U.S. patent application number 09/365406 was filed with the patent office on 2002-07-25 for flame-retardant polycarbonate resin composition and its blow moldings.
Invention is credited to HARA, KOUICHI, MITSUTA, NAOKI, NODERA, AKIO.
Application Number | 20020099116 09/365406 |
Document ID | / |
Family ID | 16920896 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020099116 |
Kind Code |
A1 |
NODERA, AKIO ; et
al. |
July 25, 2002 |
FLAME-RETARDANT POLYCARBONATE RESIN COMPOSITION AND ITS BLOW
MOLDINGS
Abstract
Provided are a flame-retardant polycarbonate resin composition
having good blow moldability, and blow moldings of the composition
having good flame retardancy and having good impact resistance,
high mechanical strength and good thermal stability intrinsic to
polycarbonate resins. The composition comprises 100 parts by weight
of a resin or resin mixture of (A) from 30 to 100% by weight of a
polycarbonate resin and (B) from 0 to 70% by weight of a styrenic
resin, from 1 to 50 parts by weight of (C) a flame retardant, and
from 1 to 20 parts by weight of (D) a methyl methacrylate polymer
having a weight-average molecular weight of at least 1,000,000, and
optionally contains (E) a fluoro-olefinic resin, (F) a rubber-like
elastomer, and (G) an inorganic filler.
Inventors: |
NODERA, AKIO; (CHIBA,
JP) ; MITSUTA, NAOKI; (CHIBA, JP) ; HARA,
KOUICHI; (CHIBA, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
16920896 |
Appl. No.: |
09/365406 |
Filed: |
August 2, 1999 |
Current U.S.
Class: |
524/127 |
Current CPC
Class: |
C08L 69/00 20130101;
C08L 69/00 20130101; C08L 33/00 20130101; C08L 2666/02 20130101;
C08L 69/00 20130101 |
Class at
Publication: |
524/127 |
International
Class: |
C08K 005/49 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 1998 |
JP |
10-231264 |
Claims
What is claimed is:
1. A flame-retardant polycarbonate resin composition comprising 100
parts by weight of a resin or resin mixture of (A) from 30 to 100%
by weight of a polycarbonate resin and (B) from 0 to 70% by weight
of a styrenic resin, from 1 to 50 parts by weight of (C) a flame
retardant, and from 1 to 20 parts by weight of (D) a methyl
methacrylate polymer having a weight-average molecular weight of at
least 1,000,000.
2. The flame-retardant polycarbonate resin composition as claimed
in claim 1, wherein the polycarbonate resin has a branched
structure.
3. The flame-retardant polycarbonate resin composition as claimed
in claim 1, wherein the flame retardant is a halogen-free
phosphate.
4. The flame-retardant polycarbonate resin composition as claimed
in any one of claims 1 to 3, which further contains from 0.05 to 5
parts by weight, relative to 100 parts by weight of the resin or
resin mixture of (A) and (B), of (E) a fluoro-olefinic resin.
5. The flame-retardant polycarbonate resin composition as claimed
in claim 4, wherein the fluoro-olefinic resin has the ability to
form fibrils.
6. The flame-retardant polycarbonate resin composition as claimed
in any one of claims 1 to 5, wherein the resin mixture comprises
(A) from 70 to 95% by weight of a polycarbonate resin and (B) from
5 to 30% by weight of a styrenic resin, and the styrenic resin is a
rubber-modified styrenic resin.
7. The flame-retardant polycarbonate resin composition as claimed
in any one of claims 1 to 6, which further contains from 1 to 30
parts by weight, relative to 100 parts by weight of the resin or
resin mixture of (A) and (B), of (F) a rubber-like elastomer.
8. The flame-retardant polycarbonate resin composition as claimed
in claim 7, wherein the rubber-0like elastomer (F) is a core/shell
type, grafted rubber-like elastomer.
9. The flame-retardant polycarbonate resin composition as claimed
in any one of claims 1 to 8, which further contains from 1 to 50
parts by weight, relative to 100 parts by weight of the resin or
resin mixture of (A) and (B), of (G) an inorganic filler.
10. A blow molding of the flame-retardant polycarbonate resin
composition of any one of claims 1 to 9.
11. The blow molding as claimed in claim 10, which is for housings
or parts of office automation appliances, or for those of electric
and electronic appliances for household use or industrial use.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a flame-retardant
polycarbonate resin composition and its blow moldings. More
precisely, it relates to a flame-retardant polycarbonate resin
composition having the advantage of flame retardancy, thermal
stability and draw-down resistance and cable of being formed into
large-size moldings through blow molding, vacuum molding or
pneumatic compression molding, and also to blow moldings of the
composition.
[0003] 2. Description of the Related Art
[0004] As having the advantages of impact resistance, heat
resistance and good electric properties, polycarbonate resins have
many applications in various fields of, for example, office
automation appliances, electric and electronic appliances for
industrial and household use, car parts and building materials.
However, there are some problems with polycarbonate resins in that
they require high molding and working temperatures and their melt
fluidity is low. As requiring relatively high molding and working
temperatures, polycarbonate resins, especially those containing
various additives are often problematic in that their thermal
stability is poor while they are molded and worked and that their
moldings could not exhibit their good properties. As a rule,
polycarbonate resins are self-extinguishable. However, some of
their applications to office automation appliances, electric and
electronic appliances for industrial and household use and others
require high-level flame retardancy. To meet the requirement,
various flame retardants are added to polycarbonate resins.
[0005] In general, polycarbonate resins are formed into moldings of
office automation appliances, electric and electronic appliances
for industrial and household use and others, through injection
molding, and such their moldings are required to be lightweight and
thin-walled from the viewpoint of resources saving. However,
injection molding of polycarbonate resins to give thin-walled
products is naturally limited because of the limited melt viscosity
of the resins and of the intended rigidity of the molded products.
For these reasons, blow molding of polycarbonate resins is tried
for producing lightweight moldings of those appliances and
components. However, in order to ensure high-level flame retardancy
of polycarbonate resins, a relatively large amount of a flame
retardant must be added to the resins. In particular, polymer
alloys of polycarbonate -resin and rubber-like polymer-modified
styrenic resin that are intended to have both good moldability and
good impact resistance are problematic in that their blow
moldability is poor and stable production of blow moldings of such
polymer alloys is impossible.
