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Claims  |
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What is claimed is:
1. A polyamide resin composition comprising resin components and
antioxidants,
said resin components comprising:
(A) aromatic polyamide in an amount of 50 to 85% by weight, which comprises
repeating units formed from dicarboxylic acid constituent units and
diamine constituent units, said dicarboxylic acid constituent units
comprising 40-100% by mol of terephthalic acid constituent units, 0-50% by
mol of aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units and/or 0-60% by mol of aliphatic
dicarboxylic acid constituent units having 4 to 20 carbon atoms, said
diamine constituent units comprising aliphatic diamine constituent units
and/or alicyclic diamine constituent units,
said aromatic polyamide having an intrinsic viscosity, as measured in a
concentrated sulfuric acid at 30.degree. C., of 0.5 to 3.0 dl/g and a
melting point of higher than 290.degree. C.;
(B) at least one modified polymer selected from the group consisting of a
graft-modified .alpha.-olefin polymer, a graft-modified product of a
cycloolefin copolymer which is an addition polymer of cycloolefin and
ethylene, a graft-modified aromatic vinyl type hydrocarbon/conjugated
diene copolymer, a hydrogenation product of this copolymer and an ethylene
copolymer containing a carboxyl group and a carboxylic metal salt in the
side chain, in an amount of 10 to 40% by weight, wherein said
graft-modified polymers have been graft-modified with a modifier selected
from the group consisting of an unsaturated carboxylic acid, an
unsaturated carboxylic acid anhydride, an unsaturated carboxylic acid
halide, an unsaturated carboxylic acid imide and an unsaturated carboxylic
acid ester; and
(C) aliphatic polyamide in an amount of 1 to 15% by weight;
said antioxidants comprising:
(D) a hindered phenol type antioxidant having a molecular weight of not
less than 500 and a 10% weight loss temperature of not lower than
300.degree. C. in a thermogram measured in air; and
(E) a sulfur type antioxidant having a molecular weight of not less than
600 and a 10% weight loss temperature of not lower than 280.degree. C. in
a thermogram measured in air;
wherein, the total amount of the hindered phenol type antioxidant (D) and
the sulfur type antioxidant (E) is in the range of 0.2 to 4 parts by
weight based on 100 parts by weight of the resin components, and a weight
ratio between the hindered phenol type antioxidant (D) and the sulfur type
antioxidant (E) is in the range of 1:5 to 5:1.
2. The polyamide resin composition as claimed in claim 1, said polyamide
resin composition further comprising (F) graft-modified crystalline
polyolefin in an amount of 1 to 20% by weight as the resin component
wherein said graft-modified crystalline polyolefin has been graft-modified
with a modifier selected from the group consisting of an unsaturated
carboxylic acid, an unsaturated carboxylic acid anhydride, an unsaturated
carboxylic acid halide, an unsaturated carboxylic acid imide and an
unsaturated carboxylic acid ester.
3. The polyamide resin composition as claimed in claim 1 or claim 2,
wherein the hindered phenol type antioxidant (D) is
3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dime
thylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane and/or
N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxycinnamamide).
4. The polyamide resin composition as claimed in claim 1 or claim 2,
wherein the sulfur type antioxidant (E) is a compound represented by the
following formula [VI]:
(R.sup.1 S--R.sup.2 --COOCH.sub.2).sub.4 C [VI]
wherein R.sup.1 is a hydrocarbon group of 3 to 20 carbon atoms, and R.sup.2
is a divalent hydrocarbon group of 1 to 5 carbon atoms.
5. The polyamide resin composition as claimed in claim 1 or claim 2,
wherein the sulfur type antioxidant (E) is
penta(erythrityl-tetra-.beta.-mercaptolauryl)propionate.
