differential analysis in polysulfide silane coupling ... · chromatograms (ticcs) (fig. 5). it was...

ASMS 2011

Hiroki Nakajima1, Takahiro Goda1, Satoshi Yamaki1,

Ichiro Hirano1, Tsutomu Nishine1, Yuko Sekine2,

Fumito Yatsuyanagi2 1 SHIMADZU CORPORATION, Kyoto, Japan 2 THE YOKOHAMA RUBBER CO.,LTD., Kanagawa,

JAPAN

Differential Analysis in Polysulfide Silane Coupling Agents by High Mass Accuracy MSn and Multivariate Statistical Technique

TP343

2

Introduction

Background of this work

Silane coupling agents are organosilicone compounds having two functional groups with different reactivity. One of the two functional groups reacts with organic materials and the other reacts with inorganic materials. Therefore, they are effective for the improved adhesion at the interface between the organic and inorganic materials. Recently, they have been used in the manufacture of tires. Usually, fillers are added to rubber compound to enhance the strength and improve the performance of tires. Siliceous fillers that are nonpetroleum resources have recently been frequently utilized in the manufacture of tires (Fig. 1). Silane coupling agents can combine the siliceous

fillers with the rubber molecules here (Fig. 2). Generally, polysulfide silane coupling agents are widely used in the Silica-containing rubber compounds. Analysis of silane coupling agents in tires is therefore important for the evaluation or improvement in developing of tires. However, it is very difficult to distinguish the same structured silane coupling agents produced by different manufacturers. Here, we present an example demonstrating the differential analysis of four same structured polysulfide silane coupling agents produced by different manufacturers using high mass accuracy MSn and multivariate statistical technique (Fig. 3).

Fig. 1 Utilization of silica with silane coupling agent for tire tread compounding Fig. 2 Roles of silane coupling agent for silica tread compound

Fig. 3 Procedure of multivariate statistical analysis

Utilization of Silica with Silane Coupling Agent

is key technology for tire tread compound to

contribute for environmental preservation & safety.

Fuel

Efficient

Use of Nonpetroleum Resource

High Breaking

Performance

Requirement

EnvironmentalPreservation &

Safety

Silica : hydrophilic Rubber : hydrophobic

Silane Coupling Agent (bifunctional: hydrophilic/hydrophobic)

Dispersion & Adhesion

Stro

ng

A

dh

esio

n

Good Dispersion

Effects of silane coupling agent on the mechanical properties of silica compound

Schematic representation of silica/rubber interface

Analytical Instrument

Software ofStatistical AnalysisA large number of date One array of date

Differential Analysis in Polysulfide Silane Coupling Agents

by High Mass Accuracy MSn and Multivariate Statistical Technique

Si O

S

O Sx

O Si

Si

Si

OOH

Si

Si

OO

Si OO

Si OO

Si S

Rubber

OEt

OEt

OEt

OEt

Silica

3

ExperimentFour Bis (triethoxysilylpropyl) polysulfide (TESPP; sample A, B, C, D) produced by different manufacturers were used in this study (Fig. 4). Sample solutions were prepared at 1/10,000 dilution with methanol. Equal amount of all sample solutions were mixed and it was used as a quality

control (QC) sample to identify robust and reproducible ion signals. LC-MS measurement was performed using Prominence UFLC and LCMS-IT-TOF (SHIMADZU CORPORATION). SIMCA-P (Umetrics) was used for multivariate statistical analysis.

Results and discussionsThe main compound peaks of 4 polysulfide silane coupling agents were able to detect in Total Ion Current Chromatograms (TICCs) (Fig. 5). It was suggested that they had a distribution of the number of sulphur element.TICCs of sample A and B were very similar. And, on the score plot, the plots of them were located at the same site (Fig. 6a). From the above result, it was showed that they had almost common components.The unique peaks of each sample C and D were observed on the loading plot (Fig. 6b).The formula of compound 1 was predicted as C18H42O6Si2S (Bis(triethoxysilylpropyl)monosulfide (TESPM)) by high mass accuracy MSn data and formula prediction software

“Formula Predictor 4.3” (SHIMADZU CORPORATION).The formula of compound 2 and 3 were predicted as C17H40O6Si2S3 and C17H40O6Si2S4, respectively. Considering MSn spectra and neutral loss ions, it was determined that compound 2 had the structure of Bis(triethoxysilylpropyl)trisulfide (TESPT) substituted –OCH3 for –OCH2CH3 (Fig. 8).Compound 2 and 3 were regarded as impurities or by-product in the process of synthesis. We also could determine the structure of other characteristic compounds by the same method (Table 2). It was showed that those compounds, as well as main compound, had a distribution of the number of sulphur element.

Fig. 4 Structure of TESPP

C18H42O6Si2Sx (x=2 -10)

Table 1 LC-MS analytical conditions

Column

Flow rate

Column temp.

Mobile phaseA

Mobile phaseB

Time prog.

