U.S. patent application number 10/947874 was filed with the patent office on 2007-08-16 for microgel-containing composition.
Invention is credited to Thomas Fruh, Ludger Heiliger, Martin Muller, Volker Muller, Werner Obrecht, Robert Hans Schuster, Heiko Tebbe.
Application Number | 20070191545 10/947874 |
Document ID | / |
Family ID | 34353156 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070191545 |
Kind Code |
A1 |
Heiliger; Ludger ; et
al. |
August 16, 2007 |
Microgel-containing composition
Abstract
The present invention relates to a composition containing
thermoplastic materials and crosslinked microgels that have not
been crosslinked by high-energy radiation, to a process for its
preparation, to its use in the production of thermoplastically
processable molded articles, and to molded articles produced from
the composition.
Inventors: |
Heiliger; Ludger; (Neustadt,
DE) ; Fruh; Thomas; (Limburgerhof, DE) ;
Muller; Volker; (Philippsburg, DE) ; Tebbe;
Heiko; (Dormagen, DE) ; Obrecht; Werner;
(Moers, DE) ; Schuster; Robert Hans; (Hannover,
DE) ; Muller; Martin; (Hannover, DE) |
Correspondence
Address: |
LANXESS CORPORATION
111 RIDC PARK WEST DRIVE
PITTSBURGH
PA
15275-1112
US
|
Family ID: |
34353156 |
Appl. No.: |
10/947874 |
Filed: |
September 23, 2004 |
Current U.S.
Class: |
525/191 |
Current CPC
Class: |
C08L 21/00 20130101;
C08L 23/10 20130101; C08L 21/00 20130101; C08L 23/10 20130101; C08L
2666/08 20130101; C08L 2666/02 20130101 |
Class at
Publication: |
525/191 |
International
Class: |
C08F 8/00 20060101
C08F008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2003 |
DE |
103 45 043.2 |
Claims
1. Composition comprising at least one thermoplastic material (A)
and at least one microgel (B) based on homopolymers or random
copolymers that has not been crosslinked by high-energy
radiation.
2. Composition according to claim 1, wherein primary particles of
the microgel (B) exhibit approximately spherical geometry.
3. Composition according to claim 2, wherein variation in diameters
of an individual primary particle of the microgel (B), defined as
[(d1-d2)/d1].times.100, wherein d1 and d2 are any two diameters of
any desired section of the primary particle and d1>d2, is less
than 250%.
4. Composition according to claim 1, wherein primary particles of
the microgel (B) have an average particle size of from 5 to 500
nm.
5. Composition according to claim 1, wherein the microgels (B)
comprise at least about 70 wt. % portions that are insoluble in
toluene at 23.degree. C.
6. Composition according to claim 1, wherein the microgels (B) have
a swelling index in toluene at 23.degree. C. of less than about
80.
7. Composition according to claim 1, wherein the microgels (B) have
glass transition temperatures of from -100.degree. C. to
+50.degree. C.
8. Composition according to claim 7, wherein t the microgels (B)
have a glass transition temperature of greater than about 5.degree.
C.
9. Composition according to claim 1, wherein the microgels (B) are
prepared by emulsion polymerization.
10. Composition according to claim 1, wherein the thermoplastic
materials (A) have a Vicat softening temperature of at least
50.degree. C.
11. Composition according to claim 1, wherein the thermoplastic
material (A) is selected from thermoplastic polymers (A1) and
thermoplastic elastomers (A2).
12. Composition according to claim 1, wherein the thermoplastic
material (A) and the microgel (B) have a difference in glass
transition temperature is from 0 to 250.degree. C.
13. Composition according to claim 1, wherein thermoplastic
material (A)/microgel (B) have a weight ration from 1:99 to
99:1.
14. Composition according to claim 13, wherein the weight ratio
thermoplastic material (A)/microgel (B) is from 10:90 to 90:10.
15. Composition according to claim 14, wherein the weight ratio
thermoplastic material (A)/microgel (B) is from 20:80 to 80:20.
16. Composition according to claim 1 further comprising at least
one conventional plastics additive.
17. Composition according to claim 1, prepared by mixing at least
one thermoplastic material (A) and at least one microgel (B) based
on homopolymers or random copolymers that has not been crosslinked
by high-energy radiation.
18. Composition according to claim 1, wherein the microgel (B)
contains functional groups.
19. Process for the preparation of compositions according to claim
1 comprising mixing at least one thermoplastic material (A) and at
least one microgel (B) based on homopolymers or random copolymers
that has not been crosslinked by high-energy radiation.
20. Process for the preparation of compositions according to claim
20, wherein the microgel (B) is prepared before it is mixed with
the thermoplastic material (A).
21. A molded acticle comprising a composition according to claim 1.
Description
[0001] The present invention relates to a composition containing
thermoplastic materials and crosslinked microgels that have not
been crosslinked by high-energy radiation, to a process for its
preparation, to its use in the production of thermoplastically
processable molded articles, and to molded articles produced from
the composition.
BACKGROUND OF THE INVENTION
[0002] The use of microgels for controlling the properties of
elastomers is known (e.g. EP-A-405216, DE-A 4220563, GB-PS 1078400,
DE 19701487, DE 19701489, DE 19701488, DE 19834804, DE 19834803, DE
19834802, DE 19929347, DE 19939865, DE 19942620, DE 19942614, DE
10021070, DE 10038488, DE 10039749, DE 10052287, DE 10056311 and DE
10061174). EP-A-405216, DE-A-4220563 and GB-PS-1078400 disclose the
use of CR, BR and NBR microgels in mixtures with
double-bond-containing rubbers. DE 19701489 describes the use of
subsequently modified microgels in mixtures with
double-bond-containing rubbers such as NR, SBR and BR.
[0003] None of these specifications teaches the use of microgels in
the production of thermoplastic elastomers.
[0004] Chinese Journal of Polymer Science, Volume 20, No. 2,
(2002), 93-98 describes microgels that have been completely
crosslinked by high-energy radiation and their use to increase the
impact strength of plastics. Similarly, US 20030088036 A1 discloses
reinforced heat-curing resin compositions in whose preparation
radiation-crosslinked microgel particles are likewise mixed with
heat-curing pre-polymers (see also EP 1262510 A1). In these
publications, a radioactive cobalt source is mentioned as the
preferred radiation source or the preparation of the microgel
particles. The use of radiation crosslinking yields very
homogeneously crosslinked microgel particles. However, this type of
crosslinking has the particular disadvantage that it is not
realistic to transfer this process from a laboratory scale to a
large-scale installation both from an economic viewpoint and from
the point of view of working safety. Microgels that have not been
crosslinked by high-energy radiation are not used in the mentioned
publications. Furthermore, when completely radiation-crosslinked
microgels are used, the change in modulus from the matrix phase to
the dispersed phase is immediate. In the case of sudden stress,
this can lead to tearing effects between the matrix and the
dispersed phase, with the result that the mechanical properties,
the swelling behavior and the stress corrosion cracking, etc. are
impaired.
[0005] DE 3920332 discloses rubber-reinforced resin compositions
which comprise (i) a matrix resin having a glass transition
temperature of at least 0.degree. C. and (ii) from 1 to 60 wt. % of
rubber particles dispersed in the matrix resin. The dispersed
particles are characterized in that they consist of hydrogenated
block copolymers of a conjugated diene and a vinyl aromatic
compound. The particles inevitably have two glass transition
microphase structure of separate microphase with segments and
temperatures, one being at -30.degree. C. or less. The particles
exhibit a soft segments, in which the hard segments and the soft
segments are alternately laminated with one another in the form of
concentric multiple layers. The preparation of these specific
particles is very expensive because it is first necessary to
prepare a solution of the starting materials for the particles
(block copolymers) in organic solvents. In the second step, water
and optionally emulsifiers are added, the organic phase is
dispersed in suitable apparatuses, the solvent is then removed and
the particles dispersed in water are then fixed by crosslinking
with a peroxide. In addition, it is very difficult to produce
particle sizes less than 0.25 .mu.m by this process, which is
disadvantageous for the flow behavior.
[0006] Polymeric materials can be divided into several groups
according to their structure, their deformation-mechanical behavior
and hence according to their properties and fields of use.
Traditionally there are on the one hand the amorphous or
semi-crystalline thermoplastics, which consist of long,
uncrosslinked polymer chains. Thermoplastics are brittle to
viscoelastic at room temperature. These materials are plasticized
by pressure and temperature and can then be molded. On the other
hand there are the elastomers or rubber materials. Elastomers are a
crosslinked rubber product. It may be natural or synthetic rubber.
Rubbers can only be processed in the uncrosslinked state. They then
exhibit viscoplastic behavior. Only with the addition of
crosslinking chemicals such as, for example, sulfur or peroxide is
there obtained upon subsequent heating a vulcanization product or
the elastic rubber. In this "vulcanization procedure", the loosely
fixed individual rubber molecules are linked together chemically by
the formation of chemical bonds. The amorphous preliminary product
rubber changes hereby into the elastomer with typical rubber
elasticity. The vulcanization procedure is not reversible, except
by thermal or mechanical decomposition.
[0007] The thermoplastic elastomers (abbreviated to TPE herein
below) exhibit completely different behavior. These materials
become plastic when heated and elastic again when cooled. In
contrast to chemical crosslinkinq, crosslinking in the case of
elastomers is physical Accordingly, the TPEs stand between the
thermoplastics and the elastomers in terms of their structure and
their behavior, and they combine the ready processability of the
thermoplastics with the fundamental properties of rubber. Above Tg
to the melting point or to the softening temperature, the TPEs
behave like elastomers, but they are thermoplastically processable
at higher temperatures. As a result of physical crosslinking, for
example via (semi-)crystalline regions, a thermoreversible
structure with elastic properties is formed on cooling.
[0008] In contrast to the processing of rubber, the processing of
TPE materials is based not on a cold/warm process but on a
warm/cold process. If in the case of soft, highly elastic TPE
materials in particular the pronounced intrinsically viscous
melting or softening behavior is taken into account, then it is
possible when processing TPEs to use the typical thermoplastic
processes such as injection molding, extrusion, blow molding and
deep drawing. The product properties depend primarily on the
structure and phase morphology; in elastomer alloys a large part is
played, for example, by the particle size, the particle size
distribution or the particle stretching of the disperse phase.
