Note: Descriptions are shown in the official language in which they were submitted.
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Biodegradable polyesteramides having nolyester segments and polyamide
settments of
block construction
Compostable aliphatic polyesteramides are known (for example, EP-A 641 817).
Compostable
aliphatic-aromatic polyesteramides are also described (WO 92/21689, WO
96/21690, WO
96/21691 and WO 96/21692.
The structures described are constructed purely statistically and have no
segmented block
construction at all.
Polyesteramides of block construction are also known. Polyesteramides of block
construction
obtained by transesterification-/transamidation reactions of higher-molecular
weight polyamides
with higher molecular weight polyesters are described in EP-A 717 064, JP 0
430 6229, JP 0
701 0988 and JP 0 715 7557. Such reactions are reproducible only with
difficulty, as the extent
of the reactions depends very greatly on the operating conditions.
Polyesteramides having such a
block construction are not however sufficiently biodegradable.
The object of this invention is to provide segmented polyesteramides in block
form, which are
completely degradable biologically and by enzymes.
It has been found that acid-, ester-, hydroxyl- or amine-terminated short
oligomers having amide
or ester structures and molecular weights of not more than 3,000 are reacted
with one another
under mild conditions in such a way that this segmented structure is
preserved.
The invention accordingly provides polyesteramides of block construction and
having an amide
structure or ester structure, which polyesteramides can be synthesised from
the following
monomers:
.'
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- aliphatic dialcohols having preferably 2 to 12 carbon atoms, such as
ethylene
glycol, diethylene glycol, 1,4-butanediol, 1,3-propanediol, 1,6-hexanediol and
cycloaliphatic diols such as cyclohexanedimethanol, and/or
- aliphatic dicarboxylic acid having preferably 2 to 12 carbon atoms, such as
oxalic acid, succinic acid, adipic acid, and others, also in the form of its
respective esters (methyl, ethyl, etc.), and/or
- aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid,
phthalic
acid, and others, also in the form of their respective esters (methyl, ethyl,
etc.),
and/or
- Hydroxycarboxylic acids having preferably 2 to 12 C atoms, lactones, such as
caprolactone and others, and/or
- aminoalcohols having preferably 2 to 12 C atoms, such as ethanolamine,
propanolamine, etc., and/or
- cyclic lactams, such as ~-caprolactam or lauryl lactam, etc., and/or
- w-aminocarboxylic acids, such as aminocaproic acid, etc., and/or
- mixtures (1 : 1 salts) of dicarboxylic acids having preferably 2 to 12 C
atoms,
such as adipic acid, succinic acid, terephthalic acid, etc., and of diamines
having preferably 2 to 10 C atoms in the alkyl group, such as
hexamethylenediamine, diaminobutane, etc.,
the polyesteramides being obtainable by polycondensation of a hydroxyl-, acid-
or
ester-terminated ester block and of an amino acid-terminated or ester-
terminated amide
block, the ester content of the polyesteramide being from 20 to 80 wt.%,
preferably
from 30 to 70 wt.%, and the amide content being from 80 to 20 wt.%, preferably
from
70 to 30 wt.%.
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For the synthesis of the polyesteramides, it is preferable to use caprolactam
or AH salt
or mixtures thereof with butanediol and/or diethylene glycol and terephthalic
acid
(ester) and adipic acid (ester).
The short blocks produced, consisting of amide units or ester units, are
prepared from
the monomers according to methods known in polymer chemistry, by selecting the
monomeric composition. For example, a polyamide block having a molecular
weight
of 598 and with acid end groups can be prepared from 3 mol adipic acid and 2
mol
hexamethylenediamine.
Equally, a polyester block having a molecular weight of 490 can be prepared
from 2
mol adipic acid and 3 mol butanediol. If these two blocks are now reacted with
one
another in stoichiometric ratio, one obtains polyesteramides of block
construction,
containing short amide segments and ester segments, which do not interfere
with the
biodegradation process.
In the preparation of the short blocks and also of the polyesteramides,
suitable catalysts
can be used in order to catalyse the esterification or amidation reaction.
These include,
for example, titanium compounds for the esterifications and phosphorus
compounds
for the amidation reactions. These catalysts are in accordance with prior art.
They must
not, however, subsequently restrict the use of the degradable polymer in the
compost
and they must not interfere with the biodegradability. For this reason
catalysts based on
heavy metals such as antimony or lead, for example, are completely dispensed
with.
The polyesteramides prepared in this way are completely biodegradable and
compostable according to DIN 54 900 and have very good mechanical properties.
The capacity of a polymer to be decomposed by enzymes is termed enzymic
degradability. Here, the bonds by which the structural units of the polymer
are linked
together are broken. The resulting breakdown products are the monomers of the
polymer and its oligomers. The enzymic degradation of the polymer leads to a
decrease
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in its molecular weight. Enzymic degradation differs from biodegradation in
that it
does not as a rule lead to naturally-occurnng metabolites.
In principle, all enzymes which are capable of breaking the bonds present in
the
polymer can be used as enzymes which degrade the biodegradable polymers. In
selecting the enzymes, care is to be taken to ensure that these are capable of
rapidly and
completely degrading the polymer. The degradation is carned out in an aqueous
solution, which can be buffered. The pH can be between 3 and 11, is preferably
between 5 and 9 and particularly preferably between 6 and 8. The temperature
at which
the enzymic degradation is carried out can be between 5°C and
95°C, is preferably
between 20°C and 70°C and particularly preferably between
30°C and 50°C.
