Note: Descriptions are shown in the official language in which they were submitted.
WO 95/181782 1~ 8 716 PCT/US94/14887
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TITLE
A FLAME RETARDANT
POLYAMIDE RESIN COMPOSITION
BACKGROUND OF THE INVENTION
5The present invention concerns a flame retardant polyamide
resin composition that yields moldings which are characterized by
excellent high-tempelaL~I~c stability and mechanical characteristics and
which are impervious to corrosion even when used for a long time.
Polyamide resins are characterized by excellent mechanical
characteristics, moldability, and chemical resistance and have therefore
been used in automotive parts, electric/electronic components,
mechanical components, and many other applications. In particular, the
need for flame retardancy is strong in the case of electric and electronic
components, so the resins must satisfy Class V-O requirements of the UL
standard. This is the reason that flame retardant polyamide resins
obtained, for example, by compounding l)lol~linated polysly~elles and
antimony oxide into polyamide resins are now widely known.
The shollcoll,il,gs of resin compositions obtained by the
compounding of bro~inated poly~lylc,les and antimony oxide are that
when the components are kneaded in highle",~ldl~le conditions or
when the shear rate is high during the kneading of the components, the
resin compositions undergo decomposition, their processing during
manllf~ lring and molding is m~rke~ly impaired, and the mechanical
characteristics of moldings are adversely affected.
To overcome these shol Lco"""gs, stability at high temperatures
is improved by compounding sodium antimonate instead of antimony
oxide, but sodium antimonate must be compounded in a larger amount
than antimony oxide in order to obtain a fire retardancy comparable to
that of a polyamide resin composition containing compounded antimony
oxide.
The mechanical characteristics of resin compositions, however,
tend to be impaired when a large amount of sodium antimonate is
compounded with the aforementioned polyamide resin composition.
Another disadvantage is that an increase in process temperature
additionally impairs the thermal stability of the resin composition when
the brominated poly~ly,c,le contained in the resin composition obtained
SUBSTITUTE SHEET (RULE 26)
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,
by the compounding of sodium antimonate and the brominated
polystyrene has a high viscosity, that is, when, for example, the viscosity
is at least 700 pascals at a temperature of 250C and a shear rate of 100
sec~1. In addition, sodium is eluted and corrosion develops when
moldings are used for a long time.
The objective of the present invention is to offer a flame
retardant polyamide resin composition capable of offering moldings
which are highly stable at high temperatures, do not decompose during
kneading and molding, possess excellent mechanical characteristics, and
are unlikely to undergo corrosion even when used for a long time.
The present invention, which allows the stated objective to be
attained, concerns a flame retardant polyamide resin composition which
is characterized by essentially comprising 100 weight parts of a
polyamide resin, 10 to 100 weight parts of a blolllinated polysLy~ e, and
1 to 20 weight parts of magnesium hydroxide or magnesium oxide.
The polyamide resin used in the present invention is one which
is obtained by random ring-opening polymerization, aminocalboxylic
acid polycondensation, diamine and dicarboxylic acid polycondensation,
or diamine and aromatic carboxylic acid polycondensation. Specific
examples include polyamides 6, 12, 11, 6-6, 6-10, and 6-12. An aromatic
polyamide with a melting point of 280 to 340C is ~re~lled. It is
particularly suitable to use an aromatic polyamide resin which comprises
aromatic c~l,oxylic acid component units that consist of terephthalic acid
or a lllixL~lle of terephthalic acid and isophthalic acid containing no more
than 40 mol% of isophthalic acid, and aliphatic diamine component units
that consist of a ll~xL.lre of hexamethylene~ mine and 2-
methylpentamethylenP/li~mine collLdillillg 40 to 90 mol% of
hexamethylene~ mine. Stability at high lel,.~elaLures is markedly
imploved by the use of an aromatic polyamide with a melting point of
280 to 340C. Such an aromatic polyamide resin can be manufactured by
a known polycondensation techni~ue. Polyamide 6-6 may be blended
into the aromatic polyamide resin; terephthalic acid, a m~xL~lle of
terephthalic acid and isophthalic acid, adipic acid,
hexamethylenec1i~mine, and 2-methylpentamethylenediamine may also
be subjected to polycondensation togther with the resin.
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WO 95118178 ~ 17 g ~ 16 PCT/US94/14887
Examples of the brominated polystyrenes of the present
invention include poly(dibromostyrene), poly(tribromostyrene), and
poly(pentabromostyrene). The content ranges from 10 to 100 weight
parts with respect to the polyamide resin. When the content is lower than
5 10 weight parts, it is impossible to attain Class V-O fire retardancy, and
when the conlellt exceeds 100 weight parts, the mechanical strength
becomes inadequate.
The content of the magnesium hydroxide or magnesium oxide
used in the present invention should be 1 to 20 weight parts, and
10 ~lefeldbly 2 to 8 weight parts. A conlellt that is lower than 1 weight part
produces no fire retardancy effect. When the content exceeds 20 weight
parts, the mechanical strength and tensile elongation decrease, and the
polyamide resin decomposes when a large amount is compounded.
Magnesium hydroxide and magnesium oxide may be used individually
15 or as a combination.