6. A connector having housing made of a polyamide resin composition
comprising resin components and antioxidants,
said resin components comprising:
(A) aromatic polyamide in an amount of 50 to 85% by weight, which comprises
repeating units formed from dicarboxylic acid constituent units and
diamine constituent units, said dicarboxylic acid constituent units
comprising 40-100% by mol of terephthalic acid constituent units, 0-50% by
mol of aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units and/or 0-60% by mol of aliphatic
dicarboxylic acid constituent units having 4 to 20 carbon atoms, said
diamine constituent units comprising aliphatic diamine constituent units
and/or alicyclic diamine constituent units,
said aromatic polyamide having an intrinsic viscosity, as measured in a
concentrated sulfuric acid at 30.degree. C., of 0.5 to 3.0 dl/g and a
melting point of higher than 290.degree. C.;
(B) at least one modified polymer selected from the group consisting of a
graft-modified .alpha.-olefin polymer, a graft-modified product of a
cycloolefin copolymer which is an addition polymer of cycloolefin and
ethylene, a graft-modified aromatic vinyl type hydrocarbon/conjugated
diene copolymer, a hydrogenation product of this copolymer and an ethylene
copolymer containing a carboxyl group and a carboxylic metal salt in the
side chain, in an amount of 10 to 40% by weight, wherein said
graft-modified polymers have been graft-modified with a modifier selected
from the group consisting of an unsaturated carboxylic acid, an
unsaturated carboxylic acid anhydride, an unsaturated carboxylic acid
halide, an unsaturated carboxylic acid imide and an unsaturated carboxylic
acid ester; and
(C) aliphatic polyamide in an amount of 1 to 15% by weight;
said antioxidants comprising:
(D) a hindered phenol type antioxidant having a molecular weight of not
less than 500 and a 10% weight loss temperature of not lower than
300.degree. C. in a thermogram measured in air; and
(E) a sulfur type antioxidant having a molecular weight of not less than
600 and a 10% weight loss temperature of not lower than 280.degree. C. in
a thermogram measured in air;
wherein, the total amount of the hindered phenol type antioxidant (D) and
the sulfur type antioxidant (E) is in the range of 0.2 to 4 parts by
weight based on 100 parts by weight of the resin components, and a weight
ratio between the hindered phenol type antioxidant (D) and the sulfur type
antioxidant (E) is in the range of 1:5 to 5:1.
7. The connector as claimed in claim 6, wherein the polyamide resin
composition further comprises (F) graft-modified crystalline polyolefin in
an amount of 1 to 20% by weight as the resin component wherein said
graft-modified crystalline polyolefin has been graft-modified with a
modifier selected from the group consisting of an unsaturated carboxylic
acid, an unsaturated carboxylic acid anhydride, an unsaturated carboxylic
acid halide, an unsaturated carboxylic acid imide and an unsaturated
carboxylic acid ester.
8. The connector as claimed in claim 6 or claim 7, wherein the hindered
phenol type antioxidant (D) is
3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dime
thylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane and/or
N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxycinnamamide).
9. The connector as claimed in claim 6 or claim 7, wherein the sulfur type
antioxidant (E) is a compound represented by the following formula [VI]:
(R.sup.1 S--R.sup.2 --COOCH.sub.2).sub.4 C [VI]
wherein R.sup.1 is a hydrocarbon group of 3 to 20 carbon atoms, and R.sup.2
is a divalent hydrocarbon group of 1 to 5 carbon atoms.
10. The connector as claimed in claim 6 or claim 7, wherein the sulfur type
antioxidant (E) is
penta(erythrityl-tetra-.beta.-mercaptolauryl)propionate. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates to a thermoplastic resin composition of
excellent heat resistance and a connector having housing formed from this
thermoplastic resin composition. More particularly, the invention relates
to a lightweight thermoplastic resin composition which is hardly reduced
in toughness even after heating and is hardly reduced in heat resistance
for a long period of time, and also relates to a connector having housing
formed from this thermoplastic resin composition, particularly a connector
suitable for automobile.
BACKGROUND OF THE INVENTION
Connectors used as connecting terminals of electrical circuits have been
conventionally formed from thermosetting resins such as phenol resin, but
in these years, thermoplastic resins having high moldability have come to
be used instead of the thermosetting resins. Further, the connectors have
come to be used not only under mild conditions such as conditions within
OA machine, for example, as connectors of electric devices, but also under
extremely severe conditions such as those within an automotive engine
room. Therefore, the connectors used under the severe conditions such as
those within an automotive engine room are required to have extremely high
heat resistance. In addition, the connectors are required to have such new
features that they are hardly changed in their properties even after
repeated heating due to engine heating and that they are hardly changed in
their properties even if they are brought into contact with water, oil,
etc.
Furthermore, under the world-wide proposal of efficient utilization of
petroleum energy, it has been studied to make more lightweight automobiles
for the purpose of reducing fuel cost of automobiles and it has been also
studied to develop small sized automotive parts.
