U.S. patent application number 09/876344 was filed with the patent office on 2002-01-24 for thermoplastic elastomer molding compositions with improved processability.
Invention is credited to Brandt, Rainer, Funk, Hans-Werner, Schledjewski, Ralf, Schultze, Dirk.
Application Number | 20020010240 09/876344 |
Document ID | / |
Family ID | 7645556 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010240 |
Kind Code |
A1 |
Schledjewski, Ralf ; et
al. |
January 24, 2002 |
Thermoplastic elastomer molding compositions with improved
processability
Abstract
Described is a thermoplastic molding composition comprising: a)
0.05 to 1.5 wt. %, with respect to the entire molding composition,
of a fatty acid amide ester wax; b) 0.5 to 10 wt. %, with respect
to the entire molding composition, of a silica selected from
natural silica, synthetic silica and mixtures thereof; c) 0 to 1
wt. %, with respect to the entire molding composition, of a montan
wax; and d) at least one thermoplastic elastomer. Also described
are a method of preparing the thermoplastic molding composition,
and methods of preparing articles from the thermoplastic molding
composition.
Inventors: |
Schledjewski, Ralf;
(Kaiserslautern, DE) ; Funk, Hans-Werner;
(Bomlitz, DE) ; Schultze, Dirk; (Dusseldorf,
DE) ; Brandt, Rainer; (Walsrode, DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7645556 |
Appl. No.: |
09/876344 |
Filed: |
June 7, 2001 |
Current U.S.
Class: |
524/218 |
Current CPC
Class: |
C08G 18/0895 20130101;
C08L 91/06 20130101; C08L 67/025 20130101; C08L 77/00 20130101;
C08K 5/20 20130101; C08L 75/06 20130101; C08K 5/101 20130101; C08L
67/025 20130101; C08L 91/06 20130101; C08L 75/06 20130101; C08L
91/06 20130101; C08L 77/00 20130101; C08L 91/06 20130101 |
Class at
Publication: |
524/218 |
International
Class: |
C08L 001/00; C08J
003/00; C08K 005/20; C08K 005/36; C08K 005/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2000 |
DE |
10029076.0 |
Claims
What is claimed is:
1. A thermoplastic molding composition comprising: a) 0.05 to 1.5
wt. %, with respect to the entire molding composition, of a fatty
acid amide ester wax; b) 0.5 to 10 wt. %, with respect to the
entire molding composition, of a silica selected from natural
silica, synthetic silica and mixtures thereof; c) 0 to 1 wt. %,
with respect to the entire molding composition, of a montan wax;
and d) at least one thermoplastic elastomer.
2. The composition of claim 1 wherein said composition contains a
thermoplastic elastomer selected from the group consisting of
thermoplastic polyurethanes, thermoplastic polystyrenes,
thermoplastic polyetheresters, thermoplastic polyether block amides
and mixtures thereof.
3. The composition of claim 1 wherein a portion of the montanic
acid of said montan wax is esterified with butylene glycol, and the
remainder of the montanic acid of said montan wax is saponified
with calcium hydroxide.
4. The composition of claim 1 wherein the thermoplastic elastomer
is a block copolymer.
5. The composition of claim 1 wherein the thermoplastic elastomer
is a copolyetherester.
6. The composition of claim 1 wherein the thermoplastic elastomer
is a polyether block amide.
7. The composition of claim 1 wherein the thermoplastic elastomer
is a thermoplastic polyurethane elastomer.
8. A method of preparing the thermoplastic molding composition of
claim 1 comprising, mixing a concentrate of said fatty acid amide
ester wax a), said silica b) and said montan wax c) with said
thermoplastic elastomer d).
9. A method of preparing a tubular semi-finished product comprising
extruding the thermoplastic molding composition of claim 1 in an
extrusion device having a downstream die.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to mixtures of thermoplastic
elastomers, readily soluble waxes and inorganic antiblocking agents
(i.e., molding compositions), which have improved ease of passage
through machines during extrusion processing.
BACKGROUND OF THE INVENTION
[0002] The ease of passage through machines of thermoplastic
materials during extrusion processing can be affected by the
constructional design of the mould used to work up the material.
