CA2077683A1

CA2077683A1 - Segmented block copolymers

Info

Publication number: CA2077683A1
Application number: CA 2077683
Authority: CA
Inventors: Reinoud J. Gaymans; Jeanette L. De Haan
Original assignee: Individual
Current assignee: Dow Chemical Co
Priority date: 1990-03-06
Filing date: 1991-03-06
Publication date: 1991-09-07
Also published as: AU7660291A; JPH05506680A; WO1991013930A1; EP0519012A1

Abstract

The invention is directed to a segmented block copolymer comprising non-crystallizable segments and partly crystallizable segments, in which the partly crystallizable segments have the following formula:
-NH-R2-NH-[C(O)-R1-C(O)-NH-R2-NH]n-C(O)-R1-C(O)-[NH-R2-NH-C(O)-R1-C(O)]n-and/or -NH-R3-C(O)- or a reaction product thereof with a diamine or a dicarboxylic acid or a derivative of a dicarboxylic acid, in which formula n is an integer which equals 1, 2, or 3, each of R1 and R2 are independently an aliphatic, an alicyclic, or a wholly or partly aromatic group, and R3 is a hydrocarbon radical which may or may not be substituted, and in which block copolymers the partly crystallizable segments have a substantially uniform block length.

Description

Wr~ 91/13930 PCl`/NLgl/00036 2~77~83 Title: Segmented block copolymers The invention relates tO segmented block copolymers based on non-crystallizable segments and partly crystallizable segments. Depending on the type and properties of the materials constituting the blocks, such blockcopolymers may have different properties.
Block copolymers comprising non-crystallizable segments and partly crystallizable segments exhibit the behaviour of semi-crystalline polymers, the difference being that the Tg/Tm ratio is not invariably 0.66 (the 2/3 rule), but may have a different value.
When this ratio is lower than 0.6 ~he materials usually have a thermoplastic elastomer character. At hiyher values the materials mostly behave as semi-crystalline polymers, such as PET, PBT, nylon 6 and the like.
When the value for Tg/Tm exceeds 0.7 for the semi-crystalline block copolymers, the materials have an improved balance of properties, since the range between Tg and Tm~ in which range the modulus is from 3-20 times lower than the modulus below the Tg, is smaller.
Thermoplastic elastomers consist in principle of two types of blocks, namely soft or flexible blocks and hard or non-flexible blocks. The soft blocks are typically formed by amorphous flexible segments with a glass transition temperature of below 0 C. The hard blocks. consist of crystallizable ~5 segments with a high melting temperature.
Thermoplastic elastomers behave as .elastomers at temperatures below the melting temperature, while.above.that temperature a thermoplastic behaviour is found. Owing to this, .., ., .. , ., ~ .. ... . .. .. .. . . . .. .. .. . .
these products are easy..to process:.~.easier, often, than pure elastomers, which often.combine..their elastomeric..behaviour -.
with di~ficult~processabil,lty.

','''~

, .. ... , ... . ~ . . . . . . - - . . . . . .

