AU629003B2

AU629003B2 - Cryoextensible thermoplastic elastomer, process for its preparation

Info

Publication number: AU629003B2
Application number: AU58619/90A
Authority: AU
Inventors: Michel Glotin; Emmanuel Okoroafor; Jacques Rault
Original assignee: Atochem SA
Current assignee: Arkema France SA
Priority date: 1989-07-04
Filing date: 1990-07-03
Publication date: 1992-09-24
Anticipated expiration: 2010-07-03
Also published as: JPH0747635B2; FR2649402A1; NO902965D0; PT94577A; CA2020290A1; FI903353A0; DD300107A5; KR940002186B1; IE902414A1; AU5861990A; JPH0350231A; EP0409678A1; NO902965L; FR2649402B1; KR910002958A

Description

Association.

Registered Patent Attorney To: THE COMMISSIONER OF PATENTS.

WATERMARK PATENT TRADEMARK ATTORNEYS i rl I i-'9 r r

I

Ai 777 i Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: S' Priority Related Art Related Art 629003 Name of Applicant

ATOCHEM

Address of Applicant Actual Inventor: 'Address for Service 4 8, Cours Michelet, La Defense 10, 92800 Puteaux, France MICHEL GLOTIN, JACQUES RAULT and EMMANUEL OKOROAFOR WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO. 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Complete Specification for the invention entitled: CRYOEXTENSIBLE THERMOPLASTIC ELASTOMER, PROCESS FOR ITS PREPARATION The following statement is a full description of this invention, including the best method of performing it known to :-us

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respect of the invention the subject of the application.

DECLARED th is d ay o f J n e L a 0 4 e 3 CouArs Mich.eleti S;gaturc. laude TREUIL 2800 PUTUX Frnce S f :R Nanir-r9-t2 7Q r9 0 80 I .T l 1 1 1 'Ij 1, I I 1 CRYOEXTENSIBLE THERMOPLASTIC ELASTOMER, PROCESS FOR ITS PREPARATION The present invention relates to the thermoplastic elastomers which are cryoextensible, that is to say which exhibit a macroscopic dilation on cooling after drawing.

Low-temperature dilation phenomena have been observed in the case of drawn rubbers Smith, C.P. Saylor, Bur. Stand. J. Research, 21, 257 (1938)), and in the case of crosslinked and drawn polyethylene Machin, A. Keller, J.

Macromol. Sci., (Phys.) B1(1), 41 (1967).

1 0 The invention relates firstly to thermoplastic elastomers whose characteristic is that of being cryoextensible.

In its broadest aspect the invention provides a thermoplastic elastomer characterised in that said elastomer is cryoextensible in a reversible and reproducible manner and consists of block or multisequence copolymers which comprise rigid 1 5 sequences and crystallizable flexible sequences.

The crystallizable flexible sequences are intended to mean sequences or blocks which are not crystalline at room temperature or whose degree of crystallinity is lower than or equal to approximately 0.5 times that of the homopolymers of the same chemical nature and of the same molecular mass as the said sequences, cooled under the 20 same conditions from the molten state to room temperature at a rate of approximately S"4 44 4 t 94

C

II.

So a t e E 4 is 4 t^LA L i These flexible sequences can, for example, be crystallized by drawing and/or at low temperature.

In the present application, room temperature corresponds to a temperature range of between 15 and 400C, and in general close to 200C.

Drawing is intended to mean a uniaxial or tensile stress applied to a sample, which produces an elongation of the latter in the drawing direction.

The expression "cooling to low temperature" means that the sample is taken to a temperature below room temperature, generally between 20 and -100°C and preferably between 20 and -400C.

The crystallizable flexible sequences of the thermoplastic elastomers according to the invention most preferably consist essentially of polyether and/or polyester, preferably of high molecular weight (Mn 2 1000 and preferably Mn 2 2000) though other polymers may be used.

In addition to the crystallizable flexible sequences, these thermoplastic 1 5 elastomers contain rigid sequences or blocks of a thermoplastic nature alternating with flexible sequences which form the nodes of thermally reversible physical crosslinking.

