Urethane Chemistry and Applications - American Chemical Society

35 A New Aromatic D i o l Chain Extender for Urethane Elastomers D. KLEMPNER and K. C. FRISCH

Downloaded by EAST CAROLINA UNIV on October 27, 2014 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0172.ch035

Polymer Institute, University of Detroit, Detroit, MI 48221

A significant effort has been carried out in recent years on chain extenders for urethane elastomers. This has been prompted primarily by the search for a suitable replacement for 4,4'-methylene bis(o-chloroaniline) (MOCA), a widely used chain extender and curing agent which gives a positive Ames test (screening test for mutagenicity). A number of different hindered diamines have been inves tigated as a substitute for MOCA (1). In addition to diamine curing agents, which are used most frequently with elastomers based on polyether polyols and toluene diisocyanate (TDI), prepolymers based on polyether or polyester polyols and 4,4'diphenylmethane diisocyanate (MDI), can be cured with diols to yield elastomers with similar properties to those of diaminecured polyester-TDI elastomers. The most common chain extender is butanediol. However, to achieve improved mechanical proper ties, especially at elevated temperatures, aromatic diols are often used. The most common one is hydroquinone di-(beta-hydroxyethyl) ether (HEQ). One basic problem with HEQ is its high melting point (102ºC). As a r e s u l t , the chain extension process must take p l a c e above 102 C, normally around 120 C. I f lower temperatures are used, " s t a r r i n g " ( c r y s t a l l i z a t i o n or p r e c i p i t a t i o n of t h i s c u r a t i v e out of the system) occurs, s i n c e HEQ i s not s o l u b l e i n the r e s t of the components at temperatures below i t s m e l t i n g p o i n t . In order to a l l e v i a t e these processing problems, the meta-substituted analog of HEQ was s t u d i e d . This m a t e r i a l , r e s o r c i n o l d i - ( b e t a - h y d r o x y e t h e l ) ether (HER ) has a lower m e l t i n g p o i n t (89 C ) , due to the l a c k of symmetry i n the molecule. In t h i s study, the p r o p e r t i e s and processing of e l a s tomers cured w i t h HER were compared w i t h those cured w i t h HEQ. Studies were made u s i n g a v a r i e t y of prepolymers and catalysts.

0097-6156/81/0172-0533$05.00/0 © 1981 American Chemical Society

In Urethane Chemistry and Applications; Edwards, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

534

URETHANE CHEMISTRY AND

APPLICATIONS

Experimental


M a t e r i a l s . The m a t e r i a l s used are d e s c r i b e d i n Tables I and I I . A l l m a t e r i a l s were used as r e c e i v e d , w i t h no further p u r i f i c a t i o n . The t e n t a t i v e s p e c i f i c a t i o n s of HER are as f o l l o w s : Appearance

White to tan f l a k e

Hydroxyl number

547-545

E q u i v a l e n t wt.

99.1

M o l e c u l a r wt., e m p i r i c a l

198.2

M e l t i n g p o i n t , °C

89 min.

B o i l i n g p o i n t , °C/5

206-212

Water content

0.1 wt. %,

max.

S o l u b i l i t y 25°C, approximate wt. %: Water

2

Acetone

11

Ethanol

13

E t h y l acetate

3

Benzene

^

1

Hexane

^

1

S p e c i f i c heat

0.25

cal/°C/gm

Melt d e n s i t y

1.16

gm/cc at 100°C

Melt v i s c o s i t y

13.50

cc at 100°C

Elastomer P r e p a r a t i o n Phase I . In t h i s phase of the study, the f e a s i b i l i t y of chain extending polyurethane elastomers w i t h HER was determined. A v a r i e t y of elastomers were prepared by chain extending the f o l l o w i n g prepolymers w i t h HER (see Table I f o r t h e i r chemical d e s c r i p t i o n s ) ;



35.

KLEMPNER AND FRiscH

Aromatic Diol Chain Extender

535

Eq. Wt.

