Author: Hubert Oggermüller
Susanne Reiter
Translation: Dr. Horst E. Toussaint
Approval: December 2010
VM / Dr. Alexander Risch
Neuburg Siliceous Earth –
Functional Filler for
Automotive Primer Surfacer
Water Based
HOFFMANN MINERAL GmbH · PO Box 14 60 · D-86619 Neuburg (Donau) · Phone (0 84 31) 53-0 · Fax (0 84 31) 53-3 30 Internet: www.hoffmann-mineral.com · eMail: [email protected]
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Contents
1 Introduction
2 Experimental
2.1 Base formulation and variations
2.2 Preparation
3 Results
3.1 Filler replacement at equal volume
3.2 Filler replacement at equal weight
3.3 Gloss development as a function of the time period
between finalization and application
3.4 Gloss and storage stability
3.5 Stone chipping resistance
4 Summary and outlook
page 2
1 Introduction Automotive filler coats have to meet a number of requirements. The primer surfacer has to cover the surface structure of the substrate, ensure good adhesion to the anti-corrosion EDP (cataphoretic electrodeposition paint) as well as to the base and top coat, and allow them an optimum appearance. In addition, the resistance against stone-chipping should be maximized, and good and rapid sandability will facilitate a possible finish treatment. A filler suitable for automotive filler coats should offer the following properties:
- small particle size (fineness)
- low grit content
- no buffer effect
- low electrical conductivity
- good dispersion properties
- low sedimentation tendency, no hard sediment
- good pigment dispersion (spacer effect)
- low abrasivity
- good corrosion protection
- stone-chipping resistance
- good sanding
- good „filling“
This property profile goes with Neuburg Siliceous Earth, while the question about the best-suited grade remains to be answered. Neuburg Siliceous Earth, extracted in the surrounding of Neuburg (Danube), is a natural combination of corpuscular, crypto-crystalline and amorphous silica and lamellar kaolinite: a loose mixture impossible to separate by physical methods. As a result of natural aging, the silica portion exhibits a round grain shape and consists of aggregated, crypto-crystalline primary particles of about 200 nm diameter which are coated partially opal-like.
page 3
2 Experimental
2.1 Base formulation and variations
The starting point of the study was the base formulation „PTJ 5839 / B“ from Bayer MaterialScience as given in Fig. 1. The pigments and fillers which are incorporated into Batch 1 are shown in colors. The ingredients of Batch 2 are added in the finalization step.
Fig. 1
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Base FormulationPTJ 5839 / B from Bayer
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
Bayhydrol D 270 4.23 Batch 1
Water, deionized 16.00
Dimethylethanolamine, 10 % in water 0.60
Surfynol 104 E 0.52
Additol XW 395 0.52
Borchigen PP 100 0.47
Special Black 4 0.65
Tronox R-FD-I 1.38 Pigments and
Barium Sulfate ppt, micronized 19.44 Fillers
Talkum IT extra 2.23
Aerosil R972 0.36
Bayhytherm 3146 42.81 Batch 2
Bayhydrol PT 241 7.06
Cymel 328 5.23
Byk 011 0.96
Dimethylethanolamine, 10 % in water 0.80
Total 103.26
page 4
Fig. 2 The influence factors were laid down in four categories, as listed in Fig 2. The assessment was based on the criteria quoted. Within the category “fillers”, three different grades of Neuburg Siliceous Earth were compared with a reference filler, barium sulfate. Within the dispersing agents, Disperbyk 111 was chosen because of its gloss enhancing activity (Fig. 3), as it became known from preliminary tests. In these formulations, also an effect of the time between finalization and application was observed, and consequently systematic time intervals starting with 2.5, 24, 72 and 168 hours were introduced. In view of the low pH of Disperbyk 111, the study included also the effect of the concentration of dimethylethanolamine which was used for neutralization along with a corresponding rise of the pH level.
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Experimental
Influence of
» functional fillers
» dispersing agents
» time between adding of batch 2 (finalization) and application
» content of amine based neutralization additive (DMEA)
Test criterions
» gloss 60 °
» storage stability
» stone chipping resistance
Formulation variations
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 5
Fig. 3
2.2 Preparation Fig. 4 gives a summary of the preparation and application parameters used. Noteworthy is the low baking temperature of this coating, as made possible by the specially selected binders.