Optimisation is generally possible only with regard to certain raw
materials characteristics of the material being processed. When
processing different materials on one extrusion device, this can
provide optimised ease of passage through the machine only in
exceptional cases.
[0003] Thermoplastic resins are typically processed, for example,
in screw-type tools. A review of their structures is given, for
example, in: Wortberg, Mehleke and Effen in: Kunststoffe, 84
(1994), S. 1131-1138, Pearson in: Mechanics of Polymer Processing,
Elsevier Publishers, New York 1985, Fa. Davis-Standard in: Paper,
Film & Foil Converter 64 (1990), S. 84-90. Moulds for extruding
the melts, for example to give tubular semi-finished products, are
described inter alia, by: Michaeli in: Extrusionswerkzeuge, Hanser
Verlag, Munich 1991.
[0004] Thermoplastic elastomers are a group of materials where the
essential characteristics are thermoplastic processability combined
with elastomer materials behaviour. The main members of the group
of thermoplastic elastomers (TPE) are block copolymers. These,
apart from thermoplastic polyurethanes (TPE-U), include but are not
limited to thermoplastic styrene-based systems (TPE-S),
thermoplastic polyetheresters (TPE-E) and thermoplastic polyether
block amides (TPE-A).
[0005] As a result of the thermoplastic processability, these
materials can be extruded in an extrusion process and then further
processed with the aid of a die to give, for example, a profiled
section, a cable sheath or a tubular semi-finished product. Films
based on TPE-E are described, for example, in U.S. Pat. No.
5,859,083. Those based on TPE-A are described in EP-A 0 761 715.
TPE-S materials suitable for extrusion and their uses are
described, for example, in DE-A 19 628 834. Semi-finished products
made of TPE-U, processes for preparing them and their use are known
from the prior art, for example, from EP-A 0 308 683, EP-A 0 526
858, EP-A 0 571 868 or EP-A 0 603 680. The preparation of TPE-U
semi-finished products using substantially incompatible polymers as
matting agents in the TPE-U is also described, for example, in
DE-A-41 26 499. A review of the group of thermoplastic elastomers
is given, for example, in: Thermoplastic elastomers: a
comprehensive review, ed. N. R. Legge, G. Holden and H. E.
Schroeder, Carl Hanser Verlag, Munich, 1987 and Thermoplastische
Elastomere--Herausforderung an die Elastomerverarbeiter, eds.:
VDI-Gesellschaft Kunststofftechnik, VDI Verlag, Dusseldorf,
1997.
[0006] Auxiliary substances and additives may be used during the
thermoplastic processing of TPE's. The following may be mentioned
by way of example here: waxes which act as friction-reducing
internal and external lubricants. In addition, waxes take on the
task of a separating agent in order to prevent sticking of the
material to the surrounding material (e.g. the die). They are also
used as dispersants for other additives, e.g. pigments or
colorants.
[0007] Waxes used in the plastics processing sector include, for
example, fatty acid amides, e.g. stearyl amides and oleic acid
amides, fatty acid esters, e.g. montanates and stearates, and also
polyethylene waxes. A detailed review of this topic is available:
Taschenbuch der Kunststoff-Additive, eds. R. Gchter, H. Muller,
Hanser Verlag, Munich, Vienna, 1979, p. 229 et seq.
[0008] The specific processing and application temperatures of
various thermoplastic materials and their different chemical
reactivities typically leads to a situation in which not all waxes
can be used in the same way. Substantially amide waxes, for
example, are used for TPE-U. These exhibit a high tendency to
migrate, which provides a very good separating effect. On the other
hand, the lubricating effect of these waxes is expressed only
weakly. Montanate waxes, for example, exhibit good lubricating
properties in TPE-U (EP-A 0 308 683; EP-A 0 670 339). However, in
this case the separating effect is inadequate, even at high
concentrations. A reduction in internal and external friction
during melt processing can also be produced with a TPE-U, for
example, by the use of 0.2 to 5 wt. % of at least one polyolefin or
polystyrene (U.S. Pat. No. 3,358,052).
[0009] The use of antiblocking agents as an additive is important
when preparing flat semi-finished products. As a result of using
these, for example, a surface topography is typically produced,
which prevents the sticking together of flat plastics items during
further processing, less so during melt-processing moulding (e.g.
film preparation). Natural or synthetic silicas are used here for
example. Additives consisting of incompatible materials such as
e.g. polyolefins or also polystyrene are also known for use in
TPE-U (DE-A-41 26 499).
