On the synthesis of some heterochain polymers in diene elastomers

ON T H E S Y N T H E S I S OF SOME H E T E R O C H A I N POLYMERS IN D I E N E E L A S T O M E R S * D. B. BOGUSLAVSKII, G. M. LEVIT, K. V. BOGUSLAVSKAYA,

KH. 1~. BORODUSHKL~A and S. A. UVAROVA Dnieprepetrovsk Branch of the Tyro Industry Research Institute Dniepropetrovsk Tyro Factory

(Received 18 June 1973) Polyarylates and polyurethanes were synthesized in dienc clastomers. Results of electron microscope examinations sho.w that the polyurethanes formed in an elastomer medium have a globular structure. Polymers differing in their viscosities and melting points were obtained, depending on the nature of the reagents used for the synthesis. The effectiveness of the modification of carbochscin elastomer by polyarylates and polyurethanes is reflected in considerably increased stress values at fixed elongations, as well as higher tensile strength, and higher values obtained for the hardness and puncture strength of the ~flcanizates, along with improved fatigue strength under repeated flexing. Compositions containing rubbers and rigid chain polyarylates have increased heat resistance and thermooxidative stability.

I~ ~.CE~T years polyarylates and polyurethanes have been of interest to authors investigating their use as modifying additions for vuleanizates with a view to the production of articles combining the special characteristics of elastomers and plastics. Extensive use of compositions of this type discouraged by the high softening points and by the incompatibility of heterochain and diene polymers owing to major differences in the chemical nature of the molecular chains. It was found in previous investigations [1, 2] that it is possible to prepare combined systems of elastomers with polyamides synthesized from the monomers directly in a highly viscous rubber medium, and that polymers prepared in this way have increased hardness and higher resistance to heat and wear, as well ~s good fatigue strength under repeated deformations. This paper relates to features of the preparation of compositions of rubbers with polyarylates and polyurethanes. EXPERIMENTAL

Polyarylates were prepared by polycondensation of diearboxylic acid dichlorides with dihydric phenols nCIOC--I~--COC1 + n i l e - - A t - - O H - , (--OArOOC---I%--Co)~ + 2nHCI through mechanical treatment of butadione-styreno rubber with reagents in a mixer at high (175 °) and relatively low (50 °) temperatures in the presence of triethylamine, as catalyst, * Vysokomol. soyed. A16: No. 11, 2560-2564, 1974. 2976