As the thermoplastic resins for connectors, there have been conventionally
used poypropylene (PP), aliphatic polyamide (NY) such as polycapramide
(nylon 6, NY 6) or polyhexamethylene adipamide (nylon 66, NY 66),
polyphenylene ether (PPE) and acrylonitrile/butadiene/styrene resin (ABS
resin).
In these thermoplastic resins, PP is insufficient in heat resistance and
low in rigidity as the resin for a connector used under severe conditions.
Moreover, PP has such a problem that the rate of crystallization is slow.
PPE has a certain level of heat resistance, but it is low in chemical
resistance, particularly oil resistance, so that PPE is unsuitable as a
resin for a connector used near machines such as an engine room. In
addition, PPE has such a problem that the moldability thereof is bad
because of its low flowability. The ABS resin is also unsuitable as a
resin for a connector used under severe conditions in viewpoints of heat
resistance, chemical resistance and rigidity, and additionally, it has
such a problem that the moldability thereof is bad because of its low
flowability.
Of the above-mentioned thermoplastic resins, the polyamide resin is
relatively well balanced between the characteristics. Generally used as
the polyamide resin is an aliphatic polyamide, but this aliphatic
polyamide has a high water absorption rate. Therefore, a connector formed
from this aliphatic polyamide varies in its dimension, electrical
resistance value, etc. when the connector absorbs water. Especially when
the connector is warped, the connector is unable to be connected with the
device.
By the way, an aromatic polyamide is known as a polyamide other than the
aliphatic polyamide. The aromatic polyamide is obtained from an aromatic
dicarboxylic acid as a dicarboxylic acid component and diamine and
subjecting this aromatic dicarboxylic acid and diamine to polycondensation
reaction.
The aromatic polyamide has a low water absorption rate differently from the
aliphatic polyamide, and hence the above-mentioned problems such as
decrease of dimensional accuracy and change of electrical resistance value
occurring associated with the water absorption of the connector can be
solved by using the aromatic polyamide.
However, as a result of further studies on the connector formed from the
aromatic polyamide in more detail, the followings have been found. That
is, when the connector is exposed to a high temperature, the aromatic
polyamide is sometimes thermally deteriorated, and this thermal
deterioration of the aromatic polyamide causes lowering of toughness of
the connector. The connector thus lowered in toughness becomes poor in
stretchability, and thereby the connector is hardly connected smoothly
with the device.
Particularly in these years, electrical parts such as connectors are often
incorporated into a device by soldering them through an infrared reflow
method. If the connector is lowered in toughness by the heat of the
infrared reflowing, reduction of workability in the assembly operation of
the device or lowering of durability of the device is induced. Further,
especially when the connector is used under such conditions that heating
and cooling are repeatedly carried out, for example, under conditions
within an automotive engine room, the toughness of the connector is easily
reduced.
Japanese Patent Laid-Open Publication No. 60(1985)-44362 by the present
applicant describes a composition of an aromatic polyamide having improved
toughness. Concretely, the composition described in this publication
contains the aromatic polyamide and a modified .alpha.-olefin elastic
polymer.
In the above publication, studies on heat resistance required for
engineering plastic products formed from the polyamide composition by a
conventional melt molding method are disclosed, but there is not taken
into account any property required for the case where a product made of
the polyamide composition is exposed to an extremely high temperature as
in the case of a connector of automobile. Accordingly, in order to improve
reliability of connectors, resin molded products should be further
improved in the long-term heat resistance.
For improving heat resistance of polyamide, there is known a method of
adding various stabilizers to the polyamide, as well as the method of
adding other resins to the polyamide. For example, Japanese Patent
Laid-Open Publications No. 2(1990)-212533, No. 2(1990)-214752, No.
2(1990)-173059 and No. 62(1987)-273256 disclose a polyamide resin
composition comprising a specific phenol type stabilizer, a specific
sulfur type stabilizer and a specific phosphorus type stabilizer and an
aliphatic polyamide such as polyamide 66 or
polyamide(.epsilon.-caprolactam)/66. The aliphatic polyamide is used as
the polyamide and the melting point of the aliphatic polyamide is much
lower than that of the aromatic polyamide. Therefore, molded products
formed from the compositions comprising the aliphatic polyamide and the
stabilizers as described in the above publications exhibit excellent
properties. However, if the aromatic polyamide is used instead of the
aliphatic polyamide in the composition, foaming of the stabilizers is
brought about during the preparation of a composition or the molding
procedure of the composition, since the melting point of the aromatic
polyamide is high.
