010014708 09/809520 |
Document ID | / |
Family ID | 26429553 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014708 |
Kind Code |
A1 |
Murouchi, Satoshi ; et
al. |
August 16, 2001 |
Method of producing thermotropic liquid crystalline copolyester,
thermotropic liquid crystalline copolyester composition obtained by
the same method, and molding made of the same composition
Abstract
A method of producing a thermotropic liquid crystalline
copolyester having an extremely small amount of out-gases
comprising the steps of: (1) charging in a reactor 5-100 mol % of
aromatic hydroxycarboxylic acid, 0-47.5 mol % of aromatic
dicarboxylic acid and 0-47.5 mol % of aromatic diol, so that the
sum of mol % of each material is 100 mol % and the mol % of
aromatic dicarboxylic acid and that of aromatic diol are
substantially equal; (2) adding acetic anhydride of an amount which
satisfies the formula, (B-C)/A.gtoreq.1.04, "A" representing the
total molar number of the hydroxy group in a reaction system, "B"
representing the molar number of acetic anhydride to be added, and
"C" representing the molar number of water present in the reaction
system prior to addition of acetic anhydride; (3) acetylation; (4)
melt polymerization; and (5) solid-phase polymerization.
Inventors: |
Murouchi, Satoshi;
(Kanagawa-ken, JP) ; Yamada, Yoshikuni;
(Kanagawa-ken, JP) ; Kobayashi, Toshitaka;
(Chiba-ken, JP) |
Correspondence
Address: |
Dilworth & Barrese, LLP
333 Earle Ovington Blvd.
Uniondale
NY
11553
US
|
Assignee: |
NIPPON PETROCHEMICAL CO.,
LTD.
|
Family ID: |
26429553 |
Appl. No.: |
09/809520 |
Filed: |
March 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09809520 |
Mar 15, 2001 |
|
|
|
09538623 |
Mar 29, 2000 |
|
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|
Current U.S.
Class: |
524/108 ;
524/109; 524/110; 524/120; 524/128; 524/710 |
Current CPC
Class: |
Y10T 428/12528 20150115;
Y10T 428/12007 20150115; C08K 5/524 20130101; Y10T 428/31786
20150401; C08G 63/80 20130101; Y10T 428/31681 20150401; Y10T
428/31989 20150401; Y10T 428/12569 20150115; C08L 67/00 20130101;
C08K 5/524 20130101; C08G 63/605 20130101 |
Class at
Publication: |
524/108 ;
524/109; 524/110; 524/128; 524/120; 524/710 |
International
Class: |
C08K 005/1575; C08K
005/52; C08L 067/02; C08L 067/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 1999 |
JP |
88111/1999 |
Mar 30, 1999 |
JP |
88217/1999 |
Claims
What is claimed is:
1. A method of producing a thermotropic liquid crystalline
copolyester which the amount of out-gases emitted therefrom is very
small comprising the steps of: (1) charging in a reactor 5-100 mol
% of aromatic hydroxycarboxylic acid, 0-47.5 mol % of aromatic
dicarboxylic acid and 0-47.5 mol % of aromatic diol, so that the
sum of mol % of each material is 100 mol % and the mol % of
aromatic dicarboxylic acid and that of aromatic diol are
substantially equal; (2) adding acetic anhydride of an amount which
satisfies the formula below, (B-C)/A.gtoreq.1.04 "A" represents the
total molar number of the hydroxy group in a reaction system, "B"
represents the molar number of acetic anhydride to be added, and
"C" represents the molar number of water present in the reaction
system prior to addition of acetic anhydride; (3) acetylation; (4)
melt polymerization; and (5) solid-phase polymerization.
2. A method of claim 1, further comprising a step of measuring
water content in the reaction system between the step (1) and the
step (2).
3. A method of claim 1, wherein the value of (B-C)/A is within the
range of 1.04 to 1.08.
4. A method of claim 1, wherein the aromatic hydroxycarboxylic acid
contains 90-100 mol % of p-hydroxybenzoic acid and 0-10 mol % of
other aromatic hydroxycarboxylic acid, such that the sum of each
mol % is 100 mol %, the aromatic dicarboxylic acid contains 45-100
mol % of terephthalic acid and 0-55 mol % of other aromatic
dicarboxylic acid, such that the sum of each mol % is 100 mol %,
and the aromatic diol contains 60-100 mol % of p,p'-biphenol and
0-40 mol % of other aromatic diol, such that the sum of each mol %
is 100 mol %.
5. A method of claim 1, wherein the aromatic hydroxycarboxylic acid
contains 90-100 mol % of p-hydroxybenzoic acid and 0-10 mol % of
2-hydroxy-6-naphthoic acid, such that the sum of each mol % is 100
mol %, the aromatic dicarboxylic acid contains 45-100 mol % of
terephthalic acid and 0-55 mol % of isophthalic acid, such that the
sum of each mol % is 100 mol %, the and aromatic diol contains
60-100 mol % of p,p'-biphenol and 0-40 mol % of hydroquinone, such
that the sum of each mol % is 100 mol %.
6. A thermotropic liquid crystalline copolyester resin composition
comprising: (1) 100 parts by weight of the thermotropic liquid
crystalline copolyester obtained by the method of claim 1; and (2)
0.001-1 parts by weight of at least one phosphite ester having the
general formula (1): 3wherein R and R' each represent a group
selected from the group consisting of alkyl group, alkenyl group,
aryl group and aralkyl group, and R and R' may represent the same
group.
7. A thermotropic liquid crystalline copolyester resin composition
compring: (1) 100 parts by weight of the thermotropic liquid
crystalline copolyester obtained by the method of claim 1; (2)
0.001-1 parts by weight of at least one phosphorous acid ester
having the general formula (1): 4wherein R and R' each represent a
group selected from the group consisting of alkyl group, alkenyl
group, aryl group and aralkyl group, and R and R' may represent the
same group; and (3) inorganic or organic fillers within the range
of 10 to 90 weight % of the whole composition.
8. An electric/electronic component comprising: a resin portion;
and a metal-made conductive portion, wherein the resin portion is
made of the thermotropic liquid crystalline copolyester obtained by
the method of claim 1.
9. An electric/electronic component comprising: a resin portion;
and a metal-made conductive portion, wherein the resin portion is
made of the thermotropic liquid crystalline copolyester resin
composition of claim 6 or claim 7.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of producing a
thermotropic liquid crystalline copolyester which the amount of
corrosive out-gases emitted in a high temperature environment is
extremely small, a thermotropic liquid crystalline copolyester
resin composition obtained by the method, and a resin molded
article made of the same resin composition for use in
electrical/electronic components. More specifically, the present
invention relates to a method of producing a thermotropic liquid
crystalline copolyester which the amount of corrosive out-gases
(such as acetic acid and phenol) emitted in a high temperature
environment is extremely small due to the setting of the amount of
acetic anhydride in the reaction system in which acetylation is
carried out before polymerization to a specific range, a
thermotropic liquid crystalline copolyester resin composition which
the amount of corrosive out-gases (such as acetic acid and phenol)
emitted in a high temperature is further extremely small and is
made by mixing a specific phosphite compound to a thermotropic
liquid crystalline copolyester resin obtained by the same method,
and a resin molded article made of the same resin composition for
use in electrical/electronic components.
[0003] 2. Description of the Related Art
[0004] It has been recognized that thermotropic liquid crystalline
copolyesters made by known methods tend to emit corrosive out-gases
which corrode metal-made conductive portions (e.g. an electronic
circuit) of an electric/electronic component in a high temperature
environment (such as soldering and mounting-to-surface processes).
Corrosiveness of such corrosive out-gases has been recognized as a
serious problem in such cases. Studies have revealed that the main
component of such corrosive out-gases is generally acetic acid
(refer to, for example, JP-A 8-53543).
[0005] Specifically, in electric/electronic components having
metal-made conductive portions which is vulnerable to the gases
emitted from a thermotropic liquid crystalline copolyester resin
(such as a relay, a switch, a connector, a socket, a resistor, a
condenser, a motor, an oscillator, a print circuit board, and a
power module), the metal-made conductive portions are oxidized and
a corrosive film is formed thereon by the corrosive out-gases and
the like due to heat history during the mounting-to-surfaces
process. As a result, failure in the conductive portions may occur.
In addition, in a case in which the electrical/electronic component
has an electric contact which is operated in a mechanical manner, a
failure in contact may occur due to formation of layers of
carbonized materials in the contact portion (the layers are formed
mainly in the contact portion by discharge during the contact
operation).