Appearance at 75°

750

636.36

liquid

3..15

2900

1333.33

solid

B-635

7 .7

430

545.46

liquid

B-665

9 .55

540

439.79

liquid

V-6001

3 .23

3000

1300.31

solid

V-6012

6 .68

1000

628.74

solid

Polyether

% NCO

B-625

6 .6

B-605

V i s c o s i t y cps

Polyester

The c a t a l y s t used was Dabco 33LV ( t r i e t h y l e n e diamine) P r e l i m i n a r y s t u d i e s i n d i c a t e that Dabco 33LV i s an e f f i c i e n t c a t a l y s t f o r HER . Although there i s i n d i c a t i o n of good s t a b i l i t y of 33LV i n HER , the true s t a b i l i t y and r e t e n t i o n of a c t i v i t y are unknown. Elastomers were prepared using 0.06% by weight (based on HER ) Dabco 33LV as a c a t a l y s t . A 105 isocyanate index was used (95% s t o i c h i o m e t r y ) . The prepolymer and the c h a i n extender were heated to 120°C. When the c h a i n extender was completely melted, they were mixed together w i t h the r e g u i r e d amount of c a t a l y s t . The mixing temperature was 105-110 C. Castings were made using metal p l a t e s and a spacer on a heated p l a t e n p r e s s . Two cure temperatures were employed, 115 C and 130 C. The mold residence time was 1 hour. T h i s was f o l l o w e d by a post cure a t 100 C o v e r n i g h t . Green s t r e n g t h measurements were a l s o c a r r i e d out on each prepolymer. Phase I I . I n t h i s phase, polyurethane elastomers were prepared using o n l y one prepolymer, B-625, and s e v e r a l c a t a l y s t s and c o n c e n t r a t i o n s i n order to determine the optimum p r o p e r t i e s p o s s i b l e w i t h HER Phase I I I . I n t h i s phase a d i r e c t comparison of HER w i t h HEQ was made. Elastomers were prepared as above using both p o l y e t h e r and p o l y e s t e r prepolymers and both HER and HEQ as c h a i n extenders. No c a t a l y s t was used. The mixing temperature was 120 C. The elastomers were cured f o r o n e hour i n the mold a t 130 C and post-cured overnight a t 100 C. Q

Phase IV. I n t h i s f i n a l phase, the lowest p o s s i b l e p r o c e s s i n g temperatures f o r HER and HEQ extended elastomers were determined as w e l l as the pot l i v e s . Combinations of


536

URETHANE CHEMISTRY AND APPLICATIONS

TABLE I


PREPOLYMERS AND CHAIN EXTENDERS

Designation

Description

Vibrathane B605

A prepolymer based on d i pheny1-me thane diisocyanate (MDI) and polytetramethylene glycol

Vibrathane B625

%Isocyanate

Eq. Wt.

Supplier

3.02

1333

Uniroyal

Above

6.42

636

Uniroyal

Vibrathane B635

Above

7.97

545

Uniroyal

Vibrathane B665

Above

9.39

440

Uniroyal

PCA 6-3

Above

6.-6.6

635-690

Polyurethane Corp. of America

Vibrathane V6001

An MDI-terminated polyester prepolymer

3.23

1300

Uniroyal

Vibrathane V6012

Above

6.33

629

Uniroyal

HEQ

Hydroquinone d i (beta-hydroxyethyl) ether Tennessee Eastman

HER

R e s o r c i n o l d i (beta-hydroxyethyl) ether

Koppers


35.