SUMMARY OF THE INVENTION
[0010] There is the objective of improving ease of passage through
machines during the extrusion processing of thermoplastic
elastomers, no matter what the structural design of the extrusion
device.
[0011] In accordance with the present invention, there is provided
a thermoplastic molding composition comprising:
[0012] a) 0.05 to 1.5 wt. %, with respect to the entire molding
composition, of a fatty acid amide ester wax;
[0013] b) 0.5 to 10 wt. %, with respect to the entire molding
composition, of a silica selected from natural silica, synthetic
silica and mixtures thereof;
[0014] c) 0 to 1 wt. %, with respect to the entire molding
composition, of a montan wax; and
[0015] d) at least one thermoplastic elastomer.
[0016] Other than in the operating examples, or where otherwise
indicated, all numbers expressing quantities of ingredients,
reaction conditions, etc. used in the specification and claims are
to be under stood as modified in all instance by the term
"about."
DETAILED DESCRIPTION OF THE INVENTION
[0017] Surprisingly, the ease of passage through machines during
the extrusion processing of a thermoplastic elastomer is clearly
improved by the molding composition according to the invention.
While not intending to be bound by any theory, it is believed based
on the evidence at hand that this is due to improved flow
characteristics of the melt coupled with a simultaneously increased
mass throughput due to the reduced energy consumption of the
extrusion device.
[0018] Fatty acid amide waxes which can be used according to the
present invention include but are not limited to, for example,
erucic amide ethyl erucate, oleic amide ethyl stearate, stearic
amide butyl stearate, stearic amide ethyl oleate, cerotic amide
ethyl cerotate.
[0019] "The molding composition of the present invention comprises
a silica selected from natural silica, synthetic silica and
mixtures thereof".
[0020] The molding composition of the present invention may
optionally further comprise a montan wax as an additional
component. The proportion of the montan wax, according to the
invention, is typically between 0 and 1 wt. %, based on the weight
of the molding composition. In a particularly preferred embodiment
of the present invention, a portion of the montanic acid of the
montan wax is esterified with butylene glycol, and the remainder of
the montanic acid of the montan wax is saponified with calcium
hydroxide. "The montan wax may contain, based on the total weight
of the montan wax, from 0.1 % wt. to 1 % wt. of montan wax
esterified with butylene glycol, and from 0.1 % wt. to 1 % wt. of
montanic acid saponified with calcium hydroxide."
[0021] According to the invention, the molding composition contains
at least one thermoplastic elastomer. In a preferred embodiment of
the present invention, the thermoplastic elastomer is a block
copolymer such as, for example, copolyetheresters or polyether
block amides.
[0022] In a particularly preferred embodiment, at least one
thermoplastic polyurethane is used as the thermoplastic elastomer.
Preferably, a substantially linear thermoplastic polyurethane
elastomer, in which the longer-chain diol component is a polyester
or polyether and which has a Shore hardness of preferably 70 to 95
A, particularly preferably 85 to 95 A, determined according to DIN
53505, is used.
[0023] Suitable thermoplastic polyether-diol based polyurethane or
polyester-diol based polyurethane elastomers and/or mixtures
thereof may be prepared, for example, by art-recognised batch
and/or partly or fully continuous processes. An example of such an
art-recognised process involves the reaction in a screw-extruder
of:
[0024] (a) organic, preferably aromatic or cycloaliphatic
diisocyanates;
[0025] (b) polymer diols with molecular weights of preferably 500
to 8000 Mw
[0026] (c) chain-lengthening components with molecular weights of
preferably 60 to 400 Mw
[0027] (d) optionally in the presence of catalysts; and
[0028] (e) optionally in the presence of auxiliary substances
and/or additives.
[0029] The following details relate to components (a) through (e)
which can be used in the above described process for preparing
thermoplastic polyether-diol based polyurethane or polyester-diol
based polyurethane elastomers.
