U.S. patent application number 10/381501 was filed with the patent office on 2003-08-28 for impact-resistant polyoxymethylene moulding compounds with a low emission, the use thereof and moulded bodies produced therefrom.
Invention is credited to Disch, Stefan, Hofmann, Ernst, Kurz, Klaus, Witan, Kurt.
Application Number | 20030162912 10/381501 |
Document ID | / |
Family ID | 26007159 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030162912 |
Kind Code |
A1 |
Disch, Stefan ; et
al. |
August 28, 2003 |
Impact-resistant polyoxymethylene moulding compounds with a low
emission, the use thereof and moulded bodies produced therefrom
Abstract
The present invention relates to a polyoxymethylene molding
composition comprising: (A) from 0.01 to 1.0% by weight of a cyclic
stabilizer which contains at least one nitrogen atom in the ring
(B) from 0.001 to 0.5% by weight of a salt of a carboxylic acid (C)
from 5 to 50% by weight of an impact modifier (D) from 0.0 to 2.0%
by weight of a sterically hindered phenol compound (E) from 0.0 to
1.0% by weight of at least one stabilizer from the group of the
benzotriazole derivatives or benzophenone derivatives or aromatic
benzoate derivatives (F) from 0.0 to 0.8% by weight of a sterically
hindered amine as light stabilizer (HALS) (G) a polyoxymethylene
polymer to 100% by weight. The molding compositions of the
invention have substantially reduced formaldehyde emission, while
the level of mechanical properties, particularly strength and
impact strength, is retained.
Inventors: |
Disch, Stefan; (Konigsstein,
DE) ; Witan, Kurt; (Hofheim, DE) ; Hofmann,
Ernst; (Haibach, DE) ; Kurz, Klaus;
(Kelsterbach, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
1220 N MARKET STREET
P O BOX 2207
WILMINGTON
DE
19899
|
Family ID: |
26007159 |
Appl. No.: |
10/381501 |
Filed: |
March 25, 2003 |
PCT Filed: |
September 17, 2001 |
PCT NO: |
PCT/EP01/10710 |
Current U.S.
Class: |
525/539 ;
524/322; 524/351; 524/394; 524/86 |
Current CPC
Class: |
C08K 5/34 20130101; C08L
59/04 20130101; C08K 5/098 20130101; C08K 5/098 20130101; C08K 5/10
20130101; C08K 5/13 20130101; C08L 59/00 20130101; C08L 59/02
20130101; C08K 5/10 20130101; C08K 5/13 20130101; C08L 59/00
20130101; C08K 5/34 20130101; C08L 59/00 20130101; C08L 59/00
20130101; C08L 2666/08 20130101; C08L 59/00 20130101; C08L 59/00
20130101 |
Class at
Publication: |
525/539 ; 524/86;
524/394; 524/322; 524/351 |
International
Class: |
C08F 283/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2000 |
DE |
100 47 488.8 |
Jun 1, 2001 |
DE |
101 26 787.8 |
Claims
1. A polyoxymethylene molding composition comprising Component (A)
from 0.01 to 1.0% by weight of a cyclic stabilizer which contains
at least one nitrogen atom in the ring Component (B) from 0.001 to
0.5% by weight of a salt of a carboxylic acid Component (C) from 5
to 50% by weight of an impact modifier Component (D) from 0.0 to
2.0% by weight of a sterically hindered phenol compound Component
(E) from 0.0 to 1.0% by weight of at least one stabilizer from the
group of the benzotriazole derivatives or benzophenone derivatives
or aromatic benzoate derivatives Component (F) from 0.0 to 0.8% by
weight of a sterically hindered amine as light stabilizer (HALS)
Component (G) a polyoxymethylene homo- or copolymer to 100% by
weight.
2. A polyoxymethylene molding composition comprising Component (A)
from 0.03 to 0.3% by weight of a cyclic stabilizer which contains
at least one nitrogen atom in the ring Component (B) from 0.001 to
0.5% by weight of a salt of a carboxylic acid Component (C) from 5
to 40% by weight of an impact modifier Component (D) from 0.1 to
1.0% by weight of a sterically hindered phenol compound Component
(E) from 0.0 to 0.8% by weight of at least one stabilizer from the
group of the benzotriazole derivatives or benzophenone derivatives
or aromatic benzoate derivatives Component (F) from 0.0 to 0.5% by
weight of a sterically hindered amine as light stabilizer (HALS)
Component (G) a polyoxymethylene homo- or copolymer to 100% by
weight.
3. A polyoxymethylene molding composition comprising Component (A)
from 0.01 to 1.0% by weight of a cyclic stabilizer which contains
at least one nitrogen atom in the ring Component (B) from 0.001 to
0.5% by weight of a salt of a carboxylic acid Component (C) from 7
to 30% by weight of an impact modifier Component (D) from 0.2 to
1.0% by weight of a sterically hindered phenol compound Component
(E) from 0.0 to 1.0% by weight of at least one stabilizer from the
group of the benzotriazole derivatives or benzophenone derivatives
or aromatic benzoate derivatives Component (F) 0.4% by weight of a
sterically hindered amine as light stabilizer (HALS) Component (G)
a polyoxymethylene homo- or copolymer to 100% by weight.
4. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 3, where the component (A) used comprises
aminopyridines, 2,6-diaminopyridine, substituted and dimeric
aminopyridines, pyrrolidone, imidazolidinone, hydantoin, allantoin,
triamino-1,3,5-triazine(melamine), melamine-formaldehyde
condensates, methylolmelamine, individually or as a mixture.
5. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 4, where the component (B) used comprises
carboxylates of an alkali metal and/or of an alkaliene earth metal
having from 10 to 32 carbon atoms.
6. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 5, where the component (B) used comprises
magnesium stearate.
7. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 6, where the component (C) comprises a
polyurethane, a 2-phase mixture made from polybutadiene and
styrene-acrylonitrile (ABS), modified polysiloxanes or,
respectively, silicone rubbers, or graft copolymers made from an
elastomeric, single-phase core based on polydiene and from a hard
outer graft layer, with fine distribution.
8. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 7, where component (C) comprises graft
copolymers made from an elastomeric, single-phase core based on
polydiene and from a hard outer graft layer, and where the outer
layer of the particles has a single- or dual-shell structure, and
in the case of single-shell particles is composed of
poly(meth)acrylate and poly(meth)acrylonitrile, and where in the
case of dual-shell particles the inner shell is composed of
crosslinked polystyrene and the outer shell is composed of
crosslinked polymethacrylate.
9. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 8, where component (D) comprises
pentaerythrityl
tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and/or
triethylene glycol
bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propriona- te] and/or
3,3'-bis[3-(3,5,-di-tert-butyl-4-hydroxyphenyl)propiono] hydrazide
and/or hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyp-
henyl)propionate] and/or 3,5-di-tert-butyl-4-hydroxytoluene.
10. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 9, where the component (E) used comprises
2-[2'-hydroxy-3',5'-bis(1,1-dimethylbenzyl)phenyl]benzotriazole.
11. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 10, where component (F) comprises
2,2,6,6-tetramethyl-4-piper- idyl compounds,
bis-(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and/or the polymer
made from dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2-
,6,6-tertamethyl-4-piperidine.
12. The polyoxymethylene molding composition as claimed in one or
more of claims 1 to 11, where component (G), the polyoxymethylene,
has been prepared using trifluoromethanesulfonic acid as
initiator.
13. The use of the thermoplastic molding composition as claimed in
one or more of claims 1 to 12 for producing moldings or films.
14. A molding produced from a thermoplastic molding composition as
claimed in one or more of claims 1 to 12.
Description
[0001] The present invention relates to impact-modified
polyoxymethylene molding compositions which are suitable for
producing molding or extrudates. The products produced therewith
are particularly stable during processing and have low formaldehyde
emission and little odor.
[0002] This application relates to the German Patent Applications
DE 10126787.8 and DE 10047488.8, which are expressly incorporated
herein by way of reference. They are therefore part of the
disclosure of this Patent Application.
[0003] Since their introduction to the market about 40 years ago,
polyoxymethylenes have become established as extremely useful
technical materials in many applications. Polyoxymethylene is
particularly widely used as an engineering material in automotive
construction, in the electrical industry, and in medical
technology. In these applications, polyoxymethylene molding
compositions are subject to a requirement for a certain level of
mechanical properties, such as stiffness, hardness, and toughness,
this level being an essential requirement for the use of these
materials for technical components like gear wheels and levers,
among many other examples. The published values for yield stress
are from 60 to 70 N/mm.sup.2. The values found for the tensile
modulus of elasticity of unmodified copolymers are from 2400 to
3100 N/mm.sup.2. The values found for tensile strain at break are
from 10 to 30%.
[0004] However, the impact strength of polyoxymethylenes is too low
for many potential applications. Another desirable property in
these applications is the capability of the products to retain
their good impact strength properties even at relatively low
ambient temperatures.
[0005] It is known that polyoxymethylenes can be toughened by
adding impact modifiers. Impact modifiers used comprise organic
additives, such as crosslinked or non-crosslinked elastomers, or
graft copolymers made from an elastomeric, single-phase core and
from a hard outer graft layer. Impact-modified polyoxymethylene
molding compositions are known from the patent literature, e.g.
polyoxymethylene modified with polyurethanes (DE 1 193 240),
polyoxymethylene modified with a 2-phase mixture made from
polybutadiene and styrene-acrylonitrile (ABS) (DE 1 931 392),
polyoxymethylene modified with a graft copolymer prepared from
acrylatebutadiene (DE 1 964 156), a polyoxymethylene provided with
modified polysiloxanes and, respectively, silicone rubbers (DE 2
659 357), and finally polyoxymethylene modified with a graft
copolymer composed of an elastomeric, single-phase core based on
polydiene and of a hard, single- or multiphase outer graft layer,
e.g. made from poly(alkyl)acrylates, poly(alkyl)acrylonitriles or
polystyrene (EP 0156285 B1).
[0006] However, these foreign materials can cause degradation of
the materials during processing, followed by release of
formaldehyde, severely restricting the usefulness of the material
for the production of moldings. Impact-modified polyoxymethylene
molding compositions therefore often have high formaldehyde
emission. Contaminants such as residual monomers or solvents
present in the impact modifiers are released during the processing
of impact-modified polyoxymethylene molding compositions and during
the use of the moldings produced therefrom. The emission of
formaldehyde and contaminants from the impact modifiers causes an
unpleasant odor, restricting the use of these materials in many
application sectors.
[0007] A particular requirement during the processing of
impact-modified polyoxymethylene molding compositions is that the
degradation of the material is surpressed, to avoid any impairment
of the properties of the product or of the material. Stabilizers
are added for this purpose. EP 0156285 mentions the following
stabilizers for the polyacetal phase: polyamides, amides of
polybasic carboxylic acids, amidines, hydrazines, ureas,
poly(N-vinyllactams), and the alkaline earth metal salts of
aliphatic mono- to tribasic carboxylic acids having from 2 to 20
carbon atoms and preferably containing hydroxy groups. Mention is
also made of oxidation stabilizers and light stabilizers. However,
even the addition of stabilizers has not hitherto removed the
shortcoming of high emission. Known stabilizers and stabilizer
systems which reduce formaldehyde emission moreover cause
impairment of mechanical property profile.
[0008] None of the formulations described hitherto for
impact-modified polyoxymethylene molding compositions gives
sufficiently low formaldehyde emission together with retention of
mechanical property profile.
[0009] The object of the present invention is to provide
polyoxymethylene molding compositions in which the formaldehyde
emission found hitherto has been reduced while mechanical property
profile is retained. The moldings produced from these molding
compositions are to have little odor.
[0010] The object is achieved by means of a polyoxymethylene
molding composition comprising:
[0011] (A) from 0.01 to 1.0% by weight of a cyclic stabilizer which
contains at least one nitrogen atom in the ring
[0012] (B) from 0.001 to 0.5% by weight of a salt of a carboxylic
acid
[0013] (C) from 5 to 50% by weight of an impact modifier
[0014] (D) from 0.0 to 2.0% by weight of a sterically hindered
phenol compound
[0015] (E) from 0.0 to 1.0% by weight of at least one stabilizer
from the group of the benzotriazole derivatives or benzophenone
derivatives or aromatic benzoate derivatives
[0016] (F) from 0.0 to 0.8% by weight of a sterically hindered
amine as light stabilizer (HALS)
[0017] (G) a polyoxymethylene polymer to 100% by weight.
[0018] Surprisingly, it has been found that the polyoxymethylene
molding compositions of the invention have substantially reduced
formaldehyde emission when compared with the prior art. The
reduction in emission is brought about by the interaction between
the cyclic stabilizer having at least one ring nitrogen atom and
the carboxylic salt. Unlike with other stabilizer systems which can
be used to reduce emission from polyoxymethylene molding
compositions, the level of mechanical properties, particularly
strength and impact strength, is retained.
[0019] The molding composition of the invention comprises from 0.01
to 1.0% by weight, preferably from 0.03 to 0.3% by weight, of a
cyclic stabilizer, component (A), which contains at least one
nitrogen atom in the ring. Examples are pyrrolidine, piperidine,
pyrrole, pyridine, purine, indole, carbazole, tryptophan, oxazole,
imidazole, thiazole, picoline, lutidine, collidine, quinoline,
pyridazine, pyrimidine, pyrazine, and their derivatives.