Japanese Patent Laid-Open Publication No. 57(1982)-123254 discloses a
composition comprising a polyamide, a specific phenol type stabilizer, a
specific sulfur type stabilizer and a copper compound. In this
composition, the copper compound is used as an essential component to
exhibit sufficient thermal aging resistance, and hence the composition can
be enhanced in heat stability when the copper compound is used in
combination with the specific phenol type stabilizer and the specific
sulfur type stabilizer. However, the composition sometimes suffers evil
effects of metal caused by the copper compound which is added as the
stabilizer. Especially when the composition is contaminated with metallic
copper liberated from the copper compound, electrical properties of the
resin sometimes vary, and the resin having such variability of electrical
properties should not be used as a connector. Further, this resin
composition also has such a problem that foaming is brought about during
the preparation of the composition or the molding procedure thereof,
similarly to the above-mentioned case. In other words, formulation of
stabilizers having been conventionally applied to the aliphatic polyamide
is not always satisfactory for the aromatic polyamide.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a thermoplastic resin
composition suitable for a lightweight molded product having high impact
strength and heat resistance, particularly suitable for a connector.
It is another object of the present invention to provide a connector having
housing formed from the above-mentioned resin composition, said connector
being excellent in heat resistance.
It is a further object of the present invention to provide a thermoplastic
resin composition capable of forming a molded product excellent in heat
resistance, toughness, low water absorption properties and thermal aging
resistance, said resin composition being free from foaming during the
preparation of the composition and the processing procedure such as a
molding procedure of the composition, having no evil effects of metal, and
being free from gas burning during the molding procedure.
It is a still further object of the present invention to provide a
connector having housing formed from the above-mentioned resin
composition, said connector being excellent in heat resistance.
SUMMARY OF THE INVENTION
The polyamide resin composition of the present invention is a polyamide
resin composition containing resin components and antioxidants,
said resin components comprising:
(A) aromatic polyamide in an amount of 50 to 85% by weight, which comprises
repeating units formed from dicarboxylic acid constituent units and
diamine constituent units, said dicarboxylic acid constituent units
comprising 40-100% by mol of terephthalic acid constituent units, 0-50% by
mol of aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units and/or 0-60% by mol of aliphatic
dicarboxylic acid constituent units having 4 to 20 carbon atoms, said
diamine constituent units comprising aliphatic diamine constituent units
and/or alicyclic diamine constituent units,
said aromatic polyamide having an intrinsic viscosity, as measured in a
concentrated sulfuric acid at 30.degree. C., of 0.5 to 3.0 dl/g and a
melting point of higher than 290.degree. C.;
(B) at least one modified polymer selected from the group consisting of a
graft-modified .alpha.-olefin polymer, a graft-modified product of a
cycloolefin copolymer which is an addition polymer of cycloolefin and
ethylene, a graft-modified aromatic vinyl type hydrocarbon/conjugated
diene copolymer, a hydrogenation product of this copolymer and an ethylene
copolymer containing a carboxyl group and a carboxylic metal salt in the
side chain, in an amount of 10 to 40% by weight; and
(C) aliphatic polyamide in an amount of 1 to 15% by weight;
said antioxidants comprising:
(D) a hindered phenol type antioxidant having a molecular weight of not
less than 500 and a 10% weight loss temperature of not lower than
300.degree. C. in a thermogram measured in air; and
(E) a sulfur type antioxidant having a molecular weight of not less than
600 and a 10% weight loss temperature of not lower than 280.degree. C. in
a thermogram measured in air;
wherein, the total amount of the hindered phenol type antioxidant (D) and
the sulfur type antioxidant (E) is in the range of 0.2 to 4 parts by
weight based on 100 parts weight of the resin components, and a weight
ratio between the hindered phenol type antioxidant (D) and the sulfur type
antioxidant (E) is in the range of 1:5 to 5:1.