[0006] For improving the blow moldability of polycarbonate resins,
it is known that polycarbonate resins having a branched structure
are favorable to blow molding. However, depending on the size and
the shape of the moldings to be formed therefrom, such
polycarbonate resins having a branched structure are often still
problematic in that their melt fluidity, blow moldability and
pinch-off strength are not satisfactory.
[0007] On the other hand, in these days, blow molding is being
tried, in place of injection molding, for producing lightweight and
thin-walled moldings of covers or housings for office automation
appliances such as duplicators and others, from the viewpoint of
resources saving. However, those moldings generally have a
relatively large surface area and substantially differ from
ordinary blow moldings having a hollow inner space such as
containers. Specifically in producing them, ribs must be formed for
which a parison is welded between the surface parts, so as to
prevent the depression in the strength and the rigidity of the
thin-walled moldings. Therefore, in producing these moldings, not
only their pinch-off strength but also the weld strength of the
ribs as welded inside them is needed. In particular, when a
relatively large amount of a flame retardant is added to
polycarbonate resins so as to increase the flame retardancy of the
resins, a rubber-like polymer-modified styrenic resin is added
thereto thereby to ensure the impact resistance and other physical
properties of the moldings of the resin compositions. The
polycarbonate resin compositions comprising them are desired to
have good blow moldability.
[0008] Compositions of polycarbonate resins to which are added
styrenic resins such as acrylonitrile-butadiene-styrene resins (ABS
resins), acrylonitrile-styrene resins (AS resins) and the like for
the purpose of improving the melt fluidity of the resin
compositions are known as polymer alloys, and have many
applications typically in the field of injection moldings as having
good heat resistance and impact resistance. Of their applications,
where such polycarbonate resin compositions are used for office
automation appliances, electric and electronic appliances and
others, they are required to have high flame retardancy of not
lower than a predetermined level so as to ensure and increase the
safety of their moldings.
[0009] To meet the requirements as above, various methods have
heretofore been proposed. Concretely, JP-A-61-55145 discloses a
thermoplastic resin composition comprising (A) an aromatic
polycarbonate resin, (B) an ABS resin, (C) an AS resin, (D) a
halogen compound, (E) a phosphate, and (F) a
polytetrafluoroethylene component. JP-A-2-32154 discloses a molding
polycarbonate composition with high flame retardancy and high
impact resistance, comprising (A) an aromatic polycarbonate resin,
(B) an ABS resin, (C) an As resin, (D) a phosphate, and (E) a
polytetrafluoroethylene component. JP-A-8-239565 discloses a
polycarbonate resin composition comprising (A) an aromatic
polycarbonate, (B) an impact-resistant polystyrene resin with
rubber-like elasticity, (D) a halogen-free phosphate, (C) a
core/shell type, grafted rubber-like elastomer, and (E) talc.
[0010] These are all to improve the melt fluidity and therefore the
moldability of polycarbonate resins, and to improve the impact
resistance and the flame retardancy of the moldings of
polycarbonate resins. As having such improved properties, the
polycarbonate resin compositions proposed are formed into various
practicable moldings. However, they are targeted to injection
moldings, and it is difficult to directly apply them to blow
moldings. In particular, it is difficult to directly apply them to
relatively large-sized moldings or to blow moldings having nearly
tabular ribs such as those mentioned above.
[0011] In order to improve the blow moldability of polycarbonate
resins, various methods have been proposed. For example, (1)
JP-A-1-268761 discloses a method of mixing an engineering resin
such as a polycarbonate resin or the like with an acrylic polymer
having a weight-average molecular weight of at least about 500,000;
(2) JP-B-5-422 discloses use of a copolymer of methyl methacrylate
and a vinylic monomer as prepared through emulsion polymerization
in the presence of a specific emulsifier, as a working promoter for
thermoplastic resins; and (3) JP-B-8-6022 discloses a thermoplastic
resin composition comprising a polycarbonate resin or a
polybutylene terephthalate resin, and containing a copolymer of an
alkyl methacrylate and an alkyl acrylate having a specific relative
viscosity, and carbon black having a specific relative surface area
and a specific degree of oil absorption. However, the composition
in (3) is problematic in that it indispensably requires carbon
black and could not be formed into white moldings, and therefore
its applications are limited. In addition, none of those (1) to (3)
refers to the flame retardancy of resin compositions.
[0012] On the other hand, some flame-retardant resin compositions
for blow moldings have been proposed. For example, (4)
JP-A-9-310011 discloses a resin composition comprising an aromatic
polycarbonate resin, a styrene-acrylonitrile resin, a phosphate
serving as a flame retardant, and ultra-fine grains of anhydrous
silica; and (5) JP-A-10-158497 discloses a resin composition for
blow moldings, comprising a polycarbonate resin, an ABS resin, a
SAN resin, a flame retardant, and a polytetrafluoroethylene. In
those compositions, the additive of ultra-fine grains of anhydrous
silica or styrene-acrylonitrile resin improves the blow moldability
of the compositions. However, depending on the type of the blow
moldings to be formed from the compositions, the additive is not
still satisfactory for improving the blow moldability of the
compositions.
SUMMARY OF THE INVENTION
[0013] In that situation, the object of the present invention is to
provide an improved, flame-retardant polycarbonate resin
composition having good flame retardancy, good thermal stability,
good moldability especially good blow moldability, and satisfactory
pinch-off strength, and capable of being formed into moldings
especially blow moldings having good impact resistance and high
strength and well applicable even to lightweight, thin-walled and
complicated office automation appliances, electric and electronic
appliances for industrial and household use and car parts, and also
to provide blow moldings of the composition.
