Some features of the plasticization and stabilization of polyvinyl chloride with hexahydrophthalate oxides

Some features of the plasticization and stabilization of polyvinyl chloride with hexahydrophthalate oxides

SOME FEATURES OF THE PLASTICIZATION AND STABILIZATION OF POLYVINYL CHLORIDE WITH HEXAHYDROPHTHALATE OXIDES* T . B. ZkVA~OVA,K . S. ~¢~INSKER, G. T ...

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SOME FEATURES OF THE PLASTICIZATION AND STABILIZATION OF POLYVINYL CHLORIDE WITH HEXAHYDROPHTHALATE OXIDES* T . B.

ZkVA~OVA,K .

S. ~¢~INSKER, G. T . FEDOSEYEVA, B. :F. TEPLOV,

V. D . AI~DXStt~IKOV)~ a n d A. I. KUTSElgKO I n s t i t u t e of Acid Chloride Products and Acrylates (Received 17 ~Vlarch 1965)

IT IS well known that certain epoxy compounds are able both to stabilize and plasticize polyvinyl chloride composition [1-3]. Among such compounds described in the literature one frequently encounters a large number of dialkyl esters of 4,5-epoxyhexahydrophthalic acid [2] °

~/\c,/° \og (I~ indicates ethyl, butyl, 2-ethylhexyl, n-decyl, n-hexyl, iso-octyl). In contrast to already-published works, the present report de~ls with a more detailed study of the plasticizing and stabilizing capacities of epoxyhexahydrophthalates on the example of dibutyl (BEP) and di-2-ethylhexyl-4,5-epoxyhexahydrophthalate (OEP). The two compounds were prepared b y esterifying n - b u t y l and 2-ethylhexyl alcohols with tetrahydrophthahe anhydride (m.p. 101-101"5 °) i n vacuo using H~SO4 as catalyst. The tetrahydrophthalic esters produced were epoxidized with 20O/o anhydrous solutions of peracetic acid in an organic solvent (Table). For the investigation we used polyvinyl chloride (PVC) with a density of 1.37 g/cm a, intrinsic thermal stability of 3 rain and absolute viscosity in dichloroethane t/abs----2-26. I t was prepared b y suspension polymerization (methyl cellulose as emulsifier) using azobis-isobutyronitrile as initiator. The epoxy compounds were purified b y heating with charcoal type AG-3 and added to the PVC in methanol solution, after which the solvent was removed at an elevated temperature with the mixture continually stirred. The plasticizing and stabilizing effect of the epoxy hexahydrophthalie esters was studied b y the procedures described in [4-6]. The plasticizing activity was evaluated from the v(triation in the glass point of PVC modified b y addition of these compounds in a wide range of concentrations. The glass point was measured on the apparatus described in [7], modified * Vysokomol soyed. 8: No. 4, 599-603, 1966. 657

658

T . B . ZAVAROVAet al. PHYSICO C H E M I C A L

PROPERTIES

Specimens

d20

OF S Y N T H E S I Z E D

n20

EPOXYHEXAHYDROPHTHALATES

Acid No., mg KOH/g

T, °C

Bromine No.

Epoxy group content, %

t

Di.2-ethylhexyl-4,5epoxyhexahydrophthalate Dibutyl-4,5-epoxyhexahydrophthalate

0-999

1"4676

0"55

200

0"86

1"068

1"4642

0"48

171

3"36

i

Ii

8.46 11.5

and automated for operating with plasticized PVC pellets in a wide temperature range (--78 to +120°). The stabilizing activity was found from the influence of addition of the esters on the length of the induction period (v, rain) for the liberation of hydrogen chloride as shown by a Congo-red indicator (thermal stability) and its influence on the rate of PVC dchydrochlorination in an air current (0.5 1./min) at 175 °. The liberated hydrogen chloride was absorbed in water and its concentration determined by potentiometric titration using a 0.001 ~ solution of AgNO8 with a mercury-silver electrode. T ,°l

\

140

-qO 0

8

/5' ZL/ P l a s t i c i z e r ~ mole %

FIG. 1. Glass point of PVC v. plasticizer concentration: 1--DOP, 2--BEP, 3--OEP. F i g u r e 1 shows T g = ~ (N, mole. %) for B E F a n d O E F as c o m p a r e d w i t h dioctylp h t h a l a t e (DOP), w h e r e Tg is t h e glass p o i n t of t h e plastic, "N t h e plasticizer conc e n t r a t i o n o f t h e p o l y v i n y l chloride c o m p o s i t i o n (mole.%). I t c a n b e seen t h a t t h e plasticizing p o w e r o f B E F a n d O E F is a p p r o x i m a t e l y t h e s a m e as t h a t o f D O F . I t m u s t be r e m e m b e r e d h e r e t h a t t h e e p o x y c o m p o u n d s t e s t e d h a v e g o o d c o m p a t i b i l i t y w i t h PVC. T h e plasticizer does n o t e x u d e f r o m t h e film if it is s t o r e d in diffused light or d a r k .