These structural features can be influenced to a certain extent
during processing. A further fundamental advantage of TPE materials
over the conventional, chemically crosslinked elastomers can be
seen in their fundamental suitability for recycling. As with all
plastics, a fall in viscosity that increases with the number of
processing steps is to be observed in the case of the TPE
materials, but this does not lead to a significant impairment of
the product properties.
[0009] Since the discovery of the TPEs, this class of materials has
been distinguished by the fact that it is formed by a combination
of a hard phase and a soft phase. The TPEs known hitherto are
divided into two main groups: [0010] block copolymerization
products and [0011] alloys of thermoplastics with elastomers. Block
Copolymerization Products:
[0012] The composition of the comonomers determines the ratio of
hard phase to soft phase, determines which phase constitutes the
matrix and determines the final properties. A true morphology is
recognizable at molecular level when, for example, the deficient
component aggregates or crystallizes. The temperature dependence of
this physical morphology fixing is a problem with these materials,
that is to say there is a limit temperature at which the morphology
fixing is undone. This can cause problems during processing owing
to changes in the properties associated therewith.
[0013] The block polymers include, for example, styrene block
copolymers (TPE-S), such as butadiene (SBS), isoprene (SIS) and
ethylene/butylene (SEBS) types, polyether-polyamide block
copolymers (TPE-A), thermoplastic copolyesters, polyether esters
(TPE-E) and thermoplastic polyurethanes (TPE-U), which are
described in greater detail herein below in connection with the
starting materials that can be used according to the present
invention.
[0014] The second main group of the material TPE are the elastomer
alloys. Elastomer alloys are polymer blends which contain both
thermoplastic and elastomeric constituents. They are prepared by
"blending" the raw materials, that is to say mixing them
intensively in a mixing device (internal mixer, extruder or the
like). Very different mixing ratios between the hard phase and the
soft phase can occur. The soft phase can be either uncrosslinked
(TPE-0) or crosslinked (TPE-V). In the ideal TPE blend there are
small elastomer particles which are uniformly distributed in finely
dispersed form in the thermoplastic matrix. The finer the
distribution and the higher the degree of crosslinking of the
elastomer particles, the more pronounced the elastic properties of
the resulting TPE. These TPE blends are prepared, for example, by
so-called "dynamic vulcanization" or reactive extrusion, in which
the rubber particles are crosslinked in situ during the mixing and
dispersing process. The property profile of these blends is
accordingly substantially dependent on the proportion, degree of
crosslinking and dispersion of the rubber particles. Very different
combinations can be produced by this blend technology. The
physico-mechanical properties and the chemical resistance and
compatibility with contact media are substantially determined by
the individual properties of the blend components. By optimizing
the "blend quality" and the degree of crosslinking it is possible
to improve specific physical properties. Nevertheless, it is a
characteristic of this class that the dispersed phase is present in
irregular and coarsely dispersed form. The less compatible the
polymers, the more coarse the resulting structure. The
non-compatible combinations, such as, for example, a dispersed
phase of NBR rubber in a PP matrix, are of particular technical
interest. In order to improve the compatibility in such cases and
accordingly influence the final properties of the resulting
material in the desired manner, a homogenizing agent can be added
prior to the dynamic vulcanization. About 1% of the homogenizing
agent is sufficient for many applications. The homogenizing agents
are generally based on block copolymers whose blocks are compatible
with in each case one of the blend phases. Depending on the
relative proportions, the two phases may constitute both the
continuous and the discontinuous phase. Hitherto it has not been
possible to adjust the morphology of this material in a reliable
manner. In order to produce particularly finely divided dispersed
phases, large amounts of the homogenizing agent may be necessary,
which in turn adversely affects the boundary properties of the
final material. Industrially produced and commercially available
thermoplastic vulcanization products exhibit a maximum distribution
of the diameter of the dispersed phase of from 2 .mu.m to 4 .mu.m
with individual volume elements up to 30 .mu.m.
[0015] Among the elastomer alloys, the most commonly used
combinations are based on EPDM with PP. Other elastomer alloys are
based on NR/PP blends (thermoplastic natural rubber), NBR/PP blends
(NBR=acrylonitrile-butadiene rubber), IIR (XIIR)/PP blends (butyl
or halobutyl rubbers as elastomeric phase constituents), EVA/PVDC
blends ("Alcryn" blend of ethylene-vinyl acetate rubber (EVA) and
polyvinylidene chloride (PVDC) as the thermoplastic phase) and
NBR/PVC blends. A targeted adjustment of the morphology of the
dispersed phase and hence a targeted adjustment of the desired
properties of the TPEs in these polymer blend TPEs is virtually
impossible, however, owing to the in situ formation of the
dispersed phase and the many parameters involved therein.
[0016] The present inventors relates to novel compositions having
thermoplastic elastomer properties which can easily be prepared
from starting materials known per se and whose properties can be
adjusted in a simple and foreseeable manner. The novel compositions
can be prepared on an industrial scale, and they should not give
rise to problems relating to working safety. Furthermore, there
should be no tearing effects in the compositions between the matrix
and the dispersed phase on sudden stress so that the mechanical
properties, the swelling behavior and the stress corrosion
cracking, etc. are impaired. The preparation of the microgels for
the composition should be simple and allow the particle size
distributions of the microgel particles to be adjusted in a
targeted manner to very small average particle sizes.
SUMMARY OF THE INVENTION
[0017] Surprisingly it has been found in the present invention
that, by incorporating crosslinked microgels, which have not been
crosslinked by high-energy radiation, based on homopolymers or
random copolymers into thermoplastic materials, it is possible to
provide compositions having a novel combination of properties. By
the provision of the novel composition it is surprisingly possible
to overcome the above-mentioned disadvantages of the known
conventional thermoplastics and TPEs and at the same time provide
thermoplastic elastomer compositions having outstanding use
properties. Because thermoplastic elastomer compositions are
obtained by the incorporation of microgels into the thermoplastic
materials, it is possible to separate the adjustment of the
morphology of the dispersed phase from the production of the TPE
material in terms of both space and time. The morphology production
can be reliably reproduced because the dispersed phase is a
microgel whose morphology can be controlled in a manner known per
se during preparation and which substantially does not change
further on incorporation into the thermoplastic material. In the
compositions prepared according to the invention, the polymer
microstructure of both the dispersed phase and the continuous phase
can be varied within wide limits, so that customized TPEs can be
produced from any desired thermoplastic materials, which was not
possible according to the known processes for the production of
conventional TPEs. By controlling the degree of crosslinking and
the degree of fictionalization in the surface and in the core of
the dispersed microgels, the desired properties of the resulting
TPEs can be controlled further. The glass transition temperature of
the dispersed microgel phase can also be adjusted in a targeted
manner within the range of from -100.degree. C. to less than
50.degree. C., as a result of which the properties of the resulting
TPEs can in turn be adjusted in a targeted manner. As a result, the
difference in glass transition temperature between the dispersed
phase and the continuous phase can also be adjusted in a targeted
manner and can be, for example, from 0.degree. C. to 250.degree. C.
With the novel class of TPEs provided by the present invention it
is additionally possible to combine thermodynamically compatible
and thermodynamically incompatible polymers to form new TPEs which
were not obtainable by conventional processes. In the novel TPEs
provided by the present invention, the dispersed phase and the
continuous phase may each constitute the hard phase and the soft
phase. By controlling the properties of the microgels and the
relative proportions, the dispersed phase can be present in the
matrix in the form of aggregated clusters or in uniformly
distributed form and in all intermediate forms.
[0018] This is not possible in the TPEs prepared by conventional
processes, in which the dispersed phase is formed in situ during
the production of the TPEs.
[0019] Furthermore, it has been surprisingly found not only that
the incorporation of microgels into thermoplastic plastics permits
the production of thermopastic elastomers, but also that the
incorporation of microgels into, for example, thermoplastic
elastomers produced by conventional processes allows a targeted
improvement in their properties, such as, for example, dimensional
stability and transparency.
[0020] The compositions according to the present invention can be
prepared on an industrial scale by a simple process, without using
microgels crosslinked by high-energy radiation. The microgels used
according to the present invention permit a less immediate change
in modulus between the matrix phase and the dispersed phase, which
leads to an improvement in the mechanical properties of the
composition.
[0021] Also surprisingly, the physical properties, such as, for
example, transparency and oil resistance, can be improved when
using thermoplastic elastomers as component (A).
[0022] Accordingly, the present invention provides a composition
which contains at least one thermoplastic material (A) and at least
one microgel (B) based on homopolymers or random copolymers that
has not been crosslinked by high-energy radiation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 illustrates an image of the composition according to
Example 4.
[0024] FIG. 2 illustrates an image of the composition according to
Example 1.
[0025] FIG. 3 illustrates an AFM image of a dynamically vulcanized
TPV from Example 5.
[0026] FIG. 4 illustrates hot air storage of the test specimens at
different temperature.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Microgel or Microgel Phase (B)
[0027] The microgel (B) used in the composition according to the
present invention is a crosslinked microgel based on homopolymers
or random copolymers. Accordingly, the microgels used according to
the present invention are crosslinked homopolymers or crosslinked
random copolymers. The terms homopolymers and random copolymers are
known to the person skilled in the art and are explained, for
example, in Vollmert, Polymer Chemistry, Springer 1973.
[0028] The crosslinked microgel (B) used in the composition
according to the present invention is a microgel that has not been
crosslinked by high-energy radiation. High-energy radiation here
preferably means electromagnetic radiation having a wavelength of
less than 0.1 .mu.m.
[0029] The use of microgels completely homogeneously crosslinked by
high-energy radiation is disadvantageous because it is virtually
impossible to implement on an industrial scale and causes problems
associated with working safety. Furthermore, in compositions
prepared using microgels completely homogeneously crosslinked by
high-energy radiation, tearing effects between the matrix and the
dispersed phase occur on sudden stress, with the result that the
mechanical properties, the swelling behavior and the stress
corrosion cracking, etc. are impaired.