[0014] To attain the object as above, we, the present inventors
have assiduously studied various additives applicable to
blow-moldable, flame-retardant polycarbonate resin compositions. As
a result, we have found that, when a specific resin is selectively
added to a flame-retardant polycarbonate resin composition,
especially to that containing a rubber-modified styrenic resin,
then it significantly improves the blow moldability of the resin
composition without interfering with the flame retardancy and the
thermal stability thereof, and that the resin composition-could be
well stably and accurately formed into high-quality articles
through blow molding. In particular, we have found that the resin
composition could be molded even into large-sized, complicated and
nearly tabular articles through blow molding. On the basis of these
findings, we have completed the present invention.
[0015] Specifically, the invention provides the following:
[0016] (1) A flame-retardant polycarbonate resin composition
comprising 100 parts by weight of a resin or resin mixture of (A)
from 30 to 100% by weight of a polycarbonate resin and (B) from 0
to 70% by weight of a styrenic resin, from 1 to 50 parts by weight
of (C) a flame retardant, and from 1 to 20 parts by weight of (D) a
methyl methacrylate polymer having a weight-average molecular
weight of at least 1,000,000.
[0017] (2) The flame-retardant polycarbonate resin composition of
(1), wherein the polycarbonate resin has a branched structure.
[0018] (3) The flame-retardant polycarbonate resin composition of
(1), wherein the flame retardant is a halogen-free phosphate.
[0019] (4) The flame-retardant polycarbonate resin composition of
any one of (1) to (3), which further contains from 0.05 to 5 parts
by weight, relative to 100 parts by weight of the resin or resin
mixture of (A) and (B), of (E) a fluoro-olefinic resin.
[0020] (5) The flame-retardant polycarbonate resin composition of
(4), wherein the fluoro-olefinic resin has the ability to form
fibrils.
[0021] (6) The flame-retardant polycarbonate resin composition of
any one of (1) to (5), wherein the resin mixture comprises (A) from
70 to 95% by weight of a polycarbonate resin and (B) from 5 to 30%
by weight of a styrenic resin, and the styrenic resin is a
rubber-modified styrenic resin.
[0022] (7) The flame-retardant polycarbonate resin composition of
any one of (1) to (6), which further contains from 1 to 30 parts by
weight, relative to 100 parts by weight of the resin or resin
mixture of (A) and (B), of (F) a rubber-like elastomer.
[0023] (8) The flame-retardant polycarbonate resin composition of
(7), wherein the rubber-like elastomer (F) is a core/shell type,
grafted rubber-like elastomer.
[0024] (9) The flame-retardant polycarbonate resin composition of
any one of (1) to (8), which further contains from 1 to 50 parts by
weight, relative to 100 parts by weight of the resin or resin
mixture of (A) and (B), of (G) an inorganic filler.
[0025] (10) A blow molding of the flame-retardant polycarbonate
resin composition of any one of (1) to (9).
[0026] (11) The blow molding of (10), which is for housings or
parts of office automation appliances, or for those of electric and
electronic appliances for household use or industrial use.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The invention is described in detail hereinunder. First
mentioned are the components (A) to (D) constituting the
flame-retardant polycarbonate resin composition of the
invention.
[0028] (A) Polycarbonate Resin (PC):
[0029] The polycarbonate resin (PC) serving as the component (A) in
the flame-retardant polycarbonate resin composition of the
invention is not specifically defined, and may be any and every one
known in the art. Generally used are aromatic polycarbonates to be
produced from diphenols and carbonate precursors. For example, used
are polycarbonates as produced by reacting a diphenol and a
polycarbonate precursor in a solution method or in a melt method,
such as those as produced through reaction of a diphenol and
phosgene or through interesterification of a diphenol and a
diphenyl carbonate.
[0030] Various diphenols are usable, including, for example,
2,2-bis(4-hydroxyphenyl)propane [bisphenol A],
bis(4-hydroxyphenyl)methan- e, 1,1-bis(4-hydroxyphenyl)ethane,
2,2-bis(4-hydroxy-3,5-dimethylphenyl)pr- opane,
4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)cycloalkanes,
bis(4-hydroxyphenyl) oxide, bis(4-hydroxyphenyl) sulfide, bis
(4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide,
bis(4-hydroxyphenyl) ether, bis(4-hydroxyphenyl) ketone, etc.
[0031] As the diphenols for use herein, preferred are
bis(hydroxyphenyl)alkanes, especially bisphenol A. The carbonate
precursors for use in the invention include, for example, carbonyl
halides, carbonyl esters, haloformates, concretely, phosgene,
diphenol dihaloformates, diphenyl carbonate, dimethyl carbonate,
diethyl carbonate, etc. Other diphenols such as hydroquinone,
resorcinol, catechol and the like are also usable in the invention.
The diphenols mentioned herein may be used either singly or as
combined.
[0032] The polycarbonate resin may have a branched structure, for
which the branching agent includes
1,1,1-tris(4-hydroxyphenyl)ethane,
.alpha.,.alpha.',.alpha."-tris(4-hyroxyphenyl)-1,3,5-triisopropylbenzene,
phloroglycine, trimellitic acid, isatin-bis(o-cresol), etc. For
controlling the molecular weight of the polycarbonate resin,
employable are phenol, p-t-butylphenol, p-t-octylphenol,
p-cumylphenol, etc.
[0033] The polycarbonate resin for use in the invention may be a
copolymer having a polycarbonate moiety and a polyorganosiloxane
moiety, or it may have a moiety of the copolymer. The copolymer may
be a polyester-polycarbonate resin to be produced through
polymerization of a polycarbonate in the presence of an ester
precursor, such as a difunctional carboxylic acid (e.g.,
terephthalic acid) or its ester-forming derivative. Various types
of different polycarbonate resins may be mixed to give mixed
polycarbonate resins for use in the invention. Preferably, the
polycarbonate resin serving as the component (A) in the invention
contains no halogen. In view of its mechanical strength and
moldability, the polycarbonate resin preferably has a
viscosity-average molecular weight of from 10,000 to 100,000, more
preferably from 14,000 to 40,000.
