Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Mo3244
LeA 26,438
PROCESS FOR THE PREPARATION OF MOLDED
ARTICLES AND THE MOLDED ARTICLES
OBTAINABLE BY SAID PROCESS
BACKGROUND OF THE INVENTION
This invention relates to an improved process for the
preparation of single-layered or multilayered molded articles
from certain polyisocyanate polyaddition products by
thermoplastic shaping and to the molded articles thereby
obtained.
o According to German Patent Application P 3,733,756.4,
molded articles can be prepared by thermoplastic shaping of
granulates, shavings, or other small and very small particles
of the kind obtained from the preparation and processing of
polyisocyanate polyaddition products. According to German
Patent Application P 3,809,524.6, complex structures and
laminates can be prepared from such small particles and used
either as such or in the form of semi-finished goods produced
by a separate step.
It has been found, however, that disintegration may
occur if materials differing substantially in their properties,
for example, in their surface tension, are to be molded
together in a single complex material. This problem can arise,
for example, when using materials differing greatly in their
hardness or materials not formulated to be readily releasable
from the mold and containing internal mold release agents.
Such disintegration may also occur, for example, when lacquered
and unlacquered materials are to be bonded together.
It is, therefore, an object of the present invention
to provide an improved process by which all types of
size-reduced polyisocyanate polyaddition products of the type
mentioned below can be joined to form composite materials,
regardless of their chemical composition and their physical
properties.
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It has surprisingly been found that problem described
above can be solved with the aid of certain processing
auxiliaries described below.
SUMMARY OF THE INVENTION
The present invention relates to a process for the
preparation of single-layered or multilayered molded articles
from small and very small particles of polyisocyanate-
polyaddition products comprising thermoplastically shaping
under pressure
(i) polyisocyanate-polyaddition products prepared by reacting,
in a single stage or multistage process at an isocyanate index
of from about 60 to about 140,
(a) aliphatic, cycloaliphatic, or aromatic
polyisocyanates;
(b) compounds having a molecular weight of from about
1800 to about 12,000 and containing, on statistical
average, at least 2.5 isocyanate-reactive groups;
(c) optionally, diamines having a molecular weight of
from about 108 to about 400 with two primary and/or
secondary aromatically bound amino groups;
(d) optionally, alkane polyols, cycloalkane polyols,
alkane polyamines, and/or cycloalkane polyamines
having a molecular weight of from about 60 to about
1799 and containing ether groups; and
(e) optionally, auxiliary agents and additives
conventionally used in polyurethane chemistry;
with the proviso that at least one of components (c) or
(d) has a molecular weight of from about 60 to about 400
and comprises at least 5% by weight based on the weight of
component (b);
in the presence of
(ii) one or more processing auxiliaries selected from the group
consisting of solvents that swell the surface of the
polyisocyanate-polyaddition products, compounds that can
undergo an addition or condensation reaction with the
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polyisocyanate-polyaddition products, radical formers, and
materials that are different from said polyisocyanate-
polyaddition products and that can be thermoplastically
processed under the conditions of the process.
This invention also relates to the molded articles
prepared by the process of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the invention not only
enables widely differing polyurethane materials or
poly(urethane)urea materials to be combined without
preselection but often also enables the thermoplastic shaping
to be carried out under much milder operating conditions. The
small and very small particles to be used in the process
according to the invention may be, for example, granulates,
shavings, sawdust, or other small and very small particles of
polyisocyanate-polyaddition products based on the starting
materials mentioned above.
Suitable aromatic polyisocyanates for the preparation
of the polyisocyanate-polyaddition products include, in
particular, the compounds described in European Patent
Application 81,701 at column 3, line 30, to column 4, line 25,
of which the polyisocyanates mentioned as preferred are also
preferred for the purpose of the present invention.
Suitable aliphatic and cycloaliphatic polyisocyanates
(a) include any organic diisocyanates having a molecular weight
abo~e about 137 (preferably from 168 to 290) and containing
only aliphatically or cycloaliphatically bound isocyanate
groups. Examples of suitable aliphatic and cycloaliphatic
diisocyanates include 1,6-diisocyanatohexane, 1,12-diiso-
cyanatododecane, 1,3-diisocyanatocyclobutane, 1,3- and
1,4-diisocyanatocyclohexane and any mixtures of these isomers,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(~IPDI~), 2,4'- and/or 4,4'-diisocyanatodicyclohexylmethane,
and any mixtures of such polyisocyanates. Also suitable are
polyisocyanates based on the aliphatic or cycloaliphatic
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diisocyanates exemplified above (or mixtures thereof) that are
modified with urethane, allophanate, isocyanurate, urea,
biuret, or uretdione groups. Mixtures of unmodified
diisocyanates with the above-mentioned modified polyisocyanates
may also be used as component (a).