[0006] The corrosion of this type has particularly been a serious
problem in components such as a relay and a switch in which good
contact properties must be maintained for a long period.
[0007] Recently, thermotropic liquid crystalline copolyesters are
also used in various components in HDD (e.g. a carriage, a chassis
and a VCM coil holding member for an actuator, a member for
installing a head in a non-operationphase and the like), in FDD and
in similar components in an optical disc drive and the like. With
respect to the magnetic or optical data reading portions which are
essential to these devices, deterioration of performances due to
corrosive out-gases emitted from the resin are now likewise being
concerned.
[0008] As thermotropic liquid crystalline copolyesters can be
molded so as to have thin walls (i.e. these copolyesters have
excellent molding/fluxional properties) and have excellent
soldering properties (i.e. these copolyesters have excellent heat
resistance properties), they have been employed as forming
materials of various electric/electronic components so that
excellent dimensional precision obtained in the copolyesters be
most advantageously utilized. In addition, the electric/electronic
components are now required to be far smaller and operated at a
lower voltage. Accordingly, formation of corrosive film and
generation of layers of carbonized materials as described above
could cause much worse, more often initial failures or malfunction
in these electric/electronic components than now. Therefore, there
is a demand for a thermotropic liquid crystalline copolyester which
the amount of corrosive gases is extremely small. This may be
especially a concern in a relay component and a switch component.
Note that the layers of carbonized materials are formed in these
components probably because the corrosive out-gases are carbonized
by arc discharge and deposited, causing abnormality in
conductance.
[0009] As methods for reducing corrosive out-gases from themotropic
liquid crystalline copolyester, there have been proposed a method
of blending a gas absorbing material (JP-A 8-333505), a method of
blocking the end of the molecular chain with mono-functional
monomer (JP-A 3-203925, JP-A 4-249528 and JP-A 8-53543). However,
these methods are not necessarily satisfactory.
[0010] These conventional methods propose, assuming that the main
component of the corrosive gases is acetic acid emitted from the
thermotropic liquid crystalline copolyester, techniques for
suppressing the generation of acetic acid and capturing the
generated acetic acid. However, it has not been determined what
actually are the corrosive out-gases which cause corrosive damages
to metal-made conductive portions of electric/electronic
components. Therefore, although emission of acetic acid is
prevented, it does not necessarily mean that a thermotropic liquid
crystalline copolyester which is satisfactory in terms of its
corrosive out-gas effect on an electric/electronic component can be
obtained. Especially, if the technique pays too much attention to
suppression of acetic acid emission and rather increases emission
of other corrosive out-gases, such technique or methods inevitably
have to face a serious limitation.
[0011] With respect to this problem, the inventors have discovered
that thermotropic liquid crystalline copolyester may emit phenol,
which is corrosive and could be carbonized, together with acetic
acid in a high temperature environment. Based on this discovery,
the inventors were convinced that a thermotropic liquid crystalline
copolyester which the amount of corrosive out-gases is very small
and thus can be used as a reliable forming material for an
electric/electronic component (in other words, a thermotropic
liquid crystalline copolyester which satisfies the demand from an
electric/electronic component) is effected by suppressing the
generation of phenol. The present invention was completed as a
result of industrious study according to this theory.
[0012] The detailed mechanism in which corrosive out-gases are
emitted from thermotropic liquid crystalline copolyester is not
known yet. The inventors, however, discovered for the first time in
the world that the amount of emission of both corrosive out-gases
(acetic acid and phenol) can be suppressed by setting the amount of
acetic anhydride in the reaction system in which acetylation is
carried out before polymerization within a specified range,
resulting in the present invention.
[0013] Generation of corrosive gases tends to be accelerated by the
existence of inorganic or organic fillers blended into the
copolyester. In the case of engineering plastics such as
thermotropic liquid crystalline copolyester, inorganic or organic
fillers are normally blended in practice. Accordingly, it is
required that generation of corrosive gases be reliably suppressed
in the resins in which inorganic or organic fillers are
blended.
[0014] The inventors of the present invention have achieved
reliably suppressing generation of out-gases at a practically
acceptable level in the resin compositions in which fillers are
blended, by adding a specific phosphate compound into a
thermotropic liquid crystalline copolyester obtained by the
aforementioned method.
OBJECTS OF THE INVENTION
[0015] One object of the present invention is to provide a method
of producing a thermotropic liquid crystalline copolyester which
the amount of corrosive out-gases (such as acetic acid and phenol)
in a high temperature environment is extremely small, a resin
composition containing a thermotropic liquid crystalline
copolyester obtained by the method, and electric/electronic
components formed by molding the resin composition. Another object
of the present invention is to reliably suppress generation of
out-gases at a practically acceptable level in the resin
compositions in which fillers are blended.
SUMMARY OF THE INVENTION
[0016] As a result of assiduous study carried out by the inventors
in order to achieve the aforementioned objects, it has been
discovered that the amount of emission of corrosive out-gases (both
acetic acid and phenol) can be suppressed by setting the amount of
acetic anhydride in the reaction system in which acetylation is
carried out prior to polymerization within a specific range. The
present invention was completed on the basis of this discovery
(method).
[0017] In addition, the inventors of the present invention have
discovered that a more excellent thermotropic liquid crystalline
copolysester which the amount of corrosive out-gases emitted in a
high temperature environment is extremely small can be obtained by
blending a specific phosphite compound into the thermotropic liquid
crystalline copolysester obtained by the method. This discovery
also contributes to the completion of the present invention.
[0018] Accordingly, in the first aspect of the present invention, a
method of producing a thermotropic liquid crystalline copolyester
which the amount of out-gases is extremely small comprises the
steps of: (1) feeding in a reactor 5-100 mol % of aromatic
hydroxycarboxylic acid, 0-47.5 mol % of aromatic dicarboxylic acid
and 0-47.5 mol % of aromatic diol, so that the sum of mol % of each
material is 100 mol % and the mol % of aromatic dicarboxylic acid
and that of aromatic diol are substantially equal; (2) adding
acetic anhydride of an amount which satisfies the formula
below,
(B-C)/A.gtoreq.1.04
[0019] "A" represents the total molar number of the hydroxy group
in a reaction system, "B" represents the molar number of acetic
anhydride to be added, and "C" represents the molar number of water
present in the reactions system prior to addition of acetic
anhydride; (3) acetylation; (4) melt polymerization; and (5)
solid-phase polymerization.
[0020] In the second aspect of the present invention, a
thermotropic liquid crystalline copolyester resin composition
comprises: (1) 100 parts by weight of the thermotropic liquid
crystalline copolyester obtained by said method of producing a
thermotropic liquid crystalline copolyester; and (2) 0.001-1 parts
by weight of at least one phosphite ester having the general
formula: 1
[0021] In the formula, R and R' each represent a group selected
from the group consisting of alkyl group, alkenyl group, aryl group
and aralkyl group. R and R' may represent the same group.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention will be described in detail
hereinafter.
[0023] In a producing method of the present invention, as a first
step (1), 5-100 mol % of aromatic hydroxycarboxylic acid, 0-47.5
mol % of aromatic dicarboxylic acid and 0-47.5 mol % of aromatic
diol are charged in a reactor, so that the sum of mol % of each
material is 100 mol % and the mol % of aromatic dicarboxylic acid
and that of aromatic diol are substantially equal. Types of the
reactor and methods of charging the reaction materials are not
particularly limited and any suitable known methods may be
employed.
[0024] Monomers charged as the materials are, specifically,
monomers which are derived to a repeating structural unit shown in
formulae (2) to (4) below.
--O--(X)--CO-- (2)
--CO--(Y)--CO (3)
--O--(Z)--O-- (4)
[0025] The monomer derived to the repeating unit of (2) is an
aromatic hydroxycarboxylic acid. Examples of the aromatic
hydroxycarboxylic acid include p-hydroxybenzoic acid,
2-hydroxy-6-naphthoic acid, m-hydroxybenzoic acid and the like.
These examples may be used solely or in combination. Preferably,
p-hydroxybenzoic acid or a combination of p-hydroxybenzoic acid and
2-hydroxy-6-naphthoic acid are used.
[0026] The monomer derived to the repeating unit of (3) is an
aromatic dicarboxylic acid. Examples of the aromatic decarboxylic
acid include terephthalic acid, isophthalic acid,
2,6-dicarboxynaphthalene, 4,4'-biphenyldicarboxylic acid and the
like. These monomers may be used solely or in combination.
Preferably, terephthalic acid or a combination of terephthalic acid
and isophthalic acid are used.
