Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-11-13
2002-10-01
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S056000, C521S138000, C521S182000
Reexamination Certificate
active
06458858
ABSTRACT:
The invention relates to expandable or expanded polymer beads based on biodegradable saturated polyesters.
It is known that some naturally occurring materials, e.g. cellulose and starch, are biodegradable, i.e. are decomposed by microorganisms, in particular during composting, to give low-molecular-weight substances. Some synthetic polymers, for example polyesters, are also biodegradable. Although purely aliphatic polyesters have good biodegradability they have low suitability for practical applications, since they have a low level of mechanical and thermal properties. In contrast, aromatic polyesters have good mechanical properties but are not biodegradable.
WO 96/07687 has disclosed that copolyesters in which the monomer components are firstly aliphatic diols and secondly aliphatic and aromatic dicarboxylic acids have good mechanical and thermal properties and are at the same time biodegradable. This publication also mentions foamed moldings, but says nothing about their production.
WO 96/15173 also describes biodegradable copolyesters made from aliphatic diols and from a mixture of adipic acid and terephthalic acid, which have been modified by incorporating other transesterification components. These polyesters can be used to produce foams, by mixing a polymer melt with blowing agents and extruding the mixture as a foam.
WO 97/43329 relates to biodegradable branched copolyesters with increased melt viscosity containing polyfunctional polyols and, respectively, polycarboxylic acids incorporated by condensation. Again, the copolyesters can be processed to give foams by extruding the melt.
Finally, WO 97/44388 also describes foams made from moisture-resistant biodegradable mixtures of naturally occurring polymers, e.g. starch, with polyesters having hydroxyl functions. These biodegradable materials, too, were foamed by extruding a foam.
A disadvantage of extruding foams is that they can produce only simply shaped foam moldings, e.g. sheets or profiles. It is known that foam moldings of any desired shape can be produced by expanding expandable or expanded polymer beads, e.g. those based on polystyrene and/or on polyolefins, to give a foam and sintering these.
It is an object of the present invention to provide expanded or expandable particles based on biodegradable polyesters. We have found that this object is achieved by means of the processes as claimed in claims
1
and, respectively, 2.
EP-A 601390 describes degradable moldings made from foamed polylactides produced by foaming a mixture of amorphous polylactide pellets comprising blowing agent and finely divided polylactide in which no blowing agent is present. The polylactide pellets comprising blowing agents may be attained by suspending polylactide pellets in water and injecting blowing agents, e.g. pentane, at pressures of up to 100 bar over a period of up to 10 h, at temperatures below 50° C. This is a very complicated and time-consuming operation. Moldings made from polylactides are not directly biodegradable. They first have to be hydrolyzed at elevated temperatures to give lactic acid, and this is then further biodegraded.
Polyesters suitable for the novel process are described in claims 3 and 4, and also in the publications which have been cited: WO 96/07687, WO 96/15173, WO 97/43329 and WO 97/44388.