[0030] The primary particles of the microgel (B) present in the
composition according to the present invention preferably exhibit
approximately spherical geometry. According to DIN 53206:1992-08,
primary particles are the microgel particles dispersed in the
coherent phase which can be individually recognized by means of
suitable physical processes (electron microscope) (see e.g. Rompp
Lexikon, Lacke und Druckfarben, Georg Thieme Verlag, 1998). An
"approximately spherical" geometry means that the dispersed primary
particles of the microgels recognizably form substantially a
circular surface when a thin section is viewed using an electron
microscope (see e.g. FIG. 1). As a result, the compositions
according to the present invention differ substantially from the
dispersed phases produced by the in situ processes, which are
generally larger and have an irregular shape (see e.g. FIG. 3). The
substantially uniform spherical shape, resulting from the separate
preparation process for the microgels, of the microgel particles
dispersed according to the invention is retained substantially
unchanged on dispersion in the thermoplastic material On the basis
of this criterion, it is easily possible to distinguish between the
microgel-containing compositions according to the invention and
conventionally produced TPEs. In conventionally produced TPEs, the
dispersed phase does not have uniform morphology, and for that
reason individual primary particles cannot be located therein.
[0031] In the compositions according to the present invention there
may be used, for example, all known TPEs, especially TPE-Us or
TPE-As, as the continuous phase. By incorporating the microgels (B)
into the known TPEs, preferably TPE-Us or TPE-As, the dimensional
stability under heat of the TPEs, preferably TPE-Us or TPE-As, can
surprisingly be improved. The transparency of the
microgel-containing compositions according to the invention based
on TPE-U or TPE-A is also improved. The known TPE-Us are not
transparent, while the microgel-containing compositions according
to the present invention based on TPE-U are transparent. By
incorporating the microgels into TPE-As, it is surprisingly
possible to greatly improve their oil resistance, for example, in
addition to their optical properties, such as transparency.
[0032] In the primary particles of the microgel (B) present in the
composition according to the present invention, the variation in
the diameters of an individual primary particle, defined as
[(d1-d2)/d1].times.100, wherein d1 and d2 are any two diameters of
any desired section of the primary particle and d1>d2, is
preferably less than 250%, more preferably less than 200%, most
preferably less than 100%.
[0033] Preferably at least 80%, more preferably at least 90%, yet
more preferably at least 95%, of the primary particles of the
microgel exhibit a variation in the diameters, defined as
[(d1-d2)/d1].times.100, wherein d1 and d2 are any two diameters of
any desired section of the primary particle and d1>d2, of less
than 250%, preferably less than 200%, more preferably less than
100%.
[0034] The above-mentioned variation in the diameters of the
individual particles is determined by the following process. A TEM
image of a thin section of the composition according to the present
invention is first prepared as described in the Examples. An image
is then recorded by transmission electron microscopy at a
magnification of, for example, from 10,000 times to 85,000 times.
In an area of 833.7.times.828.8 nm, the largest and smallest
diameters d1 and d2 are determined on 10 microgel primary
particles. If the variation is less than 250%, more preferably less
than 200%, yet more preferably less than 100%, in all 10 microgel
primary particles, then the microgel primary particles exhibit the
above-defined feature of variation.
[0035] If the concentration of the microgels in the composition is
so high that pronounced overlapping of the visible microgel primary
particles occurs, the evaluatability can be improved by previously
diluting the measuring sample in a suitable manner.
[0036] In the composition according to the present invention, the
primary particles of the microgel (B) preferably have an average
particle diameter of from 5 to 500 nm, more preferably from 20 to
400 nm, most preferably from 50 to 300 nm (diameter data according
to DIN 53206).
[0037] Because the morphology of the microgels remains
substantially unchanged during incorporation into the thermoplastic
material (A), the average particle diameter of the dispersed
primary particles corresponds substantially to the average particle
diameter of the microgel used.
[0038] In the composition according to the present invention, the
microgels (B) that are used advantageously contain at least about
70 wt. %, more preferably at least about 80 wt. %, most preferably
at least about 90 wt. %, portions that are insoluble in toluene at
23.degree. C. (gel content). The portion that is insoluble in
toluene is determined in toluene at 23.degree. C. For this purpose,
250 mg of the microgel are swelled in 25 ml of toluene at
23.degree. C. for 24 hours, with shaking. After centrifugation at
20,000 rpm, the insoluble portion is separated off and dried. The
gel content is obtained from the difference between the weighed
portion and the dried residue and is given in percent.
[0039] In the composition according to the present invention, the
microgels (B) that are used advantageously exhibit a swelling index
in toluene at 23.degree. C. of less than about 80, more preferably
of less than 60, yet more preferably of less than 40. For example,
the swelling indices of the microgels (Qi) can preferably be
between 1-15 and 1-10. The swelling index is calculated from the
weight of the solvent-containing microgel swelled in toluene at
23.degree. C. for 24 hours (after centrifugation at 20,000 rpm) and
the weight of the dry microgel: Qi=wet weight of the microgel/dry
weight of the microgel.
[0040] In order to determine the swelling index, 250 mg of the
microgel are allowed to swell in 25 ml of toluene for 24 hours,
with shaking. The gel is removed by centrifugation and weighed and
then dried at 70.degree. C. until a constant weight is reached and
then weighed again.
[0041] In the composition according to the present invention, the
microgels (B) that are used preferably have glass transition
temperatures Tg of from -100.degree. C. to +50.degree. C., more
preferably from -80.degree. C. to +20.degree. C.
[0042] In the composition according to the present invention, the
microgels (B) that are used advantageously have a breadth of glass
transition of greater than 5.degree. C., preferably greater than
10.degree. C., more preferably greater than 20.degree. C. Microgels
that have such a breadth of glass transition are generally not
completely homogeneously crosslinked--in contrast to completely
homogeneously radiation-crosslinked microgels. This has the result
that the change in modulus from the matrix phase to the dispersed
phase does not lead to tearing effects between the matrix and the
dispersed phase, with the result that the mechanical properties,
the swelling behavior and the stress corrosion cracking, etc. are
advantageously affected.
[0043] The glass transition temperature (Tg) and the breadth of the
glass transition (.DELTA.Tg) of the microgels are determined by
differential scanning calorimetry (DSC). For determining Tg and
.DELTA.Tg, two cooling/heating cycles are carried out. Tg and
.DELTA.Tg are determined in the second heating cycle. For the
determinations, 10 to 12 mg of the chosen microgel are placed in a
DSC sample container (standard aluminum ladle) from Perkin-Elmer.
The first DSC cycle is carried out by first cooling the sample to
-100.degree. C. with liquid nitrogen and then heating it to
+150.degree. C. at a rate of 20 K/min. The second DSC cycle is
begun by immediately cooling the sample as soon as a sample
temperature of +150.degree. C. has been reached. Cooling is carried
out at a rate of about 320 K/min. In the second heating cycle, the
sample is again heated to +150.degree. C., as in the first cycle.
The rate of heating in the second cycle is again 20 K/min. Tg and
.DELTA.Tg are determined graphically on the DSC curve of the second
heating operation. To that end, three straight lines are plotted on
the DSC curve. The first straight line is plotted on the part of
the DSC curve below Tg, the second straight line is plotted on the
branch of the curve passing through Tg with the point of
inflection, and the third straight line is plotted on the branch of
the DSC curve above Tg. Three straight lines with two points of
intersection are thus obtained. The two points of intersection are
each characterized by a characteristic temperature. The glass
transition temperature Tg is obtained as the mean of these two
temperatures, and the breadth of the glass transition .DELTA.Tg is
obtained from the difference between the two temperatures.
[0044] The microgels (B) based on homopolymers or random copolymers
present in the composition according to the present invention,
which microgels have not been crosslinked by high-energy radiation,
can be prepared in a manner known per se (see, for example,
EP-A-405 216, EP-A-854171, DE-A 4220563, GB-PS 1078400, DE 197 01
489.5, DE 197 01 488.7, DE 198 34 804.5, DE 198 34 803.7, DE 198 34
802.9, DE 199 29 347.3, DE 199 39 865.8, DE 199 42 620.1, DE 199 42
614.7, DE 100 21 070.8, DE 100 38 488.9, DE 100 39 749.2, DE 100 52
287.4, DE 100 56 311.2 and DE 100 61 174.5). In patent
(applications) EP-A 405 216, DE-A 4220563 and in GB-PS 1078400, the
use of CR, BR and NBR microgels in mixtures with
double-bond-containing rubbers is claimed. DE 197 01 489.5
describes the use of subsequently modified microgels in mixtures
with double-bond-containing rubbers such as NR, SBR and BR.
Microgels are understood as being rubber particles which are
obtained especially by crosslinking the following rubbers: [0045]
BR: polybutadiene [0046] ABR: butadiene/acrylic acid C1-4 alkyl
ester copolymers [0047] IR: polyisoprene [0048] SBR: random
styrene-butadiene copolymerization products having styrene contents
of from 1 to 60 wt. %, preferably from 5 to 50 wt. % [0049] X-SBR:
carboxylated styrene-butadiene copolymerization products [0050]
FKM: fluorine rubber [0051] ACM: acrylate rubber [0052] NBR:
polybutadiene-acrylonitrile copolymerization products having
acrylonitrile contents of from 5 to 60 wt. %, preferably from 10 to
50 wt. % [0053] X-NBR: carboxylated nitrile rubbers [0054] CR:
polychloroprene [0055] IIR: isobutylene/isoprene copolymerization
products having isoprene contents of from 0.5 to 10 wt. % [0056]
BIIR: brominated isobutylene/isoprene copolymerization products
having bromine contents of from 0.1 to 10 wt. % [0057] CIIR:
chlorinated isobutylene/isoprene copolymerization products having
chlorine contents of from 0.1 to 10 wt. % [0058] HNBR: partially
and completely hydrogenated nitrile rubbers [0059] EPDM:
ethylene-propylene-diene copolymerization products [0060] EAM:
ethylene/acrylate copolymers [0061] EVM: ethylene/vinyl acetate
copolymers [0062] CO and [0063] ECO: epichlorohydrin rubbers [0064]
Q: silicone rubbers [0065] AU: polyester urethane polymerization
products [0066] EU: polyether urethane polymerization products
[0067] ENR: epoxidized natural rubber or mixtures thereof.
[0068] The preparation of the uncrosslinked microgel starting
products is advantageously carried out by the following methods:
[0069] 1. emulsion polymerization [0070] 2. naturally occurring
latices, such as, for example, natural rubber latex, can
additionally be used.
[0071] The microgels (B) used in the composition according to the
present invention are preferably those which are obtainable by
emulsion polymerization and crosslinking.