Advantageous compounds are heterocyclic compounds having at least
one nitrogen atom as heteroatom adjacent either to an
amino-substituted carbon atom or to a carbonyl group, examples
being pyridazine, pyrimidine, pyrazine, pyrrolidone, aminopyridine,
and compounds derived therefrom. Advantageous compounds of this
type are aminopyridine and compounds derived therefrom. In
principle, any of the aminopyridines is suitable, e.g. melamine,
2,6-diaminopyridine, substituted and dimeric aminopyridines, and
also pyrrolidone and compounds derived therefrom, and mixtures made
from these compounds. Examples of suitable pryrolidones are
imidazolidinone and compounds derived therefrom, e.g. hydantoin,
the derivatives of which are particularly advantageous, and of
these compounds allantoin and its derivatives are particularly
advantageous. Other particularly advantageous compounds are
triamino-1,3,5-triazine (melamine) and its derivatives, e.g.
melamine-formaldehyde condensates and methylolmelamine. Very
particular preference is given to melamine, methylolmelamine,
melamine-formaldehyde condensates and allantoin. The cyclic
stabilizers which contain at least one nitrogen atom in the ring
may be used individually or in combination.
[0020] The component (B) used comprises from 0.001 to 0.5% by
weight of a metal salt of a carboxylic acid. Salts of fatty acids
are advantageous, in particular salts of higher fatty acids having
from 10 to 32 carbon atoms, preferably from 14 to 32 carbon atoms,
and particular preference is given to salts of montanic acids and
stearic acid. Preferred metals are those which occur in the form of
mono- or divalent ions, e.g. alkali metals and alkaline earth
metals, in particular alkaline earth metals. Particular preference
is given to magnesium and calcium, an example being calcium
stearate. Magnesium stearate is very particularly preferred as
component (B).
[0021] The component (C) used comprises from 5 to 50% by weight,
preferably from 5 to 40% by weight, particularly preferably from 7
to 30% by weight, of an impact modifier. Impact modifiers which may
used, individually or as a mixture, are polyurethanes, 2-phase
mixtures made from polybutadiene and styrene-acrylonitrile (ABS),
modified polysiloxanes and, respectively, silicone rubbers, or
graft copolymers made from an elastomeric, single-phase core based
on polydiene and from a hard outer graft layer (core-shell
structure). In the latter case, component (C) is composed of
particles most of which, preferably more than 70% of which, have a
structure of core and outer layers. The core here is formed from an
elastomeric polymer phase onto which has been grafted the hard
outer layer, which may also be composed of two or more layers. The
core is preferably single-phase, meaning that the core is composed
mainly, preferably completely, of the elastomeric soft phase and
comprises only small amounts of, preferably no, inclusions made
from hard polymer constituents of the outer layer. The graft
copolymer is mostly composed of from 40 to 95% by weight,
advantageously from 60 to 90% by weight, particularly
advantageously from 70 to 80% by weight, of the elastomeric core.
The proportion of the outer layers (shells) is from 5 to 60% by
weight, advantageously from 10 to 40% by weight, particularly
advantageously from 20 to 30% by weight. The core is generally
composed of polydienes, e.g. polybutadiene or polyiosprene, and can
contain up to 10% by weight, advantageously up to 5% by weight, of
comonomer units. Styrene or acrylonitrile may advantageously be
used as comonomer. The core polymer may also have been crosslinked
and have a gel content, measured in toluene, generally greater than
70%, and preferably greater than 80%. An example of a crosslinker
which may be used is divinylbenzene. The outer layer of the
particles is composed of hard polymers which have been grafted onto
the core as graft substrate. The outer layer here may have a
single- or multishell structure, advantageously a dual-shell
structure. If there is more than one outer layer, it is
advantageous for the various layers to be composed of different
polymers or copolymers. It is advantageous here for the first layer
to have been crosslinked. However, where appropriate, the other
layers may also have been crosslinked.
[0022] Examples of suitable monomers which give suitable polymers
for the outer layer of the particles are unsaturated nitrites,
acrylates, methacrylates, vinyl esters, styrene derivatives,
advantageous monomers being acrylonitrile, methacrylonitrile
acrylates and methacrylates having an alcohol component which has
from 1 to 6, preferably from 1 to 4, carbon atoms, examples being
methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate,
methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl
methacrylate, and tert-butyl methacrylate. Vinyl compounds which
may also be used with advantage are vinyl acetate, vinyl ethers,
N-vinyl-N-methylacetamide, and vinylpyrrolidone, and examples of
styrene derivatives which may be used with advantage are styrene,
.alpha.-methylstyrene and vinyltoluene. Copolymers made from at
least two of the abovementioned monomer groups and monomers may
also be used in the structure of the outer layer, in particular
copolymers of the specified styrene derivatives with the other
monomers. Particularly advantageous copolymers are those prepared
from a mixture comprising from 20 to 80% by weight of acrylonitrile
or methacrylonitrile with from 80 to 20% by weight of the other
specified monomers, in particular acrylates, methacrylates and
vinyl esters. Preference is also given to graft polymers which have
a dual-shell outer layer structure, the first shell being composed
of polystyrene and the second, outer, shell being composed of a
poly(meth)acrylate, which has particularly preferably been
crosslinked to some extent. The crosslinking monomers used may in
principle comprise any of the compounds suitable for this purpose,
for example multifunctional olefins, such as bivinylbenzene,
ethylene glycol dimethacrylate, butylene glycol dimethacrylate, or
else triallyl cyanurate.
[0023] According to the invention, the glass transition temperature
of the component (C) described above is from -40 to -120.degree.
C., preferably below -60.degree. C., in particular from -80 to
-120.degree. C. The preparation of the graft copolymers which can
be used as component (C) and have a core-shell structure is known
and can use single-stage polymerization in the case of a
single-shell outer layer or multistage polymerization in the case
of a multishell outer layer, for example as described in the Patent
Specification U.S. Pat. No. 39,875,704, which is incorporated
herein by way of reference. The graft copolymerization is carried
out using water-soluble initiators or using activated initiator
systems of which one component at least is water-soluble, for
example as described in C. B. Bucknall, "Toughened Plastics", p.
98, Applied Science Publishers Ltd. 1977 (London)). For the single-
or multistage graft copolymerization the starting material is a
polydiene, preferably in the form of an aqueous latex with defined
average particle size, particularly preferably in the range from
0.1 to 5 .mu.m, where the polydiene has particularly preferably
been partially crosslinked.
[0024] For the preparation, the monomer or the monomer mixture is
polymerized in the presence of the polydiene, whereupon the major
portion of the monomers is grafted onto the polydiene particles.
The amount of polydiene is generally 40 to 95% by weight, and the
amount of the monomers or monomer mixture is generally from 5 to
60% by weight, based in each case on the total amount. The graft
yield achieved varies from 60 to 95%, preferably from 80 to 90%.
The graft polymerization is carried out in solution or emulsion,
preferably in aqueous dispersion. For this purpose, the
fine-particle polydiene latex forms an initial charge with addition
of the usual polymerization auxiliaries, such as emulsifying agents
or suspending agents, free-radical initiators, regulators, etc.,
and the monomer or the monomer mixture is added and polymerized at
temperatures from 30 to 95.degree. C., preferably from 50 to
80.degree. C. For a single-stage reaction the initiator is
water-soluble, and examples of initiators which may be used are
water-soluble peroxides, percarbonates or perborates. In the case
of a multicomponent initiator system (redox system) at least one
component has to be water-soluble. Examples of emulsifiers which
may be used, and are also termed dispersing agents, are aliphatic
and aromatic sulfates, sulfonates, and salts of carboxylic acids,
for example dresinates. The compounds suitable for this purpose are
well known to the skilled worker.