The rigid sequences of the cryoextensible thermoplastic elastomers are preferably based on polyurethane, polyester and/or polyamide though other polymers may be used.

It is important that the segregation between the flexible sequences and the rigid sequences should *a o tIP Ci 3 be sufficient to permit the crystallization of the flexible sequences, in other words that the structural defects linked with the copolymerization of the various sequences should not prevent the crystallization of the crystallizable flexible sequences.

In the case of a thermoplastic elastomer whose rigid sequences are crystalline, such as polyamide or polyester sequences, it is desirable that the difference between the melting temperature of rigid sequences within the copolymer and the melting temperature of these same sequences before copolymerization should not be greater than approximately 1000 and preferably than The low-temperature elongation or cryoextensibility of the thermoplastic 1 0 elastomers in accordance with the invention and drawn uniaxially can attain 20% of the dimension along the drawing axis after drawing and relaxation.

As will be understood, cryoextensibility is reversible, that is to say that when the thermoplastic elastomer is brought back to room temperature it regains its permanent dimensions, that is to say those which it had after drawing and relaxation 1 5 (and/or annealing) and before cooling.

This reversibility is reproducible: each time the thermoplastic elastomer is cooled it will elongate and, when returned to room temperature, it will regain its permanent dimensions.

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Ttc l 1C 0 lsoesi codnewt h neto addanuixal a tan2%o h dimensio aln h rwn xsate rwn neaain 4 As an example of thermoplastic elastomers there may be mentioned: polyurethane-based block copolymers which may be obtained by a combined reaction of a diol of high molecular mass which constitutes the crystallizable flexible sequence of the elastomer, with a diisocyanate and a diol of low molecular mass, which give rise to the rigid sequence, SC polyester-based block copolymers such as 10 those obtained by copolymerization of a polybutylene S(PBT) or of a polyethylene terephthalate (PET) which constitutes the rigid and crystalline sequences and of a glycol of low molecular weight (butanediol, diethylene glycol) which, in combination with a 15 polyalkylene ether glycol forms the crystallizable 4 i flexible sequence, 4.

the polyamide-based block copolymers whose rigid sequences consist of polyamide and the crystallizable S flexible sequences of polyether, also called polyetheramides.

These block polyether amides can result especially from the copolycondensation of polyamide sequences containing reactive ends with polyether sequences containing reactive ends, such as, among others: a) polyamide sequences containing diamine chain ends with polyoxyalkylene sequences containing dicarboxylic chain ends; b) polyamide sequences containing dicarboxylic chain ends with polyoxyalkylene sequences containing diamine chain ends, obtained by cyanoethylation and hydrogenation of aliphatic alpha,omega-dihydroxylated polyoxyalkylene sequences, called polyetherdiols; c) nolyamide sequences containing dicarboxylic chain ends with polyetherdiols, the polyetheramides obtained being, in this particular case, polyetheresteramides, which are particularly preferred by the Applicant Company.

The composition and the manufacture of such polyetheresteramides have been described in French patents No. 74/18913 and 77/26678 in the name of the Applicant Company and the content thereof is added to the present description.

The number-average molecular mass of these polyamide sequences is generally between 500 and 10,000 and more particularly between 600 and 5,000. The polyamide sequences of the polyetheresteramides are preferably made up of polyamide 6, 66, 612, 11 or 12 and/or of amorphous polyamide or of copolyamide resulting from the polycondensation of their monomers.

The number-average molecular mass of the polyethers is generally between 1,000 and 10,000 and preferably higher than 2,000.

The polyether sequences preferably consist essentially of polytetramethylene glycol (PTMG). In 6 addition to PTMG, they may, for example, contain polyethylene glycol (PEG) and/or polypropylene glycol

(PPG).

The inherent viscosity of the polyetheresteramides is advantageously between 0.8 and 2.05. It is measured in meta-cresol at 20 0 C with an initial concentration of 0.5 g of polymer per 100 g of metacresol.

The polyetheresteramides may be made up of to 85 by weight of polyether, and of 90 to 15 by weight of polyamide, and preferably of 30 to 80 by weight of polyether and of 70 to 20 by weight of S" polyamide.