The connector of the present invention is a connector having housing made
of a polyamide resin composition containing resin components and
antioxidants,
said resin components comprising:
(A) aromatic polyamide in an amount of 50 to 85% by weight, which comprises
repeating units formed from dicarboxylic acid constituent units and
diamine constituent units, said dicarboxylic acid constituent units
comprising 40-100% by mol of terephthalic acid constituent units, 0-50% by
mol of aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units and/or 0-60% by mol of aliphatic
dicarboxylic acid constituent units having 4 to 20 carbon atoms, said
diamine constituent units comprising aliphatic diamine constituent units
and/or alicyclic diamine constituent units,
said aromatic polyamide having an intrinsic viscosity, as measured in a
concentrated sulfuric acid at 30.degree. C., of 0.5 to 3.0 dl/g and a
melting point of higher than 290.degree. C.;
(B) at least one modified polymer selected from the group consisting of a
graft-modified .alpha.-olefin polymer, a graft-modified product of a
cycloolefin copolymer which is an addition polymer of cycloolefin and
ethylene, a graft-modified aromatic vinyl type hydrocarbon/conjugated
diene copolymer, a hydrogenation product of this copolymer and an ethylene
copolymer containing a carboxyl group and a carboxylic metal salt in the
side chain, in an amount of 10 to 40% by weight; and
(C) aliphatic polyamide in an amount of 1 to 15% by weight;
said antioxidants comprising:
(D) a hindered phenol type antioxidant having a molecular weight of not
less than 500 and a 10% weight loss temperature of not lower than
300.degree. C. in a thermogram measured in air; and
(E) a sulfur type antioxidant having a molecular weight of not less than
600 and a 10% weight loss temperature of not lower than 280.degree. C. in
a thermogram measured in air;
wherein, the total amount of the hindered phenol type antioxidant (D) and
the sulfur type antioxidant (E) is in the range of 0.2 to 4 parts by
weight based on 100 parts weight of the resin components, and a weight
ratio between the hindered phenol type antioxidant (D) and the sulfur type
antioxidant (E) is in the range of 1:5 to 5:1.
As described above, the polyamide resin composition of the invention
comprises at least three kinds of resin components, a specific hindered
phenol type antioxidant and a specific sulfur type antioxidant, and hence
the resin composition has extremely high heat stability. Particularly,
since no foaming takes place in the process for preparing the resin
composition of the invention and the process for preparing a molded
product from the resin composition, a molded product almost free from
defects and having high accuracy can be prepared from the composition.
Further, the resin composition of the invention contains no metal
compound, so that any evil effect of metal is not brought about.
The connector of the present invention has housing made of at least three
kinds of resin components, a specific hindered phenol type antioxidant and
a specific sulfur type antioxidant as described above, and hence the
connector has a low specific gravity and is lightweight. Moreover, the
connector of the invention shows extremely high heat resistance and is
hardly reduced in toughness even when exposed to a high temperature for a
long period of time.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view showing one example of female housing of a
connector according to the present invention.
FIG. 2 is a perspective view showing one example of male housing of a
connector according to the present invention.
FIG. 3 is a schematic sectional view of a connector according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
The polyamide resin composition and the connector according to the present
invention are described in detail hereinafter.
First, the polyamide resin composition of the invention is described below.
The polyamide resin composition of the invention comprises at least three
kinds of resin components, namely, a specific aromatic polyamide (A), a
specific graft-modified polymer (B) and an aliphatic polyamide (C), and a
specific hindered phenol type antioxidant (D) and a specific sulfur type
antioxidant (E), all described below.
The aromatic polyamide (A) for the polyamide resin composition of the
invention comprises a specific dicarboxylic acid constituent unit [a] and
a specific aliphatic diamine constituent unit or a specific alicyclic
diamine constituent unit [b].
The specific dicarboxylic acid constituent unit [a] for the polyamide has a
terephthalic acid constituent unit (a-1) as an essential constituent unit.
The repeating unit having the terephthalic acid constituent unit (a-1) can
be represented by the following formula [I-a].
##STR1##
wherein R.sup.1 is a divalent aliphatic or alicyclic hydrocarbon group,
preferably an alkylene group of 4 to 18 carbon atoms.
All of the dicarboxylic acid constituent units [a] are not necessarily
constituent units represented by the above formula [I-a], and a part of
the above-mentioned terephthalic acid constituent units (a-1) may be other
dicarboxylic acid constituent units.
The dicarboxylic acid constituent units other than terephthalic acid
constituent units include (a-2) aromatic dicarboxylic acid constituent
units other than terephthalic acid constituent units and (a-3) aliphatic
dicarboxylic acid constituent units.