Component (b) consists of compounds in the molecular
weight range of from about 1800 to about 12,000 (preferably
from 3000 to 7000) containing isocyanate-reactive groups, or of
mixtures of such compounds. The compounds used as component
(b) have an (average) functionality in isocyanate addition
reactions greater than 2.5 (preferably from 2.6 to 3.0 and most
preferably from 2.8 to 3.0). In accordance with this
definition, polyether polyols and mixtures of polyether polyols
disclosed in German Auslegeschrift 2,622,951 at column 6, line
65, to column 7, line 47, are particularly suitable compounds
for use as component (b). Also preferred are polyether polyols
in which at least 50% of the hydroxyl groups (preferably at
least 80%) are primary hydroxyl groups. The hydroxyl-
containing polyesters, polythioethers, polyacetals,
polycarbonates, and polyester amides disclosed as examples in
German Auslegeschrift 2,622,951 are in principle also suitable
for use as component (b), provided they conform to the
conditions mentioned above, but are less preferred than
polyether polyols.
Suitable starting components (b) also include
aminopolyethers and mixtures of aminopolyethers conforming to
the above conditions, that is, polyethers containing
isocyanate-reactive groups and comprising at least 50
equivalents percent (preferably at least 80 equivalents
percent) of primary and/or secondary aromatic or aliphatic
(preferably aro~atic) amino groups, with the remainder being
primary and/or secondary aliphatic hydroxyl groups. Examples
of suitable aminopolyethers of this type include compounds
described in European Patent Application 81,701 at column 4,
line 26, to column 5, line 40.
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Polyesters in the above-mentioned molecular weight
range containing amino groups are also suitable as starting
component (b) but are less preferred.
Mixtures of the polyhydroxyl compounds described
above with the aminopolyethers may, of course, also be used as
component (b).
Optional component (c) consists of aromatic diamines
of the type described in European Patent Application 81,701 at
column S, line 58, to column 6, line 34, of which the diamines
mentioned as preferred are also preferred for the purpose of
the present invention. Preferred aromatic diamines include
diethyltolylenediamines or isomeric mixtures thereof,
especially a mixture of 65 percent by weight 1-methyl-3,5-
diethylphenylene-2,4-diamine and 35 percent by weight
1-methyl-3,5-diethylphenylene-2,6-diamine (~DETDAn).
The polyols and polyamines optionally used as
additional starting components (d) include non-aromatic
compounds in the molecular weight range of from about 60 to
about 1799 (preferably from 62 to 500 and especially from 62 to
400) containing at least two isocyanate-reactive groups.
Examples of such compounds include polyhydric alcohols such as
those described in European Patent Application 81,701 at column
9, lines 32 to 50. Other suitable compounds for use as
component (d) include aliphatic polyamines containing ether
groups, such as polypropylene oxides in the above-mentioned
molecular weight range containing primary amino end groups.
Also suitable are cycloaliphatic-containing polyols, such as
1,4-dihydroxycyclohexane and 1,4-bis(hydroxymethyl)cyclohexane,
and polyamines, such as 1,4-cyclohexanediamine, isophorone-
diamine, bis(4-aminocyclohexyl)methane and bis(3-methyl-4-
aminocyclohexyl)methane.
It is preferred to use at least one of the components
(c) or (d) for the preparation of the elastomers, preferably in
such quantities that the proportion by weight of components (c)
and/or (d) based on the weight of component (b) is at least 5%
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by weight (preferably at least 10% by weight). The nature and
quantitative proportions of components (b), (c) and/or (d) are
preferably chosen so that the molar ratio of urea groups to
urethane groups in the elastomers is at least 2:1 (most
5 preferably at least 5:1).
The auxiliary agents and additives (e) optionally
used in the preparation of polyisocyanate-polyaddition products
may be, for example, internal mold release agents, catalysts
for the polyisocyanate-polyaddition reaction, blowing agents,
surface-active additives, cell regulators, pigments, dyes, UV
stabilizers, plasticizers, and fungistatic or bacteriostatic
substances, such as those described in European Patent
Application 81,701 at column 6, line 40, to column 9, line 31.