[0027] The monomer constituting the repeating unit of (4) is an
aromatic diol. Examples of the aromatic diol include 4,4'-biphenol,
hydroquinone, 2,6-dihydroxynaphthalene and the like. These monomers
may be used solely or in combination. Preferably, 4,4'-biphenol or
a combination of 4,4'-biphenol and hydroquinone are used.
[0028] In the thermotropic liquid crystalline copolyester produced
by the present invention, the preferable examples of monomer
combination include:
[0029] 1. p-hydroxybenzoic acid, terephthalic acid,
p,p'-biphenol
[0030] 2. p-hydroxybenzoic acid, terephthalic acid and isophthalic
acid, p,p'-biphenol
[0031] 3. p-hydroxybenzoic acid, terephalic acid and isophthalic
acid, p,p'-biphenol and hydroquinone
[0032] 4. p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid
[0033] 5. p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid,
terephalic acid and isophthalic acid, p,p'-biphenol
[0034] 6. p-hydroxybenzoic acid, terephthalic acid, isophthalic
acid, 2,6-dicarboxynaphthalene, p,p'-biphenol
[0035] The amount of the repeating structural unit (2) derived from
the aromatic hydroxy acid such as p-hydroxybenzoic acid of the
present invention is preferably set within the range of 5 to 100
mol % of the structure unit as a whole of the copolyester produced
by the method of the present invention. When the amount of the
repeating structural unit (2) is less than 5 mol %, the melting
point of the copolyester rises up and the fluxional properties and
the mechanical strength thereof deteriorate. This is not
preferable.
[0036] Examples of more preferable combinations of the monomers
include: aromatic hydroxycarboxylic acid containing 90-100 mol % of
p-hydroxybenzoic acid and 0-10 mol % of other aromatic
hydroxycarboxylic acid (the sum of each mol % is 100 mol %);
aromatic dicarboxylic acid containing 45-100 mol % of terephthalic
acid and 0-55 mol % of other aromatic dicarboxylic acid (the sum of
each mol % is 100 mol %); and aromatic diol containing 60-100 mol %
of p,p'-biphenol and 0-40 mol % of other aromatic diol (the sum of
each mol % is 100 mol %).
[0037] Examples of the most preferable combinations of the monomers
include: aromatic hydroxycarboxylic acid containing 90-100 mol % of
p-hydroxybenzoic acid and 0-10 mol % of 2-hydroxy-6-naphthoic acid
(the sum of each mol % is 100 mol %); aromatic dicarboxylic acid
containing 45-100 mol % of terephthalic acid and 0-55 mol % of
isophthalic acid (the sum of each mol % is 100 mol %); and aromatic
diol containing 60-100 mol % of p,p'-biphenol and 0-40 mol % of
hydroquinone (the sum of each mol % is 100 mol %).
[0038] By employing these preferable monomer combinations, the
balance between the molding/fluxional properties, the heat
resistance properties and the mold processing temperature is
further improved, enabling more excellent adaptation and
performances when the resulting resin composition is molded to form
an electric/electronic component having thin walls. In addition to
the aforementioned effect, the shear stress history during the
molding process is reduced, the stability in a high temperature
environment and at the mold processing temperature is increased and
the basic properties of suppressing the emission of corrosive
out-gases are improved, further enhancing the effect of the present
invention.
[0039] With respect to the monomers and acetic anhydride (described
in detail below), those which are industrially available may
directly be used. The monomers may be dried before charging into
the reactor or the monomers may be dried after being charged into
the reactor. One example of a method of drying the monomers after
the monomers are charged into the reactor is follows. The
temperature of the materials is raised to 70.degree. C. or so and
then the "pressure reduction and nitrogen injection" process is
repeated several times with stirring. By carrying out this process
for several hours, nitrogen-substitution and drying of the monomers
are effected. Normally, drying in such a manner is sufficient in
order to achieve the task. In a case in which the process is
carried out in a batch system, catalysts, stabilizer and the like
may be charged into the reaction reactor according to necessity. As
the catalysts, types thereof are not particularly limited and any
suitable known catalysts may be used.
[0040] The reactions (including the acetylation step and the melt
polymerization step described below) may be carried out in a batch
system or in a continuous system.
[0041] In the step (1), the monomers of predetermined type are
charged into the reactor and heated according to necessity.
Thereafter, as the step (2), the amount of water contained in the
reaction system is measured prior to charging of acetic
anhydride.
[0042] Specifically, the factor to be first selected and controlled
among the variable factors associated with the reaction system in
which acetylation is carried out is the amount of acetic anhydride
to be charged next. The amount of acetic anhydride to be charged
next is expressed by the following relationship, given that the
total molar number of the hydroxy group of the monomers present in
the reation system when the acetylation reaction is started is
represented as "A" and the molar number of acedic anhydride is
represented as "B" and the molar number of water present in the
reaction system before the addition of acetic anhydride is
represented by "C".
(B-C)/A.gtoreq.1.04
[0043] In the present invention, it is more preferable that "A",
"B" and "C" satisfy the following formula:
1.04.ltoreq.(B-C)/A.ltoreq.1.08
[0044] The value (B-C)/A is a parameter for determining the amount
to be added of acetic anhydride. When the value of the parameter is
less than 1.04, the amount of emission of phenol gas may increase
and thus such a value is not desirable. When the value of the
parameter is larger than 1.08, the amount of emission of acetic
acid gas may significantly increase and thus such a value is not
desirable, either. In short, as long as the value of the parameter
is no less than 1.04, it is possible to suppress emission of phenol
gas at a practically acceptable level, although a large amount of
fillers has not been blended into the molded body.
[0045] In the present invention, in order to effect the
aforementioned control on the parameter, the amount of water
present in the reaction system must be known and thus the water
content in the reaction system is measured prior to the starting of
the acetylation process. As the method of measuring the water
content, any suitable known method may be employed as long as the
method allows reliable measurement of water of a very small amount
(ppm or so). Specifically, Karl Fischer's method may be employed as
the method of measuring the amount of water.
[0046] In the present invention, the amount of water contained in
the reaction system is measured prior to adding acetic anhydride.
Even in case in which the monomers are dried before being charged
(refer to the description above), a constant amount of water is
still detected from the reaction system in a normal condition. The
amount of water detected in such a case is normally 0.2 weight % or
so at the maximum.
[0047] One of the important features of the present invention lies
in that the amount of H.sub.2O present in the reaction system is
measured in the step (2) and the amount of acetic anhydride to be
consumed as a result of the reaction between acetic anhydride and
H.sub.2O is calculated, in order that the amount of acetic
anhydride be increased as much as the calculated amount of acetic
anhydride to be consumed. Because of this, in a case in which a
batch system is employed, a portion of the charged liquid is taken
out as a sample from the reactor prior to the starting of the
acetylation reaction and the amount of water contained therein is
measured accurately. Note that any other suitable methods of
measuring water content may be employed.
[0048] Acetic anhydride added in step (2) is added in order to
acetylate the hydroxyl group of the monomers. Acetic anhydride
easily reacts with H.sub.2O and is decomposed to acetic acid.
Accordingly, when water is present in the reaction system, acetic
anhydride immediately reacts with this water and is decomposed to
acetic acid. As a result, the amount of acetic anhydride which is
substantially involved with the reaction in the acetylation process
is reduced. It should be noted that the amount of H.sub.2O present
in the reaction system significantly varies depending on the method
of producing the monomers, the conditions during storage, moisture
in air, whether or not the monomers are dried in producing
copolyester, the degree of drying and the like. Therefore, the
amount of acetic anhydride to be added in producing thermotropic
liquid crystalline copolyester should be determined in
consideration of the amount of H.sub.2O contained in the
monomers.
[0049] When acetic acid is generated as a result of the reaction
between acetic anhydride and water, acetylation should be carried
out by this newly produced acetic acid as well (at least
theoretically). However, the actual rate of acetylation reaction of
the hydroxyl group of the monomers caused by acetic acid is very
slow, although the same reaction caused by acetic anhydride
proceeds quickly. Accordingly, when the remaining amount of acetic
anhydride is scant, the rate of acetylation of the hydroxyl group
of monomers during the acetylation process drops, making the rate
of polymerization lower. In addition, the amount of acetic
anhydride not only affects the rate of polymerization, but also
affects as a key factor the emission amount of the out-gases
(acetic acid and phenol, especially) from the obtained
copolyester.
[0050] In short, the amount of acetic anhydride is calculated so
that the effective amount of acetic anhydride satisfies the
aforementioned conditions, a specific amount of acetic anhydride is
charged in the step (2) based on the calculated value, and then the
acetylation process is carried out as the step (3).