[0072] The following free-radically polymerizable monomers, for
example, are used in the preparation of the microgels used
according to the invention by emulsion polymerization: butadiene,
styrene, acrylonitrile, isoprene, esters of acrylic and methacrylic
acid, tetrafluoroethylene, vinylidene fluoride, hexafluoropropene,
2-chlorobutadiene, 2,3-dichlorobutadiene, and also
double-bond-containing carboxylic acids, such as, for example,
acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc.,
double-bond-containing hydroxy compounds, such as, for example,
hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxybutyl
methacrylate, amine-functionalized (meth)acrylates, acrolein,
N-vinyl-2-pyrrolidone, N-allyl-urea and N-allyl-thiourea, secondary
amino(meth)acrylic acid esters, such as 2-tert.-butylaminoethyl
methacrylate and 2-tert.-butylaminoethylmethacrylamide, etc.
Crosslinking of the rubber gel can be achieved directly during the
emulsion polymerization, such as by copolymerization with
multifunctional compounds having crosslinking action, or by
subsequent crosslinking as described herein below. Preferred
multifunctional comonomers are compounds having at least two,
preferably from 2 to 4, copolymerizable C.dbd.C double bonds, such
as diisopropenylbenzene, divinylbenzene, divinyl ethers,
divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl
isocyanurate, 1,2-polybutadiene, N,N'-m-phenylenemaleimide,
2,4-toluylenebis(maleimide) and/or triallyl trimellitate. There
come into consideration also the acrylates and methacrylates of
polyhydric, preferably di- to tetra-hydric, C2 to C10 alcohols,
such as ethylene glycol, 1,2-propanediol, butanediol, hexanediol,
polyethylene glycol having from 2 to 20, preferably from 2 to 8,
oxyethylene units, neopentyl glycol, bisphenol A, glycerol,
trimethylolpropane, pentaerythritol, sorbitol, with unsaturated
polyesters of aliphatic diols and polyols, as well as maleic acid,
fumaric acid and/or itaconic acid.
[0073] Crosslinking to form rubber microgels during the emulsion
polymerization can also be effected by continuing the
polymerization to high conversions or by the monomer feed process
by polymerization with high internal conversions. Another
possibility consists in carrying out the emulsion polymerization in
the absence of regulators.
[0074] For the crosslinking of the uncrosslinked or weakly
crosslinked microgel starting products following the emulsion
polymerization there are best used latices which are obtained in
the emulsion polymerization. Natural rubber latices can also be
crosslinked in this manner.
[0075] Suitable chemicals having crosslinking action are, for
example, organic peroxides, such as dicumyl peroxide,
tert.-butylcumyl peroxide,
bis-(tert.-butyl-peroxy-isopropyl)benzene, di-tert.-butyl peroxide,
2,5-dimethylhexane 2,5-dihydroperoxide, 2,5-dimethylhexane
3,2,5-dihydroperoxide, dibenzoyl peroxide,
bis-(2,4-dichlorobenzoyl) peroxide, tert.-butyl perbenzoate, and
also organic azo compounds, such as azo-bis-isobutyronitrile and
azo-bis-cyclohexanenitrile, and also di- and poly-mercapto
compounds, such as dimercaptoethane, 1,6-dimercaptohexane,
1,3,5-trimercaptotriazine and mercapto-tenminated polysulfide
rubbers, such as mercapto-terminated reaction products of
bis-chloroethylformal with sodium polysulfide.
[0076] The optimum temperature for carrying out the
post-crosslinking is naturally dependent on the reactivity of the
crosslinker and can be carried out at temperatures from room
temperature to about 180.degree. C., optionally under elevated
pressure (see in this connection Houben-Weyl, Methoden der
organischen Chemie, 4th Edition, Volume 14/2, page 848). Preferred
crosslinkers are peroxides.
[0077] The crosslinking of rubbers containing C.dbd.C double bonds
to form microgels can also be carried out in dispersion or emulsion
with the simultaneous partial, or complete, hydrogenation of the
C.dbd.C double bond by means of hydrazine, as described in U.S.
Pat. Nos. 5,302,696 and 5,442,009, or optionally other
hydrogenating agents, for example organometal hydride
complexes.
[0078] Enlargement of the particles by agglomeration can optionally
be carried out before, during or after the post-crosslinking.
[0079] The preparation process used according to the present
invention always yields incompletely homogeneously crosslinked
microgels which can exhibit the above-described advantages.
[0080] As microgels for the preparation of the composition
according to the invention there may be used both non-modified
microgels, which contain substantially no reactive groups
especially at the surface, and microgels modified by functional
groups, especially microgels modified at the surface. The latter
can be prepared by chemical reaction of the already crosslinked
microgels with chemicals that are reactive towards C.dbd.C double
bonds. These reactive chemicals are especially those compounds by
means of which polar groups, such as, for example, aldehyde,
hydroxyl, carboxyl, nitrile, etc., and also sulfur-containing
groups, such as, for example, mercapto, dithiocarbamate,
polysulfide, xanthogenate, thiobenzthiazole and/or dithiophosphoric
acid groups and/or unsaturated dicarboxylic acid groups, can be
chemically bonded to the microgels. The same is also true of
N,N'-m-phenylenediamine. The purpose of modifying the microgels is
to improve the compatibility of the microgel with the matrix, in
order to achieve a good distribution capacity during preparation as
well as good coupling.
[0081] Preferred methods of modification are the grafting of the
microgels with functional monomers and reaction with low molecular
weight agents.
[0082] For the grafting of the microgels with functional monomers,
there is preferably used as starting material the aqueous microgel
dispersion, which is reacted under the conditions of a free-radical
emulsion polymerization with polar monomers such as acrylic acid,
methacrylic acid, itaconic acid, hydroxyethyl (meth)acrylate,
hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
acrylamide, methacrylamide, acrylonitrile, acrolein,
N-vinyl-2-pyrrolidone, N-allyl-urea and N-allyl-thiourea, and also
secondary amino-(meth)acrylic acid esters such as
2-tert.-butylaminoethyl methacrylate and
2-tert.-butylaminoethylmethacrylamide. In this manner there are
obtained microgels having a core/shell morphology, wherein the
shell should be highly compatible with the matrix. It is desirable
for the monomer used in the modification step to be grafted onto
the unmodified microgel as quantitatively as possible. The
functional monomers are preferably metered in before crosslinking
of the microgels is complete.
[0083] Suitable reagents for the surface modification of the
microgels with low molecular weight agents are especially the
following: elemental sulfur, hydrogen sulfide and/or
alkylpolymercaptans, such as 1,2-dimercaptoethane or
1,6-dimercaptohexane, also dialkyl and dialkylaryl dithiocarbamate,
such as the alkali salts of dimethyl dithiocarbamate and/or
dibenzyl dithiocarbamate, also alkyl and aryl xanthogenates, such
as potassium ethylxanthogenate and sodium isopropylxanthogenate, as
well as reaction with the alkali or alkaline earth salts of
dibutyldithiophosphoric acid and dioctyldithiophosphoric acid as
well as dodecyldithiophosphoric acid. The mentioned reactions can
also be carried out in the presence of sulfur, the sulfur being
incorporated with the formation of polysulfide bonds. For the
addition of this compound, free-radical initiators such as organic
and inorganic peroxides and/or azo initiators can be added.
[0084] There comes into consideration also modification of
double-bond-containing microgels such as, for example, by
ozonolysis as well as by halogenation with chlorine, bromine and
iodine. A further reaction of modified microgels, such as, for
example, the preparation of hydroxyl-group-modified microgels from
epoxidized microgels, is also understood as being the chemical
modification of microgels.
[0085] Preferably, the microgels are modified by hydroxyl groups,
especially also at the surface thereof. The hydroxyl group content
of the microgels is determined as the hydroxyl number with the
dimension mg of KOH/g of polymer by reaction with acetic anhydride
and titration of the acetic acid liberated thereby with KOH
according to DIN 53240. The hydroxyl number of the microgels is
preferably from 0.1 to 100, more preferably from 0.5 to 50, mg of
KOH/g of polymer.
[0086] The amount of modifying agent used is governed by its
effectiveness and the demands made in each individual case and is
in the range from 0.05 to 30 wt. %, based on the total amount of
rubber microgel used, particular preference being given to from 0.5
to 10 wt. %, based on the total amount of rubber gel.
[0087] The modification reactions can be carried out at
temperatures of from 0 to 180.degree. C., preferably from 20 to
95.degree. C., optionally under a pressure of from 1 to 30 bar. The
modifications can be carried out on rubber microgels without a
solvent or in the form of their dispersion, it being possible in
the latter case to use inert organic solvents or alternatively
water as the reaction medium. The modification is preferably
carried out in an aqueous dispersion of the crosslinked rubber.
[0088] The use of unmodified microgels is especially preferred in
the case of non-polar thermoplastic materials (A), such as, for
example, polypropylene, polyethylene and block copolymers based on
styrene, butadiene, isoprene (SBR, SIR) and hydrogenated
isoprene-styrene block copolymers (SEBS), and conventional TPE-Os
and TPE-Vs, etc.
[0089] The use of modified microgels is especially preferred in the
case of polar thermoplastic materials (A), such as, for example,
PA, TPE-A, PU, TPE-U, PC, PET, PBT, POM, PMMA, PVC, ABS, PTFE,
PVDF, etc.
[0090] The mean diameter of the prepared microgels can be adjusted
with high accuracy, for example, to 0.1 micrometer (100 nm).+-.0.01
micrometer (10 nm), so that, for example, a particle size
distribution is achieved in which at least 75% of all the microgel
particles are from 0.095 micrometer to 0.105 micrometer in size.
Other mean diameters of the microgels, especially in the range from
5 to 500 nm, can be produced with the same accuracy (at least 75
wt. % of all the particles are located around the maximum of the
integrated particle size distribution curve (determined by light
scattering) in a range of .+-.10% above and below the maximum) and
used. As a result, the morphology of the microgels dispersed in the
composition according to the present invention can be adjusted
virtually "point accurately" and hence the properties of the
composition according to the present invention and of the plastics,
for example, produced there from can be adjusted.
[0091] Adjustment of the morphology of the dispersed phase of the
TPEs produced according to the prior art by in situ reactive
processing or dynamic vulcanization is not possible with such
precision.
[0092] The microgels so prepared can be worked up, for example, by
concentration by evaporation, coagulation, by co-coagulation with a
further latex polymer, by freeze coagulation (see U.S. Pat. No.
2,187,146) or by spray-drying. In the case of working up by
spray-drying, commercially available flow auxiliaries, such as, for
example, CaCO.sub.3 or silica, can also be added.