On synthesis of some heterochain polymers in diene elastomers

2977

for 10-15 min. The concentration of the monomers was 0.020 mole/100 g rubber, molar ratio 1 : 1. The a m o u n t of catalyst introduced was 2 moles per mole dicarboxylic acid di, chloride [3]. The reagents used for synthesis of the polyurethanes were dimerized 2,4-toluylenediisocyanate combined with glycerin, or ~'ith a polyester of adipic acid and ethylene glycol with O t t endgroups, or with a molecular complex of resorcinol with hexamethylenetetramine (resotropine). The polyethylene glycol adipate had m. p. 50% M = 1 8 7 0 , acid n u m b e r 0.3, water content 0.1%. Crosslinking in the linear polyurethane containing the oligomeric polyester and the diisocyanate was effected b y means of glycerin and a molecular complex of resorcinol and hexamethylenetetramine. As the dissociation temperature for dimerized 2,4-toluylenediisocyanate is in the region of 150-160 °, the butadiene-styrene elastomer was treated with the reagents at 165 ° in a mixer with a rotor speed of 60 rev/min for 10 min. The crosslinking agent was introduced at the end of the mixing cycle. The investigations were carried out with the following concentrations and molar ratios of the components: glycerin (or resotropine) : dimer ~- 1 : 1, concentration 0-030 mole/100 g rubber; otigomeric polyester : dimer~-1 : 1, concentration 0.005 mole/100 g rubber; oligomeric polyester : dimer : crosslinking a g e n t = 1 : 2 : 1, concentration 0.005 mole polyester per 100 g rubber. Removal of the polyarylates was done by extraction of the elastomer treated with the monomers, with benzene at room temperature u n t i l the rubber phase had dissolved. The polyarylate that separated out was washed with acetone to remove unreacted monomers and triethylamine hydrochloride, followed b y alternating washing with alcohol a n d distilled water, followed by v a c u u m drying at 50 ° . Polyurethanes were extracted from a 60% sulphuric acid composition for 3 days with i n t e r m i t t e n t stirring. Polymer was precipitated from the filtrate with water, and was washed to obtain a neutral reaction, followed b y v a c u u m drying at room temperature. The viscosity of the heterochain polymers was determined in an Ostwald viscosimeter at 30 ° in a tetrachloroethane-phenol mixture (40 : 60) in the case of the polyarylates, and in 60% sulphuric acid in the case of the polyurethanes. The I R spectra were recorded on a Grubb Parsons spectrometer with an l~aC1 prism. Samples in the form of thin films were prepared b y evaporation of benzene solutions of the compositions. The electron microscope investigations were carried out on t h i n film samples prepared from 0"01% solutions in benzene a n d on crack surfaces by means of single stage angular replicas which had first been shaded with palladium. The replicas were removed from broken surfaces b y means of gelatin which was afterwards washed off with water. The items were examined in an EM-100 Philips electron microscope. The X - r a y diffraction p a t t e r n s were obtained on a URS-60 apparatus in nickel filtered CuK~-radiation. I n determining mechanical properties the following ingredients were added to the rubber containing the heterochain polymers (pbw): stearic acid--2, zinc oxide--3, PM-75 b l a c k - - 50, s u l p h u r - - 1-7 a n d vulcanization accelerator-- 0.8-1.2. The mixtures were cured in a steam press at 143 ° for 50 rain.

DISCUSSION OF RESULTS T h e r e s u l t s o f I R s p e c t r o s c o p y s h o w e d t h a t g r o u p s c h a r a c t e r i s t i c of p o l y arylates and polyurethanes appear when the appropriate compounds are introd n c e d i n t o t h e e l a s t o m e r . A s c a n b e s e e n i n F i g . 1, t h e i n t e n s i t y o f t h e b a n d f o r t h e v a l e n c e v i b r a t i o n s o f b i s p h e n o l O H g r o u p s (3200 c m -1) is r e d u c e d i n t h e s p e c t r u m of the c o m p o s i t i o n c o n t a i n i n g the elastomer, p h e n o l p h t h a l e i n , ter e p h t h a l y l c h l o r i d e a n d c a t a l y s t (Fig. 1) a n d t h e r e is l i k e w i s e a r e d u c t i o n i n t h ~

~978

D.B. BOQ~SLAVSXII~ ~/.

intensity of the band due to the C--C1 bond of the terephthalyl chloride (665 cm-1), while at the same time a band appears at 1735 cm -1 (C~O) and the intensity of bands in the 1275 and 1100 cm -1 regions (C--O) is increased. Altogether these findings show that phenolphthalein interacts with the te• ephthalyl chloride to form a polyarylate.

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FIG. 1. IR spectra of the composition based on butadiene-styrcne elas~omer, terephthalio acid dichloride and phenolphthalein: 1-without a catalyst; 2--with the catalyst. Similar changes were detected in the spectrum of the composition cotalnlno~ the rubber with hydroquinone and terephthalic acid dichloride or suceinyl chloride heat treated at 175 ° in the absence of catalyst. I n the spectrum of the e l ~ t o m e r containing the polyol and the 2,4-teluylenec]~i~oeyanate dimer (Fig. 2), after heating at 165 °, there is a reduction in the intensity of the bands for polyol OH groups (3450 or 1170 em -1 for resotropine OH groups) and N ~ C - ~ O groups of the dimer (2270 em -1) and bands due to valency and deformation vibrations of N--H'(3360 and 1550 or 3210 and 1530 cm -1 for the system containing resotropine) appear as well as the bands for ester bonds in the 1220-1240 (C--O) and 1720 (C----O) cm -~ regions, pointing to urethane group formation. I n the presence of the dimer by itself the intensity of ~he band for the NCO group is considerably increased, after heat-treatment of the film, owing to dissociation of the dimer accompanied by the release of additional isocyanate groups on account of urethane ring opening. The polyarylates and polyurethanes formed in the elastomer have a globular structure (Fig. 3). The size of the globules varies within limits of 0.04-0-3/~ for the polyarylates, and 0.1-0.33/L for the polyurethanes. Larger formations mcasuring up to 0.65/~ are also present in th~ structure of the polyurethanes. It should be noted that the polyarylates prepared under the experimental conditions are crystalline products, as can be seen from the X-ray dit~raction patterns (Fig. 41; the degree of crystaUinity of the polyarylate based on hydroquinone is higher than that of the polyaryL~te synthesized from phenolphthalein.