The polyetheresteramides which are preferred by the Applicant Company are those in which the polyamide "4 15 sequences are derived from polyamide 12 and in which S":t the polyether sequences are derived from PTMG.

i. The invention also relates to a process for the preparation of the cryoextensible thermoplastic elastomers such as defined above.

According to this process, the sample of thermoplastic elastomer is subjected to a uniaxial tension resulting in a deformation which is lower than that leading to the failure of the sample for example with the aid of a tensometer.

The operation is generally carried out at a temperature of between 20 and 120°C and preferably between 20 and 70 0

C.

7 The drawing speed is generally between 1 and 500 mm/min.

The initial drawing E of the sample is equal to the ratio: length of the sample after drawing initial length E 100 Ir initial length i these two lengths being measured in the drawing direction.

,10 It can go up to 1,000 but is preferably between 100 and 400 When the sample is highly drawn (drawing a 400 the flexible sequences are crystallized during *ir the drawing, and this has the effect of significantly 15 decreasing the degree of cryoextensibility.

However, the crystallization under drawing can also be avoided by drawing at elevated temperature (a 70°C) and/or by performing an annealing of the sample during the relaxation at a temperature above the melting temperature of the crystallizable flexible sequences.

By way of example, in the case of the polyether sequences based on PTMG, the annealing is carried out at approximately Once the sample is drawn, it is relaxed for at i 8 least 1 min and preferably at least 5 min at a temperature which is generally between 20 and 120 0

C,

and preferably at room temperature.

The permanent elongation Ep is equal to the ratio: (Length of the sample after (initial length) drawing and relaxation) Ot q t Ep x 100 initial length 4$ 10 these two lengths being measured in the drawing direction.

The permanent elongation is generally smaller "o t than the initial drawing, and this is so whatever the value of this initial drawing. It increases with the 15 intensity of the initial drawing and also when the proportion of the rigid sequences within the thermoplastic elastomer increases.

The sample is then cooled to low temperature.

The operation can be carried out gradually or very rapidly by performing a kind of quenching.

No elongation of the sample is then found, except in the drawing direction.

The order of magnitude of this cryoelongation can be up to 20 of its permanent dimension.

The thermoplastic elastomers in accordance with -i 9 the invention may be employed in many applications, especially in the form of objects, films, etc. moulded, extruded and/or injection-moulded in temperature ranges where the cryoextensibility is produced.

By way of an example of application it is possible to mention seals employed at low temperature: these are moulded, drawn, relaxed and installed at room temperature.

it* By choosing the initial drawing judiciously it 1' will be possible to obtain a cryoelongation of the said seal ensuring a perfect leaktightness of the connection.

The following examples illustrate the invention without, however, limiting it: 15 EXAMPLE 1 4 Dumbbell-shaped test pieces in accordance with ASTM standard D638 type 4 are cut from plaques of various samples of polyetheresteramide in which the crystallizable flexible sequences consist of PTMG and the rigid sequences of polyamide 12.

Table I below shows the number-average molecular masses of the flexible and rigid sequences of the samples studied and the weight quantity of PA-12 in the sample.

1 TABLE I Ctf t 4 1 4 444 4 r.t 4 444 Sample No. PTMG Mn PA-12 Mn Weight of PA-12 in the copolymer A 2,000 600 23 B 2,000 850 29.8 C 2,900 850 22.7 D 2,900 1,200 29.3 The test pieces from samples A to D are then drawn uniaxially in accordance with standard D638 at room temperature.

The samples are subjected to an initial drawing E of between 100 and 500 and the permanent elongation Er is measured after relaxation at room temDerature for 5 min.

The results of the measurements are combined in Table II.

4$ 44 44 4 4 s~i- 11 TABLE II 'crr 4 4 41 L Q 4 4444 4 4 44r r f 44 4 ar S 1$4* 4 4i *L I 10 Initial drawing Permanent elongation Er of sample No.