Fig. 4
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Experimental
Fillers
» Barium sulfate, precipitated, micronized
» Sillitin Z 86
» Sillikolloid P 87
» Aktisil AM
Additives
» Borchigen PP 100
» Disperbyk 111
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
Formulation variations
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Experimental
Mixing machine: APS 1000
Batch size: 250 g Batch 1 and 300 ml glass beads
Grinding: 15 min 2000 rpm (7.9 m/s) with water cooling
Finalisation: 10 min 1200 rpm with a dissolver
with 3 cm tooth disc
Dilution: spray viscosity 30 s in 4 mm cup ISO 2431
Application: 0.8 mm pistol nozzle, pressure 4 bar, on
steel panels, Type R 48, Q-Panel
Dry film thickness: approx. 30 µm
Drying: 10 min at RT
Baking: 30 min 130 °C
Preparation
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 6
3. Results
3.1 Filler replacement at equal volume
When replacing the barium sulfate with an equal volume of Neuburg Siliceous Earth, the changes in particle size and filler morphology, in particular the lamellar kaolinite portion, exert an influence on the gloss level. In comparison with the reference formulation, the best results are obtained with Aktisil AM (Fig. 5), which is why the following studies focused on this aminosilane treated filler.
Fig. 5
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FormulationsFiller variations, replacement by volume
Recipe 1 2 3 4
Borchigen PP 100 0.47 0.47 0.47 0.47
Talkum IT extra 2.23 2.23 2.23 2.23
Barium sulfate ppt 19.44 -- -- --
Sillitin Z 86 -- 11.49 -- --
Sillikolloid P 87 -- -- 11.49 --
Aktisil AM -- -- -- 11.49
Total 103.26 95.31 95.31 95.31
PVC 20.2 20.2 20.2 20.2
Solids content (w/w %) 48.0 44.2 43.9 43.8
at spray viscosity
Gloss, 60° 81 52 45 54
application 2.5 h
after finalization
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 7
3.2 Filler replacement at equal weight
In the interest of increasing the volume solids content, the precipitated barium sulfate was replaced by an equal weight of Aktisil AM, and the dispersing agent Borchigen PP 100 was replaced by Disperbyk 111 with an increased concentration. For comparison, relevant formulations with Sillitin Z 86 are also shown (Fig 6). Note the markedly increased PVC and partly even the increased mass solids content. The mass and volume solids contents at spray viscosity are calculated figures, the mass solids content was additionally determined as the percent residue of non-volatile components after 1 h at 150 °C.
Fig. 6 The following test criteria were chosen:
- gloss at 60° - Storage stability
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FormulationsFiller variations, replacement by weight / Additive variation
Recipe 1 5 6 7 8 9
Borchigen PP 100 0.47 -- -- -- -- 0.47
Disperbyk 111 -- 0.47 0.98 1.49 0.98 --
Talkum IT extra 2.23 2.23 2.23 2.23 2.23 2.23
Barium sulfate ppt 19.44 -- -- -- -- --
Sillitin Z 86 -- -- -- -- 19.44 19.44
Aktisil AM -- 19.44 19.44 19.44 -- --
Total 103.26 103.26 103.77 104.28 103.77 103.26
PVC 20.2 27.5 27.5 27.5 27.5 27.5
Solids content calculated at spray viscosity (v/v %)
36.1 38.2 39.7 40.9 39.8 37.4
Solids content calculated at spray viscosity (w/w %)
49.9 49.9 51.3 52.6 51.4 49.0
Solids content determined at spray viscosity (w/w %)
48.0 48.5 49.8 51.5 49.8 47.2
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 8
3.3 Gloss development as a function of the time period between
finalization and application
As shown in Fig. 7, the final gloss can definitely be affected by the time period between finalization and application. The gloss values of the formulation with precipitated barium sulfate come out independent of the time with a 60° gloss of around 80 units. Aktisil AM in combination with 1.49 parts Disperbyk 111 attains the high gloss levels of the reference after 72 hours. Even the addition of 0.98 parts Disperbyk 111 allows to arrive almost at the same level. By contrast, with Sillitin Z 86 in spite of the addition of 0.98 parts Disperbyk 111, no improvement of the gloss levels can be observed (Fig. 7). The addition of Aktisil AM and 0.98 parts Disperbyk 111 makes it possible to reach a gloss level of 70-80 units already after 72 hours.
