Preparation of modified monomer and studies on EB radiation curing of polyurethane-acrylate in the air

Preparation of modified monomer and studies on EB radiation curing of polyurethane-acrylate in the air

~ Pergamon Radiat. Phys. Chem. Vol. 52, Nos 1- 6, pp. 265 269, 1998 :~ 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: ...

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Pergamon

Radiat. Phys. Chem. Vol. 52, Nos 1- 6, pp. 265 269, 1998 :~ 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: S0969-806X(98)00153"4 0969-806X/98 S19.00 + 0.00

P R E P A R A T I O N O F M O D I F I E D M O N O M E R AND STUDIES ON EB R A D I A T I O N C U R I N G O F P O L Y U R E T I I A N E - A C R Y L A T E IN T I I E AIR"

H U A N G W E I , X I A O B I N . Z H A O P E N G J I , J I A N G BO +

Z H O U Y O N G ~, HA H O N G F E I +'~

China Southwest Institute of Nuclear Physics and Chemistry, 610003, Chengdu, China + Institute of Nuclear Science and technology, Sichuan University, 610064, Chengdu ,China ++ Department of teclmical Physics, Peking University, 100871, Beijing, China

ABSTRACT Preparation of the monomer modified by phosphite is described. According to the results oflR, MS and ~H-NMR, the possible synthesis path was dcduced. The coating was made up of polyurethane acrylate, modified monomer, active diluent and so on. A non-tacky transparent fihn can be obtained aflcr EB curing in the air. The expcriment indicated that the modified monomer plays a great role in resisting oxygen inhibition. FurthermOre, it reduces the radiation dose that the curing needs, and takes effect on radiation sensitization. The optimum radiation condition is 40 KGy. The gel content was used to express tile curing extent and the relationship between dose and P-H bond conversion was studied.

KEYWORDS Electron beam (EB) curing: oxygen inhibition: polyurethane-acrylate: the monomer modified by phosphite: gel content: P-H bond conversion. INTRODUCTION At room temperature tile coating system conducts a path of free radical polymerization in the process of radiation curing. But tile free radical polymerization is subjected to oxygen inhibition, which makes coating surface tacky, curing uncomplcte and so on(Dcmarlcau W. et al. 1987 ). In order to avoid this disadvantage, the EB curing is carried out under protcctivc gas such as nitrogen ,carbon dioxide and so on. But this method needs high energy consumption and cost(Deckcr C., Jenkins A. D,, 1985). An attempt has bccn made to modify monomer for purposc of avoiding oxygen inhibition and realizing the EB curing in the air.

*: This subjcc! is supported by China Nuclcar Industry Science Fund aud Open Laboratory for Radiation Physics and Tcclmology of State Education Comission of P.R.China. 265

266

Huang Wei et at.

EXPERIMENT Materials 1.

Oligomer

Tile Oligomer is polyurethane-acrylate. It was synthesized in our laboratory. 2. Monomers

The modified monomer (named P) is a kind of phosphite including diester and monoester. It was prepared by the reaction of trimethylol propane triacrylate (TMPTA) and phosphorus trichloride and distilled in the reduced pressure. Diethyl phosphite (reference sample, named E) was obtained from Ciba Geigy co. Ltd. 3.Active diluent

2-hydroxypropyl acrylate was chosen as an active diluent. Radiation curing

Tile coating systems were prcparcd onto the glass shccts. The radiation was carried out at room temperature in the air, using our 600kev Van De Graft electrostatic accelerator. Measurements and Testing I

The modified monomer P was analysed by IR, MS and H-NMR. The gel content was measured by the Soxhlet extraction method. In addition, the P-H bond conversion in the coating before and after radiation had been calculated by the decreasing of P-H characteristic peak at 2424cm" 1 or so. RESULTS AND DISCUSSION 1. Synthesis and assesments o f P monomer

Figure 1 and 2 are tile IR spectra ofdiethyl phosphite E and synthesized monomer P. Comparing tile 1R -I

spectra of P with that of E, we can see that 2240~2350cm is the P-H character peak, 1250~1150cm': is the P=O stretching vibration peak and 1050~990cm ~ the P-O-C aliphatic group stretching vibration. These representative peaks can prove that the synthesised product P is phosphite. r B o

~2r~

l,¢P m

r-

ii

s bll~ VIEN ~Ye~l~

Fig. 1 Tile 1R spectrum of E(Diethyl phosphite, used as standard sample)

t,~vl~tmor.~

ditto

Fig. 2 The IR of synthesised monomer P

400

10th International Meeting on Radiation Processing

267

Table 1 The MS attalysis of P

Position of absorption

Chemical slructurc

pcak () Ii

181

- P-t I I

yl I201 t

OC112- 7 - C I I2Ctl s Ci I2011

(1)