:Plasticization and stabilization of polyvinyl chloride

659

~'igure 2 shows the rate of PVC dehydrochlorination in the presence of epoxy hexahydrophthalate esters (curves 4-11) as compared with the unstabilized polymer (curves 1, 2) and a polymer with 1.5 DOF parts by weight (curve 3). Besides the plasticizing effect (Fig. 1) the compounds tested can be seen to have an appreciable stabilizing effect. The shapes of the curves were calculated from the equation

kt----

-

-

In

t~

d-A,

a--x

where a is t h e initial chlorine c o n c e n t r a t i o n of t h e m o n o m e r , x t h e a m o u n t of chlorine l i b e r a t e d u p to t i m e t. I t is e v i d e n t f r o m Fig. 3 t h a t curve 1, which gives t h e r a t e of PVC d e h y d r o chlorination w i t h o u t a stabilizer, is satisfactorily a p p r o x i m a t e d b y a first-order equation. The r a t e c o n s t a n t at 175 ° calculated f r o m t h e e x p e r i m e n t a l figures ( k = 5 . 5 ~ 0 . 3 × 10 -5 rain -1) is in good a g r e e m e n t w i t h t h e results of [8] ( k = 7 - 8 × × 10 -5 min -1 on e x t r a p o l a t i o n of t h e e x p e r i m e n t a l curves to t h e t e m p e r a t u r e of our experiments).

A 8[



'''L-'~ ×'--

tl I

]0.--7

7 . .X-"-

.X-'8 X..- - ' y "

,,I

....>e"'" .........

5 11 G

~¢ " "

i

0

GO

12O

180

Time, min FIG. 2. PVC dehydroehlorination rate v. heating time of composition: 1--unstabilized PVC, 2-- ditto after exposure to UV light, 3-- 1½parts by weight dioetylphthalate; 4, 5, 6--0.3, 1.2 and 2 naole.~o dibutyl-4,5-epoxyhexahydrophthalate respectively; 7, 8--0"2 and 0.71 naole.~o di-2-ethylhexyl-4,5-epoxyhexahydrophthalate respectively, 9, 10, 11--0.3, 1.2 and 2 naole.°~ BEP after exposure to UV light. Ordinate axis: Ax nag I-IC1 from 1 g PVC/hr (A). C u r v e s / - 8 (Fig. 3), which give t h e d e h y d r o e h l o r i n a t i o n o f PVC in t h e presence of different a m o u n t s of B E F a n d O E P , do n o t in t h e first stage follow a first-order e q u a t i o n a n d h a v e a n order o f r e a c t i o n w i t h respect to t h e liberated chlorine

T. ]3. ZAVAROVAet al.

660

below the first ~n=0.3-0.9 depending on the concentration of test stabilizer: the •higher the concentration the lower the order of the reaction). B u t during the dehydroehlorination of PVC with a stabilizer a first-order reaction with respect to HCI is established with a rate constant approximately the same as that of the dehydrochlorination of the unstabilized polymer (5.5~=0.3 × 10 -5 rain-l). The higher the molar concentration of plasticizer and stabilizer, the greater the interval of time required to establish the first-order of reaction (comp. curves 4-8 in Fig. 3, see also Fig. 4). I t can be assumed that this time is 0, the period of effectiveness of the stabilizer at given temperature. The higher 0 at constant molecular concentration of stabilizer, the more effective is the stabilizer. The experimental figures show that the stabilizing activity of the two esters is the same (Fig. 5). The experimental points for the integral rates of PVC dehydrochlorination after 180 min as a function of the molar plasticizer-stabilizer concentration (for B E F and OEF) of the composition plot into a smooth curve which satisfies the equation 3.88--1.68c Vint =-0.7+1.5c Analysis of this equation shows that an ester concentration of more than 1 mole. % referred to polymer is sufficient for highly effective stabilization. A

~9

30

20

GO

120

180

2170 300 Time ~ rain

3617

q20

FIG. 3. --2"3log(co--Cx)/eo v. heating time: 1 - 1 1 - - a s for Fig. 2. Ordinate axis: --2"3 log (Co--Cx)/CoX 10-3 see -1 (A).