E A B C D 100 7 13 11 300 90 132 107 147 500 221 265 250 300 The drawn test pieces are cooled and then relaxed from room temperature to -40"C, the rate of cooling being 15 The change in length 6(L) in the drawing direction is measured as a function of the temperature and for various values of the preliminary drawing (of between 0 and 700 6(L) is equal to the difference between the length of the sample at the cooling temperature T and the length of the sample at room temperature after drawing and relaxation.

Figure 1 expresses the curves of change in length 6(L) for a given initial drawing.

It is seen that in the case of an initial drawing lower than 100 there is a contraction of the sample a 0).

%i 12 It is also noted that, whatever the initial drawing applied 100 the maximum increase in length 6(L) is produced at a temperature of approximately And the maximum increase in length 6(L) corresponds to an initial drawing of the order of 350 Also determined for each drawn sample is the cryoelongation X between 20'C and -40°C and along the ,tt drawing axis: t length at -40°C length at '10 X x 100 length at 20 C the length at 20°C corresponding to the length after drawing <rtn' and relaxation at room temperature.

C It is observed that in the case of the polyether- 15 esteramide of sample A there is no cryoelongation in the case of an initial drawing lower than 100 The results are expressed in Table III below.

.i ~jjj 13 TABLE III E 0 -2.12 100 -2.56 200 1.67 350 5.82 500 3.9 700 2.22 d~lzf~ .4 .10

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*4 4 4 'I 44 4 4 EXAMPLE 2 V 15 4i 4 .4 4 4.

4 4 44* U* V.

4 4

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The samples B, C, and D are taken again and are drawn and relaxed as indicated in Example 1.

Each drawn sample is then cooled from 20*C to -40*C, also in the some conditions as those described in Example 1.

6(L) is measured and X, as defined in Example 1, is determined as a function of the initial drawing

E.

The curves of X as a function of the initial drawing E are plotted in Figure 2.

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Claims

1. Thermoplastic elastomer characterised in that said elastomer is cryoextensible in a reversible and reproducible manner and consists of block or multisequence copolymers which comprise rigid sequences and crystallizable flexible sequences.

2. Thermoplastic elastomer according to Claim 1, characterised in that the number average molecular mass of crystallizable flexible sequences is higher than or equal to 1,000.

3. Thermoplastic elastomer according to claim 2 characterised in that the number average molecular mass of crystallizable flexible sequences is greater than or equal to 2,000.

4. Thermoplastic elastomer according to any one of claims 1 to 3, characterised in that the crystallizable flexible sequences are based on at least one member of the group consisting of polyether and polyester. Thermoplastic elastomer according to any one of the preceding claims characterised in that the crystallizable flexible sequences are based on polytetramethylene glycol.

6. Thermoplastic elastomer according to any one of the preceding claims characterised in that the rigid sequences are based on at least one member of the group consisting of polyester and polyamide.

7. Thermoplastic elastomer according to any one of the preceding claims characterised in that it is of the polyetheresteramide type. S* S S 4 4, 4 t t I 1 1 I I I I. l i i B I 14a

8. Thermoplastic elastomer according to any one of claims 1 to 3 comprising rigid sequences based on (co)polyamide or on a mixture of aliphatic polyamide(s), and crystallizable flexible sequences consisting of polytetramethylene glycol.

9. Process for the manufacture of a thermoplastic elastomer such as defined in any one of Claims 1 to 8, characterised by the following stages: the said elastomer is drawn uniaxially at room temperature; it is relaxed either at room temperature or by carrying out an annealing; the thermoplastic elastomer is cooled to low temperature. Process for the manufacture of a thermoplastic elastomer according to claim 9, characterised in that the initial drawing is less than or equal to 1,000

11. Process for the manufacture of a thermoplastic elastomer according to claim 8 characterised in that the initial drawing is between 100% and 400% .4 I I 4, SIl i i 4 t i J( the production of moulded, extruded and/or injection-moulded objects or film.

13. Use of a thermoplastic elastomer as defined in any one of claims 1 to 8 for the production of moulded, extruded or injection moulded objects or films in the temperature region where cryoextensibility is produced. DATED this 29th day of June, 1992. ATOCHEM WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA 4 4 Ir C t 44 44 4