[0030] Suitable organic diisocyanates (a) are preferably aromatic
or cycloaliphatic diisocyanates. The following may be mentioned in
detail: aromatic diisocyanates such as 2,4- and 2,6-toluylene
diisocyanate, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate or
mixtures thereof; cycloaliphatic diisocyanates, such as isophorone
diisocyanate, 1,4-cyclohexane diisocyanate and 4,4'-, 2,4'- and
2,2'-dicyclohexylmethan- e diisocyanate or mixtures thereof.
[0031] Suitable higher molecular weight diol compounds (b) with
preferred molecular weights of 400 to 8000 Mw are preferably
molecules with a linear structure and a low glass transition or
softening point. These include polyetherols and polyesterols.
However, the following are also suitable: hydroxyl group-containing
polymers, for example polyacetals such as polyoxymethylene and in
particular water-insoluble formals and aliphatic polycarbonates, in
particular those prepared by transesterification from diphenyl
carbonate and hexanediol-1,6. Also suitable are hydroxyl
group-capped diol compounds formed from polyolefins, in particular
aliphatic hydroxyl group-capped copolymers of ethylene and
butylene. The diol compounds are preferably at least substantially
linear, i.e., having a structure which is to be difunctional in the
context of the isocyanate reaction. The diol compounds mentioned
may be used as individual components or in the form of
mixtures.
[0032] Suitable chain-lengthening agents (c) with molecular weights
of 60 to 400, preferably 60 to 300 .mu.W are preferably alkanediols
with 2 to 12 carbon atoms, preferably with 2, 4 or 6 carbon atoms,
e.g., ethanediol, hexanediol-1,6 and in particular butanediol and
dialkylene ether glycols, e.g., diethylene glycol and dipropylene
glycol. Also suitable, however, are diesters of terephthalic acid
with alkanediols with 2 to 4 carbon atoms, e.g., bis-ethanediol
terephthalate or bis-butanediol-1,4 terephthalate, hydroxyalkylene
ethers of hydroquinone, (cyclo)aliphatic diamines, e.g., isophorone
diamine, ethylene diamine and aromatic diamines, e.g., 2,4- and
2,6-toluylene diamine.
[0033] Suitable catalysts (d) which accelerate in particular the
reaction between isocyanate groups in category (a) and the hydroxyl
groups in categories (b) and (c) are known to those of ordinary
skill in the art and include: conventional tertiary amines, e.g.,
triethylamine, dimethylcyclo-hexyl amine, N-methylmorpholine,
N,N'-dimethylpiperazine, 2-(dimethyl-amino-ethoxy)-ethanol,
diazabicylo(2.2.2)-octane and the like; and in particular organic
metal compounds such as titanates, iron compounds such as e.g.
iron(III) acetylacetonate, tin compounds, e.g., tin diacetate, tin
dioctoate, tin dilaurate or tin dialkyl salts of aliphatic
carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate
and the like. The catalysts are typically used in amounts of 0.001
to 0.2 parts per 100 parts of hydroxyl compound (b).
[0034] Apart from catalysts, the auxiliary substances and/or
additives (e) may also be added to structural components (a) to
(c). Examples of auxiliary substances (e) that may be used include,
but are not limited to: lubricants, inhibitors, stabilisers against
hydrolysis, light, heat, oxidation or discoloration, colorants,
pigments, inorganic and/or organic fillers, reinforcing agents and
low molecular weight plasticisers.
[0035] Commercially available thermoplastic polyurethanes that may
be used in the molding compositions of the present invention
include, but are not limited to, DESMOPAN thermoplastic
polyurethane, ELASTOLLAN thermoplastic polyurethane, ESTANE
thermoplastic polyurethane, MORTHANE thermoplastic polyurethane,
PELLETHANE thermoplastic polyurethane, PEARLTHANE thermoplastic
polyurethane, SKYTHANE thermoplastic polyurethane, TECOFLEX
thermoplastic polyurethane and TEXIN thermoplastic
polyurethane.
[0036] In an embodiment of the present invention, the molding
composition may also contain art-recognised additives selected from
the group comprising: (I) antiblocking agents, inorganic or organic
spacer pieces; (II) lubricants or mould release agents; (III)
pigments or fillers; and (IV) stabilisers. Additives (I) to (IV)
may be present in the molding composition of the present invention
in an amount of from 0 and 30 % by weight, based on the weight of
the molding composition.