Examples of the aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units (a-2) include an isophthalic acid
constituent unit, a 2-methylterephthalic acid constituent unit and a
naphthalene dicarboxylic acid constituent unit. When the aromatic
polyamide for forming the composition of the invention contains
constituent unit derived from other aromatic dicarboxylic acids than the
terephthalic acid, the isophthalic terephthalic acid constituent unit is
particularly preferably used as this constituent unit (a-2).
Among from the aromatic dicarboxylic acid constituent units other than
terephthalic acid constituent units (a-2), the repeating unit having this
preferred isophthalic acid constituent unit can be represented by the
following formula [I-b].
##STR2##
wherein R.sup.1 is a divalent aliphatic or alicyclic hydrocarbon group,
preferably an alkylene group of 4 to 18 carbon atoms.
The aliphatic dicarboxylic acid constituent unit (a-3) is derived from an
aliphatic dicarboxylic acid having an alkylene group of generally 4 to 20
carbon atoms, preferably 6 to 12 carbon atoms. Examples of the aliphatic
dicarboxylic acids employable for deriving the aliphatic dicarboxylic acid
constituent unit (a-3) include succinic acid, adipic acid, azelaic acid
and sebacic acid.
When the polyamide has the aliphatic dicarboxylic acid constituent unit,
particularly preferred as this constituent unit are an adipic acid
constituent unit and a sebacic acid constituent unit.
The repeating unit having the aliphatic dicarboxylic acid constituent unit
(a-3) for the dicarboxylic acid constituent unit [a] can be represented by
the following formula [II].
##STR3##
wherein R.sup.1 has the same meaning as defined above, and n is an integer
of generally 2 to 18, preferably 4 to 10.
The diamine constituent units [b] for forming the aromatic polyamide
together with the above-mentioned dicarboxylic acid constituent units [a]
can be derived from aliphatic alkylenediamine of 4 to 18 carbon atoms and
alicyclic diamine.
Concrete examples of the aliphatic alkylenediamine include
1,4-diaminobutane, 1,6-diaminohexane, trimethyl-1,6-diaminohexane,
1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane,
1,10-diaminodecane, 1,11-diaminoundecane and 1,12-diaminododecane. A
concrete example of the alicyclic diamine is diaminocyclohexane.
Particularly preferred as the diamine constituent units in the invention
are those derived from straight-chain aliphatic alkylenediamine. As the
straight-chain aliphatic alkylenediamine, 1,6-diaminohexane,
1,8-diaminooctane, 1,10-diaminodecane and 1,12-diaminododecane are
preferred. Also preferred are mixtures of those alkylenediamines. Of
these, 1,6-diaminohexane is particularly preferred.
A content of the terephthalic acid constituent units (a-1) in all of the
dicarboxylic acid constituents (100% by mol) for the aromatic polyamide
(A) used in the invention is in the range of 40 to 100% by mol, preferably
45 to 100% by mol, more preferably 50 to 100% by mol, most preferably 50
to 80% by mol, and the total content of the aromatic dicarboxylic acid
constituent units other than terephthalic acid constituent units (a-2)
and/or the aliphatic dicarboxylic acid constituent units (a-3) is in the
range of 0 to 65% by mol, preferably 0 to 60% by mol, more preferably 0 to
50% by mol, most preferably 0 to 30% by mol. A content of the aliphatic
dicarboxylic acid constituent units (a-3) is generally in the range of 0
to 50% by mol, preferably 1 to 45% by mol.
The aromatic polyamide (A) may contain constituent units derived from
tribasic or more basic polyvalent carboxylic acid such as trimellitic acid
or pyromellitic acid in a small amount, in addition to the above-mentioned
aromatic dicarboxylic acid constituent units, namely, the terephthalic
acid constituent units which are host constituent units, the constituent
units derived from divalent aromatic dicarboxylic acids other than the
terephthalic acid (typically isophthalic acid constituent units) and the
aliphatic dicarboxylic acid constituent units. The constituent units
derived from the polyvalent carboxylic acid are contained in the aromatic
polyamide (A) for the composition of the invention in an amount of 0 to 5%
by mol.
The aromatic polyamide (A) used for the composition of the invention may be
a mixture of aromatic polyamide mainly comprising the repeating units
represented by the aforementioned formula [I-a] and aromatic polyamide
mainly comprising the repeating units represented by the aforementioned
formula [I-b]. In this case, a content of the aromatic polyamide mainly
comprising the repeating units represented by the formula [I-a] is usually
not less than 50% by weight, preferably not less than 60% by weight.