WO91/13930 2 0 7 7 ~ 8 3 2 PCT/NL91/~036_ Although thermoplastic elastomers possess a suitable property pattern, a decrease of mechanical properties occurs at temperatures approaching the melting temperature of the hard blocks, so that the temperature range within which the products can be used is fairly limited at the upper end.
In the plastics industry a great deal of research is done into engineering plastics, i.e. plastics with a property pattern, which makes it possible to use the plastic for construction purposes or under conditions of extreme temperatures. A number of such semi-crystalline plastics are based on polyesters, such as polybutyleneterephthalate; or on polyamides.
There is also a great need for plastics for the manufacture of fibers with improved properties.
lS Although the known products for applications as engineering plastics and the manufacture of fibers have a suitable property pattern, a decrease of mechanical properties occurs at temperatures above the glass transition temperature, so that the temperature range within which the products can be 20 used is fairly limited at the upper end. '' ' An important problem which severely restricts the usability of engineering plastics resides in the fact that a dacrease of ~he modulus occurs far below the melting temperature, so that at a low temperature a decrease of the properties and the usability occurs.
For amorphous ehgineering plastics a problem is that at temperatures a little~above~the glass transition temperature the~melt process~ab~ility is not yet optimal, which makes it n~cessary~for the plastic to be processed at temperatures far 30 ~ abo~ ~the glass~transition t~.. ~erature. This is undesirabie in '' view~of p ~ r~degradation and in view of energy consumption.
It al'so~means~the cycle time is extended. '~' ~ ' ~~ -~ , , - , ........................ . ...... .. . ... .
For the proce8sing 0f polymers in general and of'''the present;eype-of block copol ~ers it is of great~importancè'that 35~ the ~crystallization^~rate~~during -cooling ~-'is high.'~ For '~
c~rystallization to take~place rapidly,~a length of at least 4 recurring units in the crystallizable segment is ~nown to be desirable (R.K. Adams, G.K. Hoeschele in Thermoplastic Elastomers ed. N . R . Legge, G. Holden and H.E. Schroeder, Publ.
Hanser Munchen, Chapter 8, page 163 (1987)).
With a l~ngth of more than 20 units, it is not possible anymore to obtain a homogeneous melt (melt-phasing).
The object of the invention is to provide new block copolymers, which do not possess the disadvantages described hereabove and which do have a numher of advantageous pxoperties hitherto not available.
These novel block copolymers can, among other things be used as fibre material or as an engineering plastic and exhibit a minor decrease of the modulus above the glass transition temperature, and a good melt processability at temperatures just above the melting temperature.
Block copolymers comprising hard, crystallizing segments and soft segments, having thermoplastic and elastomeric properties, can be employed advantageously in the automobile industry.
The present invention is based on the surprising insight tha~ by using short, uniform segments-for the crystallizable blocks, the materials possess unusual high crystallization rates and the engineering plastics have improved properties.
Accordingly, the present invention relates to segmented block copolymers comprising non-crystallizable segments and partly crystallizable segments, in which the partly crystallizable segments have the following formula:
R2-NH- ~C ~0) -Rl -C (O) -NH-R2-NH] n~
-C (O) -Rl-C (O) - ~ R2 -NH-C (O) -Rl-C ~O) ] n-30 and~or - --NH-R3-C(O)- or a reaction product thereof with a diamine or a dicarboxylic acid or a derivative of a dicarboxylic acid, in whic~ formula n is an integer which equals l, 2, or 3,~-each.of Rl and R2 are independently-an aliphatic, an alicyclic, or a wholly ox partly~aromatlc group! and-R3 is a hydrocarbon radical which may or may no~ be substituted, and in which block , ,.

...... ..... . . . ~

WO91/13930 2 0 7 7 6 8 ~ 4 PCT/NL91100036_ copolymers the partly crystallizable se5ments have a substantially uniform block length.
In this connection ~a substantially uniform block length' means that virtually all partly crystallizable segments in the polymer have the same value for n. In practice, preferably a proportion of at least 70%, preferably at least 85% of all segments have the same length. More preferably, this proportion is at least 90~, and yet more preferably at least 97~S%. Such uniform block length can be obtained by a proper selection of the starting materials for the preparation of the block copolymer. This will be further explained when these materials are discussed.
Depending on the nature of the blocks used in the block copolymer, various products can be obtained. More in particular the block copolymers of the invention are thermoplastic elastomers and/or engineering plastics.
It is observed that in principle the products accor~ing to the invention have the following structures as regards the partly crystallizable segments:
20 -N~I-R2 -NH- [C (O) -Rl -C (O) -NH-R2-NH] n--C (O) -Rl-C (O) - [N~I-R2-NH-C (O) -Rl-C (O) ] n-However, it is possible to replace these in whole or inpart with -NH-R3-C(O)- or a reaction product thereof with a diamine or a dicarboxylic acid or a derivative of a dicarboxylic acid.
Surprisinyly, it turned out that a segmented block copolymer which meets these conditions exhibits a much higher ~ degree of crystallization, and the crystallization itself takes place much faster, which is a great advantage from process-economical co~siderations.
- According to a first embodiment the flexible segments have~a glass ~transition 'temperature ~0 C.'These block copolymers possess'thermoplastic properties and the degrëe and the rate;of cryst'alliza'tion-of these copolymers `is higher than 35 ~-of-block copolymers not according to the-in~ention. ~~-~ .

- , . - . . ................................. . ... ..... ...

,, . , . ~ ".,,........................... ;... .... . . . . .
. .. . .. . .. . . . . .