[0025] For a multistage reaction the graft polymerization and the
work-up generally take place as described in U.S. Pat. No.
3,985,704. To form a multishell outer layer, a monomer or a monomer
mixture, such as styrene, is first grafted onto the core polymer,
such as butadiene-styrene copolymer, and then another monomer or
monomer mixture is used, where appropriate in the presence of a
crosslinker.
[0026] The average particle size of the particles is advantageously
from 0.1 to 5 .mu.m.
[0027] Other materials which can be used as graft copolymers for
component (C) are those in which the core is composed mainly or
completely of, preferably partially crosslinked, polyacrylates or
polymethacrylates, the alcohol component of which contains from 1
to 15 carbon atoms, preferably from 1 to 8 carbon atoms. Olefinic
monomers may be used as comonomers, advantageously butadiene,
cyclooctadiene, vinyl ethers and haloalkyl acrylates. The gel
content, measured in toluene, is preferably at least 50%,
particularly preferably at least 70%. For the outer graft layer use
may be made of the monomers and monomer mixtures described above.
The particle sizes, too, are in the same range. Graft polymers
based on polyacrylates and on polymethacrylates are described by
way of example in DE 1964156, DE 2116653, EP 50265, EP 60601 and EP
64207, incorporated herein by way of reference. The core of the
graft polymer may also be composed entirely or partially of a
silicone rubber and/or of non-crosslinked organopolysiloxanes. The
other monomers and/or monomer mixtures described above may be
grafted onto this core, which preferably contains functional groups
having graft activity. These materials are described by way of
example in DE 2659357, incorporated herein by way of reference.
Component (C) preferably comprises a diluent, and in particular if
the core of the graft polymer is composed of partially crosslinked
polyacrylates or polymethacrylates. The diluent is a low-melting,
advantageously polymeric substance which has good miscibility in
the melt with the graft polymer used as impact modifier. It is
particularly advantageous to use this diluent if the level of
crosslinking of the graft polymers is sufficiently high to make
them insoluble in the diluent, and a two-phase system forms, and
the surface tension can lead to fine distribution of the graft
polymers in the diluent. The graft polymer is preferably present
mainly in the peripheral region of the two-phase system. As the
amount of graft polymer increases it is also increasingly present
in the core, and, with a further increase in the amount of the
graft polymer, also outside the two-phase system within the matrix
polymer, component (G). It is particularly advantageous to have
uniform distribution of the two-phase system and of the graft
polymer in component (G), in particular if the graft polymer is
mainly present at the periphery of the two-phase system. The
melting point of the diluent should be below 250.degree. C.,
preferably from 180 to 210.degree. C. The amount of the diluent is
from 10 to 95%, advantageously from 30 to 70%, particularly
preferably from 40 to 60%, based on the entirety of graft polymer
and diluent. Materials which may be used with very particular
advantage as diluents are polyurethanes and segmented copolyesters
and ethylene-vinylacetate copolymers. Other suitable diluents are
known to the skilled worker and are described by way of example in
DE 2818240 and DE 2523991, incorporated herein by way of reference.
The diluent may advantageously be mixed with the graft polymer
prior to addition to component (G).
[0028] Other impact-modifying components, component (C), which may
be used are polyurethanes, preferably thermoplastic polyurethanes.
The polyurethanes which may be used according to the invention are
known products described by way of example in DE 1193240 and DE
2051028, and in Kunststoff-Taschenbuch, [Plastics Handbook]
(Saechtling, 27th edition, Hanser Verlag 1998) on pages 523-542,
incorporated herein by way of reference. They are prepared in a
known manner via polyaddition, from polyisocyanates, in particular
diisocyanates, polyesters, polyethers, polyesteramides,
polyacetalas or other suitable hydroxy or amino compounds, such as
hydroxylated polybutadiene, or mixtures of the abovementioned
compounds. Where appropriate, use is also made of chain extenders,
such as low-molecular-weight polyols, in particular diols,
polyamines, in particular diamines, or water.
[0029] Examples of suitable diisocyanates are diisocyanates of the
formula I
OCN--R--NCO I
[0030] where R is a divalent, straight-chain or branched aliphatic
radical having from 1 to 20, preferably from 2 to 12, carbon atoms,
or a divalent cycloaliphatic radical having from 4 to 20,
preferably from 6 to 15, carbon atoms, or a divalent, substituted
or unsubstituted aromatic radical having from 6 to 25, preferably
from 6 to 15, carbon atoms.
[0031] An example of a divalent, aliphatic radical is the
alkylidene radical --(CH.sub.2).sub.n--, where n=2 to 12, e.g.
ethylidene, propylidene, pentamethylene, or hexamethylene radical,
or the like, or the 2-methylpentamethylene,
2,2,4-trimethylhexamethylene or 2,4,4-trimethylhexamethylene
radical. Diisocyanates of this type which are particularly
preferred are hexamethylene diisocyanate, and 2,2,4- and
2,4,4-trimethylhexamethylene diisocyanate.
[0032] If R in formula I above is a cycloaliphatic radical, this is
preferably the unsubstituted or substituted cyclohexane radical.
Examples of diisocyanates of this type are 1,2- or
1,4-di(isocyanatomethyl)cyclohe- xane or isophorone
diisocyanate.
[0033] R in formula I above may also be a combination of divalent,
open-chain aliphatic or cycloaliphatic radicals, for example 1
[0034] where R.sub.1 is a saturated, straight-chain or branched
aliphatic radical having from 1 to 8, preferably from 1 to 3,
carbon atoms. The two rings here are preferably unsubstituted
cyclohexane, while R.sub.1 is preferably the methylene, ethylene,
methylmethylene, or dimethylmethylene group.
[0035] If R is an open-chain, divalent radical, it is preferably an
unbranched alkylidene radical --(CH.sub.2).sub.n--, where n=from 2
to 12. Examples of these are the ethylidene, propylidene,
pentamethylene and hexamethylene radicals, and also the
2-methylpentamethylene, 2,2,4-trimethylhexamethylene or
2,4,4-trimethylhexamethylene radical. Diisocyanates of this type
which are particularly preferred are hexamethylene diisocyanate and
also 2,2,4- and 2,4,4-trimethylhexamethyle- ne diisocyanate.
[0036] If R in formula I above is a divalent aromatic radical, it
is preferably the toluene, diphenylmethane, phenylene or
naphthalene radical. Examples of corresponding diisocyanates are
toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, diphenylmethane
4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane 4,4'-diisocyanate,
3,3'-dimethyldiphenylene
4,4'-diisocyanate(3,3'-bitoluene-4,4'-diisocyana- te), m-phenylene
diisocyanate, p-phenylene diisocyanate, o-phenylene diisocyanate,
chlorophenylene 2,4-(toluene diisocyanate), 3,3'-dichlorodiphenyl
4,4'-diisocyanate 4-chlorophenylene 1,3-diisocyanate, naphthalene
1,5-diisocyanate, and naphthalene 1,4-diisocyanate.