Thermoplastic Materials (A)
[0093] The thermoplastic materials (A) used in the composition
according to the invention preferably have a Vicat softening
temperature of at least 50.degree. C., more preferably of at least
80.degree. C., yet more preferably of at least 100.degree. C.
[0094] The Vicat softening temperature is determined according to
DIN EN ISO 306:1996.
[0095] In the composition according to the invention, the
thermoplastic material (A) is advantageously chosen from
thermolastic polymers (A1) and thermoplastic elastomers (A2).
[0096] If thermoplastic polymers (A1) are used as starting material
for the composition according to the invention, then compositions
having thermoplastic elastomer properties are first formed by the
incorporation of the microgels used according to the present
invention.
[0097] If, on the other hand, thermoplastic elastomers (A2) are
used as starting material for the composition according to the
present invention, then thermoplastic elastomer properties are
retained, and the properties of the thermoplastic elastomers (A2)
can be modified in a targeted manner, as shown herein below, by the
addition of the microgels (B) of suitable composition and suitable
morphology.
[0098] Accordingly, the properties of the known TPEs, such as TPE-U
and TPE-A, such as especially the dimensional stability under heat
and the transparency of the TPE-Us or the oil resistance of the
TPE-As, can be improved by the incorporation of the microgels
(B).
[0099] In the composition according to the present invention, the
difference in glass transition temperature between the
thermoplastic material (A) and the microgel (B) is advantageously
from 0 to 250.degree. C.
[0100] In the composition according to the invention, the weight
ratio thermoplastic material (A)/microgel (B) is from 1:99 to 99:1,
preferably from 10:90 to 90:10, more preferably from 20:80 to
80:20.
[0101] If thermoplastic polymers (A1) are used as the thermoplastic
materials (A), the weight ratio (A1)/(B) is preferably from 95:5 to
30:70.
[0102] If thermoplastic elastomers (A2) are used as the
thermoplastic materials (A), then the weight ratio (A2)/(B) is
preferably from 98:2 to 20:80, more preferably from 95:5 to
20:80.
Thermoplastic Polymers (A1)
[0103] The thermoplastic polymers (A1) which can be used in the
composition according to the present invention include, for
example, standard thermoplastics, so-called techno-thermoplastics
and so-called high-performance thermoplastics (see H. G. Elias
Makromolekule Volume 2, 5th Edition, Huthig & Wepf Verlag,
1992, page 443 ff).
[0104] The thermoplastic polymers (A1) which can be used in the
composition according to the present invention include, for
example, non-polar thermoplastic materials, such as, for example,
polypropylene, polyethylene, such as HDPE, LDPE, LLDPE,
polystyrene, etc., and polar thermoplastic materials, such as PU,
PC, EVM, PVA, PVAC, polyvinylbutyral, PET, PBT, POM, PMMA, PVC,
ABS, AES, SAN, PTFE, CTFE, PVF, PVDF, polyimide, PA, such as
especially PA-6 (nylon), more preferably PA4, PA-66 (Perlon),
PA-69, PA-610, PA-11, PA-12, PA 612, PA-MXD6, etc.
[0105] Preferred thermoplastic polymers (A1) include: PP, PE, PS,
PU, PC, SAN, PVC and PA.
Thermoplastic Elastomers (A2)
[0106] The thermoplastic elastomers (A2) which can be used in the
composition according to the present invention include, for
example, the above-mentioned thermoplastic elastomers known from
the prior art, such as the block copolymers, such as styrene block
copolymers (TPE-S: SBS, SIS, as well as hydrogenated
isoprene-styrene block copolymers (SEBS), thermoplastic polyamides
(TPE-A), thermoplastic copolyesters (TPE-E), thermoplastic
polyurethanes (TPE-U), the mentioned blends of thermoplastics and
elastomers, such as thermoplastic polyolefins (TPE-O) and
thermoplastic vulcanization products (TPE-V), NR/PP blends
(thermoplastic natural rubber), NBR/PP blends, IIR (XIIR)/PP
blends, EVA/PVDC blends, NBR/PVC blends, etc. Reference may also be
made to the description of the above-mentioned TPEs from the prior
art.
[0107] Examples of block polymers which can preferably be used
according to the invention as the thermoplastic elastomer (A2)
include the following:
Styrene Block Copolymers (TPE-S)
[0108] The three-block structure of two thermoplastic polystyrene
end blocks and an elastomeric middle block characterizes this
group. The polystyrene hard segments form domains, that is to say
small volume elements having uniform characteristics, which act
technically as spatial, physical crosslinking sites for the
flexible soft segments. According to the nature of the middle
block, a distinction is made between the following styrene block
copolymers: butadiene (SBS), isoprene (SIS) and ethylene/butylene
(SEBS) types. Branched types of block copolymer can be produced by
linking via polyfunctional centers.
Polyether-polyamide Block Copolymers (TPE-A)
[0109] The block copolymers based on polyether (ester)-polyamide
are formed by insertion of flexible polyether (ester) groups into
polyamide molecule chains. The polyether (ester) blocks form the
soft and elastic segments, while the hard polyamide blocks assume
the function of the thermoplastic hard phase. The hard segments
acquire their high strength as a result of a high density of
aromatic groups and/or amide groups, which are responsible for the
physical crosslinking of the two phases by hydrogen bridge
formation.
Thermoplastic Copolyesters, Polyether Esters (TPE-E)
[0110] Thermoplastic copolyesters are composed of alternate hard
polyester segments and soft polyether components. The polyester
blocks, formed from diols (e.g. 1,4-butanediol) and dicarboxylic
acids (e.g. terephthalic acid), are esterifies in a condensation
reaction by long-chain polyethers carrying hydroxyl terminal
groups. Very different hard regions can be established according to
the length of the hard and soft segments.
Thermoplastic Polyurethanes (TPE-U)
[0111] The block copolymers of polyurethane are synthesized by
polyaddition of diols and diisocyanates. The soft segments formed
in the reaction between diisocyanate and a polyol act as elastic
components under mechanical stress. The hard segments (urethane
groups) serving as crosslinking sites are obtained by reaction of
the diisocyanate with a low molecular weiaht diol for chain
extension. As in the TPE-S types the finely divided hard segments
form domains which effect quasi-crosslinking via hydrogen bridges
or generally via order states in which two or more domains enter
into relationship with one another. Crystallization of the hard
segments may occur thereby. A distinction is made between
polyester, polyether and chemically combined polyester/polyether
types according to the diol used as starting monomer.
[0112] Regarding the second group of thermoplastic TPEs (A2), the
elastomer alloys, reference may be made to the comments given above
in connection with the prior art. Elastomer alloys which can be
used according to the invention include, for example, the
following:
EPDM/PP Blends
[0113] EPDM terpolymers are generally used for the rubber phase,
polypropylene is mostly used as the polyolefin. The soft phase can
be either uncrosslinked (TPE-0) or crosslinked (TPE-V). Where the
PP component is dominant, the thermoplastic constitutes the
continuous phase. If the elastomer content is very high, the
structure can also be reversed, so that EPDM blends of high PP
content result. This class of elastomer alloys therefore covers a
wide range of hardnesses. All representatives are distinguished by
high resistance to UV radiation and ozone as well as to many
organic and inorganic media. On the other hand, resistance to
aliphatic and aromatic solvents is poor to moderate.
NR/PP Blends (Thermoplastic Natural Rubber)
[0114] In a similar manner to EPDM, NR can also be compounded with
PP and also with PP/PE mixtures to form a thermoplastically
processable natural rubber (TPNR). The dynamic crosslinking of NR
generally takes place in the presence of peroxides above
170.degree. C. In comparison with conventional NR vulcanization
products, TPNR blends have markedly higher resistance to weathering
and ozone.
NBR/PP blends
[0115] In these polymer blends, pre-crosslinked or partially
crosslinked acrylonitrile-butadiene rubber (NBR) is dispersed as
the elastomeric phase in the PP hard phase. Characteristic features
of these blends are high resistance to fuels, oils, acids and
alkalis as well as to ozone and the effects of weathering.
IIR (XIIR)/PP Blends
[0116] Butyl or halobutyl rubbers constitute the elastomeric phase
constituents in this class. On the basis of a diene rubber of
non-polar nature (comparable NR/IR), the excellent permeation
properties of butyl rubber towards many gases are used for the
property profile of the TPE blends obtainable in a blend with
PP.
EVA/PVDC Blends
[0117] These are based on a blend of ethylene-vinyl acetate rubber
(EVA) and polyvinylidene chloride (PVDC) as the thermoplastic
phase. The property profile in the middle hardness range of from 60
to 80 ShA is marked by good oil resistance and outstanding
resistance to weathering.
NBR/PVC Blends
[0118] These polymer blends, produced predominantly for improving
the properties of plasticized PVC, are mixtures of
acrylonitrile-butadiene rubber (NBR) and polyvinyl chloride (PVC).
In particular where better oil or grease resistance is required,
the plasticized PVC grades having high plasticizer contents are no
longer usable (plasticizer extraction). In these NBR/PVC blends,
NBR acts as a polymeric, non-extractable plasticizer and can be
mixed with PVC in virtually any proportion.
[0119] Preferred thermoplastic elastomers (A2) include: TPE-U,
TPE-A and TPE-V.
[0120] Preferred compositions according to the present invention
contain the following combinations of components (A) and (B):
TABLE-US-00001 Thermoplastic material (A) Microgel (B) based on
TPE-U SBR (OH-modified), peroxidically crosslinked PP SBR
(OH-modified), EGDMA- crosslinked PP SBR (unmodified),
DVB-crosslinked TPE-A SBR (OH-modified), EGDMA- crosslinked PP NBR,
peroxidically crosslinked PA NBR, peroxidically crosslinked
[0121] The compositions according to the present invention
generally behave like thermoplastic elastomers, that is to say they
combine the advantages of thermoplastic processability with the
properties of the elastomers, as described in the introduction in
connection with the TPEs from the prior art.
[0122] The compositions according to the present invention can
additionally comprise at least one conventional plastics additive,
such as inorganic and/or organic fillers, plasticizers, inorganic
and/or organic pigments, flameproofing agents, agents against
pests, such as, for example, termites, agents against marten bite,
etc., and other conventional plastics additives. These can be
present in the compositions according to the invention in an amount
of up to about 40 wt. %, preferably up to about 20 wt. %, based on
the total amount of composition.
