Study on preparation and factors of amino silicone with low viscosity

Study on preparation and factors of amino silicone with low viscosity

Yuanyuan Lei a , Guo Zheng b , Yu Sun c , Yong Zhou d

Tianjin textile fiber interfacial treatment engineering center, Tianjin Polytechnic University, Tianjin,

300160, China

a leiyuanyuan85@d92bb21d10a6f524ccbf85c2,

b zhengguo@d92bb21d10a6f524ccbf85c2,

c sunyu_1980@d92bb21d10a6f524ccbf85c2, d

starzhouy@d92bb21d10a6f524ccbf85c2.

Keywords: amino silicone, ring opening copolymerization, octamethylcyclotetrasiloxane, viscosity Abstract: Amino silicone (PDMS) with lower viscosity were synthesized at a certain temperature by ring opening copolymerization of octamethylcyclotetrasiloxane (D 4), N-β-aminoethyl-γ- aminopropyl methyl dimethoxysiloxane (YDH-602), hexamethyldisiloxane (MM) with KOH as catalyst and DMSO as accelerating agent. The chemical structure was characterized via IR and 1HNMR. And the important factors were investigated carefully and the best technology of synthesis was obtained: reaction temperature 100-110?C, time 3h, KOH 0.05%, DMSO 0.5% and MM 5-7%, distilling at 110°C/0.095Mpa for 40 min.

Introduction

Amino silicone (PDMS) with various microstructures and architectures, are among the largest used silicones for the textile industry as softening agents mainly due to their ability to form specific interactions at fiber-silicone interface [1,2]. And because of their absence of toxicity, high chain flexibility and low surface energy, PDMS are used as emollients (skin softeners), lubricants, thickeners, and volatile liquids in many applications including textile treatment, personal and home care, cosmetics, drug delivery and printing ink formulations [3,4]. Some finishing processes have been practiced routinely which are superior to other surface active agents, bringing great economic benefits. Therefore, plenty of foreign companies have been studying hard on creating more positive and profitable PDMS [5], e.g. Dow Corning-America, Shin Etsu-Japan, Wacker-Germany. And these excellent performances have attracted much attention of more and more domestic corporations and researchers [6]. At present the amine functionality is mostly as aminopropyl end groups, or as aminoethylaminopropyl side chains [7]. And the ring-opening polymerization of octamethylcyclotetrasiloxane (D 4) or the copolymerization of D 4 with functional siloxane monomers can be mainly used to prepare a wide variety of silicones, which can be divided into bulk polymerization and emulsion polymerization with different conditions [4]. Although this polymerization has been reported by lots of studies and documents and researched for many years, there are still oxidative yellowing and emulsion floating going with [8]. Obviously, more work is needed to improve it. So in this paper, we focused on the synthesis of PDMS and the factors on amino value and viscosity to reduce yellowing.

Experiments

Materials. Octamethylcyclotetrasiloxane, [(CH 3)2SiO]4, D 4, was supplied by Shangdong Dayi chemical industry. N-β-aminoethyl-γ-aminopropyl methyl dimethoxysiloxane, NH 2CH 2CH 2NH- CH 2CH 2CH 2SiCH 3OCH 3)2, YDH-602, was obtained from Nanjing Yudeheng fine chemicals company. Hexamethyldisiloxane, [SiOCH 3)3]2, MM, purchased from Rizhao Lideshi

chemical

industry. Potassium hydroxide (KOH), acetic acid and dimethyl sulfoxide (DMSO) were analytical grade and purchased from Tianjin chemical reagent factory. All reagents and other solvents were used as received without any further purification.

The synthesis for low viscosity PDMS. Fig.1 illustrates that the synthesis mechanism for low viscosity PDMS. For all the reactions similar installations were used, consisting of a four-necked round-bottom flask with stirrer, thermometer and vacuum device, the established ratio (i.e. in order to obtain the polymer with prescribed amine equivalence) of D 4, KOH, YDH-602, MM and DMSO were added into the reaction vessel. When the mixture reached desired temperature about 100-110°C, kept at this temperature scope for 2h, and then with inert gas’s protection made it continue for 1-3h. At last the calculated acetic acid was added to neutralize the catalyst, and then the reaction mixture distilled at 110°C/0.095Mpa for 40 min to remove the volatile fractions, finally getting the glutinous, colorless and transparent liquid (confirmed by IR and 1HNMR). SiO