[0034] (B) Styrenic Resin:
[0035] The styrenic resin to be the component (B) in the
flame-retardant polycarbonate resin composition of the invention
may be a polymer as prepared through polymerization of a monomer or
monomer mixture of from 20 to 100% by weight of a monovinylic
aromatic monomer such as styrene, .alpha.-methylstyrene or the
like, from 0 to 60% by weight of a vinyl cyanide-type monomer such
as acrylonitrile, methacrylonitrile or the like, and from 0 to 50%
by weight of any other vinylic monomer copolymerizable with those
monomers, such as maleimide, methyl (meth)acrylate or the like. The
polymer includes, for example, polystyrenes (GPPS),
acrylonitrile-styrene copolymers (AS resins), etc.
[0036] As the styrenic resin, preferred are rubber-modified
styrenic resins. The modified styrenic resins are preferably
impact-resistant styrenic resins as produced through grafting
polymerization of rubber-like polymers with styrenic monomers. The
rubber-modified styrenic resins include, for example,
impact-resistant polystyrenes (HIPS) as produced through
polymerization of rubber-like polymers such as polybutadiene or the
like with styrene; ABS resins as produced through polymerization of
polybutadiene with acrylonitrile and styrene; MBS resins as
produced through polymerization of polybutadiene with methyl
methacrylate and styrene, etc. These rubber-modified styrenic
resins may be combined, or may be mixed with other styrenic resins
not modified with rubber such as those mentioned above, and the
resin mixtures may be used in the invention.
[0037] In the rubber-modified styrenic resins, the amount of the
rubber-like polymer to modify them may fall, for example, between 2
and 50% by weight, but preferably between 5 and 30% by weight. If
the amount of the modifying rubber-like polymer is smaller than 2%
by weight, the resin composition will have poor impact resistance.
If, on the other hand, it is larger than 50% by weight, the thermal
stability of the resin composition will be lowered, and the melt
fluidity thereof will be also lowered. If so, the resin composition
will be unfavorably gelled or yellowed. Specific examples of the
rubber-like polymer include polybutadiene, acrylate and/or
methacrylate-having rubber-like polymers, styrene-butadiene-styrene
(SBS) rubber, styrene-butadiene rubber (SBR), butadiene-acrylic
rubber, isoprene rubber, isoprene-styrene rubber, isoprene-acrylic
rubber, ethylene-propylene rubber, etc.
[0038] Of those, especially preferred is polybutadiene. The
polybutadiene usable herein may be any of low-cis polybutadiene
(for example, having from 1 to 30 mol % of 1,2-vinyl bonds and from
30 to 42 mol % of 1,4-cis bonds) or high-cis polybutadiene (for
example, having at most 20 mol% of 1,2-vinyl bonds and at least 78
mol % of 1,4-cis bonds), and even their mixtures.
[0039] (C) Flame Retardant:
[0040] Where the moldings of the invention are for office
automation appliances, electric and electronic appliances and the
like, they shall be resistant to flames. For these, various flame
retardants must be added to the moldings. Examples of flame
retardants include organic phosphorus compounds, halogen-free
phosphorus compounds, halogen compounds, nitrogen compounds, metal
hydroxides, red phosphorus, antimony compounds, etc. The halogen
compounds include, for example, tetrabromobisphenol A,
halogenopolycarbonates, copolymerized oligomers of
halogenopolycarbonates, decabromodiphenyl ether,
halogenopolystyrenes, halogenopolyolefins, etc. The nitrogen
compounds include, for example, melamine, alkyl group or aromatic
group-substituted melamines, etc.; the metal hydroxides include,
for example, magnesium hydroxide, aluminium hydroxide, etc.; the
antimony compounds include, for example, antimony trioxide,
antimony tetroxide, etc.
[0041] However, halogen-containing flame retardants are
unfavorable, as often discharging harmful substances when moldings
comprising them are incinerated. Therefore, preferred are
halogen-free, organic phosphorus-containing flame retardants. Any
organic compounds containing phosphorus but not containing halogen
are employable herein with no limitation, so far as they serve as
flame retardants. As the flame retardants for use herein, however,
preferred are phosphate compounds having at least one esteric
oxygen atom directly bonding to a phosphorus atom.
[0042] For example, preferred are phosphate compounds of the
following formula (1): 1
[0043] wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each
independently represent a hydrogen atom or an organic group; X
represents a divalent or higher polyvalent organic group; p is 0 or
1; q is an integer of 1 or larger; and r is an integer of 0 or
larger.
[0044] In formula (1), the organic group includes, for example,
substituted or unsubstituted alkyl, cycloalkyl and aryl groups,
etc. The substituents for the substituted groups include, for
example, alkyl groups, alkoxy groups, aryl groups, aryloxy groups,
arylthio groups, etc. These substituents may be combined to give
arylalkoxyalkyl groups, or may be bonded, for example, via oxygen,
nitrogen or sulfur atom to give arylsulfonylaryl groups.
[0045] In formula (1), the divalent or higher polyvalent organic
group X is meant to include divalent or higher polyvalent groups to
be derived from the organic groups as above by removing one or more
hydrogen atoms bonding to carbon atoms. For example, it includes
alkylene groups, (substituted) phenylene groups, groups as derived
from bisphenols of polycyclic phenols. Preferred are groups derived
from bisphenol A, hydroquinone, resorcinol, diphenylmethane,
dihydroxydiphenyl, dihydroxynaphthalene, etc.
[0046] The halogen-free phosphate compounds may be monomers,
oligomers, polymers or their mixtures. Concretely, they include,
for example, trimethyl phosphate, triethyl phosphate, tributyl
phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl
phosphate, tricresyl phosphate, cresyldiphenyl phosphate,
octyldiphenyl phosphate, tri(2-ethylhexyl) phosphate,
diisopropylphenyl phosphate, trixylenyl phosphate,
tris(isopropylphenyl) phosphate, trinaphthyl phosphate, bisphenol
Abisphosphate, hydroquinone bisphosphate, resorcinol bisphosphate,
resorcinol-diphenyl phosphate, trihydroxybenzene triphosphate,
cresyldiphenyl phosphate, etc.