Particularly preferred partly aromatic polyesters include polyesters which contain, as significant components:
a) an acid component made from
a1) from 30 to 95 mol % of at least one aliphatic or cycloaliphatic dicarboxylic acid or ester-forming derivatives of these or mixtures of these,
a2) from 5 to 70 mol % of at least one aromatic dicarboxylic acid or ester-forming derivatives of these, and
a3) from 0 to 5 mol % of a compound containing sulfonate groups, and
b) a diol component made from at least one C
2
-C
12
alkanediold or from a C
5
-C
10
cycloalkanediol or mixtures of these,
and also, if desired, one or more components selected from the group consisting of
c) a component selected from the group consisting of
c1) at least one dihydroxy compound of the formula I containing ether functions
HO—[(CH
2
)
n
—O]
m
—H (I)
where n is 2, 3 or 4 and m is an integer from 2 to 250,
c2) at least one hydroxycarboxylic acid of formula IIa or IIb
HO—[—C(O)—T—T—]pH (IIa)
where p is an integer from 1 to 1500 and r is an integer from 1 to 4, and G is a radical selected from the group consisting of phenylene, —(CH
2
)
q
—, where q is an integer from 1 to 5, —C(R)H— and —C(R)HCH
2
, where R is methyl or ethyl,
c3) at least one amino-C
2
-C
12
alkanol or at least one amino-C
5
-C
10
cycloalkanol or mixtures of these,
c4) at least one diamino-C
1
-C
8
-alkane,
c5) at least one 2,2′bisoxazoline of formula III
where R
1
is a single bond, (CH
2
)
2
-alkylene, where z=2, 3 or 4, or phenylene, and
c6) at least one aminocarboxylic acid selected from the group consisting of the naturally occurring amino acids, polyamides with a molar mass of not more than 18000 g/mol obtainable by polycondensing a dicarboxylic acid having from 4 to 6 carbon atoms and a diamine having from 4 to 10 carbon atoms, compounds of the formulae IVa and IVb
HO—[—C(O)—T—N(H)—]sH (IVa)
where s is an integer from 1 to 1500 and t is an integer from 1 to 4, and T is a radical selected from the group consisting of phenylene, —(CH
2
)
n
—, where n is an integer from 1 to 12, —CR
2
H— and —CR
2
HCH
2
—, where R
2
is methyl or ethyl,
and polyoxazolines with the repeat unit V
where R
3
is hydrogen, C
1
-C
6
-alkyl, C
5
-C
8
-cycloalkyl, phenyl, unsubstituted or substituted with up to three C
1
-C
4
-alkyl groups, or tetrahydrofuryl,
or mixtures of c1 to c6,
and
d) a component selected from the group consisting of
d1) at least one compound having at least three groups capable of ester formation,
d2) at least one isocyanate,
d3) at least one divinyl ether,
or mixtures made from d1) to d3).
The acid component a in the partly aromatic polyesters comprises from 30 to 70 mol %, in particular from 40 to 60 mol %, of al and from 30 to 70 mol %, in particular from 40 to 60 mol %, of a2.
Possible aliphatic and, respectively, cycloaliphatic acids and the corresponding derivatives al are those mentioned above. Particular preference is given to adipic acid and sebacic acid, the ester-forming derivatives of each of these, or mixtures of these. Particular preference is given to adipic acid and its ester-forming derivatives, such as its alkyl esters or mixtures of these.
Aromatic dicarboxylic acids a2 which should be mentioned are generally those having from 8 to 12 carbon atoms, preferably 8 carbon atoms. Examples which may be mentioned are terephthalic acid, isophthalic acid, 2,6-naphthoic acid and 1,5-naphthoic acid, and also ester-forming derivatives of these, particularly the di-C
1
-C
6
-alkyl esters, e.g. dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-tert-butyl, di-n-pentyl, diisopentyl and di-n-hexyl esters. Other suitable ester-forming derivatives of the dicarboxylic acids of a2 are the anhydrides.
However, it is in principle also possible to use aromatic dicarboxylic acids a2 having a large number of carbon atoms, for example up to 20 carbon atoms.
The aromatic dicarboxylic acids and their ester-forming derivatives a2 may be used individually or as a mixture of two or more of these. Particular preference is given to terephthalic acid and its ester-forming derivatives, such as dimethyl terephthalate.
The polyesters preferably melt at from 70° to 150° C., in particular from 80° to 130° C. The saturated, partly aromatic polyesters under consideration here do not have precisely defined melting points, but rather a melting range. The impregnation according to the invention with the blowing agent should preferably be undertaken within this melting range.
The partly aromatic polyesters are characterized by a molar mass (Mn) of from 5000 to 100000 g/mol, in particular from 10000 to 40000 g/mol, with a viscosity number of from 50 to 400
Braun Frank
de Grave Isidoor
Glück Guiscard
Hahn Klaus
Witt Uwe
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