The aromatic polyamide (A) has an intrinsic viscosity [.eta.], as measured
in a concentrated sulfuric acid at 30.degree. C., of usually 0.5 to 3.0
dl/g, preferably 0.5 to 2.8 dl/g, more preferably 0.6 to 2.5 dl/g. This
aromatic polyamide (A) shows a melting point higher than that of aliphatic
polyamide conventionally used. In detail, the aromatic polyamide (A) used
in the invention has a melting point of higher than 290.degree. C. A
composition comprising the aromatic polyamide having a melting point of
preferably not lower than 300.degree. C., more preferably in the range of
305.degree. to 340.degree. C., particularly preferably in the range of
310.degree. to 340.degree. C., is prominently excellent in the heat
resistance. Further, the aromatic polyamide generally has a glass
transition temperature of not lower than 80.degree. C. at its
non-crystalline portion. A resin composition comprising the aromatic
polyamide having a melting point and a glass transition temperature at the
non-crystalline portion in the above ranges hardly becomes molten even
when a molded product formed from the composition is exposed to a high
temperature. Moreover, since the above-mentioned aromatic polyamide is
excellent in moldability, a molded product can be easily prepared by using
this aromatic polyamide. Furthermore, since this aromatic polyamide has a
glass transition temperature of not lower than 80.degree. C. at the
non-crystalline portion as described above, a dimensional change of a
molded product formed from the aromatic polyamide hardly takes place even
when the molded product is exposed to a high temperature.
The aromatic polyamide shows a low value with respect to the water
absorption, the water absorption properties being a problem for the
conventional aliphatic polyamide.
It is necessary that the aromatic polyamide (A) is contained in the resin
components of the polyamide resin composition of the invention in an
amount of 50 to 85% by weight. Especially when the amount of the aromatic
polyamide (A) is 66 to 84% by weight, preferably 67 to 83% by weight, more
preferably 69 to 81 by weight, particularly preferably 70 to 80% by
weight, there can be obtained a composition capable of forming a molded
product which has well balanced various properties such as heat
resistance, low water absorption properties and toughness.
The polyamide resin composition of the invention comprises at least one
modified polymer (B) selected from the group consisting of a
graft-modified .alpha.-olefin polymer (B-1), a graft-modified product of a
cycloolefin copolymer obtained by addition polymerization of cycloolefin
with ethylene (B-2), a graft-modified aromatic vinyl type
hydrocarbon/conjugated diene copolymer or a hydrogenation product of this
copolymer (B-3) and an ethylene copolymer containing a carboxyl group and
a carboxylic metal salt in the side chain (B-4).
The graft-modified .alpha.-olefin polymer (B-1) used as the modified
polymer (B) in the invention is a graft-modified .alpha.-olefin random
elastic copolymer having low-crystalline to non-crystalline properties.
The graft-modified .alpha.-olefin random elastic copolymer (B-1) is a
graft-modified product of a copolymer in which two kinds of repeating
units derived from different .alpha.-olefins are arranged at random.
This graft-modified .alpha.-olefin random elastic copolymer is a
low-crystalline to non-crystalline copolymer, preferably, substantially
non-crystalline. In other words, a crystallinity of the copolymer, as
measured by means of X-ray diffractometry, is not more than 10%,
preferably not more than 5%, particularly preferably 0%. Accordingly, most
of the graft-modified .alpha.-olefin random elastic copolymers show no
definite melting point. Further, the graft-modified .alpha.-olefin random
elastic copolymer is a soft polymer because of its low crystallinity, and
this elastic copolymer has a tensile modulus of generally not less than
0.1 kg/cm.sup.2 but less than 20,000 kg/cm.sup.2, preferably in the range
of 1 to 15,000 kg/cm.sup.2.
A melt index of the graft-modified .alpha.-olefin random elastic copolymer
(measured at 190.degree. C.) is usually in the range of 0.1 to 30 g/10
min, preferably 1.0 to 20 g/10 min, particularly preferably 2.0 to 15 g/10
min, and a Mw/Mn value thereof measured by GPC is usually not more than
5.5, preferably not more than 4.5, particularly preferably not more than
3.5.