CH 3CH 34+(CH 3)3SiOSi(CH 3)3+CH 3OSiOCH 3

CH 33H 6NHC 2H 4NH 2

(CH 3)3SiO SiO CH 3CH 3SiO CH 3

3H 6NHC 2H 4NH 2SiO(CH 3)3m n Fig.1 The synthesis principle of PDMS

Analysis and measurements. The amino value and viscosity were estimated by chemical titration and viscometer, of which the details were available elsewhere [9]. IR was recorded on a TENSOR-37 Spectro-photometer (Bruker Co, Germany.) using KBr film technique. 1HNMR was taken on a NOVA-400 spectrometer of America using TMS as internal standard and CDCl 3 as solvent.

Results and discussion

The effect factors were so compared during preparing PDMS and the influences on silicone’s viscosity were investigated, such as the percentage of YDH-602, the reaction temperature and time, the amount for KOH, DMSO and MM, and pumpdown time.

Effect of YDH-602. When the reaction temperature, reaction time and the amount for KOH, DMSO and MM were fixed, respectively, 110°C, 3h, 0.05%, 0.5% and 5%, distilling at 110°C/0.095Mpa for 30 min, the viscosity and amino value would emerge wide fluctuation with only changing YDH-602 (shown in Fig.2). From Fig.2, it showed that with the increase of the amount of YDH-602, the amino value originally presented straightly upward trend, while viscosity firstly quickly reduced, afterwards had not much change. Therefore, the amount of YDH-602 played an important role on affecting the amino value having not been influenced by other conditions which were related to performance of products. And during adding the percentage of YDH-602, there would be more amino groups to make the molecular weight of oligomers decrease, leading to reduce for viscosity. Thus, we can get PDMS with scheduled amino value and suitable viscosity by adjusting the calculated YDH-602.

Effect of the reaction temperature and time. With the purpose of obtain the optimum reaction temperature and time, the amount for YDH-602, KOH, DMSO and MM were as followed: 5%, 0.05%, 0.5% and 5%, when having reaction temperature and time changed, as was shown in Fig.3. It was obvious that the temperature influenced the viscosity a lot. When

the temperature was no higher than 120°C, with the reaction time extending, the viscosity of silicone oil gradually increased. But when it was higher than 120°C, amino silicone oil viscosity reached the max plot then decrease. This was because ring-opening polymerization reaction was reversible, silicon alkoxide salt as catalyst during polymerization, which can make Si-O-Si bond broken, leading to turn reverse

direction for balance, so that the viscosity began to decrease. Another cause was water produced on aminosilane’s condensation process, playing the role of capping agent. In addition, more side effects would be imported because of the extension of time, for example, chain cyclization or rearrangement, condensation of silanol, and when the temperature exceeded 120°C, the product would be yellow, or even become turbid. So the better reaction temperature and time were 100-110°C and 3h.

The percentage of YDH-602 (%)V i s c o s i t y (m P a s )Amino value (mmol/g)

V i s c o s i t y (m P a s )Tim e(h)

Fig.2 Effect of YDH-602 Fig.3 Effect of the reaction temperature and time Effect of KOH. The reaction can take place in the presence of various catalysts: alkali metal hydroxides, quaternary ammonium and phosphorus hydroxide [10]. But the latter is so expensive and required cockamamie post treatment to make catalyst inactivation under high temperature, which would carry ammonia or phosphorus odor if not handled properly. In this paper we made up 50% KOH aqueous solution for better dispersing in homogeneous system. Reaction temperature, time, YDH-602, MM, DMSO as followed: 110°C, 3h, 5%, 1%, 0.5%, distilling at 110°C/0.095Mpa for 30 min, changing the amount of KOH observed the relation between the viscosity and the amount of KOH (Fig.4). With KOH concentration from 0.03 to 0.06%, the viscosity for PDMS grew fastest, indicating that the catalytic activity was strongest within this scope. When employing excessive amount, the ratio of active metal atoms: n(Si) increased with active centers multiplied, and under the action of the MM, the number of PDMS contrary increased too slowly to achieve the objective viscosity in prescribed time. And in the case of excess KOH, it would increase the difficulty of neutralization and impact product appearance.