KLEMPNER

AND FRiscH


TABLE I I


CATALYSTS Designation

Description

Supplier

Dabco 33LV

33% S o l u t i o n of triethylene diamine i n dipropylene glycol

A i r Products

Dabco

Triethylene

diamine

A i r Products

Dabco WT

S a l t of d i e t h y l e n e t r i a m i n e and formic acid

A i r Products

Armeen DMOD

P r o p r i e t a r y amine

Armak

T-9

Stannous octoate

Μ & Τ Chemicals

T-l

Dibutyltin

diacetate

Μ & Τ Chemicals

T-12

Dibutyltin dilaurate

M & Τ Chemicals

T-31

Dibutyltin isooctylmercaptoacetate

M & Τ Chemicals

T-20

Dibutyltin dilaurylmercaptide

C o t i n 222

Proprietary organotin

M & Τ Chemicals Cosan Chemical



538

URETHANE

CHEMISTRY A N D APPLICATIONS

HEQ and HER were a l s o s t u d i e d i n order to see i f a minimum azeotrope might r e s u l t to allow even lower processing tempera tures . Elastomers were made from B-625 at v a r i o u s i n i t i a l mixing temperatures, using an isocyanate index of 1.05. The prepolymers and the chain extenders were both heated to temperatures ranging from 130 C to as low as 70 C i n some cases, and mixed w i t h no c a t a l y s t . Temperature i n t e r v a l s o f 10 C were used and the c r y s t a l l i z a t i o n and s t a r r i n g tendencies of HER and HEQ elastomers were determined as w e l l as the pot l i v e s . ο Only one cure temperature was used, 130 C. The mold residence time was one hour. This was f o l l o w e d by a post cure of 100 C o v e r n i g h t . No t e s t i n g was performed on the samples. Test Methods The elastomers made a f t e r being aged and c o n d i t i o n e d f o r one week were subjected to the f o l l o w i n g t e s t s t o determine t h e i r p h y s i c a l p r o p e r t i e s : 1. S t r e s s - s t r a i n p r o p e r t i e s (ASTM D 412) Tensile strength, p s i E l o n g a t i o n at break, % Elongation set, % 2. Tear r e s i s t a n c e (ASTM D 1938) S p l i t tear Die C 3. Shore hardness (ASTM D 2240) Durometer A Durometer D 4. Bashore rebound (ASTM D 2632) 5. Compression s e t % , (ASTM D 395), Method Β The green strengths of the Phase I elastomers were determined by measuring the mechanical p r o p e r t i e s immediately a f t e r demolding. R e s u l t s and D i s c u s s i o n Phase I : The p r o p e r t i e s of the phase I elastomers are shown i n Tables I and I I . The mechanical p r o p e r t i e s of a l l the elastomers, both p o l y e t h e r based (Table I I I ) and p o l y e s t e r based (Table IV) were, i n g e n e r a l , comparable w i t h convention a l l y chain extended MDI-based polyurethane elastomers ( 3 ) . In g e n e r a l , the higher p r o c e s s i n g temperature (130 C) r e s u l t e d i n elastomers w i t h s u p e r i o r p r o p e r t i e s . The green s t r e n g t h s t u d i e s (Tables V and VI) showed that even s h o r t e r mold residence times could be used to o b t a i n



Β 605

868 156 544 34 42

834 191 505 34 32

111 379 42 25

180 358 38 32

104 176 51 34

114 191 51 18

107 148 64 46

141 206

61 46

Bashore rebound Compression s e t , %

3424 4169 4393 245 9.5

415

3406 4503 5081 274 11.3

414

1323 2248 3451 471 29

340

1282 2804 4372 463 22

95 66

390

1057 1745 3387 589 20.3

96 65

309

965 1572 3303 604 20.4

92 44

316

485 841 3231 646 15.1

91 44

88 39

88 39

76 24

9/11 79/11

11/110 81/130

16/115 68/115

17/130 75/130

9/115 60/115

16/130 54/130

23/110 64/115

Β665

Β 665

Β 635

Β 635

Β 625

Β 625

Β 605

Tear r e s i s t a n c e : Graves, p i ( d i e C) Split Initial, pi Max., p i

510 820 3363 742 21.2

35/110 min/°C mold, min/ C 109/130 Properties: 77 Hardness 24 Hardness

Stress-strain: 100% M, p s i 300% M, p s i TS, p s i Elongation, % Elongation set, %

Pot l i f e , Cured i n Physical Shore A Shore D

Prepolymer:

PROPERTIES OF PHASE I ELASTOMERS - POLYETHERS

TABLE I I I


S

te

ο

So

2

α

>

w

*ϋ

Μ

r


32 52 42 4 27 28

32 35

Bashore rebound Compression s e t , %

>

96 214

Η Ο 2

> *ϋ r ο >

Ο

H 5β •

Χ

H

m

*s

ci

CO

432 879 3612 697 8.9

76 31

93/130

20/105

V 6001

Ο

257 254

425 667 3546 721 15

443

1411 3499 5360 418 8.7

446

1204 2629 4440 451 10.3

76

7/115 60/115

V 6001

Tear r e s i s t a n c e : Graves, p i (die C) Split Initial, pi Max., p i

Stress-strain: 100% M, p s i 300% M, p s i TS, p s i Elongation, % Elongation set, %

90 46

12/100 42/115

12/100 47/130

Pot l i f e , min/°C Cured i n mold, min/ C Physical Properties: Shore A Hardness Shore D Hardness 93 48

V 6012

V 6012

Prepolymer:

PROPERTIES OF PHASE I ELASTOMERS - POLYESTERS

TABLE IV



KLEMPNER AND FRISCH

m

vO vO PQ


m

CO P4 ω

vO vO

>-

Η rJ PQ

- rH Ο • Ο

ο CO W

M H

Ctf

H

PH

Ο

çù P-i

m

CM νΟ PQ

rH Ο r H CM rH

o\

CM rH

Ο

Ο

Urethane Chemistry and Applications - American Chemical Society

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