[0123] The compositions according to the present invention are
obtainable by mixing at least one thermoplastic material (A) and at
least one crosslinked microgel (B) that has not been crosslinked
using high-energy radiation.
[0124] The present invention relates also to the use of crosslinked
microgels (B) that have not been crosslinked using high-energy
radiation, in thermoplastic materials (A). With regard to the
preferred variants of components (A) and (B), reference may be made
to the comments hereinbefore.
[0125] The present invention also relates also to a process for the
preparation of the compositions according to the invention by
mixing at least one thermoplastic material (A) and at least one
microgel (B). The preparation of the compositions according to the
invention is generally carried out in such a manner that the
microgel (B) is prepared separately before being mixed with the
thermoplastic material (A).
[0126] The compositions according to the present invention
containing (optionally) modified microgel (B) and the thermoplastic
material (A) can be prepared by various methods: on the one hand,
it is of course possible to mix the individual components.
Apparatuses suitable therefore are, for example, mills, multi-roll
mills, dissolvers, internal mixers or mixing extruders.
[0127] Suitable as mixing apparatuses are also the mixing
apparatuses known from rubber and plastics technology (Saechtling
Kunststoff Taschenbuch, 24th Edition, p. 61 and p. 148 ff; DIN
24450; Mixing of plastics and rubber products,
VDI-Kunststofftechnik, p. 241 ff), such as, for example,
co-kneaders, single-screw extruders (with special mixing elements),
twin-screw extruders, cascade extruders, degassing extruders,
multi-screw extruders, pin extruders, screw kneaders and planetary
extruders, as well as multi-shaft reactors. Preference is given to
the use of twin-screw extruders rotating in the same direction,
with degassing (planetary extruders with degassing).
[0128] The further mixing of the compositions according to the
present invention containing (optionally) modified microgel (B) and
the thermoplastic materials (A) with additional fillers and
optionally conventional auxiliary substances, as mentioned above,
can be carried out in conventional mixing apparatuses, such as
mills, internal mixers, multi-roll mills, dissolvers or mixing
extruders. Preferred mixing temperatures are from room temperature
(23.degree. C.) to 280.degree. C., preferably approximately from
60.degree. C. to 200.degree. C.
[0129] The present invention relates also to the use of the
compositions according to the present invention in the production
of thermoplastically processable molded articles, and to the molded
articles obtainable from the compositions according to the present
invention. Examples of such molded articles include: plug-type
connectors, damping elements, especially vibration dampers and
shock absorbers, acoustic insulating elements, profiles, films,
especially insulating films, foot mats, clothing, especially
insoles for shoes, shoes, especially ski shoes, shoe soles,
electronic components, housings for electronic components, tools,
decorative molded bodies, composite materials, moldings for motor
vehicles, etc.
[0130] The molded articles according to the present invention can
be produced from the compositions according to the invention by
conventional processing methods for thermoplastic elastomers, for
example by melt extrusion, calendering, IM, CM and RIM.
[0131] The present invention is explained further by the following
Examples. However, the present invention is not limited to the
disclosure of the Examples.
EXAMPLES
1. Preparation of Microgels (B)
Preparation Example 1
(NBR-based Microgel from Peroxidic Crosslinking (OBR 1102 C))
[0132] The preparation of the NBR microgel OBR 1102 C was carried
out as described in DE 19701487. An NBR latex was used as starting
material. The NBR latex had the following features: content of
incorporated acrylonitrile: 43 wt. %, solids concentration: 16 wt.
%, pH value: 10.8, diameter of the latex particles (d.sub.2): 140
nm, particle density: 0.9984 g/cm.sup.3, the gel content of the
latex is 2.6 wt. %, the swelling index of the gel portion in
toluene was 18.5 and the glass transition temperature (Tg) is
-15.degree. C.
[0133] 7 phr of dicumyl peroxide (DCP) was used in the preparation
of OBR 1102 C.
[0134] Characteristic data of the resulting microgel are summarized
in Table 1.
Preparation Example 2
(SBR-based Microgel from Peroxidic Crosslinking (OBR 1046 C))
[0135] The preparation of the microgel was carried out by
crosslinking an SBR latex containing 40 wt. % of incorporated
styrene (Krylene 1721 from Bayer France) in latex form with 1.5 phr
of dicumyl peroxide (DCP) and subsequently grafting with 5 phr of
hydroxyethyl methacrylate (HEMA).
[0136] The crosslinking of Krylene 1721 with dicumyl peroxide was
carried out as described in Examples 1) to 4) of U.S. Pat. No.
6,127,488, 1.5 phr of dicumyl peroxide being used for the
crosslinking. The underlying latex Krylene 1721 has the following
features: [0137] solids concentration: 21 wt. %; pH value: 10.4;
diameter of the latex [0138] particles: d10=40 nm; d.sub.z=53 nm;
d80=62 nm; O.sub.spec.=121; particle [0139] density: 0.9673
g/cm.sup.3, the gel content of the microgel is 3.8 wt. %, the
swelling index of the gel portion is 25.8 and the glass transition
temperature (Tg) is -31.5.degree. C.
[0140] After reaction with 1.5 phr of dicumyl peroxide, the product
had the following characteristic data: [0141] solids concentration:
21 wt. %; pH value: 10.2; diameter of the latex [0142] particles:
d10=37 nm; d50=53 nm; d80=62 nm; particle density: 0.9958
g/cm.sup.3, the gel content of the microgel is 90.5 wt. %; the
swelling index of the gel portion is 5.8 and the glass transition
temperature (Tg) is -6.5.degree. C.
[0143] The hydroxyl modification of the 1.5 phr-crosslinked SBR
latex was carried out by grafting with 5 phr of hydroxyethyl
methacrylate. The reaction with HEMA, stabilization and working up
of the hydroxyl-modified latex were carried out as described in
U.S. Pat. No. 6,399,706, Example 2.
[0144] The characteristic data of the hydroxyl-modified SBR gel are
summarized in Table 1.
[0145] Before the microgel is used in TPU, it is dried to constant
weight at 100 mbar in a vacuum drying cabinet from Haraeus
Instruments, type Vacutherm VT 6130.
Preparation Example 3
(SBR-based Microgel from Direct Polymerization; Crosslinking with
DVB (OBR1126E)
[0146] The preparation of this microgel was carried out by
copolymerization of 23% styrene, 76% butadiene and 1%
divinylbenzene in emulsion.
Preparation Example 4
[0147] Microgel based on hydroxyl-modified BR, prepared by direct
emulsion polymerization using the crosslinking comonomer ethylene
glycol dimethacrylate (OBR 1118).
[0148] 325 g of the Na salt of a long-chain alkylsulfonic acid (330
g of Mersolat K30/95 from Bayer AG) and 235 g of the Na salt of
methylene-bridged naphthalenesulfonic acid (Baykanol PQ from Bayer
AG) were dissolved in 18.71 kg of water and placed in a 40-litre
autoclave. The autoclave was evacuated three times and charged with
nitrogen. Then 9.200 kg of butadiene, 550 g of ethylene glycol
dimethacrylate (90%), 312 g of hydroxyethyl methacrylate (96%) and
0.75 g of hydroquinone monomethyl ether are added. The reaction
mixture was heated to 30.degree. C., with stirring. An aqueous
solution consisting of 170 g of water, 1.69 g of
ethylenediaminetetraacetic acid (Merck-Schuchardt), 1.35 g of
iron(II) sulfate*7H.sub.2O, 3.47 g of Rongalit C (Merck-Schuchradt)
and 5.24 g of trisodium phosphate*12H.sub.2O is then metered in.
The reaction was started by addition of an aqueous solution of 2.8
g of p-menthane hydroperoxide (Trigonox NT 50 from Akzo-Degussa)
and 10.53 g of Mersolat K 30/95, dissolved in 250 g of water. After
a reaction time of 5 hours, activation was carried out using an
aqueous solution consisting of 250 g of water in which 10.53 g of
Mersolat K30/95 and 2.8 g of p-menthane hydroperoxide (Trigonox NT
50) are dissolved. When a polymerization conversion of 95-99% is
reached, the polymerization was stopped by addition of an aqueous
solution of 25.53 g of diethylhydroxylamine dissolved in 500 g of
water. Unconverted monomers were then removed from the latex by
stripping with steam. The latex was filtered and stabilizer was
added as in Example 2 of U.S. Pat. No. 6,399,706, followed by
coagulation and drying.
[0149] The characteristic data of the SBR gel are summarized in
Table 1.
Preparation Example 5
(NBR-based Microgel from Peroxidic Crosslinking (OBR 1102 B))
[0150] An NBR-based microgel from peroxidic crosslinking was
prepared as in Preparation Example 1 using DCP of 5 instead of 1.5
phr. TABLE-US-00002 TABLE 1 Properties of the microgels (B) Cross-
Gel OH Acid Preparation Product Microgel linking D.sub.z Ospec.
Density content Tg .DELTA.Tg number number Example name type [phr]
[nm] [m.sup.2/g] [g/cm.sup.3] [wt. %] Ql [.degree. C.] [.degree.
C.] [mg KOH/g pol.] 1 OBR NBR DCP/7 132 462 1.0236 93.7 7.9 -0.5
15.8 16.4 2.3 1102 C 2 OBR SBR DCP/1.5 51 117 1.0112 96.3 5.9 4.5
33.8 10.3 8.4 1046 C 3 OBR SBR -- -- -- -- 83.4 14.7 -58.5 10.6 9.5
13.2 1126E 4 OBR BR EGDMA/ 50 166 0.9245 99.1 7.7 -79 7.6 21.9 3.4
1118 5% 5 OBR NBR DCP/5 129 478 1.0184 94.3 8.8 -1.5 13.2 18 3.1
1102 B
The abbreviations used in the table have the following
meanings:
[0151] DCP: dicumyl peroxide
[0152] EGDMA: ethylene glycol dimethacrylate
[0153] phr: parts per 100 rubber
[0154] O.sub.spec.: specific surface area in m.sup.2/g
[0155] d.sub.z: The diameter d.sub.z was defined according to DIN
53 206 as the median or central value, above and below which in
each case half of all the particle sizes lie. The particle diameter
of the latex particles was determined by means of
ultracentrifugation (W. Scholtan, H. Lange, "Bestimmung der
TeilchengroBenverteilung von Latices mit der Ultrazentrifuge"
[Determination of the particle size distribution of latices by
ultracentrifuge], Kolloid-Zeitschrift und Zeitschrift fur Polymere
(1972) Volume 250, Issue 8). The diameter data in the latex and for
the primary particles in the compositions according to the present
invention are almost identical, because the particle size of the
microgel particles remains practically unchanged during the
preparation of the composition according to the invention.