The following are examples of buffers which can be used according to the
invention:
citrate, acetate, phosphate, formate, carbonate,
tris(hydroxymethyl)aminomethane,
triethanolamine, imidazole, oxalate, tartrate, fumarate, maleate, phthalate,
succinate,
ethylenediamine, as well as mixtures of several of these. Preferably acetate,
phosphate
and citrate are used as buffers.
The procedure is to add the enzyme and polymer to the aqueous solution. The
biodegradable polymer can be added in the form of a film, sheet or granules.
Mouldings can be added as an intact whole or can be comminuted. Coated or
bonded
materials, or materials in the case of which coatings have been applied or
bonds
produced using biodegradable polymers, such as, for example, paper or
cardboard, as
well as coated paper or coated cardboard, can be added either as an intact
whole or in
comminuted form to the enzyme-containing solution.
The aqueous enzyme-containing solution can also be applied by spraying, or
sprayed,
onto the coating to be degraded or onto the moulding to be degraded.
The enzymes used can be lipolytic and/or proteolytic enzymes.
For the purpose of this invention, lipases, cutinases, esterases,
phospholipases and
lysophospholipases are referred to as lipolytic enzymes. The lipolytic enzymes
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originate preferably from microorganisms. They originate in particular from
bacteria,
fizngi or yeasts. The lipolytic enzymes may also be of vegetable or animal
origin.
For the purpose of this invention, proteases are referred to as proteolytic
enzymes.
These originate preferably from bacteria of the genus Bacillus; proteases of
the
organisms Bacillus alcalophilus and Bacillus licfheniformis are particularly
preferred.
They may also originate from fizngi or from plants.
The joint use of lipolytic and proteolytic enzymes as well as of lipolytic
enzymes of
varying specificity, which can lead to synergistic effects, is according to
the invention.
The addition of metal ions such as, for example, sodium ions or calcium ions,
which
accelerate the enzymic degradability, is also according to the invention. The
addition of
auxiliary substances such as anionic or nonionic surfactants such as, for
example, sec.
alcoholethoxylates, is also according to the invention.
Compostability is the capacity of a polymeric material to be biodegraded
during a
composting process. For the polymeric material to be regarded as compostable,
it has
to be proved by means of standard methods that it can be biodegraded in a
composting
system and that compost of flawless quality can be produced (according to DIN
54
900).
The biodegradation of a material is a process which is caused by biological
activity and
which leads to naturally-occurnng metabolic end products, with alteration of
the
chemical structure of the material (according to DIN 54 900).
A polymeric material is biodegradable if all organic constituents are subject
to a
complete biological degradation, which is determined by standard processes
(according
to DIN 54 900).
The mixtures according to the invention may contain in addition from 0 to 80
wt.% of
conventional additives, for example, inorganic fillers and reinforcing
materials (for
example, glass fibres, carbon fibres) and mineral fillers (for example, talc,
mica, chalk,
kaolin, wollastonite, gypsum, quartz, dolomite and others), UV stabilisers,
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antioxidants, pigments, dye, nucleating agents, accelerators or inhibitors of
crystallisation, flow-promoting agents, lubricants, mould release agents,
flameproofing
agents.
The polyesteramides according to the invention may further contain from 0.05
to 5
wt.%, preferably from 0.1 to 1 wt.%, of branching agents. These branching
agents can
be, for example, trifunctional alcohols, such as trimethylolpropane or
glycerol,
tetrafunctional alcohols such as pentaerythritol, trifunctional carboxylic
acids such as
citric acid or even tri- or tetrafunctional hydroxycarboxylic acids.
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Examples
Example 1
Preparation of a hydroxyl-terminated oligoester block having a molecular
weight of
490
292 g (2 mol) adipic acid and 270 g (3 mol) butanediol are heated together at
250°C
under nitrogen. After 1 hour a water jet vacuum is applied and after 2.5
hours, an oil
pump vacuum. Water is distilled off. After a polycondensation time of 4 hours,
a
colourless wax having a hydroxyl value of 21 is obtained.
Example 2
Preparation of an ester-terminated oligoester block having a molecular weight
of 1038
696 g (4 mol) dimethyl adipate and 270 g (3 mol) butanediol are heated
together at
250°C under nitrogen. After 1 hour a water jet vacuum is applied and
after 2.5 hours,
an oil pump vacuum. Methanol is distilled off. After a polycondensation time
of 4
hours, a colourless wax is obtained.
Example 3
Preparation of an ester-terminated amide block having a molecular weight of
626
522 g (3 mol) dimethyl adipate and 180 g (2 mol) hexamethylenediamine are
heated
together at 250°C under nitrogen. After 1 hour a water jet vacuum is
applied and after
2.5 hours, an oil pump vacuum. Methanol is distilled off. After a
polycondensation
time of 3 hours, a colourless wax is obtained.
Example 4
Preparation of an amino-terminated amide block having a molecular weight of
568
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292 g (2 mol) adipic acid and 348 g (3 mol) hexamethylenediamine are heated
together
at 250°C under nitrogen. After 1 hour a water jet vacuum is applied and
after 2.5 hours,
an oil pump vacuum. Water is distilled off. After a polycondensation time of 3
hours, a
colourless wax is obtained.
Example 5
Preparation of a polyesteramide from the individual blocks
626 g (1 mol) of an ester-terminated amide block as in Example 3 and 490 g (1
mol) of
a hydroxyl-terminated ester block as in Example 1 are heated together at
190°C under
nitrogen. After 1 hour a water jet vacuum is applied and after 2.5 hours, an
oil pump
vacuum. Methanol is distilled off. After a polycondensation time of 7 hours, a
colourless polymer having a melting point of 136°C is obtained. The
polymer obtained
has good mechanical properties and is biodegradable according to DIN 54 900.