Effect of DMSO. To avoid yellowing, add a few of non-proton polar solvents as accelerating agent, such as DMSO, increasing the catalytic activity, to properly reduce polymerization temperature. Fixed other conditions, and effect of the accelerating agent’s amount on the viscosity was observed with different content of DMSO (Fig. 5). From Fig.5, one could find that the viscosity reached its maximum at about 0.5%, and then decreased quickly with the range of 0.5% to 1%, then kept constant after that. During anionic polymerization process ionpair formed by -SiO - and K + in pairs will cause the active center to passivate , resulting in poor reaction performance. Along with the addition of DMSO into the reaction and due to its ability of drawing away ionpair each other in homogeneous reaction, the active center can be exposed out to allow anionic catalytic polymerization to go on. But the number of metal ion K + was so limited that 0.5% DMSO had been enough to make them exposed out, and more DMSO were no beneficial but only diluting and lowering viscosity.

V i s c o s i t y (m P a s )

KOH (%)

V i s c o s i t y (m P a s )

DMSO (%)

Fig.4 Effect of the catalyst KOH’s amount Fig.5 Effect of the DMSO’s amount Effect of MM. During copolymerization, both ends of the growing chain still have reactive functional groups which can keep on chain growth. So the hexamethyldisiloxane (MM) are necessary to used as chain capping agents (or chain blockers) and they play two major roles. Firstly, they determine the terminal functional groups, and secondly, they regulate the molecular weight of the obtained linear oligomer. The effect on PDMS’s viscosity was researched with different amounts of MM varying from 1 to 7% used in this study. And a typical result was given in Fig.6, which indicated that the above amounts of MM affected considerably the viscosity decrease. And PDMS with lower than 100mPas could be obtained with 5-7% MM.

Effect of pumpdown time. In principal there will be some small molecules of water, methanol and other volatile fractions produced to impacting performance of PDMS. So it must be vacuum-pumping to improve the purity. As seen in Fig.7, around the pumpdown time from 0 to 150min there was a sharp increment in the viscosity with other factors settled. As it got up to 40min, the extraneous components had been already removed completely. So the best pumpdown time was 40min.

V i s c o s i t y (m P a s )

MM(%)

V i s c o s i t y /(m P a s )

Time/(min)

Fig.6 Effect of the MM’s amount Fig.7 Effect of pumpdown time Structures

analysis. A typical IR spectrum of the synthesized PDMS, as shown in Fig. 8, displayed bands at 3360cm ?1 (-NH 2, stretching), 2851, 2920cm -1(-CH 2, -CH 3, stretching), 1260, 1420cm ?1 (Si-CH 3, stretching), 1020-1110cm ?1 (Si-O-Si, stretching) and 800cm ?1 (CH 3-Si-CH 3, stretching). These bands were characteristics of the desired compounds. Furthermore, the structure of the compounds was further supported by the 1H-NMR spectrum (Fig.9), which gave signals at &0.1ppm (Si-CH 3), 0.52ppm (Si-CH 2), 1.55ppm (CH 2-CH 2), 2.61ppm (NH-CH 2), 2.67ppm (NH-CH 2), and 3.45ppm (NH 2-CH 2). From these characterizations, it evidently confirmed that PDMS had been produced.

40003500300025002000150010005000

20

40

60

80

100

T (%)λ/cm -1ppm (t1)-1.00.01.02.03.04.05.0

500000100000

Fig.8 FTIR spectrum of the PDMS Fig.9 1H-NMR spectrum of the PDMS

Conclusions

Amino value was depended on the amount of resin acceptor YDH-602, having no connection with the process conditions. In all cases, in the previous described reaction conditions, the viscosity for PDMS was mainly determined by reaction temperature, time, the amount of catalyst, accelerating agent and capping agent, pumpdown time. Thus, the process conditions should be confirmed by considering the actual needs. And the optimum ones to get PDMS with less than 100mPas viscosity were as followed: reaction temperature 100-110°C, time 3h, KOH 0.05%, DMSO 0.5% and MM 5-7%, distilling at 110°C/0.095Mpa for 40 min.

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Equipment Manufacturing Technology and Automation

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Study on Preparation and Factors of Amino Silicone with Low Viscosity 10.4028/d92bb21d10a6f524ccbf85c2/AMR.317-319.2449

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