[0051] The acetylation process is carried out with heating so that
the refluxphase of acetic anhydride is maintained. The acetylation
process is completed in 1-10 hours in a batch system, normally.
[0052] In the present invention, in addition to the aforementioned
relationship of the molar ratio, it is preferable that the
acetylation process is carried out without discharging acetic acid
out of the reaction system during the process and, after completing
the acetylation process, the next melt polymerization reaction as
the step (5) immediately follows without removing excess acetic
anhydride and acetic acid generated by the acetylation process.
[0053] In other words, the acetylation process as described above
is carried out without discharging acetic acid in a reaction system
in which adequately excessive acetic anhydride is present, and the
process is immediately shifted to the polymerization reation. As a
result, the following effects that: (1) material balance in the
system can be maintained constant; (2) influence of water can be
reliably eliminated by carrying out removal of water contained in
the system by acetic anhydride under heating; (3) the whole amount
of the added acetic anhydride can be effectively utilized in the
acetylation reaction; and (4) occurrence of excessive generation of
oligomer can be suppressed, are probably obtained.
[0054] Although the relationship between these effects and the
suppression of emission of the corrosive out-gases (acetic acid and
phenol) is not clear, it is assumed that, due to the improvement of
the acetylation rate of the monomer groups before polymerization,
the suppression of generation of oligomers and the like, the
polymerization reaction afterwards uniformly proceeds. It is also
assumed that, by setting the value of (B-C)/A at 1.08 or less, the
control of the side-reaction between acetic anhydride molecules and
the reduction of remaining acetic anhydride and remaining acetic
acid are effected.
[0055] After completing the acetilation process, a copolyester can
be produced by the step (4) in which the temperature is raised so
that acetic acid is removed by distillation and, simultaneously
with the removal of the acetic acid, the melt polycondensation is
carried out. In a case in which p-hydroxybenzoic acid, terephthalic
acid, isophthalic acid and 4,4'-biphenol are used as the materials,
a copolyester can be produced by distillating acetic acid within a
temperature range of 150-350.degree. C. and performing,
simultaneously with the removal of acetic acid, the melt
polycondensation. The duration of polymerization can be selected
within the range of 1 hour to dozens of hours.
[0056] In the melt polymerization step (5), the reaction base
materials themselves act as reaction solvents. Accordingly,
polymerization can be effected without using reaction solvents in
particular.
[0057] Suitable catalysts may be used in the acetylation process
and/or the polymerization process. The known catalysts for
polycondensation of conventional polyesters may be used. Examples
of these catalysts include: metal salt catalysts such as magnesium
acetate, tin (I) acetate, tetrabutyl titanate, lead acetate, sodium
acetate, potassium acetate, antimony trioxide and the like; and
organic compound catalysts such as N-methyl imidazol. The catalyst
for the acetylation process may be the same one as that for the
polymerization process. Or, different catalysts may be used for
each process. Normally, the catalysts are charged with the monomers
when the monomers are charged at the step (1) and used for the
acetylation and the polymerization without being removed.
[0058] With respect to the polymerization reactor used for the melt
polymerization at the step (4), types thereof are not limited in
particular. However, the reactor is preferably a polymerization
reactor of stirring reactor type having a stirring equipment used
for high viscosity reaction in general. Such a stirring equipment
includes a stirring device of various configuration (anchor-shape,
multi-step-shape, spiral-shape, spiral shaft-shape and the like)
and a stirring device as a modification of the aforementioned
stirring device. More specifically, the polymerization reactor is
preferably selected from a Warner-type mixer, a Banbury mixer, a
pony type mixer, Muller mixer, a roll mill, a kneader which can be
continually operated, a pug mill, a gear compounder and the like.
The reactor for the acetylation process and the polymerization
reactor for the melt polymerization need not be different and the
same one reactor may be used for the two processes.
[0059] The polymers obtained by the melt polymerization at the step
(4) may further be subject to solid-phase polymerization. In the
solid-phase polymerization process, the polymer is first taken out
of the melt polymerization process at the step (4) and preferably
milled to a powdery or flake-state. The polymer milled in such a
manner is then subject to solid-phase polymerization at the step
(5) according to a known solid-phase polymerization method. In a
specific example of the solid-phase polymerization method, the
polymer is subject to a heat treating in a solid-phase for 1-30
hours within a temperature range of 200-350.degree. C. in an inert
atmosphere such as nitrogen. The solid-phase polymerization process
may be carried out with stirring or the same process may be carried
out without stirring. The melt polymerization and the solid
polymerization may be carried out in the same one reactor, if the
reactor is provided with a suitable stirring mechanism.
[0060] After the solid-phase polymerization, the obtained
thermotropic liquid crystalline copolyester may be polletized in a
known method, so that the molding process can be effected using
such a pellet.
[0061] The amount of out-gases such as acetic acid and phenol
emitted from the thermotropic liquid crystalline copolyester
obtained as described above is very small. The specific emission
limits applied to the out-gases are different depending on the type
of the electric/electronic component. In the case of acetic acid,
the emission thereof is preferably 20 ppm or less and in the case
of phenol, the emission thereof is preferably 5 ppm. When acetic
acid and phenol of amounts which exceed these limits (20ppm, 5ppm)
are emitted, the possibility that an electric/electronic component
molded from the thermotropic liquid crystalline copolyester
experiences operational failures becomes high, which is not
desirable.
[0062] In addition, the thermotropic liquid crystalline copolyester
produced as descirbed above exhibits further more excellent
properties with respect to an emission-suppression effect of the
corrosive out-gases in a high temperature environment, by adding
one or more phosphate esters as shown in the formula (1) below.
2
[0063] (In the formula, R and R' each represent a group selected
from the group consisting of alkyl group, alkenyl group, aryl group
and aralkyl group. The number of carbon atoms of R or R' is within
the range of 1 to 50. R and R' may represent the same group.)
[0064] Those having a pentaerythritol structure is preferred.
[0065] Specific examples of phosphate esters include
bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite,
bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, distearyl
pentaerythritol diphosphite, bis(dodecyl) pentaerythritol
diphosphite.
[0066] Blending of the phosphite esters may be carried out either
in the acetylation process or in the polymerization process.
However, it is preferable to blend the phophite esters into the
polymers when the solid-phase polymerization is completed. Addition
of the phosphite esters after the completion of the solid-phase
polymerization is preferable because the out-gas reduction effect
by the addition of the phosphite esters is further enhanced in that
case. The phosphite esters may blended into the polymers according
to a standard method. The timing of adding the phosphite esters may
be selected from suitable timings after the aforementioned
solid-phase polymerization. For example, the phosphite ester may be
added with other fillers which will be described below (or
separately with these other fillers) when the thermotropic liquid
crystalline polyester is pelletized after the solid-phase
polymerization.
[0067] The amount of the phosphite ester to be blended in the
present invention is preferably within the range of 0.001-1 parts
by weight with respect to 100 parts by weight of the thermotropic
liquid crystalline polyester. In a case in which the amount of the
phosphate ester blended into the polymer is less than 0.001 parts
by weight, emission of phenol gas is not sufficiently reduced. On
the other hand, in a case in which the amount of the phosphate
ester blended into the polymer is more than 1 part by weight,
emission of gases resulting from the decomposition of the phosphite
ester increases and causes an opposite effect, which is not
desirable. The amount of the phosphate ester blended into the
polymer is most preferably within the range of 0.01-0.5 parts by
weight with respect to 100 parts by weight of the thermotropic
liquid crystalline polyester.
[0068] The thermotropic liquid crystalline copolyester obtained
from the production method of the present invention may be used for
various purposes. Organic or inorganic fillers in a fiber, powder,
particle or platephase may generally be blended into the
thermotropic liquid crystalline copolyester in order to increase
the mechanical strenagth of the copolyester.
[0069] Examples of the fillers in a fiber state include glass
fiber, asbestos fiber, silica fiber, silica alumina fiber,
potassium titanate fiber, carbon or graphite fiber, and fibrous
materials made of metal such as aluminum, titanium, copper or the
like. A representative example thereof is glass fiber.
[0070] On the other hand, examples of the fillers in a particle
state include carbon black, graphite, silica, quartz powder, glass
beads, milled glass fiber, glass balloon, glass powder, calcium
silicate, aluminum silicate, talc, clay, silicates such as
diatomaceous earth, wollastonite, or various metal containing
powders such as iron oxides, titanium oxides, zinc oxides, antimony
trioxide, alumina, calcium sulfate and others.
[0071] Examples of the fillers in a plate state include mica, glass
flake, various metal foils and the like.