[0047] Commercially-available, halogen-free phosphates that are
preferably used as the component (C) to be in the flame-retardant
polycarbonate resin composition of the invention are, for example,
TPP [triphenyl phosphate], TXP [trixylenyl phosphate], PFR
[resorcinol (diphenyl phosphate)], PX200
[1,3-phenylene-tetrakis(2,6-dimethylphenyl) phosphate], PX201
[1,4-phenylene-tetrakis(2,6-dimethylphenyl) phosphate], PX202
[4,4'-biphenylene-tetrakis(2,6-dimethylphenyl) phosphate], CR733S
[phenylresorcinol polyphosphate], all from Daihachi Chemical
Industry.
[0048] The amount of the flame retardant to be in the composition
may fall between 1 and 50 parts by weight, but preferably between 2
and 30 parts by weight, more preferably between 3 and 15 parts by
weight, relative to 100 parts by weight of the resin or resin
mixture of (A) and (B). If the flame retardant content of the
composition is smaller than 2 parts by weight, the composition
could hardly have the intended flame retardancy. If, on the other
hand, it is larger than 50 parts by weight, the heat resistance and
the impact strength of the composition will be lowered. Therefore,
the flame retardant content of the composition shall be
comprehensively determined, depending on the necessary properties
of the moldings of the composition and on the amount of the other
constituent components of rubber-like elastomer, inorganic filler,
etc.
[0049] (D) Methyl Methacrylate Polymer Having a Weight-Average
Molecular Weight of at Least 1,000,000:
[0050] The methyl methacrylate polymer having a weight-average
molecular weight of at least 1,000,000, which serves as the
component (D) in the polycarbonate resin composition of the
invention, is preferably a copolymer of at least 30% by weight of
methyl methacrylate with other copolymerizable vinylic monomers.
The vinylic monomers copolymerizable with methyl methacrylate
include, for example, alkyl acrylates such as ethyl acrylate,
propyl acrylate, butyl acrylate, etc.; alkyl methacrylates such as
ethyl methacrylate, propyl methacrylate, butyl methacrylate, etc.;
aromatic vinyl compounds such as styrene, .alpha.-methylstyrene,
etc.; vinyl cyanides such as acrylonitrile, methacrylonitrile,
etc.
[0051] Especially preferred are copolymers having a methyl
methacrylate content of at least 50% by weight, as improving the
outward appearance of the moldings of the composition. The methyl
methacrylate copolymers may be produced in any known, single-stage
or multi-stage polymerization methods of solution polymerization,
suspension polymerization, emulsion polymerization of the like of
methyl methacrylate with a comonomer of, for example, methyl
acrylate or butyl acrylate. Above all, preferred are those as
produced through emulsion polymerization of the monomers in the
presence of an emulsifier that comprises, for example, a sodium or
potassium dicarboxylate at least having an alkyl or alkenyl group
with from 10 to 24 carbon atoms, in view of the thermal molding
stability of the polycarbonate resin composition of the
invention.
[0052] The methyl methacrylate polymer shall have a weight-average
molecular weight of at least 1,000,000, but preferably between
1,500,000 and 5,000,000. If its molecular weight is smaller than
1,000,000, the effect of the polymer to improve the blow
moldability of the composition is poor. As having such a large
molecular weight, it is believed that the copolymer, when in the
polycarbonate resin composition of the invention, is dispersed in
the composition through kneading, thereby exhibiting its ability to
improve the melt elasticity (rubber-like elasticity) of the melt of
the composition. Commercial products of the methyl methacrylate
polymer are available, including, for example, Metablen P series
(P-550A, P-551A, P-530A, P531) from Mitsubishi Rayon.
[0053] Basically comprising the components (A), (C) and (D), the
flame-retardant polycarbonate resin composition of the invention
attains the object of the invention to give blow moldings of the
composition with flame retardancy. Concretely, the composition
comprises 100 parts by weight of a resin or resin mixture of (A)
from 30 to 100% by weight, preferably from 50 to 95% by weight of a
polycarbonate and (B) from 0 to 70% by weight, preferably from 5 to
50% by weight of a styrenic resin, from 1 to 50 parts by weight,
preferably from 2 to 30 parts by weight of (C) a flame retardant,
and from 1 to 20 parts by weight, preferably from 1.5 to 10 parts
by weight of (D) a methyl methacrylate polymer having a
weight-average molecular weight of at least 1,000,000. If the
proportion of the component (A), polycarbonate resin is smaller
than 30% by weight in the composition, the heat resistance and the
mechanical strength of the composition will be poor. The styrenic
resin of the component (B) is to be in the composition so as to
make the composition have the necessary melt fluidity. If its
proportion is smaller than 5% by weight, the component (B) could
poorly exhibit its ability to improve the moldability of the
composition. If the proportion of the flame retardant of the
component (C) is smaller than 1 part by weight, the flame
retardancy of the composition will be poor. If, however, it is
larger than 50 parts by weight, the heat resistance, the mechanical
strength and the impact resistance of the composition will be poor.
Therefore, the proportion of the flame retardant of the component
(C) shall be suitably determined, depending on the necessary
properties of the moldings of the composition, on the moldability
of the composition, and even on the proportions of the other
components constituting the composition.
[0054] If the proportion of the component (D), methyl methacrylate
polymer having a weight-average molecular weight of at least
1,000,000 is smaller than 1 part by weight, the polymer could
poorly exhibit its ability to improve the blow moldability of the
composition. If, however, it is larger than 20 parts by weight, the
extrusion moldability of the composition will be poor and, in
addition, such a large amount of the polymer will have some
negative influences on the weld strength of the composition.
Therefore, it is desirable that the proportion of the component (D)
is determined, comprehensively depending on the ratio of the
components (A) and (B) constituting the resin mixture, on the
proportion of the flame retardant of the component (C), on the
proportions of the rubber-like elastomer of the component (F) and
the inorganic filler of the component (G) to be mentioned in detail
hereinunder, on the size, the weight and the shape of the blow
moldings of the composition, and on the blow moldability, the
pinch-off strength and the weld strength of the composition.