Fig. 7
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Gloss DevelopmentTime between finalization and application
20
30
40
50
60
70
80
90
0 24 48 72 96 120 144 168
[h]
Glo
ss 6
0°
Barium sulfate ppt. Aktisil AM Sillitin Z 86
0.47
1.49
0.98
0.98
Borchigen PP 100
Disperbyk 111
0.47
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 9
In Fig. 8, the gloss results are compared, this time in number values. The benefits of the optimized formulations with Aktisil AM versus the untreated base material Sillitin Z 86 come out very evident when comparing the formulations 6 and 8. Note: the gloss results of formulation 9 were determined only 2.5 hours after finalization, because the original result came out already much lower than the other versions.
Fig. 8
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Gloss DevelopmentNumeric Overview
Recipe 1 5 6 7 8 9
Borchigen PP 100 0.47 -- -- -- -- 0.47
Disperbyk 111 -- 0.47 0.98 1.49 0.98 --
Talkum IT extra 2.23 2.23 2.23 2.23 2.23 2.23
Barium sulfate ppt. 19.44 -- -- -- -- --
Sillitin Z 86 -- -- -- -- 19.44 19.44
Aktisil AM -- 19.44 19.44 19.44 -- --
Gloss 60°
at application
2.5 h 81 35 57 69 40 18
24 h 82 44 65 77 38 n.b.
72 h 81 58 77 80 36 n.b.
168 h 81 69 81 82 34 n.b.
after finalization
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 10
3.4 Gloss and storage stability
The influence of the addition of the amine neutralization agent dimethylethanloamine (DMEA) on gloss and storage stability was evaluated because Disperbyk 111 with its acidic groups has a low pH and, therefore, tends to consume part of the DMEA for its own neutralization. The figures indicated refer to the total dosage of DMEA in the formulation (Example formulation no. 10: DMEA addition of 1.40 parts as in the original recipe plus 1.96 parts for the neutralization of the Disperbyk 111 results in a total amount of 3.36 parts DMEA). This way, in order to bring up the pH to the level of the reference formulation, the addition of DMEA in formulations no. 10 and 12 was increased. Formulation no. 11 served as a comparison with formulations no. 6 and 7 to show how gloss and storage stability come out when the pH remains low. The formulations used are shown in Fig. 9
Fig. 9 Fig. 10 gives a summary of the gloss results obtained from the formulations after application one day after preparation, as well as the storage stabilities expressed in days up to observed gelation. The graph includes the formulation with precipitated barium sulfate as well as the version with Aktisil AM, in combination with varying levels of Disperbyk 111 and dimethylethanolamine (DMEA). The pH levels are shown as an index for the expected time to gelation. A higher pH as expected leads to an improved storage stability, a lower pH to higher gloss at rapid application 24 hours after finalization. A maturing period of one week between finalization and application allows to obtain high gloss along with good storage stability (Fig. 11).
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Gloss and Storage StabilityDosage of amine based neutralization additive (DMEA)
Recipe 1 6 7 10 11 12
Borchigen PP 100 0.47 -- -- -- -- --
Disperbyk 111 -- 0.98 1.49 0.98 0.98 1.49
Talkum IT extra 2.23 2.23 2.23 2.23 2.23 2.23
Barium sulfate ppt. 19.44 -- -- -- -- --
Aktisil AM -- 19.44 19.44 19.44 19.44 19.44
DMEA, 10 % 1.40 1.40 1.40 3.36 0.70 4.38
in total formulation
Total 103.26 103.77 104.28 105.73 103.07 107.26
Solids content (w/w%) 48.0 49.8 51.5 46.4 51.4 n.d.