When used, the preferred auxiliary agents and additives include
15 known fillers and/or reinforcing substances, such as barium
sulfate, kieselguhr, whiting, mica, and especially glass
fibers, liquid crystal fibers, glass flakes, glass balls,
aramide fibers, and carbon fibers. These fillers and/or
reinforcing materials may be added in quantities of up to 80%
20 by weight (preferably up to 30X by weight) based on the total
quantity of filled or reinforced polyisocyanate-polyaddition
products.
The polyisocyanate-polyaddition products are
preferably prepared by the one-shot process in which
25 polyisocyanate component (a) is mixed with components (b), (c),
(d), and (e) in a suitable mixing apparatus, where the mixed
components react. It is also possible in principle to react
the polyisocyanate-polyaddition products by a ~modified
one-shot process" in which polyisocyanate component (a) is
reacted with part of component (b) and, optionally, part of
component (d) to form isocyanate semiprepolymers which are then
reacted with the mixture of the remaining components in a
single stage. The elastomers can also be prepared by the
well-known prepolymer process. The isocyanate index (number of
3s isocyanate groups divided by the number of isocyanate-reactive
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groups and multiplied by 100) is always from about 60 to about
140 (preferably from 80 to 120 and more preferably from 95 to
115).
The starting materials used for the process according
5 to the invention are most preferably small or very small
particles of the kind obtained from the production and use of
molded articles based on polyisocyanate-polyaddition products
obtained from the aforesaid starting material. In the past,
such materials have been disposed of by burning.
The processing auxiliaries (ii) of the invention may
be a "solvent typen, a "reactive type", or a ~thermoplast type"
or may be radical formers.
Suitable processing auxiliaries of the solvent type
cause the surface of the polyisocyanate-polyaddition products
15 to swell, thereby rendering them softer and more plastic.
Examples of such agents include alcohols, such as methanol,
ethanol, propanol, isopropyl alcohol, and higher alcohols;
diols, such as ethylene glycol and glycol monoethers and
monoesters; ether solvents, such as dioxane, tetrahydrofuran,
20 and dimethoxyethane; halogenated hydrocarbons; ketones and
lower aliphatic aldehydes, optionally in an acetal or ketal
form; esters, such as ethyl acetate; and aprotic polar
solvents, such as acetonitrile, dimethylacetamide,
dimethylformamide, dimethyl sulfoxide, dimethyl sulfone, and
25 tetramethylurea.
Suitable processing auxiliaries of the reactive type
include, for example, the type which react with the
polyisocyanate-polyaddition products by the formation of
chemical bonds, in particular by an addition reaction with the
active hydrogen atoms present in the polyisocyanate-
polyaddition products. Examples include organic poly-
isocyanates of the type described abo~e for starting component
(a) above, prepolymers containing isocyanate groups obtained
from polyisocyanates, and compounds containing isocyanate-
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reactive groups of the type described for component (b), as
well as compounds containing epoxide groups of the type known
from the chemistry of epoxide resins, such as the known
reaction products of bisphenol-A and epichlorohydrin. Also
s suitable as processing auxiliaries of the reactive type are
phenol resins, melamine resins, and other formaldehyde resins,
provided they are capable of undergoing a condensation reaction
with the polyisocyanate-polyaddition products.
Suitable processing auxiliaries also include radical
o formers, particularly peroxidic processing auxiliaries of the
kind used as radical starters for the processing of rubber.
Particularly suitable are peroxidic processing auxiliaries
which have a short half life compared with the molding time at
the most preferred molding temperatures. Examples include
15 lauroyl peroxide, dilauroyl peroxide, cumene hydroperoxide,
t-butyl peroxide, di-t-butyl peroxide, t-butyl perbenzoate,
t-butyl hydroperoxide, benzoyl peroxide, dibenzoyl peroxide,
ethyl methyl ketone peroxide, and dicumyl peroxide (e.g.,
Perkadox SB of Akzo), as well as other radical formers, such as
20 2,2'-azobis(2-methylpropionitrile).