[0156] QI: swelling index
[0157] Tg: glass transition temperature
[0158] .DELTA.Tg: breadth of the glass transition
[0159] For the determination of Tg and .DELTA.Tg, a DSC-2 device
from Perkin-Elmer is used.
Swelling Index QI
[0160] The swelling index QI was determined as follows:
[0161] The swelling index was calculated from the weight of the
solvent-containing microgel swelled for 24 hours in toluene at
23.degree. and the weight of the dry microgel: Qi=wet weight of the
microgel/dry weight of the microgel.
[0162] In order to determine the swelling index, 250 mg of the
microgel are allowed to swell for 24 hours in 25 ml of toluene,
with shaking. The (wet) gel swelled with toluene is weighed, after
centrifugation at 20,000 rpm, and then dried to constant weight at
70.degree. C. and weighed again.
OH Number (Hydroxyl Number)
[0163] The OH number (hydroxyl number) was determined according to
DIN 53240 and corresponds to the amount of KOH, in mg, that is
equivalent to the amount of acetic acid liberated in the
acetylation of 1 g of substance using acetic anhydride.
Acid Number
[0164] The acid number is determined as already mentioned above
according to DIN 53402 and corresponds to the amount of KOH, in mg,
that was required to neutralize 1 g of the polymer.
Gel Content
[0165] The gel content corresponds to the portion that was
insoluble in toluene at 23.degree. C. It was determined as
described above.
Glass Transition Temperature
[0166] The glass transition temperatures were determined as
mentioned above.
Breadth of the Glass Transition
[0167] The breadth of the glass transition was determined as
described above.
2. General Procedure for the Mixing Process in an Internal
Mixer:
[0168] The preparation of the compositions according to the
invention was carried out by means of a laboratory internal mixer
(Rheocord 90, Rheomix 600 E mixing chamber, Haake) with tangent
rotors, compressed-air cooling and a chamber volume of 350
cm.sup.3. Mixing was carried out at a speed of 100 rpm, an initial
chamber temperature of 160.degree. C. and a degree of filling of
70%. Mixtures comprising a rubber microgel (B)/thermoplastic
material (A) in the indicated ratios of, for example, 80/20, 70/30,
60/40, 50/50, 40/60, 30/70, 20/80, 10/90 are prepared. To that end,
the thermoplastic was first placed in the mixer and melted in the
course of 4 minutes. Then the microgel is metered in, the die was
closed and mixing was carried out for 8 minutes. A rise in
temperature occurs thereby. The torque passes through a maximum
with a final plateau. After mixing, visually homogeneous samples
are removed, which exhibit approximately the coloring of the
microgel.
3. Determination of Morphology
[0169] The morphology was determined by means of transmission
electron microscope images (TEM) and by means of atomic force
microscopy (AFM).
1. TEM:
[0170] Sample preparation for transmission electron microscopic
investigations
Cryo-ultramicrotomy
Procedure:
[0171] Under cryo conditions, thin sections having a section
thickness of about 70 nm were prepared by means of diamond knives.
In order to improve the contrast, contrasting with OsO.sub.4 can be
carried out.
[0172] The thin sections were transferred to copper nets, dried and
first assessed over a large area in the TEM. Then, with 80 kV beam
potential at 12,000 times magnification, displayed area=833.7*828.8
nm, characteristic image sections were stored by means of digital
imaging software for documentation purposes and evaluated.
2. AFM: Topometrix Model TMX 2010.
[0173] For the investigation, glossy sections were prepared and
transferred to the AF microscope. The images were prepared by the
layered imaging process.
[0174] If the microgel was too highly concentrated, i.e. if the
primary particles overlap, dilution can be carried out
beforehand.
Example 1
(PP-based Composition According to the Invention)
[0175] The microgel OBR 1118 from Preparation Example 4 was mixed
with PP Atofina PPH 3060 (produced by ATOFINA) as indicated below.
The preparation of the composition was carried out using a
laboratory extruder (ZSK 25, manufacturer: Krupp Wemer u.
Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38;
throughputs: 2.0 to 5.0 kg/h, speeds: 100 to 220 rpm) having shafts
running in the same direction. Mixing is carried out at a speed of
from 100 to 220 rpm, an intake-zone temperature of 160.degree. C.
and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of
5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70%, 35/65% are prepared.
To that end, the PP and MG are first metered into the extruder
continuously by means of gravimetric metering scales. In the
extruder, a rise in temperature to 180 to 195.degree. C. takes
place. After processing, visually homogeneous samples are removed,
which have approximately the coloring of the microgel.
[0176] A conventionally prepared TPE-V (Santoprene Rubber 201-87)
from Advanced Elastomer Systems (M1) was used as a reference for
the microgel-based TPE-Vs.
[0177] The resulting compositions/test specimens exhibited the
following properties. TABLE-US-00003 TABLE 2 Results of the
physical testing of the studied microgel/TPE-V mixtures according
to the invention (M2 to M7) and of the TPE-V (M1) Material M 1 M 2
M 3 M 4 M 5 M 6 M 7 M 8 Santoprene Rubber 201-87 100 0 0 0 0 0 0 0
Atofina PPH 3060 [%] 0 95 90 85 80 75 70 65 OBR1118 [%] 0 5 10 15
20 25 30 35 Hardness, tested immediately Shore A 87 -- -- -- 96 92
89 86 Tensile strength [MPa] 15.9 34 30.6 27.1 22.7 19.8 19.2 18.5
Elongation at tear [%] 530 15 30 57 89 133 210 270 Modulus at 100%
elongation [MPa] 6.9 -- -- -- -- 7.4 7.6 7.9
Example 2
(PP-based Composition According to the Invention)
[0178] The microgel from Example 2 (OBR 1046 C) was mixed with a PP
Atofina PPH 3060 (produced by Atofina) as indicated below. The
preparation of the composition is carried out using a laboratory
extruder (ZSK 25, manufacturer: Krupp Wemer u. Pfleiderer,
Stuttgart; screw diameter d=25 mm, L/d>38; throughputs: 2.0 to
3.5 kg/h, speeds: 100 to 200 rpm) having shafts running in the same
direction. Mixing was carried out at a speed of from 100 to 220
rpm, an intake-zone temperature of 165.degree. C. and a throughput
of 5 kg/h. Mixtures having a MG/PP weight ratio of, for example,
5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70%, 35/65% are prepared.
To that end, the PP and MG were first metered into the extruder
continuously by means of gravimetric metering scales. In the
extruder, a rise in temperature to 190 to 210C. took place. After
processing, visually homogeneous samples were removed, which have
approximately the coloring of the microgel.
[0179] A conventionally prepared TPE-V (Santoprene Rubber 201-87)
from Advanced Elastomer Systems (M1) was used as a reference for
the microgel-based TPE-Vs.
[0180] The resulting compositions/test specimens exhibited the
following properties. TABLE-US-00004 TABLE 3 Results of the
physical testing of the studied microgel/TPE-V mixtures according
to the invention (M2 and M3) and of the TPE-V (M1) Material M 1 M 2
M 3 Santoprene Rubber 100 0 0 201-87 Atofina PPH 3060 [%] 0 70 65
OBR1046C [%] 0 30 35 Hardness, tested immediately Shore A 87 93 88
Tensile strength [MPa] 15.9 23.2 19.8 Elongation at tear [%] 530
168 250 Modulus at 100% elongation [MPa] 6.9 8.7 8.3
Example 3
(PP-based Composition According to the Invention)
[0181] Microgels (OBR 1126 E) from Example 3 were mixed with a PP
Moplen Q 30 P (produced by Montel Polyolefins) as indicated below.
The preparation of the composition was carried out using a
laboratory extruder (ZSK 25, manufacturer: Krupp Werner u.
Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38;
throughputs: 2.0 kg/h, speeds: 100 to 190 rpm) having shafts
running in the same direction. Mixing was carried out at a speed of
from 100 to 220 rpm, an intake-zone temperature of 165.degree. C.
and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio
of, for example, 5/95%, 10/90%, 1 5/85%, 20/80%, 25/75%, 30/70%,
35/65% are prepared. To that end, the PP and MG are first metered
into the extruder continuously by means of gravimetric metering
scales. In the extruder, a rise in temperature to 175 to
190.degree. C. takes place. After processing, visually homogeneous
samples were removed, which have approximately the coloring of the
microgel.
[0182] A conventionally prepared TPE-V (Santoprene Rubber 201-87)
from Advanced Elastomer Systems (M1) was used as a reference for
the microgel-based TPE-Vs.
[0183] The resulting compositions/test specimens exhibited the
following properties. TABLE-US-00005 TABLE 4 Results of the
physical testing of the studied microgel/TPE-V mixtures according
to the present invention (M2 and M3) and of the TPE-V (M1) Material
M 1 M 2 M 3 Santoprene Rubber 201-87 100 0 0 Moplen Q 30 P [%] 0 70
65 OBR 1126 E [%] 0 30 35 Hardness, tested immediately Shore A 87
88 85 Tensile strength [MPa] 15.9 16.2 17.8 Elongation at tear [%]
530 193 327 Modulus at 100% elongation [MPa] 6.9 9.2 8.9
Example 4
(TPE-U-based Compositions According to the Present Invention)
[0184] The microgel from Preparation Example 2 (OBR 1046C) was used
as the microgel. As the TPU added to the microgel there was used
Desmopan 385, a TPE-U from Bayer AG.
[0185] The preparation of the composition was carried out using a
laboratory extruder (ZSK 25, manufacturer: Krupp Wemer u.
Pfleiderer, Stuttgart; screw diameter d=25 mm, L/d>38;
throughputs: 2.0 to 5.0 kg/h, speeds: 100 to 220 rpm) having shafts
running in the same direction. Mixing was carried out at a speed of
from 100 to 220 rpm, an intake-zone temperature of 160.degree. C.
and a throughput of 5 kg/h. Mixtures having a MG/PP weight ratio of
5/95%, 10/90%, 15/85%, 20/80%, 25/75%, 30/70% are prepared. To that
end, the PP and MG are first metered into the extruder continuously
by means of gravimetric metering scales. In the extruder, a rise in
temperature to 195.degree. C. takes place. After processing,
visually and physically homogeneous samples were removed, which
have approximately the coloring of the microgel and were
transparent.