W~9lt13930 2~776~3 pCT/NLg1/~036 To obtain an optimally segmented block copolymer, in a preferred embodiment of the invention one starts from a hard block, which as such, i.e. as an oligomer with amide groups, exhibits a crystalline structure at temperatures below the S mel~ing point.
The melting temperature of the segmented block copolymer of this embodiment is prefexably > 100C, more preferably > 150C, so as to guarantee optimum usability. The melting temperature can be set through the appropriate selection of n, Rl, R2, nd optionally R3.
It turned out that owing to the low concentration of non-flexible segments, which are dissolved in the soft or non-crystalline phase, the segmented block copolymer according to the invention exhibits a very good phase separation, i.e. a very good separation of the flexible and the non-flexible phases, while a low glass transition temperature of the soft or flexible phase is retained. Further, a high degree o~ ordering of the hard phase occurs. However, one of the most important properties of the products of the invention is that the course of the modulus at temperatures above the glass transition temperature of the soft phase depends on the temperature to a minor extent only. In practice it has been shown possible to employ service temperatures which are fairly close to the melting t~,l~erature of the hard, non-flexible phase.
To achieve a good impact resistance of the block copolymers according to this first embodiment of the invention, especially at low temperatures, it is essential for the glass - transition- temperature of the. soft blocks to be < OC, preferably < -.25C, and more preferably < -45C. ---The flexible block is formed by the usual flexible-..segments, which consist-of a, preferably difunctional',`l'inear polymer.having a molecular-weight.'of.200-4000.-This polymer''has rubbery-3 properties :after..incorporation-~:into the-;:-b'lock copolymers according to the invention, which~ is-~refIectëd~in 35 - it8- glass. transition ~tempera~ure, among.other things.
Particularly..-suitable a~e segments. of-~ pol'yesters-'and .
~' .

. ~ . . .

WO91/13930 2 0 7 7 ~ 8 3 6 PCT/NL91/~03~

polyethers, preferably based on ethylene oxide, propylene oxide, butylene oxide, copolymers, or block copolymers of two or more of those, or hydrogenated or unhydrogenated polybutadiene and polyisobutylene. In general the flexible segments may be hydroxyl-, carboxyl-, or amine - terminal.
Naturally, the nature of these terminal groups of the flexible block may affect the choice of the hard block, because certain combi~ations of terminal groups need not necessarily be reactive with all hard blocks.
In another embodiment of the invention the glass transition temperature of the block copolymer is > 0C.
These materials have typical engineering plastic properties and can also be used as fiber material.
It turned out that the segmented block copolymers according to this embodiment of the invention, i.e. with short uniform blocks and short non-crystallizable blocks, have a combination of a Tg > 0C, a Tg/Tm > 0.6 and a high crystallization rate.
The non-crystallizable segment preferably has a molecular weight of 20 to 400, more preferably of 40 to 250.
Particularly suitable. are aliphatic or alicyclic diols, diamine, aminoalcohols, diacids, .amino acids hydroxy acids hydroxyl-terminal chains and the like.
The melting tempera~ure of the segmented block copolymer of this embodiment of the invention is preferably > 160C so as to guarantee optimum usability. The melting temperature can be set by the appropriate selection of n, Rl, ~2 and R3.
In a third embodiment of the.-invention the glass transition temperature of th~ block copolymer'is > 130C. . .
-- It :turned. out. that such segmented block copolymers-- accordiug to the invention exhibit very good mechanical properties such -as tensile..strength,:~impact resistance, -dimiensional stability,-.-.good tribologic properties a~d~~a~'good --solve~t-resistance.-.~r .35 ~. - .,Further,-these products- have a~;high-modulus up~to~the~
-glass tra~sition temperature and a-reasonably high modulus - . . ~, -. - - . . . ..

- , . . . .. , . ~ ~ . . . .. .. . ..