The processing auxiliaries of the reactive type and
the radical formers may be used in either the liquid or the
solid form, but when used as solids they must become fluid at
the stage of thermoplastic shaping. Solid processing
25 auxiliaries may also be introduced as a suitable solution using
a solvent that preferably is capable of wetting the granulate
and of escaping before processing or, at the latest, during
processing.
Suitable processing auxiliaries of the thermoplast
30 type are mainly thermoplastic resins that are themselves
thermoplastically processible under the conditions of the
process of the invention and in which the polyisocyanate-
polyaddition products become embedded when the process of the
invention is carried out. Examples of suitable auxiliary
35 agents of this type include polyolefines, aromatic polyether
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esters, polycarbonates, and other thermoplastically processible
materials.
Thermoplastic molding is generally carried out under
a pressure of at least 5 bar (preferably in the pressure range
of from 5a to 430bar) at a temperature of at least 50-C
(preferably at 10~to 200-C). The molding times under these
conditions may be from about 1 second to about 10 minutes.
Thermoplastic processing is carried out in apparatus
conventionally used for this purpose, such as deep drawing
presses, rolling mills, calendering rollers, presses, modified
extruders, and modified injection molding apparatus. When
using modified apparatus, the modifications must be such that
the particles of granulate can be forced into a given mold at
the filling pressure in a substantially unmolten state.
Examples of such modifications include the use of a large
outlet die and large conveyor channels in the extruder or
injection molding machine and in the channels leading into the
mold. Shearing forces occurring shortly before or during the
process of filling the mold help to keep the molded products
together.
The processing auxiliaries (ii) required for the
invention are preferably added before the molding process to
the polyisocyanate-polyaddition products that are to be
thermoplastically molded. Under these conditions, the small or
25 very small particles of polyisocyanate-polyaddition product
become intimately mixed with the processing auxiliaries.
Combinations of various processing auxiliaries may be used for
carrying out the process of the invention, in which case the
auxiliary agents may be added to the small particles of
polyisocyanate-polyaddition product either as a mixture or
individually in sequence. The auxiliary agents are generally
used in a quantity of from about 0.01 to about 50X by weight
(preferably from 1 to 10% by weight) based on the weight of the
polyisocyanate-polyaddition products.
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The mixture used in the process of the invention for
thermoplastic molding composed of (i) small and very small
particles of polyisocyanate-polyaddition products of the type
described above and (ii) processing auxiliaries that are
essential for the invention may be mixed with (iii) additional
auxiliary agents which serve to improve the properties of the
resulting composite products. These additional auxiliary
agents may include, for example, antistatic agents,
flame-retardants, agents for increasing the electric
o conductivity, reinforcing materials such as glass or carbon
fibers, or fillers such as barium sulfate or mica.
The products obtained by the process of the invention
may be finished parts or articles or they may be semi-finished
goods that may be converted into finished articles in a further
15 process step, either alone or in combination with any other
materials.
The process according to the invention allows the
preparation of particularly high quality composite products,
especially composite sheet products suitible for a wide variety
20 of applications. Thus, the composite products prepared
according to the invention may be used, for example, in the
form of hollow bodies for use as linings, beakers, and
containers of various dimensions and capacities, as facings for
dashboards and switchboards, as flat parts of car body elements
25 such as door panels, side parts, mudguards, hoods, or trunk
lids, and as wheel caps. In a flat form, the composite bodies
are also suitable for use as writing surfaces, indicator boards
with magnetic holders, adhesive labels, protective films, and
coatings for various purposes. Products obtained by the
process of the invention may also be used in the form of small
parts not previously economically obtainable by the RIM
process, such as keyboards parts, rigid elastic sealing parts
and sleeves, handles and recessed grips, small damping
elements, and washers and spacer discs. The products of the
process of the invention may also be used for the manufacture
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of reinforced or unreinforced cable duct sections and sealing
lips or for the production of any other solid small articles.
The following examples further illustrate details for
the process of this invention. The invention, which is set
5 forth in the foregoing disclosure, is not to be limited either
in spirit or scope by these examples. Those skilled in the art
will readily understand that known variations of the conditions
of the following procedures can be used. Unless otherwise
noted, all temperatures are degrees Celsius, all parts are
o parts by weight, and all percentages are percentages by weight.