[0072] In addition, examples of the organic fillers include fibers
thermalty stable high performance made of aromatic polyester,
aromatic polyimide and polyamide and the like.
[0073] These fillers may be treated with the conventional surface
treatment agents prior to the use according to necessity. In a case
of using fibrous fillers, a binder may be used as well.
[0074] In addition, an appropriate amount of various conventional
additives such as antioxidant, heat stabilizer, weight-increasing
agent, reinforcing agent, pigment, flame retardant agent and the
like may be added. These additives and fillers may be used as a
combination of two or more of additives and fillers.
[0075] When the fillers are used, the amount of the fillers blended
into the composition is to be within the range of 10 weight % to 90
weight % (preferably 80 weight %) of the composition overall. When
the fillers is blended more than 90 weight % of the composition,
the mechanical strength of the composition undesirably
deteriorates. The fillers may be blended according to a known
method. Whatever method is employed, the fillers are blended into
the resin produced as a result of the solid-phase polymerization.
As described above, the phophite esters may be added simultaneously
with (or separately from) the adding of the fillers.
[0076] The thermotropic liquid crystalline copolyester resin
composition produced by the method of the present invention as
described above may be subject to the conventional molding method
including the standard melt molding processing such as extrusion
molding, injection molding, compression molding, blow molding and
the like, such that the resin can be processed to molded articles
such as fibers, films, three-dimensional molded articles,
containers, hoses and the like.
[0077] The molded articles obtained in such a manner may be subject
to a heat treatment so that strength thereof be increased.
Elasticity thereof can often be increased at the same time by such
a heat treatment. The heat treatment may be carried out by heating
the molded articles at a temperature no higher than the melting
point of the polymer in an inert atmosphere (e.g. nitrogen, argon,
helium or the like) or in an atmosphere containing oxygen (e.g.
air) or in an environment in which pressure has been reduced.
[0078] The thermotropic liquid crystalline copolyester of the
present invention does not substantially emit or emits an extremely
small amount of corrosive gases in a long-term use or in the use
under a high-temperature environment (the soldering processing, the
mounting-to-surface processing, for example). Accordingly, when the
thermotropic liquid crystalline copolyester is used as a forming
material of a member in which the corrosive out-gases emitted from
the resin portion is problematic, various functions of the member
can be reliably maintained without suffering from damages due to
the corrosive out-gases.
[0079] For example, when the thermotropic liquid crystalline
copolyester of the present invention is employed as a forming
material of various components used in HDD (a carriage, a chassis,
a VCM coil holding portion of an actuator, a member for
accommodating a head in an non-operation state), FDD and an optical
disc drive, the amount of the corrosive out-gases emitted from
these components is significantly decreased and thus the stability
in the data-reading function is improved.
[0080] Especially, when the thermotropic liquid crystalline
copolyester is employed in electric/electronic components having a
metal-made conductive portion which is vulnerable to the corrosive
gases emitted from the resin (such as a relay, a connector, a
socket, a resistor, a condenser, a motor, an oscillator, a printed
circuit board, and a power module), the various functions of these
components can be reliably maintained without suffering from
damages due to the corrosive out-gases. Specifically, in an
electric/electronic component made of thermotropic liquid
crystalline copolyester and having electric contact portions (such
as a relay, a switch and the like), problems like an initial
failure caused by the formation of a corrosive film as a result of
oxidization of the contact portion by the corrosive out-gases and
the like and an contact failure caused by the formation of layers
of carbonized materials at the application of voltage can be
solved. In other words, the functions of the component can be
reliably maintained. Therefore, it is preferable that the resin
portion of such an electric/electronic component as described above
is formed by the thermotropic liquid crystalline copolyester
obtained by the method of the present invention.
[0081] When such the electric/electronic component as described
above is produced by using thermotropic liquid crystallineline
copolyester, known molding methods including the insert molding
method by injection molding, the encapsulating method or the like
may be employed.
EXAMPLES
[0082] The present invention will be described far more in detail
by the following examples.
[0083] It should be noted that, as a result of the measurement
according to a standard method, each thermotropic liquid
crystalline copolyester obtained by each of the following examples
and comparative examples showed optically anisotropic properties
when it was molten.
[0084] <Method of Measurement>
[0085] The property values shown in the examples were measured
according to the following method.
[0086] (1) Melting Point
[0087] Measurement of the melting point was carried out, using
.alpha.-alumina as a reference material, by a DSC in which a
differential scanning calorimeter manufactured by Seiko Denshi
Kogyo Co. was used. The temperature was raised from the room
temperature to 420.degree. C. at the rate of 20.degree. C./minute
so that the polymer was completely melted. The temperature was then
dropped to 150.degree. C. at the rate of 10.degree. C./minute. The
temperature was again raised to 430.degree. C. at the rate of
20.degree. C./minute and the peak temperature observed in the heat
absorption peak was recorded as the melting point.
[0088] (2) Apparent Viscosity
[0089] In measurement of the apparent viscosity, a capillary
leometer manufactured by Intesco Co. (Model 2010) was employed. A
capillary whose diameter was 1.0 mm, length was 40 mm and entrance
angle was 900 was used. Measurement was carried out at a shear rate
of 100 sec.sup.-1 from the temperature which was 30.degree. C.
below the melting point measured by DSC, by heating so that the
temperature was increased at a constant rate (specifically, at a
temperature-increasing rate of +4.degree. C./minute). The apparent
viscosity was obtained at a predetermined temperature.
[0090] (3) Water Content in the Monomer
[0091] Water content was measured at 175.degree. C. by collecting
about 2 g of the monomer and using a Karl Fischer's method water
content measuring device (Model VA-05) manufactured by Mitsubishi
Kasei Co.
[0092] (4) Amount of Out-Gases
[0093] The obtained thermotropic liquid crystalline copolyester was
subject to melt mixing and kneading by an extruder at a temperature
around the melting point in order to produce pellets. The obtained
pellets were milled in the order of 1 mm or less. The resulting
product was heat-treated at 150.degree. C. for 24 hours and the
amounts of acetic acid and phenol gases generated after the heat
treatment were each measured by a gas chromatography.
[0094] Specific examples of measuring acetic acid and phenol gases
include a method in which the product produced by milling the
pellets was air-tightly sealed in a vial bottle of 20 ml, subject
to a heat processing at 150.degree. C. for 24 hours, and the
amounts of the out-gases are each obtained by analyzing the emitted
gases by a gas chromatography. Examples of the method of injecting
the gases in the vial bottle into a gas chromatography device
include a method in which injection is manually carried out by a
syringe and a method in which injection is carried out by a head
space sampler. In order to enhance the measurement precision, it is
preferable to use a head space sampler.
[0095] The type of the vial bottle, the aluminum cap, a septum and
the like used in this measurement are not particularly limited as
long as they are adaptable to a heat processing at 150.degree. C.
and any suitable models commercially available can be employed. In
addition, the type of the column used for the gas chromatography
analysis is not particularly limited as long as it allows a
quantitative analysis of acetic acid and phenol. However, a
non-polar column is preferable. Examples of preferable columns
include a glass column G-100 manufactured by Kagakuhin Kensa Kyokai
(Chemicals Testing Association). The conditions on temperature
during measurement are not particularly limited as long as these
conditions allow the separation of the peaks of acetic acid and
phenol and the quantitative analysis thereof. Specific example of
these condition include a condition in which the temperature is
raised from 45.degree. C. to 280.degree. C. at a
temperature-increasing rate of 20.degree. C./minute.
[0096] The measurement of the amount of the out-gases was actually
carried out under the following conditions. (Pellets for
measurement and the method for measurement) The pellets were milled
by a mill having 1 mm .phi. mesh. The milled product was
air-tightly sealed in a vial bottle of 20 ml and subject to a heat
treatment at 150.degree. C. for 24 hours. The amount of the acetic
acid and phenol gases emitted as a result of heating were
quantitatively measured by a gas chromatography (HP6890) connected
to a head space sampler (HP7694) manufactured by Hewlett Packard
Co. As the column, G-100 (40 m) manufactured by Kagakuhin Kensa
Kyokai was employed. With respect to the other conditions, the
initial temperature was 45.degree. C., the temperature-increasing
rate was 20.degree. C./minute, the final temperature was 280
C.degree., the pressure of helium was 8.3 psi and the split ratio
was 2.0. Measurement was carried out by a FID detection device.
[0097] (Molded Sample for Measurement)
[0098] The injection molding from the pellets was carried out by an
injection molding device manufactured by Niigata Tekkojo Co.