A flame retardant polyamide resin composition with an even
better processibility is obtained when antimony oxide is compounded in
addition to magnesium hydroxide or magnesium oxide. The col,le~ of
components in this case should be 10 to 100 weight parts for the
20 bloll~illated polyslylelle, 0.5 to 10 weight parts for magnesium hydroxide
or magnesium oxide, and 0.5 to 10 weight parts for antimony oxide, per
100 weight parts of the polyamide resin. When the colll~llt of antimony
oxide is lower than 0.5 weight parts, no flame retardancy effect is
produced, and when the colllel,t exceeds 10 weight parts, the mechanical
25 strength and tensile elongation decrease.
Glass fiber, ~:cubol~ized fiber, potassium titanate, whiskers, talc,
mica, and other inorganic fibers may also be compounded with the
polyamide resin composition of the present invention.
Thermal stabilizers, plasticizers, antioxidants, nucleators, dyes,
30 pigments, mold-release agents, and other additives can also be
compounded in addition to the aforementioned components with the
proposed polyamide resin composition as long as its characteristics are
not adversely affected.
The undesirable toxicity induced by antimony can be reduced
35 or completely eliminated by the substitution of some or all antimony
oxide with the magnesium hydroxide or magnesium oxide compounded
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WO 95/18178 217 8 7 1 G PCT/US94/14887
into the polyamide resin composition of the present invention. In
addition, the resin composition does not decompose, nor does
processibility deteriorate markedly during manufacturing and molding,
even when the components are kneaded or molded in high-temperature
5 conditions or when a high shear rate is developed during the kneading of
the components. This makes it possible to offer a resin composition with
satisfactory thermal stability, even when a highly viscous brominated
poly~ly~ e is used.
Another advantage is that because no sodium antimonate is
10 used, there is no undesirable sodium-induced corrosion, and the
mechanical characteristics are improved in comparison with the Class
V-O characteristics obtained using sodium antimonate.
EXAMPLES
The present invention will now be described in detail through
15 practical examples.
Practical Exarnples 1 Through 9; Comparative Examples 1 and 2
Components were ~ ixed for 20 minules in a tumbler and
then made into resin pellets by being melted and kneaded at a
temperalule of 320C and a screw speed of 200 rpm using a TEM 35B
20 biaxial extruder manufactured by Toshiba Machine; thermogravimetric
analyses (TGA) were ~lfvlllled using the resulting resin pellets.
Standard test pieces were fabricated, and m~rh~nical
characteristics were measured based on the following test methods.
Tensile Strength: ASTM D 638-58T
Elongation: ASTMD638-58T
Flex Modulus: ASTM D 790-58T
Flexural Strength: ASTM D 790-58T
Notched Izod: ASTM D 256-56
For combustion testing, UL-94 combustion test pieces with a
30 thickness of 1/32 inch were molded, and tests were conducted in
accordance with UL standards.
The components shown in Table I were as follows:
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WO 95118178 2 17 8 7 1 1~ PCT/US94/14887
Polyamide Resin: Aromatic polyamide resin
comprising terephthalic acid and
a mixture of
hPx~methylenediamine and 2-
methylpentamethylene-diamine;
the diamine component
contained 50 mol% hexame-
thyle~ef~i~mine and 50 mol%
2-methylpentamethylenediamine
Poly(dibromostyrene): PDBS 80 manufactured by Great
Lakes; viscosity 300 pascals at a
temperature of 250`C and a shear
rate of 100 sec~1 ("Capillograph
lB"; Toyo Seiki)
Poly(tribromostyrene): "Pyro-Chek 68PB"; manufactured
by Nissan Ferro. Viscosity at
least 1000 pascals at a
temperature of 250`C and a shear
rate of 100 sec~1 ("Capillograph
lB"; Toyo Seiki)
Magnesium Oxide: "Micro-Mag 3-150";
manufactured by Kyowa Kagaku
Magnesium Hydroxide: "Kisuma 5EU"; manufactured by
Kyowa Kagaku
Antimony Pentoxide: "San-Epok NA 1030";
manufactured by Nissan
Chemical
Sodium Antimonate: "San-Epok NA 1070L";
manufactured by Nissan
Chemical
In comparison with any of the compositions of the comparative
examples, the compositions of the practical examples possessed improved
thermal stability and mechanical characteristics. A comparison between
the compositions of Practical Examples 1 to 3 and the composition of
35 Practical Examples 6 to 9 shows that excellent thermal stability can be
obtained even with the use of highly viscous bro~ ated polysly~elles.
SUBSTITUTE SH EET (RULE 26)
WO 95/18178 21 7 8 7 1 ~ PCT/US94/14887
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SUBSTITUTE SHEET tRULE 26)
WO 95/18178 2 17 8 7 16 PCT/US94/14887
It can thus be seen that the polyamide resin composition of the
present invention is a resin composition which possesses excellent high-
tempelaLule stability, does not decompose during kneading and molding,
and exhibits superb me~h~nical characteristics even when a highly
5 viscous brominated poly~Lyr~lle is used. In addition, the antimony-
induced toxicity is reduced, and moldings obtained using the proposed
polyamide resin composition are unlikely to undergo corrosion when
used for a long time.
SUBSTITUTE SHEET (RULE 26)