[0037] If R in formula I above is a cycloaliphatic radical, it is
preferably the unsubstituted or substituted cyclohexane radical.
Examples of diisocyanates of this type are 1,2- or
1,4-di-(isocyanatomethyl)cycloh- exane or isophorone
diisocyanate.
[0038] The diisocyanates of formula I may also be used in
oligomeric form, for example in dimeric or trimeric form. Instead
of the polyisocyanates, use may also be made in a known manner of
blocked polyisocyanates, these being obtained from the isocyanates
mentioned by reaction with phenol or caprolactam, for example.
[0039] Aliphatic polyhydroxy compounds which may be used are
polyethers, such as polyethylene glycol ethers, polypropylene
glycol ethers, and polybutylene glycol ethers, poly-1,4-butanediol
ethers or mixed polyethers made from ethylene oxide and propylene
oxide. Other compounds which may be used for this purpose are
polyesteramides, polyacetals, and preferably aliphatic polyesters,
all of these compounds having free OH end groups.
[0040] The aliphatic polyesters preferably used are mainly
non-crosslinked polyesters with molecular weights of from 500 to
10000, preferably from 500 to 5000. The acid components derive from
unbranched and/or branched aliphatic dicarboxylic acids, e.g.
dicarboxylic acids of the formula
HOOC--(CH.sub.2).sub.n--COOH,
[0041] where n=from 0 to 20, preferably from 4 to 10, in particular
adipic acid and sebacic acid. Use may also be made here of
cycloaliphatic dicarboxylic acids, such as cyclohexanedicarboxylic
acids, or of mixtures with the abovementioned aliphatic
dicarboxylic acids.
[0042] The alcohol component used for these polyesters is in
particular an unbranched or branched aliphatic primary diol, e.g. a
diol of the formula
HO--(CH.sub.2).sub.m--OH,
[0043] where m=from 2 to 12, preferably from 2 to 6. Mention may in
particular be made here of 1,4-butanediol, 1,6-hexanediol and
2,2-dimethylpropanediol-1,3 and also diethylene glycol.
Cycloaliphatic diols, such as bis-hydroxymethylcyclohexane, are
also suitable here, as are mixtures with the aliphatic diols.
[0044] Each of the polyesters may be prepared from one dicarboxylic
acid and one diol, or else, as mentioned, from a mixture of two or
more dicarboxylic acids and/or two or more diols.
[0045] Chain extenders which may be used in preparing the
polyurethanes are mainly low-molecular-weight polyols, in
particular diols, or else polyamines, in particular diamines, or
else water.
[0046] The polyurethanes used according to the invention are
preferably thermoplastic and therefore preferably substantially
non-crosslinked, i.e. capable of melting repeatedly without any
significant signs of decomposition. Their reduced specific
viscosities, measured at 30.degree. C. in dimethylformamide, are
generally from 0.5 to 3 dl/g, preferably from 1 to 2 dl/g. The
values for the tensile strains at break are advantageously from 800
to 1500%, preferably from 1000 to 1500%, while the Shore hardness A
is not more than 90, advantageously not more than 81, preferably
from 50 to 85, particularly preferably from 60 to 80, in particular
from 65 to 80, and the glass transition temperatures are mostly not
above 0.degree. C., advantageously not above -10.degree. C.,
particularly advantageously not above -20.degree. C.
[0047] The amount of sterically hindered phenol compound used,
component (D), may be from 0.0 to 2.0% by weight, preferably from
0.1 to 1.0% by weight, particularly preferably from 0.2 to 1.0% by
weight. Examples of these compounds are pentaerythrityl
tetrakis-[3-(3,5-di-tert-butyl-4-hydr- oxyphenyl)propionate]
(Irganox 1010, Ciba Geigy), triethylene glycol
bis[3-(3-tert-butyl4-hydroxy-5-methylphenyl)propionate] (Irganox
245, Ciba Geigy),
3,3'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propiono] hydrazide
(Irganox MD 1024, Ciba Geigy), hexamethylene glycol
bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 259,
Ciba Geigy), 3,5-di-tert-butyl-4-hydroxytoluene (Lowinox BHT, Great
Lakes). Irganox 1010 and especially Irganox 245 are preferred.
[0048] The component (E) present may comprise at least one
stabilizer from the group of the benzotriazole derivatives or
benzophenone derivatives or aromatic benzoate derivatives, the
amount being from 0.0 to 1.0% by weight, preferably from 0.0 to
0.8% by weight. Preference is given to
2-[2'-hydroxy-3',5'-bis(1,1,-dimethylbenzyl)phenyl]benzotriazole,
obtainable commercially as Tinuvin 234 (Ciba Geigy).
[0049] The component (F) present in the molding composition of the
invention may comprise from 0.0 to 0.8% by weight, preferably from
0.0 to 0.5% by weight, very particularly preferably from 0.4% by
weight, of a sterically hindered amine as light stabilizer (HALS).
Preference is given to 2,2,6,6-tetramethyl4-piperidyl compounds,
e.g. bis(2,2,6,6-tetramethyl- -4-piperidyl) sebacate (Tinuvin 770,
Ciba Geigy), or to the polymer made from dimethyl succinate and
1-(2-hydroxyethyl)4-hydroxy-2,2,6,6-tetrameth- yl-4-piperidine
(Tinuvin 622, Ciba Geigy).
[0050] The base material used for the molding compositions of the
invention, polyoxymethylene (G), may be homopolyoxymethylenes or
copolyoxymethylenes. Polymers of this type are known to the skilled
worker and are described in the literature. The homopolymers are
generally obtained by polymerizing formaldehyde or trioxane, and
the polymerization here may be initiated cationically or
anionically. However, preference is given to copolyoxymethylenes
which contain not only oxymethylene units but also oxyalkylene
units, where the alkylene groups may contain from 2 to 8 carbon
units, linear or branched. The polyoxymethylenes (POMs) described
by way of example in DE-A 29 47 490 are generally unbranched linear
polymers and generally contain at least 80%, preferably at least
90%, of oxymethylene units (--CH.sub.2O--). The term
polyoxymethylenes here encompasses homopolymers of formaldehyde or
of its cyclic oligomers, such as trioxane or tetroxane, and also
corresponding copolymers.
[0051] Homopolymers of formaldehyde or of trioxane are polymers of
this type whose hydroxy end groups have been chemically stabilized
in a known manner to resist degradation, e.g. by esterification or
etherification. Copolymers are polymers made from formaldehyde or
from its cyclic oligomers, in particular trioxane, and from cyclic
ethers, cyclic acetals, and/or linear polyacetals.
[0052] Homopolyoxymethylenes or copolyoxymethylenes are known per
se to the skilled worker and are described in the literature. These
polymers very generally have at least 50 mol % of --CH.sub.2O--
repeat units in the main polymer chain. The homopolymers are
generally prepared by polymerizing formaldehyde or trioxane,
preferably in the presence of suitable catalysts. Examples of
particularly suitable catalysts are boron trifluoride and
trifluoromethanesulfonic acid.