(MIN-7) in the conditions in which the molding temperature was
380.degree. C., the injection pressure 869 kg/cm.sup.2, the
injection rate 69.5 mm/sec, the dwelling pressure 790 kg/cm.sup.2,
the injection time 3 seconds, the cooling time 12 seconds and the
mold temperature 150.degree. C. As a result, a testing piece (20
mm.times.50 mm.times.1 mm thickness) for a tensile test was
obtained. Using this testing sample, the amount of emission of the
out-gases was measured in a manner similar to that described
above.
[0099] In a case in which the fillers such as milled glass fiber
are blended into the composition, emission of the out-gases are
more likely to occur as compared with a case in which the fillers
are not blended (this fact has been confirmed from the experiences
in the past). Therefore, in the examples described below, the tests
related to the out-gas emission were carried out using samples
containing the fillers, in order that the comparison of the out-gas
emission between the examples be easier).
Example 1
[0100] A polymerization reactor made of SUS316 as a material and
having a double-helical stirring wing (manufactured by Nitto Koatsu
Co.) was used. Nitrogen-substitution was carried out by repeating
the process of "pressure reduction of the polymerization reactor
and nitrogen injection into the reactor" five times. Then, 1,330.10
g (9.63 moles) of p-hydroxybezoic acid (HBA) manufactured by Ueno
Seiyaku Co., 79.99 g (0.4815 moles) of isophthalic acid (IPA)
manufactured by A.G. International Co., 453.29 g (2.7285 moles) of
terephthalic acid (TPA) maufactured by Mitsui Sekiyu Kagaku Kogyo
Co., 597.73 g (3.21 moles) of p,p'-biphenol (BP) manufactured by
Honshu Kagaku Kogyo Co. and 0.35 g of magnesium acetate as a
catalyst manufactured by Tokyo Kasei Co. were charged in the
polymerization reactor and the monomers in the polymerization
reactor were mixed by stirring at the rotation rate of the stirring
wing of 50 rpm. 2 g of the monomer mixture in the polymerization
reactor was taken out of the reactor and the water content therein
was measured. 0.176 weight % of water content was detected in the
monomer mixture. In other words, 4.33 g (0.24 moles) of H.sub.2O
was present in the polymerization reactor.
[0101] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,769.22 g (17.33 moles) of acetic
anhydride manufactured by Chisso Co. was added to the
polymerization reactor. The temperature of the mixture was raised
to 150.degree. C. in 1 hour at the rotation rate of the stirring
wing of 100 rpm and the acetylation reaction was carried out for 2
hours with acetic anhydride being refluxed. After the acetylation
reaction was completed, the temperature was raised at the rate of
0.5.degree. C./minute in a state in which distillation of acetic
anhydride was allowed. The resulting polymers were taken out of the
outlet provided at the lower portion of the polymerization reactor
at 330.degree. C.
[0102] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor manufactured by
Asahi Garasu Co. Specifically, the polymers which had been milled
as described above were charged into the reactor, the nitrogen was
circulated at a rate of 1 litter/minute and the temperature was
raised to 280.degree. C. in 2 hours at a rotation rate of 20 rpm.
The temperature was kept at 280.degree. C. for 1 hour, raised to
300.degree. C. in 30 minutes and kept at the temperature for 4
hours. The product was then cooled to the room temperature in 1
hour, resulting in the aimed polymer.
[0103] The melting point of the obtained polymer was 376.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
410.degree. C. was 1,110 poise.
[0104] 30 weight % of milled glass fiber (MJH20JMH-1-20)
manufactured by Asahi Fiber Glass Co. was blended into 70 weight %
of the obtained thermotropic liquid crystalline copolyester. The
mixture was compounded by a twin-screw extruder of 30 mm .phi.
(PCM-30) manufactured by Ikegai Tekko Co. in which the maximum
temperature of the cylinder was set at 400.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0105] Similarly, 0.1 weight % of
bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite
as the phosphate ester (manufactured by Asahi Denka Kogyo Co.,
which will be referred to as "P-1" hereinafter) was blended into
the mixture of the thermotropic liquid crystalline copolyester and
the milled glass fiber. Another pellet was thus obtained and from
this pellet, another testing piece for measurement of the out-gases
was produced.
[0106] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molding (the testing piece) made from the composition in which 30
weight % of glass fiber was blended are shown in Table 2.
Example 2
[0107] A device which was similar to that used in Example 1 was
employed. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid (HBA),
79.99 g (0.4815 moles) of isophthalic acid (IPA), 453.29 g (2.7285
moles) of terephthalic acid (TPA), 597.73 g (3.21 moles) of
p,p'-biphenol (BP) and 0.35 g of magnesium acetate as a catalyst
were charged in the polymerization reactor. The temperature in the
polymerization reactor was raised to 70.degree. C. and the process
of "pressure reduction ad nitrogen injection" was repeated five
times with rotating the stirring wing at 50 rpm, effecting the
nitrogen substitution and the drying of the monomers in 2 hours.
After the drying of the monomers was completed, 2 g of the monomer
mixture in the polymerization reactor was taken out of the reactor
and the water content therein was measured. 0.015 weight % of water
content was detected in the monomer mixture. In other words, 0.37 g
(0.02 moles) of H.sub.2O was present in the polymerization
reactor.
[0108] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,739.61 g (17.04 moles) of acetic
anhydride was added to the polymerization reactor. The temperature
of the mixture was raised to 150.degree. C. in 1 hour at the
rotation rate of the stirring wing of 100 rpm and the acetylation
reaction was carried out for 2 hours with acetic anhydride being
refluxed. After the acetylation reaction was completed, the
temperature was raised at the rate of 0.5.degree. C./minute in a
state in which distillation of acetic anhydride was allowed. The
resulting polymers were taken out of the outlet provided at the
lower portion of the polymerization reactor at 330.degree. C.
[0109] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor. Specifically, the
polymers which had been milled as described above were charged into
the reactor, the nitrogen was circulated at a rate of 1
litter/minute and the temperature was raised to 280.degree. C. in 2
hours at a rotation rate of 20 rpm. The temperature was kept at
280.degree. C. for 1 hour, raised to 300.degree. C. in 30 minutes
and kept at the temperature for 4 hours. The product was then
cooled to the room temperature in 1 hour, resulting in the aimed
polymer.
[0110] The melting point of the obtained polymer was 375.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
410.degree. C. was 930 poise.
[0111] 30 weight % of the same milled glass fiber as used in
Example 1 was blended into 70 weight % of the obtained thermotropic
liquid crystalline copolyester. The mixture was compounded by a
twin-screw extruder of 30 mm .phi. (PCM-30) in which the maximum
temperature of the cylinder was set at 400.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0112] Similarly, 0.1 weight % of the phosphite ester P-1 was
blended into the mixture of the thermotropic liquid crystalline
copolyester and the milled glass fiber. Another pellet was thus
obtained and from this pellet, another testing piece for
measurement of the out-gases was produced.
[0113] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molded testing piece made from the composition in which 30 weight %
of glass fiber was blended are shown in Table 2.
Example 3
[0114] A device which was similar to that used in Example 1 was
employed. Nitrogen substitution was carried out by repeating the
process of "pressure reduction and nitrogen injection" of the
polymerization reactor five times. 1,330.10 g (9.63 moles) of
p-hydroxybezoic acid (HBA), 132.90 g (0.80 moles) of isophthalic
acid (IPA), 400.37 g (2.41 moles) of terephthalic acid (TPA),
597.73 g (3.21 moles) of p,p'-biphenol (BP) and 0.35 g of magnesium
acetate as a catalyst were charged in the polymerization reactor.
The monomers in the polymerization reactor were mixed by stirring
at the rotating rate of the stirring wing of 50 rpm. 2 g of the
monomer mixture in the polymerization reactor was taken out of the
reactor and the water content therein was measured. 0.200 weight %
of water content was detected in the monomer mixture. In other
words, 4.92 g (0.27 moles) of H.sub.2O was present in the
polymerization reactor.
[0115] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,785.55 g (17.49 moles) of acetic
anhydride was added to the polymerization reactor. The temperature
of the mixture was raised to 150.degree. C. in 1 hour at the
rotation rate of the stirring wing of 100 rpm and the acetylation
reaction was carried out for 2 hours with acetic anhydride being
refluxed. After the acetylation reaction was completed, the
temperature was raised at the rate of 0.5.degree. C./minute in a
state in which distillation of acetic anhydride was allowed. The
resulting polymers were taken out of the outlet provided at the
lower portion of the polymerization reactor at 330.degree. C.