EXAMPLES
Preparation of a polyisocyanate-polyaddition product
(polyurea-based molded part)
The formulation described below was processed as
15 follows to prepare molded parts:
Apparatus: Laboratory piston dosing apparatus
Mold: Steel plate mold, internal dimensions
300 x 200 x 4 mm
Mixing head: MQ 8 mixing head of Hennecke, Sankt
Augustin
Operating
pressure: 180 bar
Filling time: 1 second
Temperature of
raw materials
A component: 65-C
B component: 50'C
Mold temperature: 70-C
Residence time
in mold: 30 seconds
External mold
release agent: RCTW 2006 of Chemtrend
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A Component:
58.6 parts an aromatic amino polyether (NH number of 44)
prepared by the hydrolysis at 90-C of an
isocyanate prepolymer using a mixture of 3.5
parts by weight of dimethylformamide, O.l part
by weight of sodium hydroxide, and 100 parts by
weight of water per 1000 parts by weight of the
prepolymer, followed by removal of the volatile
components by distillation
o 28.8 parts DETDA
O.9 parts commercial stabilizer based on a polyether
polysiloxane (L 5430 of Union Carbide);
5.6 parts a mixture of equal parts by weight of (i) zinc
stearate and (ii) the product of addition of
5 mol of propylene oxide to 1 mol of ethylene
diamine (internal mold release agent);
6.1 parts a high molecular weight polyricinoleic acid
having an acid number below 5 as internal mold
release agent
The isocyanate prepolymer (isocyanate content 3.4%)
was obtained by the reaction of 2,4-diisocyanatotoluene with a
subequivalent quantity of a polyether mixture. The polyether
mixture consisted of equal parts by weight of (i) the
propoxylation product (OH number 56 and OH functionality 2.4)
25 of a mixture of water and trimethylolpropane and (ii) a
polyether polyol (OH number 35) prepared by the propoxylation
of glycerol followed by the ethoxylation of the propoxylation
product (ratio by weight PO:EO - 87:13).
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B Component:
Desmodur* M 53 (polyester-modified 4,4'-diisocyanatodiphenyl-
methane having an isocyanate content of 19% by weight; product of
Bayer AG).
Components A and B were worked up under the operating
conditions indicated above at an isocyanate index of 100 to produce
elastomer plates having a density of 1.15 g/cm3.
Preparation of a ~ranulate:
A granulate with an average particle size of 2 to 3 mm was
prepared in a cutting mill from the plates described above.
FY~rnples 1-4 Process according to the invention
In the foll~wing Examples 1 to 4, the granulate particles were
compressed to 4-mm thick plates in a closed plate mold using a
laboratory press (Model 200 T press of Schwabenthan) for 2 minutes
at 180~C at a pressure of 350 bar. The plates were cut into rods
which were used to determine the elongation at break and resistance
to breakage in the tension test (see Table below).
Fxample 1
Untreated granulate described.
Example 2
The granulate described above mixed with 10% by weight,
based on the polyisocyanate-polyaddition product, of a granulate of a
commercial thermoplastic polyurethane (Desmopan* 359 of Bayer AG)
having a particle size of 2 to 3 mm. The thermoplastic polyurethane
has a Shore D hardness according to DIN 53,505 of 59, a modulus of
elasticity according to DIN 53,455 of 160 mPa, a stress at break
according to DIN 53,504 of 50 mPa, an elongation at break according
to DIN 53,504 of 350%, and a density of 1.23 g/cm3.
Fl~ample 3
The granulate described above mixed with 10% by weight,
based on the mixture, of an ABS granulate having a particle size of 2
to 3 mm. The ABS granulate was based on an
*) Trade-mark
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acrylonitrile/butadiene/styrene copolymer having a Vicat
softening temperature according to DIN 53,460 of 92-C and a
notched impact strength according to DIN 53,453 of 12 kJ/m2.
Example 4
Particles of granulate completely wetted with a
saturated solution of a polyisocyanate in toluene, dried in
air, and then treated overnight with a saturated solution of
dicumyl peroxide in heptane. The polyisocyanate was a
polyisocyanate mixture of the diphenylmethane series having a
viscosity of 200 mPa.s (23-C). The remainder of the solvent
was removed by drying in a drying cupboard (80-C, 1 h).
ExamDle 5
A reference sample of undisturbed test body
(unblended, original plate of polyisocyanate-polyaddition
product of the type described above).
TABLE
Example Tensile strength Elongation
at break (mPa) at break (%)
1 4 3
2 6 4
3 6 4
4 37 15
37 150
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