[0053] For the purposes of the invention, preference is given to
copolyoxymethylenes as component (G), in particular those which
also contain, alongside the --CH.sub.2O-- repeat units, up to 50
mol %, preferably from 0.1 to 20 mol %, and in particular from 0.5
to 10 mol %, of repeat units of the following formula 2
[0054] where R.sup.1 to R.sup.4, independently of one another, are
a hydrogen atom, a C.sub.1-C.sub.4-alkyl group, or a
halo-substituted alkyl group having from 1 to 4 carbon atoms, and
R.sup.5 is --CH.sub.2--, --CH.sub.2O--, or a C.sub.1-C.sub.4-alkyl-
or C.sub.1-C.sub.4-haloalkyl-s- ubstituted methylene group, or a
corresponding oxymethylene group, and n is from 0 to 3. These
groups may advantageously be introduced into the copolymers by the
ring-opening of cyclic ethers. Preferred cyclic ethers are those of
the formula 3
[0055] where R.sup.1 to R.sup.5 and n are as defined above. Cyclic
ethers which may be mentioned as examples are ethylene oxide,
propylene 1,2-oxide, butylene 1,2-oxide, butylene 1,3-oxide,
1,3-dioxane, 1,3-dioxolane and 1,3-dioxepan, and comonomers which
may be mentioned as examples are linear oligo- or polyformals, such
polydioxolane or polydioxepan.
[0056] Particularly advantageous copolymers are those made from
99.5-95 mol % of trioxane and 0.5-5 mol % of one of the above of
the above-mentioned comonomers.
[0057] Also suitable as component (G) are oxymethyleneterpolymers,
for example those prepared by reacting trioxane with one of the
abovementioned cyclic ethers and with a third monomer, preferably a
bifunctional compound of the formula 4
[0058] where Z is a chemical bond, --O--, or --ORO--
(R.dbd.C.sub.1-C.sub.8-alkylene or
C.sub.3-C.sub.8-cycloalkylene).
[0059] Preferred monomers of this type are ethylene diglycide,
diglycideyl ether, and diethers made from glycidyl compounds and
formaldehyde, dioxane or trioxane in a molar ratio of 2:1, and also
diethers made from 2 mol of glycidyl compound and 1 mol of an
aliphatic diol having from 2 to 8 carbon atoms, for example the
diglycidyl ether of ethylene glycol, 1,4-butanediol,
1,3-butanediol, 1,3-cyclobutanediol, 1,2-propanediol or
1,4-cyclohexanediol, to mention just a few examples.
[0060] Processes for preparing the above-described polyoxymethylene
homo- and copolymers are known to the skilled worker and are
described in the literature.
[0061] The preferred copolyoxymethylenes have melting points of
150.degree. C. or above and molecular weights (weight average)
M.sub.W in the range from 2000 to 1000000, preferably from 7000 to
150000. Particular preference is given to end-group-stabilized
polyoxymethylenes whose chain ends have carbon-carbon bonds. The
melt index (MVR 190/2.16) of the polyoxymethylenes used is
generally from 0.3 to 100 cm.sup.3/10 min (ISO 1133).
[0062] Particular preference is given to polyoxymethylenes
substantially having oxymethylene units and oxyethylene units in
the polymer chain. The proportion of the oxymethylene units, based
on structural units in the polymer chain, is from 0.1 to 15 mol %,
preferably 0.2 to 10 mol %. The melt index MFI, measured to ISO
1133 at 190.degree. C. with an applied weight of 2.16 kg is from
0.5 to 76 g/10 min, preferably from 2 to 60 g/10 min, and
particularly preferably from 5 to 35 g/10 min. The number-average
molar mass is at least 5000 g/mol and at most 100000 g/mol,
determined by GPC in dimethylacetamide at from 150 to 160.degree.
C. It is also possible to use a mixture of different
copolyoxymethylenes of differing compositions instead of a single
copolyoxymethylene. Well known preparation processes can be used to
prepare the copolyoxymethylenes. An example of a possible process
is the copolymerization of trioxane with dioxolane in the presence
of generally conventional amounts of BF.sub.3 and methylal.
Preference is given to polyoxymethylenes whose preparation uses
trifluoromethanesulfonic acid.
[0063] The molding composition of the invention may comprise other
conventional additives, individually or as a mixture, at up to 40%
by weight, examples being carbon blacks, e.g. conductivity blacks,
acid scavengers, antioxidants, UV stabilizers, coupling agents,
mold-release aids, substances to improve electrical conductivity,
antistats, nucleating agents, such as polyoxymethylene terpolymers
or talc, colorants, such as inorganic pigments, e.g. titanium
dioxide, ultramarine blue, cobalt blue, or organic pigments and
colours, such as phthalocyanines, anthrachinones, fillers, such as
glass beads, wollastonite, chalk, loam, molybdenum sulfide, or
graphite, inorganic or organic fibres, such as glass fibres, carbon
fibres or aramide fibers, lubricants, such as soaps and esters,
stearyl stearate, montanic esters, partially hydrolyzed montanic
esters, stearic acids, polar and/or non-polar polyethylene waxes,
poly-.alpha.-olefin oligomers, silicone oils, polyalkylene glycols
and perfluoroalkyl ethers, polytetrafluoroethylene,
ultrahigh-molecular-weight polyethylene, paraffins, solid and
liquid, stearic acids, and thermoplastic or thermoset polymer
additives, elastomers, and other polymers, such as EPDM
(ethylene-propylene-diene rubber), EPM (ethylene-propylene
rubbers), polyester elastomers, copolymers of ethylene with
(meth)acrylates and with (meth)acrylamides, polymethyl
methacrylate, polyethylene, polystyrene.
[0064] The polyoxymethylene molding compositions of the invention
may be prepared using the conventional and known mixing methods,
such as pelletizing, extrusion, kneading, etc. The molding
compositions of the invention are preferably prepared by mixing
polyoxymethylene with additives and stabilizers and then
pelletizing the mixture.
[0065] The colored polyoxymethylene molding compositions of the
invention have substantially reduced emission. The reduction in
formaldehyde release can be observed even during preparation of the
molding composition, e.g. during pelletizing, and also during
processing. The polyoxymethylene molding composition of the
invention therefore contributes to health and safety in the
workplace. However, there is a particularly substantial reduction
in the formaldehyde emission from moldings produced by injection
molding or extrusion. The formaldehyde emission measured to VDA 275
on plaques of wall thickness 1 mm after 24 h of storage is
advantageously less than 40 mg/kg, particularly advantageously less
than 30 mg/kg, very particularly advantageously less than 20 mg/kg.
The mechanical properties of the molding compositions of the
invention comply with the conventional requirements placed upon
commercially available polyoxymethylene products, and the
conventional application sectors and processing techniques for
polyoxymethylene are therefore applicable without restriction.