WO91i13930 2 ~ 7 7 6 8 3 CT/NLg1/00036 between the glass transition temperature and the melting temperature if it is higher. Furthermore, the block copolymers according to this embodiment exhibit a good melt processability at temperatures which are only some tens of degrees above these two transition temperatures.
In practice it has been shown possible to employ service temperatures which come fairly close tO the melting temperature of the block copolymer.
The block copolymers according to this embodiment of the invention, which are built up from blocks with amorphous segments and with semi-crystalline segments have a glass-transition temperature of at least 130C, more preferably at least 150C. The melting temperature of the segmented block copolymer according to this embodiment is preferably > 200C so as to guarantee optimum usability. The melting temperature can be set by the appropriate selection of n, Rl, R2,and/or R3. The Tg/Tm ratio (in K) is preferably at least 0.6, more in particular at least 0.7, because then the temperature range, i.e. between Tg and Tm~ where the modulus decreases, is ~0 minimized.
The block copolymers according to this embodiment can be obtained with copolymers built up from segments with an irregular chain pattern and segments with a regular chain pattern. At service temperature these block copolymers have a multiphase structure, comprising one or more amorphous phases and a partly crystalline phase.
As segments for the amorphous phase, i.e. the phase with a low degree of order, one may use, -for example, alicyclic/aromatic diols, diamines, aminoalcohols, diacids amlnoacids andlor hydroxyacids with a molecular weight between 70 and 5000.
~, ~ As amorphous segments, for example, segments with a molecular weight of at least 70 are used, for example polyamides,- polyesters,-;amorphous est~rs,:;hydroxyl-terminal ketones,imides, amides,- for-instance. semi-aromatic ketones, wholly or partly aromatic esters, amides and imides. In general WO91/13930 2 ~ ~ 7 6 8 3 8 PCT/NL91/00036 it is advantageous to use segments which yield a high glass transition temperature.
Although for each embodimPnt disclosed hereabove the choice of the ~arious components for preparing the block copolymer has to be made independently, some general remarks about materials and conditions to be used can be made.
Materials and conditions mentioned below apply only in so far as they are not defined differently hereabove for the ~arious e~bodiments.
The value of n is preferably l or 2, because that permits the best possible uniform packing of the chain parts in the crystal. For Rl one can choose from an aliphatic, alicyclic or wholly or partly aromatic group, such as a paraphenyl-or a naphthyl group, depending on the dicarboxylic acid chosen. A
paraphenyl or a 2,S-, or a 2,6-naphthyl group is preferable.
R2 iS an aliphatic, alicyclic or wholly or partly aromatic group and preferably a lower, linear alkyl group with 2-8 carbon atoms. More preferably, ethylene, butylene, h~xylene or octylene groups are used because they yield the best results. For R3 preferably an aliphatic, aromatic, cycloaliphatic, aralkyl or alkaryl radical which may or may not be substituted is used.
In this connection the term ~aromatic group or wholly or partly aromatic group' includes groups in which two or more aromatic rings are connected with each other by a non-aromatic group, including non-hydrocarbon groups, such as ether bonds and ~he like.
: The preparation of the starting products for the segments can be carried out in known manner, by reacting the diamine and the dicarboxylic acid or derivative thereof. In a pre~erred embodiment, as a diamine preferably l,2-diami~oethane, - l,4-diaminobutane, l,`6-diaminohexane, 8-dia~inooctane or paraphenylenediamine- is--used. The ;:dicarboxylic acid to be used:is preferably~terephthalic acid, :but it is also possible to use 2,6-naphthalenecarboxylic:acid. --W~91/13930 9 2 ~ 7 ~ ~ 8 ~ PCT/NL91/~036 In a first variant of the invention, which concerns theuse of an ester-terminal block, a diester-diamide is prepared by reacting a diamine with a molar excess of diester of a dicarboxylic acid, such as dimethylterephthalate. In general it S will be preferable to use at least a double excess. The reac~ion is preferably carried out in the presence of a catalyst, such as Li (OC~3) . The use of a catalyst is not requisite, but generally does promote the reaction positively.
When the reaction is carried out starting from a mixture of all components, which is supplied to the reactor prior to the beginni~g of the reaction, if desired, a fairly large excess of diester can be used, optionally followed by a fractioning of the product obtained. ~owever, it is also possible to initially supply the diester and tO gradually add the diamine, sc that in principle there will always be an excess of diester present in the reactor. In such a case, it will be sufficient to use a small excess in the total amounts to be used. It is also possible to start from the diamine and p-carboalkoxy-benzoyl chloride.
To prepare the starting product for an amide-terminal crystallizable block in a second variant of the invention, ~
similar procedure may be followed, except that the diamine and the dicarboxylic acid are changed round.
A mixture of this starting product for the crystallizable block, and the starting product for the amorphous segment is then condensed to form a prepolymer. mis prepolymer can finally be after-condensed to form a segmented block copolymer with the desired properties.
- ~ For the prepolymerisation the conditions known from the 30 ' literature can be used. When the amorphous segment is hydroxyl-tenminal, 'the methods of preparing polyester-based segmented block copolymers can be used. When the amorphous segment is - amine-termlnal, the methods of- preparing polyamide;based '"segmented block copoiymers can be us'ed~
35 ;~ -' ;'Preferably the prepolymerisatio~ -is-carried out for 15-60 min at a temperature < 225C, at a pressure 2 0.75 bar, . . -.. :.. . :, :.- :; . .... . -., . ;: .. . .. . : . . ,~ .,, ,- . - . , , ,: . ...