[0037] Art-recognised additives which may be included in molding
compositions according to the present invention are described in
further detail, for example, by Gchter and Muiller in:
Kunststoff-Additive, Carl Hanser Verlag Munich (1979).
[0038] "The molding composition of the present invention may be
prepared by mixing in a suitable mixer, e.g., in a compounder. In
an embodiment of the present invention, the thermoplastic molding
composition is prepared by a method comprising, mixing a
concentrate of the fatty acid amide ester wax a), the silica b) and
the montan wax c) with the thermoplastic elastomer d).
[0039] Molding compositions according to the present invention
improve the ease of passage through machines during extrusion
processing (i.e., they have improved processability). In
particular, products having a high ratio of surface area to
cross-section may be prepared from the molding compositions of the
present invention by means of shaping moulds, for example, by means
of film extrusion.
[0040] "The present invention also provides a method of preparing a
tubular semi-finished product or article, which method comprises
extruding the thermoplastic molding composition of the present
invention in an extrusion device having a downstream die. Extrusion
devices that may be used include those known to the skilled
artisan, e.g., single- and twin-screw co- or counter-rotating
extruders. The downstream die serves to form the extruded
thermoplastic molding composition into a tubular semi-finished
article."
[0041] The surface properties of structural parts, e.g., extruded
articles, prepared from molding compositions according to the
invention can be modified on one or more surfaces using known
physical and chemical methods of treatment, such as corona
treatment.
[0042] The present invention is more particularly described in the
following examples, which are intended to be illustrative only,
since numerous modifications and variations therein will be
apparent to those skilled in the art. Unless otherwise specified,
all parts and percentages are by weight.
EXAMPLES
[0043] The molding compositions described in the context of the
following examples were processed on a single-screw extruder with
D=60 mm using a three-zone screw, L/D=25, with a combined shear and
mixing section. The temperature in the extruder cylinder could be
set at a constant value within each of 5 zones. The temperature
profile in the extruder and also the adjustments on the downstream
measuring die were kept constant.
[0044] The examples were determined using an ester-TPE-U with
Shore-A hardness 86, measured according to DIN 53505, corresponding
to a Shore-D hardness of 36 and a Melt Volume Rate (MVR) of 26
cm.sup.3/10 min, measured according to DIN ISO 1133 at 200.degree.
C. and 10.0 kg.
[0045] Constituents that were further used in the molding
compositions are summarised in the following Table 1.
1 TABLE 1 Commercial Description Designation wax 1: W1 stearyl
amide ethyl stearate (Abril Paradigm * Wax 77) wax 2: W2 butyl
montanate partly saponified (Hoechstwachs * with Ca OP) wax 3: W3
ethylene bis-stearylamide (Hoechstwachs * C) antiblock A1* natural
silica (Superfloss E) 1: * Abbreviated designations used in the
following Table 2.
[0046] The extruder was operated with a constant speed of rotation,
38 rpm. The power consumption of the extruder, the mass throughput
and the uniformity of the extruded extrudate were measured, the
results of which are summarised in the following Table 2.
2TABLE 2 Power Ex- Addi- Proportion consumption Throughput
Uniformity of ample tive (wt. %).sup.(a) (Amps) (kg/h) the
extrudate 1 W1 0.7 42 60 uniform W2 0.1 A1 3.5 2 W1 0.8 45 55
uniform A1 3.5 3 W1 0.7 45 50 non-uniform W2 0.1 4 W1 0.4 48 54
uniform A1 3.5 5 W3 0.7 54 50 uniform A1 4.0 .sup.(a)Percent weight
based on the weight of the molding composition.
[0047] Examples 1 and 2 demonstrate the outstanding ease of passage
through the machine of the molding composition according to the
present invention. The positive effect of the presence of silica on
the uniformity of the extrudate is demonstrated in Example 3. The
sensitivity with reference to the formulation of the molding
composition is made clear in Example 4. A comparison of Examples 1,
2 and 4 with comparison Example 5 demonstrates the advantage which
can be obtained by the molding composition according to the
invention with regard to ease of passage through a machine.
Comparison Example 5 requires not only by far the highest energy
input, but also results in the lowest mass throughput, relative to
Examples 1, 2 and 4.
[0048] 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.
* * * * *