Synthetic Amorphous Silica as Anticaking Agent. Dr. Monika Maier Product Safety, Inorganic Materials, Evonik Degussa GmbH March 2010

Transcription

1 Synthetic Amorphous Silica as Anticaking Agent Dr. Monika Maier Product Safety, Inorganic Materials, Evonik Degussa GmbH March 2010

2 Agenda Definitions Production process Use as anticaking agent Toxicological data March 2010 Synthetic amorphous silica as anticaking agent Page 2

3 Polymorphs of Silica SILICA [ ] Amorphous Silica [ ] Crystalline Silica [ ] Natural By-Products Synthetic Amorphous Silica [ ] Cristobalite [ ] Kieselguhr (diatomite) [ ] Calcined [ ] Fused Silica [ ] Silica Fume ³ ) [ ] Pyrogenic Silica [ ] Silica Gel [ ] Quartz [ ) Tridymite [ ] Flux-Calcined ² ) [ ] Precipitated Silica [ ] Surface-treated Silica 1) [ ] [ ] [ ] 1) all forms of synthetic amorphous silica may be surface treated, either physically or chemically 2) by-product from electrical furnace 3) partial transformation into cristobalite March 2010 Synthetic amorphous silica as anticaking agent Page 3

4 Definitions March 2010 Synthetic amorphous silica as anticaking agent Page 4

5 ISO TC 229 Nanotechnologies ISO TS (ISO TS ) published Nanomaterial (external or internal dimensions at the nanoscale) ISO DTS In progress Nano-object one or more external dimensions at the nanoscale Nano-structured material internal or surface structure at the nanoscale Nanofibre Nanoplate Nanoparticle Nanocomposite Materials with nano-structured surfaces Assembled nanomaterial Shell structures Aggregate/ Agglomerate nanoscale smaller than 100 nm macroscale larger than 100 nm March 2010 Synthetic amorphous silica as anticaking agent Page 5

6 Nanomaterials Nanoparticles Aggregate Chemically bonded 100 nm Fused, tightly bonded primary particles Agglomerates Van der Waals forces Particles or aggregates stick together Half life time of isolated 20 nm particles above 1 mg/m³ < 3,8 s; Preining, J. Aerosol Sci. 29, (1998) March 2010 Synthetic amorphous silica as anticaking agent Page 6

7 Solid Forms of Synthetic Amorphous Silica are Nano-Structured Materials 100 nm March 2010 Synthetic amorphous silica as anticaking agent Page 7

8 Production process March 2010 Synthetic amorphous silica as anticaking agent Page 8

9 Flame Hydrolysis Process Metal halide: e.g. SiCl 4, TiCl 4, AlCl 3 SiCl H 2 + O 2 SiO HCl Closed Process! Systems are running below atmospheric pressure March 2010 Synthetic amorphous silica as anticaking agent Page 9

10 Fundamentals of Particle Formation nucleation aggregation coalescence & collision agglomeration Precursor Product hot zone cool zone Energy March 2010 Synthetic amorphous silica as anticaking agent Page 10

11 Aggregate Formation during Gas Phase Production at High Temperatures Aggregation March 2010 Synthetic amorphous silica as anticaking agent Page 11

12 Formation of Aggregates and Agglomerates in the Reactor average size of primary particles average size of aggregates residence time / ms Primary particles form aggregates and agglomerates within milli-seconds March 2010 Synthetic amorphous silica as anticaking agent Page 12

13 Use as anticaking agent March 2010 Synthetic amorphous silica as anticaking agent Page 13

14 Action of SAS as Anticaking Agent March 2010 Synthetic amorphous silica as anticaking agent Page 14

15 Synthetic Amorphous Silica (SAS) adheres to Tomato Powder SEM TEM No isolated nanoparticles could be observed by TEM March 2010 Synthetic amorphous silica as anticaking agent Page 15

16 Toxicological Data March 2010 Synthetic amorphous silica as anticaking agent Page 16

17 Routes of Exposure GI Tract Skin Lungs March 2010 Synthetic amorphous silica as anticaking agent Page 17

18 Acute Toxicity Oral Principles of available studies Test animals: rats Test substances (different types of SAS: pyrogenic, precipitated, gel) were suspended in suitable vehicles Test substances were administered orally by gavage - in graduated doses, one dose per group - at one dose level Subsequently, treatment effects and deaths were observed Observation periods from 14 days to 4 weeks March 2010 Synthetic amorphous silica as anticaking agent Page 18

19 Acute Toxicity Oral Results During the observation periods no deaths occurred and no signs of toxicity were observed There were no macroscopical findings at necropsy No signs of toxicity were observed up to mg/kg bw ECETOC JACC Report No. 51 Synthetic Amorphous Silica, September 2006 March 2010 Synthetic amorphous silica as anticaking agent Page 19

20 Repeated Dose Toxicity Oral (1 2) SAS type Species Exposure, Dose (mg/kg bw), Duration Results Pyrogenic Rat Gavage: , for 2 4 weeks Rat Diet: 0, 500, 1000, 2000 for 5 weeks high dose for 8 weeks stepwise increase to (25 % of daily food intake) Rat Diet: 500 for 6 months No clinical symptoms, no macroscopic findings Only in the high dose group clinical findings, no changes in haematological parameters, no macroscopic findings NOAEL = 1000 mg/kg bw No clinical signs or haematological changes Precipitated Rat Gavage: 0, 1500 for 4 weeks No influence on body weight, behaviour and food consumption ECETOC JACC Report No. 51 Synthetic Amorphous Silica, September 2006 March 2010 Synthetic amorphous silica as anticaking agent Page 20

21 Repeated Dose Toxicity Oral (2 2) SAS type Species Exposure, Dose (mg/kg bw), Duration Results Precipitated Rat Diet: 0, 0.5, 2, 8 %, for 13 weeks No clinical symptoms or other findings NOAEL > 8 % (4000 mg/kg bw) Gel Rat Diet: 0, 5 % (5800), 10 % (16500 ) for day % (24200) for day Rat Diet: 2420, 8980 for 6 months No clinical symptoms or other findings (behaviour, water or food consumption, body weight gain) NOAEL > mg/kg bw No treatment related findings NOAEL > 8980 mg/kg bw No substance-related abnormalities could be detected at autopsy ECETOC JACC Report No. 51 Synthetic Amorphous Silica, September 2006 March 2010 Synthetic amorphous silica as anticaking agent Page 21

22 Toxicokinetic after Single Oral Administration (1 2) Study design (based on OECD Guideline No. 417) Test animals: rats Test substance: Precipitated SAS Treatment: - single administration of the test substance orally by gavage at dosage of 1000 mg/kg/day in corn oil (particle size distribution d50% value: 8,4 µm) Observation of treatment effects and deaths throughout treatment To investigate the toxicokinetic profile blood was sampled 1, 3, 6, 9, 12 hours after dosing, urine and faeces was collected at the following intervals: 0-12, 12-24, 24-48, 48-72, hours March 2010 Synthetic amorphous silica as anticaking agent Page 22

23 Toxicokinetic after Single Oral Administration (2 2) A Results No mortality occurred during the study There were no clinical symptoms related to the treatment. Body weight was uneffected by treatment Organ weights were in the normal range for rats of this strain and age Analytical investigations showed no significant increase in silicon dioxide concentration in blood plasma. No significant amounts of silicon dioxide were excreted in urine. Based on the mass balance calculation the given silicon dioxide was excreted with faeces March 2010 Synthetic amorphous silica as anticaking agent Page 23

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