[0066] Particular application sectors for the molding compositions
of the invention are internal fittings and claddings for means of
transport, such as automobiles, aircraft, etc., other application
sectors being household goods, toys, baby items, and also devices
and components for electronics and electrical engineering. The
molding compositions of the invention are particularly suitable for
producing apparatus and instruments, or parts thereof, for medical
applications. The molding compositions prepared according to the
invention have the lowest formaldehyde emission of any currently
commercially available products, have defect-free surfaces, and
have high colorfastness when the moldings are exposed for a long
time to light or heat.
[0067] The references mentioned in this Patent Application are
expressly incorporated herein by way of reference. Those references
are therefore part of the disclosure of this Patent
Application.
EXAMPLES
[0068] In the examples below, the properties of the materials were
determined by the following methods:
[0069] Melt index (MFI) to ISO 1133 at 190.degree. C. with an
applied weight of 2.16 kg;
[0070] Tensile modulus of elasticity to ISO 527
[0071] Yield stress to ISO 527
[0072] Tensile strain at break to ISO 527.
[0073] Formaldehyde emission: Plaques of wall thickness 1 mm were
manufactured from the colored polyoxymethylene molding
compositions. The formaldehyde emission from the plaques was
determined to VDA 275 after a storage time of 24 h (VDA Guideline
No. 275, Dokumentation Kraftfahrwesen e.V. July 1994).
[0074] Production of test specimens: The polyacetal pellets are
molded by injection molding to give plaques of dimensions 80*50*1
mm. A Kraus Maffei KM 120/340 B injection molding machine is used
with the following injection molding parameters: melt temperature
195.degree. C., flow front velocity 200 mm/s, mold wall temperature
85.degree. C., hold pressure 900 bar, hold pressure time 30 s,
cooling time 10 s, back pressure from 0 to 10 bar. The test
specimens are stored for 24 h in a cabinet under standard
temperature and humidity conditions at 23.degree. C. and 50%
relative humidity prior to testing. Testing: two test specimens are
suspended on a stainless steel hook above 50 ml of deionized water
in a 1 l glass bottle and stored for 3 h in a circulating-air
drying cabinet at 60.degree. C. The test specimens are removed from
the test bottle. 5 ml of test solution are pipetted into a test
tube, which is heat-conditioned at 95.degree. C. for 10 minutes. 3
ml of acetylacetone and 3 ml of a 20% strength of ammonium acetate
solution are then added to the test tube. The formaldehyde forms
the diacetyldihydrolutidine complex with the reagents, and the
absorption of the complex at 412 nm is determined photometrically.
The formaldehyde concentration in the specimen solution is
calculated from the absorption.
[0075] Brabender Test: The polyoxymethylene molding composition is
sheared at 210.degree. C. in a twin-screw Brabender kneader. The
formaldehyde which escapes is discharged with an inert gas stream
and absorbed in sodium sulfite solution. The sodium sulfite
solution is titrated for quantitative determination of the
formaldehyde released. The result obtained is the amount of
formaldehyde released as a function of time. The degradation rate
is determined from the gradient of the curve by linear
extrapolation.
[0076] The results of testing of the material from the examples and
comparative examples are given in tables 1 to 3. The comparative
experiments are indicated by c, and the inventive examples are
indicated by e.
[0077] The polyoxymethylene used in the examples and comparative
examples comprises Hostaform C 9021. In the case of the experiments
listed in table 1, the polymer contained 3.4% of dioxolane as
comonomer, and trifluoromethanesulfonic acid was used as initiator.
In the case of the experiments listed in table 2, the polymer
contained 3.4% of dioxolane as comonomer and boron trifluoride was
used as initiator. In the case of the experiments listed in table
3, the polymer comprised 5.6% of dioxolane as comonomer, and
trifluoromethanesulfonic acid was used as initiator. Irganox 1010
from Ciba Spezialittenchemie was used as antioxidant. Licowachs E
or Licowachs C from Clariant were used as flow aids. Comparative
experiments used Eurelon from Vantico and dicyandiamide (DCD),
where appropriate in combination with magnesium stearate, to reduce
emission. The impact-modifier component used comprised Paraloid EXL
2600 from Rohm & Haas.
[0078] The pellets from the examples and comparative examples were
molded by injection molding to give the test specimens for
determining tensile modulus of elasticity, yield stress, and
tensile strain at break, and also to injection-mold the plaques for
determining formaldehyde emission.
[0079] All of the inventive examples show lower formaldehyde
emission from the moldings (VDA 275 test) and lower formaldehyde
emission during processing (Brabender test). Table 3 gives the
mechanical properties of some of the examples and comparative
examples. The mechanical properties can be seen to remain
comparably good.
[0080] Particularly low emission values can be obtained when using
polyoxymethylenes for which the initiator used comprised
trifluoromethanesulfonic acid. It can be seen from example 25 and
comparative example 25 that even in the case of colored molding
compositions it is possible to achieve a reduction in formaldehyde
emission with comparable mechanical properties.