Further, the graft-modified .alpha.-olefin random elastic copolymer has a
glass transition temperature (Tg) of usually -150.degree. to +50.degree.
C., preferably -80.degree. to -20.degree. C., an intrinsic viscosity
[.eta.] as measured in decalin at 135.degree. C. of usually 0.2 to 10
dl/g, preferably 1 to 5 dl/g, and a density of usually 0.82 to 0.96
g/cm.sup.3, preferably 0.84 to 0.92 g/cm.sup.3.
Concrete examples of the graft-modified .alpha.-olefin random elastic
copolymer (B-1) having the above-mentioned properties include:
(i) a graft-modified ethylene/.alpha.-olefin copolymer rubber prepared
mainly from ethylene, and
(ii) a graft-modified propylene/.alpha.-olefin copolymer rubber prepared
mainly from propylene.
The graft-modified .alpha.-olefin random elastic copolymer is described in
more detail with reference to its typical examples, namely, the
graft-modified ethylene/.alpha.-olefin copolymer rubber (i) and the
graft-modified propylene/.alpha.-olefin copolymer rubber (ii).
As the .alpha.-olefin for forming the graft-modified
ethylene/.alpha.-olefin copolymer rubber (i), .alpha.-olefin of 3 to 20
carbon atoms is generally employed. Examples of such .alpha.-olefin
include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene,
1-octene, 1-decene and mixtures thereof. Of these, propylene and/or
1-butene is particularly preferred.
As the .alpha.-olefin for forming the graft-modified
propylene/.alpha.-olefin copolymer rubber (ii), .alpha.-olefin of 4 to 20
carbon atoms is generally employed. Examples of such .alpha.-olefin
include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene,
1-decene and mixtures thereof. Of these, 1-butene is particularly
preferred.
In the graft-modified ethylene/.alpha.-olefin copolymer rubber (i), a molar
ratio of ethylene to .alpha.-olefin (ethylene/.alpha.-olefin) varies
depending on the kind of .alpha.-olefin, but is usually in the range of
10/90 to 99/1, preferably 50/50 to 95/5. When the .alpha.-olefin is
propylene, the molar ratio is preferably in the range of 50/50 to 90/10,
and when the .alpha.-olefin is .alpha.-olefin of 4 or more carbon atoms,
the molar ratio is preferably in the range of 80/20 to 95/5.
This .alpha.-olefin random copolymer may contain other constituent units
than those derived from .alpha.-olefin, such as constituent units derived
from diene compounds, with the proviso that the properties of the
.alpha.-olefin random elastic copolymer are not marred.
Examples of the constituent units permitted to be contained in the
.alpha.-olefin random elastic copolymer include:
constituent units derived from chain non-conjugated dienes such as
1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene,
6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene;
constituent units derived from cyclic non-conjugated dienes such as
cyclohexadiene, dicyclopentadiene, methyltetrahydroindene,
5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene,
5-isopropylidene-2-norbornene and
6-chloromethyl-5-isopropenyl-2-norbornene;
constituent units derived from diene compounds such as
2,3-diisopropylidene-5-norbornene,
2-ethylidene-3-isopropylidene-5-norbornene and
2-propenyl-2,2-norbornadiene; and
constituent units derived from cycloolefins.
These diene constituent units are contained in the .alpha.-olefin random
elastic copolymer in an amount of generally not more than 10% by mol,
preferably not more than 5% by mol.
Examples of ethylene/.alpha.-olefin copolymer forming the graft-modified
ethylene/.alpha.-olefin copolymer rubber (i) include:
copolymers such as ethylene/propylene copolymer, ethylene/1-butene
copolymer, ethylene/4-methyl-1-pentene copolymer, ethylene/1-hexene
copolymer, ethylene/1-octene copolymer and ethylene/1-decene copolymer;
and
copolymers such as ethylene/propylene/1,4-hexadiene copolymer,
ethylene/propylene/dicyclopentadiene copolymer,
ethylene/propylene/5-ethylidene-2-norbornene copolymer,
ethylene/propylene/2,5-norbornadiene copolymer,
ethylene/1-butene/dicyclopentadiene copolymer,
ethylene/1-butene/1,4-hexadiene copolymer and
ethylene/1-butene/5-ethylidene-2-norbornene copolymer.
In the graft-modified propylene/.alpha.-olefin copolymer | | |