[0055] The flame-retardant polycarbonate resin composition of the
invention may optionally contain (E) a fluoro-olefinic resin which
exhibits a resin melt-dropping preventing effect when the
composition is fired. The fluoro-olefinic resin (E) may be a
polymer or copolymer having a fluoro-ethylenic structure, for
example, including difluoroethylene polymers, tetrafluoroethylene
polymers, tetrafluoroethylene-hexafluoropro- pylene copolymers, and
copolymers of tetrafluoroethylene with fluorine-free ethylenic
monomers. Preferred is polytetrafluoroethylene (PTFE) desirably
having a mean molecular weight of at least 500,000, more desirably
from 500,000 to 10,000,000. All types of polytetrafluoroethylene
known in the art are usable herein.
[0056] More preferred is polytetrafluoroethylene having the ability
to form fibrils, as its property of preventing resin melts from
dropping is better. The fibril-forming polytetrafluoroethylene
(PTFE) is not specifically defined, but preferred is PTFE of Type 3
stipulated in the ASTM Standard. Specific examples of PTFE of Type
3 include Teflon 6-J (from Mitsui-DuPont Fluorochemical), Polyflon
D-1, Polyflon F-103, Polyflon F201L (all from Daikin Industry),
CD-076 (from Asahi ICI Fluoropolymers), etc.
[0057] Others except PTFE of Type 3 are also employable herein,
including, for example, Argoflon F5 (from Montefluos), Polyflon
MPA, FA-100 (both from Daikin Industry), etc. These
polytetrafluoroethylenes (PTFEs) may be used either singly or as
combined. The fibril-forming polytetrafluoroethylenes (PTFEs) as
above may be obtained, for example, by polymerizing
tetrafluoroethylene in an aqueous solvent in the presence of
sodium, potassium or ammonium peroxydisulfide, under a pressure of
from 1 to 100 psi, at a temperature falling between 0 and
200.degree. C., preferably between 20 and 100.degree. C.
[0058] The fluoro-olefinic resin content of the composition may
fall between 0.05 and 5 parts by weight, but preferably between 0.1
and 2 parts by weight relative to 100 parts by weight of the resin
or resin mixture of (A) and (B). If the fluoro-olefinic resin
content is smaller than 0.05 parts by weight, the resin
melt-dropping preventing ability of the composition will be not
enough for the intended flame retardancy of the composition.
However, even if the content is larger than 5 parts by weight, the
effect of the fluoro-olefinic resin added could not be augmented
any more, and such a large amount of the fluoro-olefinic resin, if
added to the composition, will have some negative influences on the
impact resistance and the outward appearance of the moldings of the
composition. Therefore, the amount of the fluoro-olefinic resin to
be added to the composition may be suitably determined, depending
on the necessary flame retardancy of the moldings of the
composition, for example, based on V-0, V-1 or V-2 in UL-94, and
depending on the amount of the other constituent components.
[0059] The flame-retardant polycarbonate resin composition of the
invention may further contain (F) a rubber-like elastomer to
further improve the impact resistance of the moldings of the
composition. The amount of the component (F) may fall between 1 and
30 parts by weight, but preferably between 2 and 15 parts by
weight, relative to 100 parts by weight of the resin or resin
mixture of the components (A) and (B) . The amount of the
rubber-like elastomer to be in the composition shall be determined,
depending on the total properties (e.g., impact resistance, heat
resistance, rigidity) of the intended moldings. The rubber-like
elastomer includes, for example, polybutadiene, polyisoprene,
styrene-butadiene-styrene (SBS) rubber, styrene-butadiene rubber
(SBR), butadiene-acrylic rubber, isoprene-styrene rubber,
isoprene-acrylic rubber, ethylene-propylene rubber,
ethylene-propylene-diene rubber, siloxane rubber, etc.
[0060] Of those, preferred are powdery or granular rubber-like
elastomers having a two-layered core/shell structure in which the
core is of a flexible rubber material and the shell that covers the
core is of a rigid resin material. After blended with a
polycarbonate resin melt, the rubber-like elastomers of that type
mostly keep their original granular condition. Since the
rubber-like elastomer keeps its original granular condition after
having been blended with a polycarbonate resin melt, it is
effective for preventing the moldings of the resin composition from
being troubled by surface layer peeling.
[0061] Known are various core/shell-type, grafted rubber-like
elastomers that are usable herein. Commercially-available products
of such elastomers include, for example, Hiblen B621 (from Nippon
Zeon), KM-330 (form Rohm & Haas), Metablen W529, Metablen
S2001, Metablen C223, Metablen B621 (all from Mitsubishi Rayon),
etc.
[0062] Above all, preferred are those to be produced through
polymerization of one or more vinylic monomers in the presence of a
rubber-like polymer as obtained from monomers of essentially alkyl
acrylates or alkyl methacrylates and dimethylsiloxane. In the alkyl
acrylates and methacrylates, the alkyl group preferably has from 2
to 10 carbon atoms. Concretely, the alkyl acrylates and
methacrylates include, for example, ethyl acrylate, butyl acrylate,
2-ethylhexyl acrylate, n-octyl methacrylate, etc. One example of
the rubber-like elastomers as obtained from monomers of essentially
those alkyl acrylates is a polymer to be prepared through reaction
of at least 70% by weight of the alkyl acrylates with at most 30%
by weight of other copolymerizable vinylic monomers such as methyl
methacrylate, acrylonitrile, vinyl acetate, styrene and the like.
To prepare the polymer, a polyfunctional monomer serving as a
crosslinking agent, such as divinylbenzene, ethylene
dimethacrylate, triallyl cyanurate, triallyl isocyanurate or the
like, may be added to the polymerization system.
[0063] The vinylic monomers to be polymerized in the presence of a
rubber-like polymer include, for example, aromatic vinyl compounds
such as styrene, .alpha.-methylstyrene, etc.; acrylates such as
methyl acrylate, ethyl acrylate, etc.; methacrylates such as methyl
methacrylate, ethyl methacrylate, etc. One or more these monomers
may be (co)polymerized, as combined, or may be copolymerized with
any other vinylic monomers such as vinyl cyanide compounds (e.g.,
acrylonitrile, methacrylonitrile), vinyl esters (e.g., vinyl
acetate, vinyl propionate), etc. The (co)polymerization may be
effected in any known method of, for example, bulk polymerization,
suspension polymerization, emulsion polymerization or the like.