[0116] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor. Specifically, the
polymers which had been milled as described above were charged into
the reactor, the nitrogen was circulated at a rate of 1
litter/minute and the temperature was raised to 290.degree. C. in 2
hours at a rotation rate of 20 rpm. The temperature was kept at
290.degree. C. for 6 hours and the product was cooled to the room
temperature in 1 hour, resulting in the aimed polymer.
[0117] The melting point of the obtained polymer was 356.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
370.degree. C. was 980 poise.
[0118] 30 weight % of the same milled glass fiber as used in
Example 1 was blended into 70 weight % of the obtained thermotropic
liquid crystalline copolyester. The mixture was compounded by a
twin-screw extruder of 30 mm .phi. (PCM-30) in which the maximum
temperature of the cylinder was set at 370.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0119] Similarly, 0.1 weight % of the phosphite ester P-1 was
blended into the mixture of the thermotropic liquid crystalline
copolyester and the milled glass fiber. Another pellet was thus
obtained and from this pellet, another testing piece for
measurement of the out-gases was produced.
[0120] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molded testing piece made from the composition in which 30 weight %
of glass fiber was blended are shown in Table 2.
Example 4
[0121] A device which was similar to that used in Example 1 was
employed. Nitrogen substitution was carried out by repeating the
process of "pressure reduction and nitrogen injection" of the
polymerization reactor five times. 1,330.10 g (9.63 moles) of
p-hydroxybezoic acid (HBA), 79.99 g (0.4815 moles) of isophthalic
acid (IPA), 453.29 g (2.7285 moles) of terephthalic acid (TPA),
597.73 g (3.21 moles) of p,p'-biphenol (BP) and 0.35 g of magnesium
acetate as a catalyst were charged in the polymerization reactor.
The monomers in the polymerization reactor were mixed by stirring
at the rotating rate of the stirring wing of 50 rpm. 2 g of the
monomer mixture in the polymerization reactor was taken out of the
reactor and the water content therein was measured. 0.180 weight %
of water content was detected in the monomer mixture. In other
words, 4.43 g (0.25 moles) of H.sub.2O was present in the
polymerization reactor.
[0122] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,703.88 g (16.69 moles) of acetic
anhydride was added to the polymerization reactor. The temperature
of the mixture was raised to 150.degree. C. in 1 hour at the
rotation rate of the stirring wing of 100 rpm and the acetylation
reaction was carried out for 2 hours with acetic anhydride being
refluxed. After the acetylation reaction was completed, the
temperature was raised at the rate of 0.5.degree. C./minute in a
state in which distillation of acetic anhydride was allowed. The
resulting polymers were taken out of the outlet provided at the
lower portion of the polymerization reactor at 330.degree. C.
[0123] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor. Specifically, the
polymers which had been milled as described above were charged into
the reactor, the nitrogen was circulated at a rate of 1
litter/minute and the temperature was raised to 280.degree. C. in 2
hours at a rotation rate of 20 rpm. The temperature was kept at
280.degree. C. for 1 hour, raised to 300.degree. C. in 30 minutes
and kept at the temperature for 6 hours. The product was then
cooled to the room temperature in 2.5 hours, resulting in the aimed
polymer.
[0124] The melting point of the obtained polymer was 378.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
410.degree. C. was 910 poise.
[0125] 30 weight % of the same milled glass fiber as used in
Example 1 was blended into 70 weight % of the obtained thermotropic
liquid crystalline copolyester. The mixture was compounded by a
twin-screw extruder of 30 mm .phi. (PCM-30) in which the maximum
temperature of the cylinder was set at 400.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0126] Similarly, 0.1 weight % of the phosphite ester P-1 was
blended into the mixture of the thermotropic liquid crystalline
copolyester and the milled glass fiber. Another pellet was thus
obtained and from this pellet, another testing piece for
measurement of the out-gases was produced.
[0127] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molded testing piece made from the composition in which 30 weight %
of glass fiber was blended are shown in Table 2.
Example 5
[0128] A device which was similar to that used in Example 1 was
employed. Nitrogen substitution was carried out by repeating the
process of "pressure reduction and nitrogen injection" of the
polymerization reactor five times. 1,330.10 g (9.63 moles) of
p-hydroxybezoic acid (HBA), 79.99 g (0.4815 moles) of isophthalic
acid (IPA), 453.29 g (2.7285 moles) of terephthalic acid (TPA),
597.73 g (3.21 moles) of p,p'-biphenol (BP) and 0.35 g of magnesium
acetate as a catalyst were charged in the polymerization reactor.
The monomers in the polymerization reactor were mixed by stirring
at the rotating rate of the stirring wing of 50 rpm. 2 g of the
monomer mixture in the polymerization reactor was taken out of the
reactor and the water content therein was measured. 0.175 weight %
of water content was detected in the monomer mixture. In other
words, 4.31 g (0.24 moles) of H.sub.2O was present in the
polymerization reactor.
[0129] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,835.58 g (17.98 moles) of acetic
anhydride was added to the polymerization reactor. The temperature
of the mixture was raised to 150.degree. C. in 1 hour at the
rotation rate of the stirring wing of 100 rpm and the acetylation
reaction was carried out for 2 hours with acetic anhydride being
refluxed. After the acetylation reaction was completed, the
temperature was raised at the rate of 0.5.degree. C./minute in a
state in which distillation of acetic anhydride was allowed. The
resulting polymers were taken out of the outlet provided at the
lower portion of the polymerization reactor at 330.degree. C.
[0130] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor. Specifically, the
polymers which had been milled as described above were charged into
the reactor, the nitrogen was circulated at a rate of 1
litter/minute and the temperature was raised to 280.degree. C. in 2
hours at a rotation rate of 20 rpm. The temperature was kept at
280.degree. C. for 1 hour, raised to 300.degree. C. in 30 minutes
and kept at the temperature for 4 hours. The product was then
cooled to the room temperature in 2.5 hours, resulting in the aimed
polymer.
[0131] The melting point of the obtained polymer was 376.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
410.degree. C. was 1,250 poise.
[0132] 30 weight % of the same milled glass fiber as used in
Example 1 was blended into 70 weight % of the obtained thermotropic
liquid crystalline copolyester. The mixture was compounded by a
twin-screw extruder of 30 mm .phi. (PCM-30) in which the maximum
temperature of the cylinder was set at 400.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0133] Similarly, 0.1 weight % of the phosphate ester P-1 was
blended into the mixture of the thermotropic liquid crystallineline
copolyester and the milled glass fiber. Another pellet was thus
obtained and from this pellet, another testing piece for
measurement of the out-gases was produced.
[0134] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molded testing piece made from the composition in which 30 weight %
of glass fiber was blended are shown in Table 2.
Example 6
[0135] A device which was similar to that used in Example 1 was
employed. 1,330.10 g (9.63 moles) of p-hydroxybezoic acid (HBA),
79.99 g (0.4815 moles) of isophthalic acid (IPA), 453.29 g (2.7285
moles) of terephthalic acid (TPA), 597.73 g (3.21 moles) of
p,p'-biphenol (BP) and 0.35 g of magnesium acetate as a catalyst
were charged in the polymerization reactor. The temperature in the
polymerization reactor was raised to 70.degree. C. and the process
of "pressure reduction ad nitrogen injection" was repeated five
times with rotating the stirring wing at 50 rpm, effecting the
nitrogen substitution and the drying of the monomers in the
polymerization reactor. After the drying of the monomers was
completed, 2 g of the monomer mixture in the polymerization reactor
was taken out of the reactor and the water content therein was
measured. 0.013 weight % of water content was detected in the
monomer mixture. In other words, 0.32 g (0.02 moles) of H.sub.20
was present in the polymerization reactor.
[0136] The monomer which had been taken out of the reactor for the
measurement of water content therein was returned to the
polymerization reactor and 1,671.21 g (16.37 moles) of acetic
anhydride was added to the polymerization reactor. The temperature
of the mixture was raised to 150.degree. C. in 1 hour at the
rotation rate of the stirring wing of 100 rpm and the acetylation
reaction was carried out for 2 hours with acetic anhydride being
refluxed. After the acetylation reaction was completed, the
temperature was raised at the rate of 0.5.degree. C./minute in a
state in which distillation of acetic anhydride was allowed. The
resulting polymers were taken out of the outlet provided at the
lower portion of the polymerization reactor at 330.degree. C.