On synthesis of some heterochain polymers in dieno elastomers

2979

The results of analysis of the polyarylates and polyurethanes extracted from rubber mixtures (Table 1) confirm existing views regarding the effect of the structural groups in the molecular chains on the behaviour of the polymers.

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FIG. 2. I R spectra of compositions based on butadiene-styrene elastomer with compounds reacting to form polyurethanes: /--rubber; 2--rubber+glycerin-Fdimerized 2,4-toluylene. diisoeyanate; 3-- rubber-{- polyethylene glycol adipate -{-dimerized 2,4-toluylencdiisocyanate; 4--rubber+resotropine-Fdimerized 2,4-toluylenediisocyanatc; 5--rubber-Fdlmerized 2,4-toluylenediisocyanate. Solid line-- before heating, broken line-- after heating at 165° for 30 min.

The high softening point of the polyarylate prepared from terephthalyl chloride and phenolphthalein is matched by good solubility owing to the existence in the latter of large side groups which reduce the packing density of the polymer chains. The polyurethanes based on aliphatic polyols--low molecular glycol or oligomeric polyester--are characterized by softening points of the order of 100-130°. By using a hydroxyl containing compound with aromatic units for

,2980

D . B . ,BoGusI.~vsxii et al.

FIG. 3. Photo-micrographs of: a~d--films; e-h--replicas of the fracturing surface of buta-

diene-styrene rubber treated in the presence of compounds forming hetero-chain polymers during their reaction: a--rubber (× 2200); b--rubber+terephthalic acid chloride+hydroquinone (×2200); c--as b but ×6000; d--rubber~-terephthalic acid chloride Wphenolphthalein+triethylamine (×2200); e--unfilled vulcanizate free from modifier addition; ] - - a s e but ethylene glycol and the dimer of 2,4-toluylene diisocyanate present; g--as e, but in the presence of polyethylene glycol adipate, dimer and glycerol as modifiers. synthesis of t h e p o l y u r e t h a n e s it is possible to raise t h e softening p o i n t s of t h e l a t t e r t o 310 ° . T h e effectiveness o f m o d i f i c a t i o n of c a r b o c h a i n e l a s t o m e r s b y m e a s o f p o l y a r y l a t e s a n d p o l y u r e t h a n e s a p p e a r s in t h e m u c h higher stress v a l u e s a t a

On synthesis of some heterochain polymers in diene elastomers

2981

FIG. 4. The X - r a y diffraction pictures of polyarylates synthesized in a rubber m e d i u m produced from a - - t e r e p h t h a l i e acid chloride and hydroquinone; b - terephthalic acid chloride a n d phenolphthMein in the presence of triethylamine.

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2982

T ~ L E 1.

D.B. CHARACTERISTICS

OF THE

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e~ a/. ~ P O L ~

SY~THw.SIZED

I~¢ A R U B B E R

MEDIUM

P o l y m e r based on

Succinyl ehloride-~ hydroquinone Terephthalyl chloride-~-hydroquinone T h e r e p h t h a l y l chloride phenolphthalein E t h y l e n e glycol-~ dimer Gliceryn-]- dimer Polyester ~ dimer Same

~ , dl/g

175 °

0"26

80

175 °

Insoluble

46

0"46 0"11 0"12 0"22

54 87 90

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Insoluble Insoluble

78 83

50 ° , c a t a l y s t 165 ° 165 °

165 ° 165 °, crosslink. ing a g e n t - glycerin 165 °, crosslink. ing a g e n t - resotropine 165 °