Preferred is emulsion polymerization.
[0064] It is desirable that the core/shell-type, grafted
rubber-like elastomers thus produced in the manner mentioned above
contain at least 20% by weight of the rubber-like polymer moiety.
Typical examples of the core/shell-type, grafted rubber-like
elastomers are MAS resin elastomers such as graft copolymers of
styrene and methyl methacrylate with from 60 to 80% by weight of
n-butyl acrylate. Other examples are composite rubber grafted
copolymers to be prepared through graft copolymerization of a
composite rubber with at least one vinylic monomer, in which the
composite rubber comprises from 5 to 95% by weight of a
polysiloxane component and from 5 to 95% by weight of a polyacryl
(meth) acrylate rubber component as so entangled that they are not
separated from each other, and has a mean grain size of from 0.01
to 1 .mu.m or so. The composite rubber grafted copolymers are
better than single rubber grafted copolymers, as their effect of
improving the impact resistance of resin moldings is higher than
that of the latter, single rubber grafted copolymers. Commercial
products of such composite rubber grafted copolymers are available,
for example, Metablen S-2001 from Mitsubishi Rayon.
[0065] The flame-retardant polycarbonate resin composition of the
invention may further contain (G) an inorganic filler which is to
further increase the rigidity and the flame retardancy of the
moldings of the composition and to further improve the blow
moldability of the composition. The inorganic filler includes, for
example, talc, mica, kaolin, diatomaceous earth, calcium carbonate,
calcium sulfate, barium sulfate, glass fibers, carbon fibers,
potassium titanate fibers, etc. Of those, preferred are tabular
fillers of talc, mica, etc., and fibrous fillers. Talc is a hydrous
silicate of magnesium, and any commercially-available products of
it are employable herein. Talc may contain a minor amount of
aluminium oxide, calcium oxide and iron oxide, in addition to the
essential components of silicic acid and magnesium oxide. In
producing the resin composition of the invention, any talc even
containing such minor components is employable. The inorganic
filler such as talc for use in the invention generally has a mean
grain size of from 0.1 to 50 .mu.m, but preferably from 0.2 to 20
.mu.m. Containing the inorganic filler as above, especially talc,
the rigidity of the moldings of the invention is further increased
and, in addition, the amount of the flame retardant, halogen-free
phosphate to be in the composition could be reduced.
[0066] The amount of the component (G), inorganic filler may fall
between 1 to 50 parts by weight, but preferably between 2 ad 30
parts by weight, relative to 100 parts by weight of the resin or
resin mixture of (A) and (B). If its amount is smaller than 1 part
by weight, the inorganic filler added could not satisfactorily
exhibit its effect of improving the rigidity and the flame
retardancy of the moldings of the composition and of improving the
blow moldability of the composition. However, if the amount is
larger than 50 parts by weight, the impact resistance of the
moldings will lower and the melt fluidity of the composition will
lower. The amount of the inorganic filler to be in the composition
shall be suitably determined, depending on the size, the weight and
the necessary properties of the moldings and on the blow
moldability of the composition.
[0067] Apart from the essential components (A), (C) and (D) and one
or more optional components selected from (B) and (E) to (G), the
flame-retardant polycarbonate resin composition of the invention
may further contain any other additives which are generally added
to ordinary thermoplastic resins, if desired. The additives are for
further improving the blow moldability and the flame retardancy and
for improving the outward appearance, the weather resistance and
the rigidity of the moldings of the composition. For example, the
additives include phenolic or phosphorus- or sulfur-containing
antioxidants, antistatic agents, polyamide-polyether block
copolymers (for permanent static electrification resistance),
benzotriazole-type or benzophenone-type UV absorbents, hindered
amine-type light stabilizers (weather-proofing agents),
microbicides, compatibilizers, colorants (dyes, pigments), etc. The
amount of the optional additive is not specifically defined,
provided that it does not interfere with the properties, especially
the blow moldability of the flame-retardant polycarbonate resin
composition of the invention.
[0068] The method for producing the flame-retardant polycarbonate
resin composition of the invention is described. The composition
may be produced by mixing and kneading the components (A), (C) and
(D) in a predetermined ratio as above, optionally along with the
optional components (B) and (E) to (G) and with additives as above
in any desired ratio. Formulating and mixing them may be effected
in any known manner, for example, by pre-mixing them in an ordinary
device, such as a ribbon blender, a drum tumbler or the like,
followed by further kneading the resulting pre-mix in a Henschel
mixer, a Banbury mixer, a single-screw extruder, a double-screw
extruder, a multi-screw extruder, a cokneader or the like. The
temperature at which the components are mixed and kneaded generally
falls between 240 and 300.degree. C. Other components than the
polycarbonate resin and the styrenic resin may be previously mixed
with the polycarbonate or styrenic resin or with any other
thermoplastic resin to prepare a master batch, and it may be added
to the other constituent components.
[0069] Having been prepared in the manner noted above, the
flame-retardant polycarbonate resin composition of the invention
may be molded into various moldings in the melt-molding devices as
above, or, after it is pelletized, the resulting pellets may be
molded into various moldings through injection molding, injection
compression molding, extrusion molding, blow molding, press
molding, vacuum molding or foaming. Preferably, the composition is
pelletized in the melt-kneading manner as above, and the resulting
pellets are molded into sheet moldings through extrusion blow
molding or extrusion sheet molding. Then, the resulting sheets
are-further worked for vacuum molding or the like that specifically
requires the draw-down resistance of resin melts, more favorably
for blow molding.
[0070] The blow moldings of the flame-retardant polycarbonate resin
composition of the invention have many applications with no
specific limitation. For example, they are usable as covers or
housings of various office automation appliances requiring flame
retardancy, such as duplicators, etc.; as housings and parts of
various electric and electronic appliances for household use such
as refrigerators, microwave ovens, etc.; and as car parts, etc.
[0071] The invention is described in more detail with reference to
the following Examples and Comparative Examples, which, however,
are not intended to restrict the scope of the invention.