WO91/13930 2 0 7 7 6 8 ~ lo PCT/NLgli~03~

followed by maintaining the temperature at a value of 2 200C
for at least 60 min, at a pressure < O.l bar. More preferably, this second phase can be carried out in such a way that first the temperature is raised to a value between 200 and 300C, at a press~re between lO and 50 mbar, for 10-45 min, and then is carried out at a temperature 2 220C and at a pressure < 5 mbar, for 45-120 min.
In a conventional manner the prepolymer thus obtained is after-condensed in solid state at a temperature between 150C
and a temperature of some degrees below the melting point of ~he polymer, in the presence of a noble gas.
The segmented block copolymers according to the in~ention can be processed into objects in the conventional manner, for example by injection moulding at a temperature above the melting point. The conventional techniques are also used for processing the present copolymers, where appropriate, to form fibres. Also, the conventional additives may be incorporated into the polymer, such as colouring matter, pigments, W stabilizers, heat stabilizers, as well as fillers, such as soot, silicic acid, clay or glass fibers. It is also possible to mix the products according to the invention with one ox more other plastics.
The in~ention will now be illustrated in and by the following Examples without prejudice to the scope of the invention.

- A segmented block-copolymer was prepared starting from a hydroxyl-terminal polytetramethylene glycol having a molecular . .
weight of 250, and a diester-diamide prepared in the following manner.
A mixture of l mol 1,4-diaminobutane and 2.5 mol dim~thylterephthalate was i~itially supplied to a reactor and then reacted in the presence of Li(0CH3). Thus a-diester-diamide with one diamide block was obtained,;terminated with : .
two diester blocks.

WO91/13930 112 ~ 7 7 6 8 ~ PCT/NL91/~036 The segmented block copolymer was prepared from thesetwo components by polycondensation for 30 min at 160C and 1 bar. Then the reaction product was heated to 250C and at that temperature condensed for 10 min by means of a vacuum created S by a water jet pump and for 60 min by means of a vacuum created by an oil vacuum pump (0.05 mm Hg).
The block copolymer obtained had an ~inh in m-cresol (0.5% solu~ion at 25C) of 0.65, a Tg (G~maX) at 39C, a Tm at 179C (measured in DSC at a heating rate of 20C/min, second heating) and a (Tm-TC) (difference in melting and crystallization temperature at heating and cooling rates of 20~C/min) of 10C.

- A segmented block copolymer was prepared in ~he manner described in Example 1 using the same diester-diamide and a mixture of diols. Per mole diester-diamide 0.5 mol hexanediol and 0.5 mol octanediol were used, dissolved in ethanediol. The block copolymer thus obtained had an ~inh of 0.42, and one of 0.49 after 24 h of after-condensation at 150C in the solid phase under nitrogen.
The block copolymer had a Tg of 103C, a Tm of 229C and a Tm-TC of 32C.
: :

A segmented block copolymer was prepared ln the manner described in Example 1 using the same diester-diamide and 1 mol 1',4-bis~hydroxy.methyl)cyclohexane dissolved in ethanediol per ' mol diester-diamide.'The~block copolymer thus obtalned had a ~iDh of 0-29, and one of 0.47 after 24 h of'after-condensation .
at 200C in'the solid'phà'se~'undér nitrogen.
30The block''copolymer'had a'Tg of 114C, a Tm of 231C and a Tm-Tc'of'19C. ` '~ ''` ~ ''' '` - '' " . ,, , .. , " , , ., ,, . , . . ~ . . . . . .. . . . ... . . . .. , .. . , ~ . .