Injection volume

Ionization mode

Probe voltage

CDL temperature

BH temperature

Nebulizing gas flow

Drying gas pressure

Scan range

: Shim-pack XR-ODS (2.0 mmI.D.x75 mm, 2.2 µm)

: 0.45 mL/min

: 40 °C

: water containing 5 mmol ammonium formate

: acetonitrile

: 70%B(0 – 0.11 min) – 100%B(6.67 – 12 min)

–70%B(12.01 – 15 min)

: 1 µL

: ESI(+)

: 4.5kV

: 200 °C

: 200 °C

: 1.5 L/min

: 0.1 MPa

: m/z 100 - 1000



4

Fig. 5 TICCs and Extracted Ion Chromatograms (XICs) of Sample A, B, C and D

Trapping system

Characteristic component 1

Characteristic components 2

3

x=2 x=3 x=4 x=5 x=6 x=7 x=8

x: The number of sulphur element

(x10,000,000)

(x10,000,000)

(x10,000,000)

(x10,000,000)

B

D

C

A

447.1180 (10.00)542.1580 (10.00)510.1860 (10.00)465.2140 (5.00)295.0840 (5.00)397.1900 (5.00)323.1150 (5.00)TIC (1.00)

447.1180 (10.00)542.1580 (10.00)510.1860 (10.00)465.2140 (5.00)295.0840 (5.00)397.1900 (5.00)323.1150 (5.00)TIC (1.00)

447.1180 (10.00)542.1580 (10.00)510.1860 (10.00)465.2140 (5.00)295.0840 (5.00)397.1900 (5.00)323.1150 (5.00)TIC (1.00)

447.1180 (10.00)542.1580 (10.00)510.1860 (10.00)465.2140 (5.00)295.0840 (5.00)397.1900 (5.00)323.1150 (5.00)TIC (1.00)

x=2 x=3 x=4 x=5 x=6 x=7 x=8

Fig. 6 Result of principal component analysis (PCA) for sample A,B,C and D (a: score plot , b: loading plot)

a

Sample C

Sample D

Sample A & Sample B

QA/QC

b

Sample D

Sample C

Fig. 8 MSn spectra of compound 2

Fig. 7 MSn spectra of TESPT

(TESPT+NH4)+

Measured m/z : 524.2018 Predicted m/z : 524.2020 Error: -0.38ppm

C16H37O5Si2S3+

NL 63.0653

C12H27O4Si2S3+

NL 74.0755

MS

C10H23O4Si2S3+

NL 102.1064

MS2

MS3

S3Si

O

O

SiO

O

O

CH3

CH3

CH3

OCH3

CH3

CH3

m/z 461 C16H37O5Si2S3

+

m/z 387 C12H27O4Si2S3

+

m/z 359 C10H23O4Si2S3

+

MS

MS2

MS3

461.1265 C16H37O5Si2S3+

NL 49.0593

C12H27O4Si2S3+

NL 60.0508

C15H35O5Si2S3+

NL 63.0691

(TESPT-CH2+NH4)+

Measured m/z : 510.1858 Predicted m/z : 510.1864 Error: -1.18 ppm

C11H25O4Si2S3+

NL 74.0718

S3Si

OCH3

O

SiO

O

O

CH3

CH3

CH3

OCH3

CH3

m/z 447 C15H35O5Si2S3

+

m/z 461 C16H37O5Si2S3

+

m/z 387 C12H27O4Si2S3

+

m/z 373 C11H25O4Si2S3

+

Inten.

(x1,000,000)

524.2018(1)

461.1354(1)

530.1612(1)

Inten. (x100,000)

387.0610

359.0301

Inten. (x100,000)

461.1365

507.1741

Inten.

(x1,000,000)

510.1858(1)

447.1178(1)

533.1017(1)

Inten. (x100,000)

447.1167

Inten. (x10,000)

373.0449

387.0659



5

ConclusionWe could demonstrate that the combination of high mass accuracy MSn and multivariate statistical technique could be a remarkably-helpful analytical method to distinguish the same structured polysulfide silane coupling agents produced by different manufacturers. The summaries are as follows.

It was showed that sample A and B consisted of almost common components.　　Characteristic compounds of each sample C and D were detected, and we could determine the structure of those compounds.It was confirmed that the level of impurity incorporation in each of 4 polysulfide silane coupling agents differed from manufacturer to manufacturer.

Table 2 Result of structure analysis for characteristic compounds

Characteristic Compounds

C16H38O6Si 2S 2 δ-1.07 ppm

Sample C Sample D

C16H38O6Si 2S 3 δ-3.39 ppm

C16H38O6Si 2S 4 δ+1.69 ppm

C17H40O6Si 2S 4 δ-0.92 ppm

C17H40O6Si 2S 3 δ-1.18 ppm

C15H36O6Si 2S 2 δ-1.75 ppm

Main product C18H42O6Si 2S(TESPM) δ -3.01 ppm

C16H38O6Si 2S 2 δ-1.07 ppm



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differential analysis in polysulfide silane coupling ... · chromatograms (ticcs) (fig. 5). it was...

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