EXAMPLES 1 to 4, AND COMPARATIVE EXAMPLES 1 and 2
[0072] The components shown in Table 1 below were blended in the
ratio indicated therein (the components (A) and (B) are in terms of
% by weight, and the other components are in terms of parts by
weight relative to 100 parts by weight of the total of (A) and
(B)), fed into an extruder (VS40 from Tanabe Plastic Machinery),
melted and kneaded therein at 260.degree. C., and then pelletized.
To all compositions of Examples and Comparative Examples, added
were 0.2 parts by weight of Irganox 1076 (from Ciba-Geigy) and 0.1
parts by weight of Adekastab C (from Asahi Denka Industry) both
serving as an antioxidant. The melt index and the melt tension of
the pellets were measured. In addition, the pellets were dried at
80.degree. C. for 12 hours, and then molded into test pieces
through injection molding at 260.degree. C. These test pieces were
tested for their flame retardancy. The data obtained are all in
Table 1.
[0073] The materials used for producing the test samples, and the
methods for testing the samples are mentioned below.
[0074] (A) Polycarbonate Resins (Bisphenol A Polycarbonate
Resins):
[0075] PC-1:
[0076] Toughlon A2700 (from Idemitsu Petrochemical), having a
viscosity-average molecular weight of 27000.
[0077] PC-2:
[0078] Toughlon A2500 (from Idemitsu Petrochemical), having a
viscosity-average molecular weight of 25000.
[0079] PC-3:
[0080] Toughlon IB2500 (branched polycarbonate from Idemitsu
Petrochemical), having a viscosity-average molecular weight of
25000.
[0081] (B) Styrenic Resin (Impact-Resistant Polystyrene Resin,
HIPS): Idemitsu PS HT52 (From Idemitsu Petrochemical).
[0082] This is a polystyrene-grafted polybutadiene having MI of 2
g/10 min (at 200.degree. C, under a load of 5 kg)
[0083] (C) Flame Retardant (Phosphate): PFR (From Asahi Denka
Industry).
[0084] This is resorcinol-bis(diphenol phosphate).
[0085] (D) Methyl Methacrylate Polymer (MMA):
[0086] Metablen P-530A (from Mitsubishi Rayon), having a
weight-average molecular weight of 3,000,000.
[0087] (E) Polytetrafluoroethylene (PTFE):
[0088] F201L (from Daikin Chemical Industry), having a molecular
weight of from 4,000,000 to 5,000,000.
[0089] (F) Rubber-Like Elastomer (Core/Shell-Type, Grafted
Rubber-Like Elastomer): Metablen S2001 (From Mitsubishi Rayon).
[0090] This is a composite rubber-grafted copolymer having a
polydimethylsiloxane content of at least 50% by weight.
[0091] (G) Talc: FFR (From Asada Flour Milling), Having a Mean
Grain Size of 0.7 .mu.m.
[0092] Testing Methods:
[0093] (1) Melt Index (MI):
[0094] Measured at 280.degree. C. under a load of 2.16 kg.
[0095] (2) Flame Retardancy:
[0096] Tested according to the UL94 combustion test. Samples tested
had a thickness of 1.5 mm.
[0097] (3) Melt Tension (g):
[0098] A sample was extruded through a capillary having a diameter
of 2 mm, at a shear rate of 1 sec.sup.-1, at a temperature of
250.degree. C. and at a taking away speed of 3.1 m/min, whereupon
the load for taking the sample away through the capillary was
measured.
[0099] (4) Blow Moldability:
[0100] Using a molding machine (Placo's DAC-50), a sample was
molded into blow moldings (blow panels to be tested, for which the
parison weighed 2 kg). The molding resin temperature was
240.degree. C., and the mold temperature was 40.degree. C. The
parison and the blow panel were tested for the following:
[0101] Draw-down time (sec): After the parison was extruded out,
the time taken by it for 20% elongation was measured. The longer
time indicates better draw-down resistance and better moldability
of the sample.
[0102] Pinch-off strength: A test piece of 25 mm.times.40 mm in
size was cut out of the pinch-off part of a blow panel sample, and
subjected to a tear test to measure its pinch-off strength
(MPa).
1 TABLE 1 Comp. Comp. Ex. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 2 Ex. 4
Composition (A) PC-1 80 80 -- -- -- -- PC-2 -- -- 80 80 80 -- PC-3
-- -- -- -- -- 80 (B) HIPS 20 20 20 20 20 20 (C) Flame retardant,
PFR 11 11 10 10 10 8 (D) MMA P-530A 3 -- 6 6 -- 3 (E) PTFE 0.2 0.2
0.2 0.2 0.2 0.2 (F) Rubber-like elastomer 4 4 4 4 4 4 (G) Talc --
-- -- 5 5 5 Test Results (1) MI 19 22 20 18 24 17 (2) Flame
retardancy, UL-94 V-0 V-0 V-0 V-0 V-0 V-0 (3) Melt tension (g),
250.degree. C. 2.8 2.0 2.9 2.8 2.3 4.0 (4) Blow moldability
Draw-down time (sec) 4.0 2.0 4.0 4.0 2.0 6.0 Pinch-off strength
(MPa) 150 80 135 130 70 125 Total evaluation .largecircle. X
.largecircle. .largecircle. X .largecircle. strength (MPa). Total
evaluation: .largecircle.: Good parisons were formed, and good
moldings were obtained. X: Good parisons were not formed.
[0103] As described in detail hereinabove, the flame-retardant
polycarbonate resin composition of the invention comprises a resin
component of a polycarbonate resin (PC) and optionally a styrenic
resin (PS), and contains a flame retardant and a methyl
methacrylate polymer having an ultra-high molecular weight. The
composition has good flame retardancy and good blow moldability.
Preferably, the composition contains a halogen-free phosphate as
the retardant and further contains a fluoro-olefinic resin, and its
blow moldability is much improved to give blow moldings having
better flame retardancy with no problem of environmental pollution.
Also preferably, the composition further contains a rubber-like
elastomer and an inorganic filler, which further improve the impact
resistance, the rigidity, the heat resistance and the flame
retardancy of the moldings of the composition. The moldings of the
composition have many applications, for example, for lightweight
and resources-saving office automation appliances, etc.
[0104] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
* * * * *