Resotropine-~ dimer

Softening point, oC

Conditions of synthesis

Yield,

%

77

fixed elongation, as well as in the higher values obtained for the hardness and the puncture energy of the vulcanizates, without loss of strength, and in the greater fatigue strength under repeated flexing (see Table 2). The latter is al~TABLE 2. MEC~-IC~m

PROPERTIES ]~N'E R U B B E R

System of reagents for the synthesis of heterochain polymers

T h e r e p h t h a l y l chloride, phenolphthalein, t r i e t h y l a m i n e Glycerin, dimerized 2,4-toluylenediisocyanate Polyethylene glycol adipate, dimer, glycerin Resotropine, dimer

O F ~:~tE F I L L E D WITH

COMPOSITIONS

HE~EROC]~Ar~

OF

ED~JI~ADIENE--S~

Fatigue strength under repeated flexing, thou. cycles *

Tensile strength, kgf/cm s

Shore hardness

Conven tional puncture stress, kgf/cm'

96

201

68

808

85

156

210

83

905

310

184

228

76

156

149 216

217 222

72 78

186 167

300% stress, kgf/cm'

o

POLYMERS

• F a t i g u e s t r e n g t h d e t e r m i n e d w h e n the degree o f c r o e s l i n k i ~ in the control v u l c a n i z a t e a n d t h e m ~ l l f l e d v u l o ~ n i z a t e s w a s identical.

N]YIR investigation of molecular motion in some oligomerie systems

2983

parently the result of relaxation processes at the eiastomer-piastic interface associated with the difference in the moduli of the polymers [4]. Vulcanizates modified by rigid chain polyaryiates have greater heat resistance and higher thermo-oxidative stability (Fig. 5). Superiority in resistance to high temperature action is exhibited by the systems containing the polyarylate based on terephthalic acid dichloride and hydroquinone, owing to the exceptionally good heat resistance of the latter. Thus, by synthesizing polyaryiates and polyurethanes directly in carbochain eiastomers it is possible to influence the performance characteristics of materials, taking account of the particular properties of the different types of polymers. Translated by R. J. A. HENX)RY REFERENCES

1. D. B. BOGUSLAVSKII, K. V. BOGUSLAVSKAYA, Kh. N. BORODYSHI~NA, L. M. VOLCHENOK, T. R. GENDLER, G. M. LEVIT and V. A. SAPRONOV, Auth. Cert. 241659, 1967; Byull. izobr. No. 14, 1969 2. G. M. LEVIT, D. B. BOGUSLAVS~H, Kh. N. BORODUSHKINA and K. V. BOGUSLAVSKAYA, Vysokomol. soyed. A18: 1881, 1971 3. 8. V. VINOGRADOVA, V. A. VASNEV and V. V. KORSHAK, Vysokomol. soyed. Bg: 522, 1967 V. N. KULEZNEV, V. D. KLYKOVA, B. A. DOGADKIN, Kolloidn. zh. 30: 707, 1968

NMR INVESTIGATION OF MOLECULAR MOTION IN SOME 0LIGOMERIC SYSTEMS* V. F . CHUVAYEV, I . V. POTAPOVA, L . A . SUKHAREVA, G. l~. YASHCHEI~KO a n d M. R . KISELEV Physical Chemistry Institute, U.S.S.R. A c a d e m y of Sciences

(Received 18 June 1973) N~R was used to analyse molecular motion in some oligomerie systems. I t is shown t h a t the structure a n d flexibility of the oligomerie block are factors underlying the m o b i l i t y of individual groups and of the system as a whole. The position and intensity of the m a x i m u m on the t e m p e r a t u r e curve of the coefficient of t h e r m a l conductivity, which is associated with the formation of a three dimensional network consisting of oligomer molecules, d e p e n d on the m o b i l i t y of the molecules forming the associates. The regularities observed in changes in the NMR lines of individual groups in relation to t e m p e r a t u r e p o i n t to dissimilarity in the mechanism of erosslinking in the oligomerie systems. * Vysokomol. soyed. A16: No. 11, 2565-2570, 1974.