WO91J13930 2 ~ 7 7 6 ~ ~ 12 PCT/NL91/~036 E~a~LE 4 an~ Com~rative Ex~m~les 1 a~~
A segmented block copolymer was prepared starting from a hydroxyl-terminal polytetramethylene glycol having a molecular weight of 700, and a diester-di~mide prepared in the following manner.
A mixture of 1 mol 1,4-diaminobutane and 2.5 mol dimethylterephthalate was initially supplied to a reactor and then reacted in the presence of Li(OCH3). Thus a dies~er-diamide with one diamide block was obtained, termi~ated with two diester blocks.
The segmented block copolymer was prepared from these two compcnents by polycondensation for 30 min at 160C and 1 bar. Then the reaction product was heated tO 250C and at that temperature further condensed for 10 min by means of a vacuum generated by a water jet pump and for 60 min by means of a vacuum generated by an oil vacuum pump (0.05 mm Hg).
The block copolymer (A) obtained had the properties listed in the Table.
For the purpose of comparison a product was prepared starting from the same diol, but with dimethylterephthalate only. The properties of the resultant polymer (B) are also listed in the Table. (Comparative Example 1) Further, a seg~ented block copolymer was made wlth 1 mol of the same polyether, 5 mol dimethylterephthalate and excess l,~-butanediol (12 mol). This is the comparative polymer C.
(Comparative Example 2) Further, torsion damping curves were made for these products. These curves are represented as Figs 1, 2 and 3, where Fig. 1 concerns the product according to the invention, and Figs 2 and 3 concern the comparative products B and C.
Thes~ Figures clearly show what the advantages are of the segmented block copolymer A according to the invention.
.
1 ':

.: . .-. . . .

WO 91/13930 13.! . , .~ PCT/NL91/00036 2~7~3~

- T~BLE
. ~ _ _ . __ . . .
Tg(C) Tm,2(C) Tkr(C) ~Hm,2Gi) Tlinh. ~(G') . . .. ~ ....... _ A -60 167 156 80.7 1.06 1.6 B -61 122 n.p. 32.3 1.58 7 : ~:
(Comp. .
C -57 183 155 55.9 0.44 2.?
10 (Com~. _ .
* G'20/G'lO0;Decrease in the modulus of shear between 20 and 100C :
~ Crystallization temperature; cooling rate 20C/min **~. Melting temperature; 2nd heating curve; heating curve 20C ::
~*~ Not perceptible Calculated on the hard phase : :

.
.. . ..
.~ ., ,. . . ... . ~ . . ... " , .. . . . -, ~ . , .. -. . - r - -' ' '. , ' ', ~ l' " , ", ' ,, ~ ' ,' ', ' , ',- ,',' ', '"~''""~ '"; " ~, , " , ~

Claims

1. A segmented block copolymer comprising non-crystallizable segments and partly crystallizable segments, in which the partly crystallizable segments have the following formula:
-NH-R2-NH- [C(O)-R1-C(O)-NH-R2-NH]n--C(O)-R1-C(O)-[NH-R2-NH-c(O)-R1-C(O)]n-and/or -NH-R3-C(O)- or a reaction product thereof with a diamine or a dicarboxylic acid or a derivative of a dicarboxylic acid, in which formula n is an integer which equals 1, 2, or 3, each of R1 and R2 are independently an aliphatic, an alicyclic, or a wholly or partly aromatic group, and R3 is a hydrocarbon radical which may or may not be substituted, and in which block copolymers the partly crystallizable segments have a substantially uniform block length.

2. A block copolymer according to claim 1, wherein that at least 70%, and preferably at least 85% of all partly crystallizable blocks have the same length.

3. A block copolymer according to claim 2, wherein that at least 90%, and preferably at least 97.5% of all partly crystallizable blocks have the same length.

4. A block copolymer according to claim 1-3, wherein it is a fast crystallizing material.

5. A block copolymer according to claim 1-4, wherein the melting point is at least 100°C, and preferably at least 150°C.

6. A block copolymer according to claim 1-5, wherein the melting point is at least 160°C, preferably at least 200°C.

7. A block copolymer according to claim 1-6, wherein the glass transition temperature of the flexible blocks is < 0°C.

8. A block copolymer according to claim 7, wherein the glass transition temperature of the flexible block is < -25°C, and preferably < -45°C.

9. A block copolymer according to claims 1-8, wherein R1 is a paraphenyl or a naphthyl group.

10. A block copolymer according to claims 1-9, wherein R2 is a C2-C8-alkyl group.

11. A block copolymer according to claims 10, wherein R2 is an ethylene, a butylene, a hexylene or an octylene radical.

12. A block copolymer according to claims 1-6, wherein its glass transition temperature is > 0°C.

13. A block copolymer according to claim 12, wherein its glass transition temperature is > 40°C.

14. A block copolymer according to claim 12 or 13, wherein the non-crystallizable block has an average molecular weight of 20 to 400, preferably of 40 to 250.

15. A block copolymer according to claims 1-6, wherein its glass transition temperature is > 130°C.

16. A block copolymer according to claim 15, wherein the Tg/Tm ratio (in K) is at least 0.6, preferably at least 0.7.