[0137] The polymers which had been taken out of the reactor were
milled by a mill in the order of 1 mm or less and the solid-phase
polymerization was carried out by a solid-phase polymerization
device having a cylindrical rotational reactor. Specifically, the
polymers which had been milled as described above were charged into
the reactor, the nitrogen was circulated at a rate of 1
litter/minute and the temperature was raised to 280.degree. C. in 2
hours at a rotation rate of 20 rpm. The temperature was kept at
280.degree. C. for 1 hour, raised to 300.degree. C. in 30 minutes
and kept at the temperature for 6 hours. The product was then
cooled to the room temperature in 2.5 hours, resulting in the aimed
polymer.
[0138] The melting point of the obtained polymer was 379.degree. C.
when measured by DSC. The apparent viscosity at the temperature of
410.degree. C. was 890 poise.
[0139] 30 weight t of the same milled glass fiber as used in
Example 1 was blended into 70 weight % of the obtained thermotropic
liquid crystalline copolyester. The mixture was compounded by a
twin-screw extruder of 30 mm .phi. (PCM-30) in which the maximum
temperature of the cylinder was set at 400.degree. C. The
composition in which 30 weight % of glass fiber was blended
(pellet) was obtained. A testing piece for measurement of the
out-gases was injection-molded from this pellet according to the
aforementioned molding method.
[0140] Similarly, 0.1 weight % of the phosphite ester P-1 was
blended into the mixture of the thermotropic liquid crystalline
copolyester and the milled glass fiber. Another pellet was thus
obtained and from this pellet, another testing piece for
measurement of the out-gases was produced.
[0141] The effective amount of acetic anhydride is shown in Table
1. The measurement results of the out-gases from the pellet and the
molding (the testing piece) made from the composition in which 30
weight % of glass fiber was blended are shown in Table 2.
Examples 7-10
[0142] 30 weight % of the same milled glass fiber as used in
Example 1 was likewise blended into the thermotropic liquid
crystalline copolyester obtained as a result of the solid-phase
polymerization in Example 1. Further, in Example 7,
bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (which
will be referred to as "P-2" hereinafter) was added as 0.1 weight %
of the phosphite ester. In Example 8, distearyl pentaerythritol
diphosphite (which will be referred to as "P-3" hereinafter) was
added as 0.1 weight % of the phosphate ester. In Example 9,
2,2'-methylene bis(4,6-di-tert-butylphenyl) octylphosphite (which
will be referred to as "P-4" hereinafter) was added as 0.1 weight %
of the phosphate ester. In Example 10, tri(2,4-di-tert-butylphenyl)
phosphate (which will be referred to as "P-5" hereinafter) was
added as 0.1 weight % of the phosphate ester. A pellet was thus
produced in each of Examples 7-10. A molding (testing piece) was
injection-molded from each pellet. It should be noted that the
phosphate ester P-4 used in Example 9 and the phosphate ester P-5
used in Example 10 are phosphate esters which are not represented
by the aforementioned general formula (1).
[0143] The measurement results of the out-gases from the molding
(the testing piece) made from the composition in which 30 weight %
of glass fiber was blended are shown in Table 2.
1TABLE 1 Effective Amount of Acetic Anhydride in the Preparation of
Thermotropic Liquid Crystalline Copolyester Effective Monomer OH
Added Acetic H.sub.2O in Acetic mole Anhydride Monomer Anhydride A
mole B mole C (B - C)/A Example 1 16.05 17.33 0.24 1.065 Example 2
16.05 17.04 0.02 1.060 Example 3 16.05 17.49 0.27 1.073 Example 4
16.05 16.69 0.25 1.024 Example 5 16.05 17.98 0.24 1.105 Example 6
16.05 16.37 0.02 1.019
[0144]
2TABLE 2 Measurement Results of Acetic Acid and Phenol Gas-Emission
Acetic Phenol Presence/Absence of Pellet or Acid Gas Example No.
Phosphite Additive Molded piece Gas (ppm) (ppm) Example 1 Absent
Pellet 8 2 Molded piece 7 7 P-1 added Pellet 8 2 0.1 wt % Molded
piece 6 4 Example 2 Absent Pellet 3 2 Molded piece 2 9 P-1 added
Pellet 3 1 0.1 wt % Molded piece 3 3 Example 3 Absent Pellet 15 1
Molded piece 13 6 P-1 added Pellet 14 1 0.1 wt % Molded piece 14 3
Example 4 Absent Pellet 0 35 Molded piece 0 49 P-1 added Pellet 0
23 0.1 wt % Molded piece 0 34 Example 5 Absent Pellet 89 1 Molded
piece 82 6 P-1 added Pellet 88 1 0.1 Wt% Molded piece 86 3 Example
6 Absent Pellet 0 44 Molded piece 0 52 P-1 added Pellet 0 29 0.1 wt
% Molded piece 0 34 Example 7 P-2 added Molded piece 8 2 0.1 wt %
Example 8 P-3 added Molded piece 7 2 0.1 wt % Example 9 P-4 added
Molded piece 8 8 0.1 wt% Example 10 P-5 added Molded piece 6 7 0.1
wt %
[0145] As shown in Table 1, the effective amount of acetic
anhydride is within the range of 1.04 to 1.08 in Example 1, Example
2 and Example 3. On the other hand, in Example 4 and Example 6, the
effective amount of acetic anhydride is less than 1.04. In Example
5, the effective amount of acetic anhydride is larger than 1.08.
According to the measurement results of the out-gas emission shown
in Table 2, in a case in which the effective amount of acetic
anhydride is relatively small as in Example 4 and Example 6, acetic
anhydride was not detected but a relatively large amount of phenol
was detected. In a case in which the effective amount of acetic
anhydride is relatively large as Example 5, a very small amount of
phenol gas was detected but a relatively large amount of acetic gas
was emitted.
[0146] As compared with Examples 4-6, Examples 1-3 whose effective
amount of acetic anhydride was within the range of 1.04 to 1.08
showed excellent results in which the amount of emission of acetic
acid and phenol gases was very small.
[0147] From these results, it is clearly understood that the
thermotropic liquid crystalline copolyester produced according to
the production method of the present invention emits a very small
amount of acetic acid and phenol gases.
[0148] According to the present invention, in a method in which a
thermotropic liquid crystalline copolyester is produced by first
acetylating the hydroxyl group of monomers by acetic anhydride and
then performing melt polymerization (or two-stage polymerization of
melt polymerization and solid-phase polymerization), it is possible
to provide a liquid crystalline copolyester which emits a very
small amount of acetic acid and phenol gases by limiting the amount
of acetic anhydride to a specific range.
[0149] Further, in the present invention, a phosphite ester having
a specific structure is blended into the thermotropic liquid
crystalline copolyester produced by first performing acetylation by
a specific amount of excessive acetic anhydride and then melt
polymerization or two-stage polymerization of melt polymerization
and solid-phase polymerization. As a result, it is possible to
provide a thermotropic liquid crystalline copolyester resin
composition which emits a very small amount of phenol gas.
[0150] The thermotropic liquid crystalline copolyester of the
present invention emits a very small amount of the corrosive
out-gases which may corrode metal-made conductive portions (such as
a circuit) of an electric/electronic component, although the
copolyester is used for a long period or in a high temperature
environment (e.g. the soldering process, the mounting-to-surface
process). Accordingly, various functions of the component in which
said resin is used as a forming material can be reliably
maintained.
[0151] For example, when the thermotropic liquid crystalline
copolyester of the present invention is employed as a forming
material of various components used in HDD (a carriage, a chassis,
a VCM coil holding portion of an actuator, a member for
accommodating a head in an non-operation state), FDD and an optical
disc drive, the amount of the corrosive out-gases emitted from
these components is decreased and thus the stability in the
data-reading function is improved.
[0152] Especially, when the thermotropic liquid crystalline
copolyester is employed in electric/electronic components having a
metal-made conductive portion which is structurally vulnerable to
the corrosive gases emitted from the resin (such as a relay, a
connector, a socket, a resistor, a condenser, a motor, an
oscillator, a printed circuit board, and a power module), problems
like an initial failure caused by the formation of a corrosive film
as a result of oxidization of the contact portion by the corrosive
out-gases and the like and an contact failure caused by the
formation of layers of carbonized materials at the application of
voltage can be solved. Accordingly, the various functions of these
components can be reliably maintained. Specifically, in a relay and
a switch having electric contact portions, solving the
aforementioned problems means that the various functions of these
components can be reliably maintained and thus the quality of these
components is improved as a whole.
[0153] The emission of the corrosive gases tends to be accelerated
by blending fillers into the resin. However, emission of the
corrosive gases can be suppressed at a practically acceptable level
by preferably blending a specific phosphate ester into the resin,
although the resin itself would easily emit the corrosive gases by
blending of fillers.
* * * * *