1 TABLE 1 Stabilization Lico- Lico- Paraloid VDA Brabender Irganox
Ca wachs wachs Mela- Mg Eure- EXL 275 test Op. 1010 citrate C E
mine stearate Ion DCD T 1020 2600 test [Degr. No. [%] [%] [%] [%]
[%] [%] [%] [%] [%] [%] [mg/kg] ppm/h] c1 0.8 0.1 0.2 -- 0.07 -- --
-- 0.5 13 943.39 -- c2 0.8 0.1 -- 0.2 0.07 -- -- -- 0.5 13 791.79
1653 c3 0.8 0.1 0.2 -- -- -- 0.05 0.03 0.5 13 661.96 895 c4 0.8 0.1
-- 0.2 -- -- 0.05 0.03 0.5 13 717.40 1024 c5 0.8 0.1 0.2 -- 0.07 --
-- -- 0.5 25 506.33 579 c6 0.8 0.1 -- 0.2 0.07 -- -- -- 0.5 25
489.52 565 c7 0.8 0.1 0.2 -- -- -- 0.05 0.03 0.5 25 455.16 378 c8
0.8 0.1 -- 0.2 -- -- 0.05 0.03 0.5 25 425.08 343 e1 0.8 0.1 0.2 --
0.07 0.1 -- -- 0.5 13 22.12 -- e2 0.8 0.1 -- 0.2 0.07 0.1 -- -- 0.5
13 21.21 111 c9 0.8 0.1 0.2 -- -- 0.1 0.05 0.03 0.5 13 42.56 180
c10 0.8 0.1 -- 0.2 -- 0.1 0.05 0.03 0.5 13 47.08 164 e3 0.8 0.1 0.2
-- 0.07 0.1 -- -- 0.5 25 24.73 85 e4 0.8 0.1 -- 0.2 00.7 0.1 -- --
0.5 25 36.31 158 c11 0.8 0.1 0.2 -- -- 0.1 0.05 0.03 0.5 25 44.48
145 c12 0.8 0.1 -- 0.2 -- 0.1 0.05 0.03 0.5 25 43.43 -- c13 0.8 0.1
0.2 -- 0.07 -- -- -- 0.5 13 427.06 1083 c14 0.8 0.1 0.2 -- 0.07 --
-- -- 0.5 13 449.77 1538
[0081]
2TABLE 2 Lico- Paraloid VDA Brabender Irganox Ca wachs Mela- Mg
Eure- EXL 275 test Op. 1010 citrate C mine stearate Ion DCD T 1020
2600 test [Degr. No. [%] [%] [%] [%] [%] [%] [%] [%] [%] [mg/kg]
ppm/h] c15 0.8 0.1 0.2 -- -- 0.05 0.03 0.5 -- 40.24 -- c16 0.8 0.1
0.2 -- -- 0.05 0.03 0.5 13 303.67 276 c17 0.8 0.1 0.2 0.07 0 -- --
0.5 13 871.02 466 e5 0.8 0.1 0.2 0.07 0.01 -- -- 0.5 13 276.95 285
e6 0.8 0.1 0.2 0.07 0.03 -- -- 0.5 13 114.97 210 e7 0.8 0.1 0.2
0.07 0.05 -- -- 0.5 13 71.90 169 e8 0.8 0.1 0.2 0.07 0.07 -- -- 0.5
13 68.39 191 e9 0.8 0.1 0.2 0.07 0.07 -- -- 0.5 13 62.82 171 c18
0.8 0.1 0.2 -- -- 0.05 0.03 0.5 25 253.54 309 c19 0.8 0.1 0.2 0.07
0 -- -- 0.5 25 338.12 507 e10 0.8 0.1 0.2 0.07 0.01 -- -- 0.5 25
266.67 362 e11 0.8 0.1 0.2 0.07 0.03 -- -- 0.5 25 173.27 359 e12
0.8 0.1 0.2 0.07 0.05 -- -- 0.5 25 102.81 311 e13 0.8 0.1 0.2 0.07
0.07 -- -- 0.5 25 99.55 336 e14 0.8 0.1 0.2 0.07 0.10 -- -- 0.5 25
80.86 293
[0082]
3 TABLE 3 Notched Heat- Bra- impact con- Lico- Paraloid bender
strength ditioned Irganox Ca wachs Mela- Mg Eure- T EXL VDA test
Charphy 24 h/ Tensile Test Op. 1010 citrate C mine stearate Ion DCD
1020 2600 275 test [Degr. ISO 120.degree. C. Et .sigma.B .epsilon.B
No. [%] [%] [%] [%] [%] [%] [%] [%] [%] [mg/kg] ppm/h] 179/1eA
[KJ/m.sup.2] [MPa] [MPa] [%] c20 0.8 0.1 0.2 -- -- 0.05 0.03 0.5 --
48.92 -- -- -- -- -- -- c21 0.8 0.1 0.2 -- -- 0.05 0.03 0.5 13
407.43 1182 15.25 10.42 2121 42.66 59.12 c22 0.8 0.1 0.2 0.07 0 --
-- 0.5 13 377.96 1586 14.01 9.58 2136 41.59 70.24 e15 0.8 0.1 0.2
0.07 0.05 -- -- 0.5 13 32.38 155 -- -- -- -- -- e16 0.8 0.1 0.2
0.07 0.10 -- -- 0.5 13 29.80 157 15.61 10.16 2136 41.66 68.04 e17
0.8 0.1 0.2 0.07 0.15 -- -- 0.5 13 34.58 181 -- -- -- -- -- e18 0.8
0.1 0.2 0.07 0.20 -- -- 0.5 13 29.95 188 -- -- -- -- -- e19 0.8 0.1
0.2 0.07 0.30 -- -- 0.5 13 26.83 209 15.36 10.84 2134 41.97 60.01
c23 0.8 0.1 0.2 -- -- 0.05 0.03 0.5 25 387.01 441 -- -- -- -- --
c24 0.8 0.1 0.2 0.07 0 -- -- 0.5 25 375.74 791 -- -- -- -- -- e20
0.8 0.1 0.2 0.07 0.05 -- -- 0.5 25 26.13 173 -- -- -- -- -- e21 0.8
0.1 0.2 0.07 0.10 -- -- 0.5 25 37.14 244 -- -- -- -- -- e22 0.8 0.1
0.2 0.07 0.15 -- -- 0.5 25 -- 197 -- -- -- -- -- e23 0.8 0.1 0.2
0.07 0.20 -- -- 0.5 25 36.34 215 -- -- -- -- -- e24 0.8 0.1 0.2
0.07 0.30 -- -- 0.5 25 32.65 320 -- -- -- -- --
Example 25
[0083] Preparation of Base Polymer (copolyoxymethylene)
[0084] 94.4% by weight of trioxane, 5.6% by weight of dioxolane and
350 ppm of methylal form an initial charge in a batch reactor at a
temperature of 80.degree. C. and a pressure of about 1 bar. 30 ppm
of BF.sub.3 are added. The amounts given are based on the entire
monomer mixture. The crude polymer formed was suspended in a
water/triethylamine mixture and then hydrolyzed at 170.degree. C.
in a water/methanol (10/90) mixture. On cooling to room temperature
the polymer precipitated in the form of a fine powder and was
filtered off with suction, washed with water, and dried. The
product had a melt index (MFI) of 9 g/10 min. The following
components were combined and intimately mixed in a Henschel mixer:
190 g of acetylene black, 330 g of Kronos 2220, 240 g of Sicotan
Yellow K 2112, 20 g of Renol Brown EKX 851, 300 g of Irganox 245,
200 g of Lichowachs E, 70 g of melamine, 50 g of magnesium
stearate, 400 g of Tinuvin 234, 400 g of Tinuvin 770, 13 kg of
Paraloid EXL 2600 (producer Rohm & Haas), and polyoxymethylene
base polymer to 100 kg. A twin-screw extruder is used to pelletize
the mixture. Mechanical Properties: Tensile modulus of elasticity
2100 N/mm.sup.2, yield stress 44.6 N/mm.sup.2, tensile strain at
break 61%; formaldehyde emission to VDA 275: 16 mg/kg.
Comparative Example 25
[0085] The following components are combined and intimately mixed
in a Henschel mixer: 190 g of acetylene black, 330 g of Kronos
2220, 240 g of Sicotan Yellow K 2112, 20 g of Renol Brown EKX 861,
600 g of Irganox 245, 200 g of Licowachs C, 50 g of Eurelon, 30 g
of dicyandiamide, 400 g of Tinuvin 234, 400 g Tinuvin 770, 13 kg of
Paraloid EXL 2600 (producer Rohm & Haas), and polyoxymethylene
base polymer to 100 kg. A twin-screw extruder is used to pelletize
the mixture. The base polymer is identical with the base polymer
used in Example 25. Mechanical properties: tensile modulus of
elasticity 2050 N/mm.sup.2, yield stress 42.9 N/mm.sup.2, tensile
strain at break 55%, formaldehyde emission to VDA 275:225
mg/kg.
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