When the absorption spectra of B E P were recorded in the ultraviolet and visible ranges of the spectrum on a SF-4, strong light absorption was found in the range 300-380/z, i.e. in the light absorption range of polyvinyl chloride. It was

Plasticization and stabilization of polyvinyl chloride

661

therefore interesting to assess the light stabilizing power of the esters. Figure 2 ~urves 1 and 2 show the rate of PVC dehydrochlorination at 175 ° after exposure to UV radiation for 4 hr at 40 ° under a P R K - 2 lamp (40 cm between source and specimen). Comparison of these curves shows t h a t the dehydrochlorination rate of unstabilized PVC is much greater after exposure to UV light (k2= 1.2 × 10 -4 min -z) t h a n before (k1=5.5× 10 -5 rain-l), The addition of B E P (1.5-2 mole.%) has a marked stabilizing effect under exactly the same experimental conditions (Fig. 2, curves 10, 11).

rain 36o -

Vz.nt

200 ~

5

lO0I

[

1 2 3tabil[zer,mole%

~6 12 1,8 StQbilizen,mole%

Fic. 4

Fro. 5

F~o. 4. Time required to establish first-order reaction of PVC

dehydroehlorination

v. the amount of stabilizer. Fzo. 5. Integral rate of PVC dehydrochlorination v. the amount of stabilizer. I t is not sufficient to assess the effect of stabilizers from only one determination o f the dehydrochlorination rate of a stabilized powder [9]. A series of experiments was therefore performed with films prepared b y milling for 10 rain at 168 °, from the following compositions: 100 g PVC, 1.5 g Ba stearate, 0.5 g transformer oil, B E F concentration ranging between 1.5 and 10 parts by weight. The change in the coIour of the film was studied as a function of storing time in an air thermostat at 175 °. The film containing I0 parts by weight B E F began to darken rapidly after 120 min, while the control film retained the same colour even after 60 min. The results obtained b y measuring the rate of dehydrochlorination on irradiated and normal films are analogous to those on powders (Figs. 2 and 3). CONCLUSIONS

(1) Dibutyl and di-2-ethylhexyl-4,5-epoxyhexahydrophthalate are plasticizers for PVC, with the same strength as dioctyIphthalate. (2) Dibutyl- and di-2-ethylhexyl-4,5-epoxyhexahydrophthalates are lightand heat stabilizers for polyvinyl chloride. The optimum concentration for effective stabilization has been determined.

662

V . I . SrITSY.Wet al.

(3) The thermal dehydroehlorination of unstabilized polyvinyl chloride follows a first-order equation. The addition of the stabilizer reduces the order of the reaction, but this is re-established during the process of dehydrochlorination. (4) The time required to establish the first-order of the reaction of polyvinyl chloride dehydrochlorination characterizes the efficiency of the stabilizer. Translated by V. ALFORD REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.

E. DACItSELT, Plaste u. Kautschuk 1O: 260, 1963 F. P. GREENPAN and R. I. GALL, Industrial and Engineering Chem. 50: 865, 1958 R. VAN CLEVE and D. H. MULLINS, Industrial and Engineering Chem. 50: 873, 1958 {~. M. MOELTER and E. SCHWEIZER, Industrial and Engineering Chem. 41: 684, 1949 L. H. WARTMANN, Industrial and ]Engineering Chem. 47: 1013, 1955 A. A. BERLIN, Z. V. POPOVA and D. M. YANOVSKII, Zh. prikl, khim. 33; 871, 1960 S. A. ARZHAKOV, S. Z. ZAINULIN a n d B. P. SHTARKMAN, Dokl. Akad. ~qauk SSSR 154: 181, 1964 G. TELA1MXNI and G. PEZZIN, Makromol. Chem. 39: 26, 1960 R. De BROUTELLES Rev. gen caoutchouc 34: 902, 1957; RZhKhim., No. 3, 10157, 1959

EFFECT OF RADIATION ON POLYETHYLENE ADHESION TO ALUMINIUM* V. I. SPITSY~,P. I. ZVBOV, V. YA. KABA~OVand Z. P. GROZIICSKAYA I n s t i t u t e of Physical Chemistry, U.S.S.R. Academy of Sciences

(Received 18 March 1965)

IT HAS been established in a number of works that, besides crosslinking and degradation, the ionizing irradiation of polyethylene also promotes the formation of polar (acid-containing) groups. An increasd in the number of such groups in non-polar or slightly polar polymers improves their adhesive bond to the oxide film of a metal. The effect of ageing on various physicomechanical and adhesion properties of polyethylene coatings was studied in [1-3]. The present investigation aimed at establishing the possibility of using radiation to improve the adhesion of polyethylene to an aluminium base in the presence of atmospheric oxygen and i n vacuo. The attempt was also justified by the fact that only a few works have so far been * Vysokomol. soyed. 8: :No. 4, 604-612, 1966.

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