at spray viscosity
pH 8.2 7.4 7.1 8.1 7.2 7.8
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 11
Fig 10
Fig. 11
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Gloss and Storage StabilityApplication 24 h after finalization
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 90 100
Storage Stability, time to Gelation [days]
Glo
ss 6
0°
Barium sulfate ppt. Aktisil AM
Borchigen PP 100
Disperbyk 111
Dimethylethanolamine
pH
0.98
1.40
7.4
0.98
0.70
7.2
0.98
3.36
8.1
1.49
4.38
7.8
1.49
1.40
7.1
0.47
1.40
8.2
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
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Gloss and Storage Stability
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 90 100
Storage Stability, time to Gelation [days]
Glo
ss 6
0°
Barium sulfate ppt. Aktisil AM
Application 168 h after finalization
0,98
1,40
7,4
0,47
1,40
8,20,98
0,70
7,20,98
3,36
8,1
1,49
4,38
7,8
1,49
1,40
7,1
Borchigen PP 100
Disperbyk 111
Dimethylethanolamine
pH
EINLEITUNG
EXPERIMENTELLES
ERGEBNISSE
ZUSAMMEN-
FASSUNG
page 12
Fig 12 shows a summary of the two preceding graphs, with a representation of the development of gloss levels during a maturing period of 24 to 168 hours after finalization. All formulations after one week show a high gloss level of at least 70 units which should be absolutely sufficient for the majority of end users.
Fig 12
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Gloss and Storage Stability
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 90 100
Storage Stability, time to Gelation [days]
Glo
ss 6
0°
Barium sulfate ppt. Aktisil AM
Application 24 h and 168 h after finalization
0.98
1.40
7.4
0.47
1.40
8.20.98
0.70
7.2
0.98
3.36
8.1
1.49
4.38
7.8
1.49
1.40
7.1
Borchigen PP 100
Disperbyk 111
Dimethylethanolamine
pH
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 13
3.5 Stone chipping resistance
The tests for stone chipping resistance were carried out at Bayer MaterialScience under the following conditions: filler coat onto DC-KTL 10’ 80°C + 20’ 140°C waterborne base coat 10’ 80°C + 2K-clearcoat 10’RT + 20'135 °C. Formulation: filler replacement at equal volume, additive: 0.47 parts Borchigen PP 100. After VDA stone chipping test (2x500 g, 1.5 bar, 45°), the coating with Aktisil AM shows at least the same behavior as the reference with precipitated barium sulfate. The BMW stone chipping test with the single impact hammer at -30 °C confirms for the coating with Aktisil AM a better result. The flaked-off surface area is distinctly smaller than for the coating formulated with precipitated barium sulfate (Fig. 13).
Fig. 13
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Stone Chipping Resistance
BMW stone
chipping test
(single impact
hammer)
at -30 °C
VDA stone
chipping test
(multi impact)
2 x 500 g
1.5 bar / 45 °
Aktisil AMBarium sulfate ppt.INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
page 14
4. Summary and outlook
Aktisil AM in combination with Disperbyk 111 offers despite of the equal weight replacement (higher volume filler portion in the formulation and, therefore a higher PVC), very good gloss levels in comparison with the precipitated micronized barium sulfate. Formulations with high gloss and good storage stability can be designed via an increased DMEA addition and sufficiently long time between finalization and application. Aktisil AM also imparts an improved resistance against stone chipping, in particular when tested with the BMW stone chipping test (single impact hammer) at -30°. Fig. 14 gives a recommendation for a formulation with Aktisil AM.
Fig. 14 Our technical service suggestions and the information contained in this report are based on experience and are made to the best of our knowledge and belief, but must nevertheless be regarded as non-binding advice subject to no guarantee. Working and employment conditions over which we have no control exclude any damage claims arising from the use of our data and recommendations. Furthermore, we cannot assume any responsibility for any patent infringements which might result from the use of our information.
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RecommendationFor use with Aktisil AM
INTRODUCTION
EXPERIMENTAL
RESULTS
SUMMARY
Bayhydrol D 270 4.23 Batch 1
Water, deionized 16.00
Dimethylethanolamine, 10 % in water 0.60
Surfynol 104 E 0.52
Additol XW 395 0.52
Disperbyk 111 0.98
Special Black 4 0.65
Tronox R-FD-I 1.38 Pigments and
Aktisil AM 19.44 Fillers
Talkum IT extra 2.23
Aerosil R972 0.36
Bayhytherm 3146 42.81 Batch 2
Bayhydrol PT 241 7.06
Cymel 328 5.23
Byk 011 0.96
Dimethylethanolamine, 10 % in water 0.80
Total 103.77