[0186] A conventionally prepared TPU (Desmopan 385) (M1) was used
as a reference for the microgel-based TPE-Us.
Injection Molding:
[0187] Standard tensile test specimens were injection-molded from
the resulting granules of the MG-based TPE-Us and of the pure
Desmopan 385. This was carried out using an injection-molding
machine (type 320S from Arburg) at a machine temperature of
205-215.degree. C., a ram pressure of 10 bar and a tool temperature
of 60.degree. C. The residence time of the sample in the machine
and in the tool was 50 seconds. The shot was 29.5 g.
[0188] FIG. 1 shows an electron microscope image of the material
obtained in Example 4. The dispersed, approximately spherical
microgels are clearly visible.
Preparation of the Test Specimens:
[0189] 50% F3 standard test rods were prepared from all the
samples. This was carried out for all materials by
injection-molding of test sheets. The test specimens were prepared
from the test sheets. All the standard rods have a width of 14 mm
in the head region and a web width of 7 mm. The thickness of the
standard rods was 2 mm.
Physical Testing:
[0190] 1. Tensile Test
[0191] The tensile test of the samples was carried out on 50% F3
standard test rods (see above) according to DIN 53455. The testing
was carried out using a universal testing machine (type 1445,
Frank) with optical length pick-ups. The measuring range of the
force pick-up was 0 to 1000 N. The results of the measurements were
summarized in Table 5. The following machine parameters were
specified: TABLE-US-00006 preliminary force 0.1 N speed to
preliminary force 1 mm/min load 1000 N Vtest 400 mm/min
[0192] The breaking elongation and stress at break values of the
microgel-based TPE-Us were above the values of the pure constituent
TPU phase even at high loads. The calculated values were summarized
in Table 2.
Shore A Hardness:
[0193] As a comparison with room temperature, the test specimens
were additionally stored at +80.degree. C. and at -2.degree. C. in
each case for 64 hours and conditioned for 1 hour at RT before the
measurement. Within the scope of measuring accuracy, the samples
with microgel exhibit no significant changes in Shore A hardness.
The calculated values were summarized in Table 6.
Determination of Color:
[0194] The color of the test sheets was determined according to DIN
standards DIN 5033 and DIN 6174 using a Match Rite CFS57
colour-measuring device from X-Rite GmbH. The calculated color
values were summarized in Table 6. Although the microgel-containing
test sheets have an inherent color, they remained transparent even
with a content of 30% MG. TABLE-US-00007 TABLE 5 Results of the
physical testing of the studied microgel/TPU mixtures according to
the present invention (M2 to M7) and of the TPU Desmopan 385 (M1)
Material M 1 M 2 M 3 M 4 M 5 M 6 M 7 Desmopan 385 [%] 100 95 90 85
80 75 70 OBR 1046 C [%] 0 5 10 15 20 25 30 Hardness, tested
immediately Shore A 87 87 87 87 85 84 84 Hardness, stored for 64 h
at +80.degree. C. Shore A 87 85 84 84 82 81 81 Hardness, stored for
64 h at -21.degree. C. Shore A 88 89 88 88 87 87 87 Tensile
strength [N/mm.sup.2] 9.6 19.1 17.9 17.4 16.6 15.8 13.2 Elongation
at tear [%] 160 450 424 385 362 350 310 Colour L 70.26 56.24 54.35
53.39 51.56 50.25 49.90 Colour A -0.86 0.83 1.00 1.44 1.74 2.18
3.13 Colour B 4.80 10.36 10.77 10.81 11.02 11.18 12.56
Hot-air Ageing:
[0195] Hot-air ageing was carried out at 130.degree. C. and
180.degree. C., in each case for one hour. The test specimens were
then evaluated for appearance, shape and color. Test specimens
which had not been stored in hot air were evaluated at the same
time for comparison purposes. The results are shown in FIG. 4.
Surprisingly, it is found that the test specimens according to the
invention are more dimensionally stable with the addition of the
microgel than without, the dimensional stability increasing as the
microgel content increases.
Example 5
(TPE-A-based Compositions According to the Present Invention and
Comparison Compositions)
Preparation Process
[0196] The preparation of the TPE-As was carried out by means of a
laboratory internal mixer (Rheocord 90, Rheomix 600 E mixing
chamber, Haake) with tangent rotors, compressed-air cooling and a
chamber volume of 350 cm.sup.3. Mixing was carried out at a speed
of 100 rpm, an initial chamber temperature of 190.degree. C. and a
degree of filling of 70%. Mixtures having a rubber
microgel/thermoplastic ratio of 70/30 were prepared (samples 1 and
2). To that end the thermoplastic (Grilamid L 112 G) was first
placed in the mixer and melted in the course of 4 minutes. Then the
microgel was metered in, the die was closed and mixing was carried
out for 8 minutes. A rise in temperature occurred thereby (samples
1 and 2: T.sub.max=251.degree. C.). The torque passed through a
maximum. After mixing, visually and physically homogeneous samples
were removed, which exhibited approximately the coloring of the
microgel. This material was then granulated.
[0197] A conventional TPE-A (sample 5) having the same
rubber/thermoplastic ratio was prepared as a reference for the
microgel-based TPE-As according to the present invention. The PA
used had the name (Grilamid L 1120 G) from EMS-GRIVORY and the
nitrile rubber used has the name (Perbunan NT 3465) from BAYER AG.
The crosslinker used is a dicumyl peroxide. It has the name
Poly-Dispersion E(DIC)D-40 from Rhein Chemie Corporation. It is a
40% blend of DCP in an EPM binder. 5 phr of the chemical were
metered in. Mixing of these TPE-As was carried out in the same
mixer, but an initial temperature of 180.degree. C., a rotor speed
of 75 rpm and a total mixing time of 12 minutes were chosen. The
Grilamid L 1120 G (64.3 g) was first placed in the vessel. After it
had melted, the NBR rubber (Perbunan NT 3465 (149 g) and the
Poly-Dispersion E(DIC)D-40 crosslinker (18.6 g) were metered in
succession and the die was closed. After mixing, visually and
physically homogeneous samples were removed. This material was then
granulated. The resulting morphology is shown in FIG. 3a). In FIG.
3b), an additional 5 phr of the phase mediator Trans-Polyoctenamer
(Vestenamer 8012 from Degussa AG) were metered into the internal
mixer after the addition of the NBR rnbber (Perbunan NT 3465),
before the crosslinker was added.
[0198] As a further reference for the microgel-based TPE-As
according to the present invention, pure PA (Grilamid L 1120 G
(sample 3)) and pure NBR vulcanization product (Perbunan NT 3465
crosslinked with 5 phr of Poly-Dispersion E(DIC)D-40 (sample 4))
were used.
Injection Molding
[0199] Rods were injection-molded from the granules of the TPE-As
and the pure thermoplastics. This was carried out using a
laboratory injection-molding machine (Injektometer, Gottfert) at a
machine temperature of 230-240.degree. C., a pressure of 10 bar and
a tool temperature of 120.degree. C. The residence time of the
sample was about one minute in the machine and in the tool.
Preparation of the Test Specimens
[0200] S2 standard rods were prepared from all the samples. This
was carried out by cutting in the case of the pure thermplastic
materials (sample 3). The standard rods of all the other samples
were stamped out. All the prepared standard rods had a width of
only 10 mm in the head region because the injection-molded blanks
had a diameter of only 10 mm. The thickness of the standard rods is
4 mm.
Physical Testing
Tensile Test
[0201] The tensile test of the samples was carried out on S2
standard rods (see above) according to DIN 53504. The testing was
carried out using a universal testing machine (type 1445, Frank)
with optical length pick-ups. The measuring range of the force
pick-up is 0 to 2000 N. The results of the measurements are
summarized in Table 1.
[0202] The breaking elongation and stress at break values of the
microgel/PA-based TPE-As were between the values of the pure
constituent elastomer and thermoplastic phase. The level of
properties of a conventionally prepared TPE-A having the same
polymers (sample 5) can be reached. When the microgel OBR1102C
(Preparation Example 1) having the high ACN content was used, the
stronger TPE-A was achieved.
Swelling
[0203] The swelling of the samples was carried out on S2 standard
rods (see above) according to DIN 53521 at a temperature of
125.degree. C. and for a duration of 4 days in the reference test
liquid IRM 903 (Industry Reference Material, highly hydro-treated
heavy naphthene distillate). When the contact time has elapsed, the
test specimens were tempered by storage in unused test agent for 30
minutes at 23.degree. C.
[0204] The results of the swelling test in oil are summarized in
Table 6. The swelling in oil of the microgel/PA-based TPE-As was
very slight. The swelling resistance of a conventionally prepared
TPE-A containing the same polymers (PA (Grilamid L 1120 G) from
EMS-GRIVORY and (Perbunan NT 3465) from BAYER AG) (sample 5) was
exceeded by far. When the microgel OBR1102C having the high ACN
content was used, the lower swelling in oil was noted.
TABLE-US-00008 TABLE 6 Test results of the physical testing of the
PA samples .epsilon. at Swelling by Swelling by Sample
.sigma..sub.B .epsilon..sub.B .sigma..sub.max .sigma..sub.max
volume weight No. Material Mpa % MPa % vol. % wt. % 1 OBR1102B/PA
17.7 136.5 17.7 136.5 2.3 1.9 2 OBR1102C/PA 18.5 110.2 18.5 110.2
1.6 1.3 3 PA (Grilamid L 28.4 81.5 43 7.7 0.9 0.5 1120 G) 4 NBR
(Perbunan NT 3.8 434.7 3.8 434.7 13.7 12.7 3465) 5 NBR/PA (Grilamid
L 14.1 149.7 14.1 149.7 11 10 1120 G/(Perbunan NT 3465)
[0205] As illustrated in the Examples above according to the
present invention, the microgel domains, that is to say the domains
of the elastomer phase, are smaller and more uniform by orders of
magnitude than the elastomer domains, formed by dynamic
vulcanization, of conventional dynamically vulcanized TPVs, both
with (>5 to 30 .mu.m) and without phase mediator (>10 to 35
.mu.m, FIG. 3).
[0206] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
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