II -- pI

164 Fragments 117

99

~112011

OCH 2- (~--CII:CI I~ CII2011 (2) CII 2CI I:~CII:-- (~--CI IzOI I

~H,OH

(3)

CII2-- CII2C112-~_CII2011 t CII 2 -

(4)

CII 2-

81

.~Cl ICI 12- ~ -- CI t201 I I

CII~

monophosphite

(5)

198

MI +

181

Same (1): Mj -- OH

164

Santo (2): Mj -- 2OH

117

Same (3): M I - - 2 O H a n d P O

99

Same (4): MI -- 3OH and POH

314

M2 "

+

C112Oli

181

ClljCtl2- ~2-cI t2OH /

Same (1): M2--

C1120C! I2OI I CIIsCII2--~--C112OH

164 Di-

Cl1120 -

Same (2): M2 -and - - O H

phosphite

0 II

133 M2

--

- PI -II rlt2OH T 0CII2 ~ CII2CIIj CII~Oll

o~cu, ~ clboll

117

Cll20

. P

(I)

Samc (3): M2 --

tl

268

Huang Wet et al.

In the IR spectrum there exists P=O peak It doesn't indicate that P monomer is phosphate. A literature

9,

(Li Er-cheng,et al. 1988) says that the structure of dialkyl phosphite is not (RO)2P-OH but (Ro),r,-H There are typical P-H peak, P=O peak and P-O-C peak in the IR spectra, which can fully demonstrate the synthesised product P is phosphite. Figure 3 and 4 are MS and JH-NMR of modified tnonomcr P, respectively. They are analysed in detail in table 1 and 2. From the analysis results we can deduce that P is made up of di-phosphite and monophosphite.

13] 175 80 L[ tilt 1 60 140 [ [ ~69 .

,! ,IL.,

152

i 259

I

|~ 366

4

~3

I 580

i 687

. , . . .tt. . ,

6

....

3. . . .2. . . . .I. . 0

Fig. 4 The JH-NMR spectrum of P monomer Fig.3 The mass spectrum of P monomer

Table 2 ~H-NMR study for P monomer

Chemical shift(ppm)

Chemical structure

1.3~ 1.6

CHS

2.062

Solvent

4.0~-4.7

O--H

7.232

P--H

2. Extent o f cure

Figure 5 is the relationship between dose and gel content of tile white sample W (decluding P monomer) and the coating containing ten percent P monomer. It is clearly seen in Figure 5 that gel content increases very quickly when the radiation dose is low. With the rise of dose gel content continue increasing. But the curves are increasing slowly when dose is over 40 kGy. It shows that increasing dose is favourable to the curing. But if dose is too high, the curing extent can not be improved and the fihn gets brittle. So 40 kGy was chosen as the optimum radiation condition. 3. P - H b o n d conversion

Figure 6 is about lhe effect of dose on P-H bond conversion. P-H bond conversion in the coatings containing different monomer concentration gradually increase with the progress of dose. In tile

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269

radiation, phosphitc combines with tile oxygen solved in the coating and converts into phosphate. The reaction essence is that P-tt bond breaks and P-O bond forms. That the content of P-t-I bond reduce reflects the consumption of solved oxygen and shows the resisting oxygen property of phosphite.

100

lOC

Pro P2o

o= 80

~ 8O

.g

~ 6o 8

~ 6o

40

4o

"r' ,,' 20

20

0 |

|



,

,,,

0

Dose (10KOy)

Fig. 5 The effect of dose on curing extent Pro - - ten percent P monomer W - - white sample

!

i

|

2

i

3 4 5 Dose ( 10KGy )

I

6

7

Fig6 The relation between P-I{ bond conversion and irradiation dose P02 - - two percent P monomer P~0 - - ten percent P monomer 150 - - twenty percent P monomer

CONCLUSION In this paper tile monomer modified by phosphite was prepared successfully. The coating composed of the modified monomer and polyurethane-acrylale was cured by EB curing in the air. The studies indicate that phosphite has some effect on resisting oxygen inhibition, and reduces the radiation dose that the curing needs. REFERENCES Demarteau W., Giet P. and Lontz J.M. (1987) Radiation Curing. Decker C., Jenkins A. D. (1985) Kinetic approach of 0 2 Inhibition in ultraviolet and laser-induced polymerizations. Macromolecules 18,1241-1244. Li Er--cheng. Zhou Jian-cheng, Xu Guang-zhi (1988) The study of organic Hg phosphite, Journal of Spectroscopy (Chinese), 5( 1), 15-18.