Silica for car paint, what kind of silica is used? Is it meteorological method, precipitation method or silicon dioxide? What are the requirements?

It is micron grade, the particle size is 10-20, and the fineness is less than 10 micron. Fumed silica (as an anti-precipitation).

Medium paint:

Pigments and fillers are all made in China. Pigment provides hiding power for intermediate paint, and filler plays a filling role.

Pigments include domestic anatase titanium dioxide (A 10 1, B 10 1), lithopone and carbon black.

Fillers include precipitated barium sulfate, superfine barium sulfate, superfine talcum powder, superfine kaolin and superfine calcium carbonate, and hollow microspheres are the best. The purpose of using superfine filler is to meet the requirements of high fineness of intermediate coating and the fineness of intermediate coating.

Talcum powder and calcium carbonate in the filler are light-absorbing, and only half light can be achieved when the dosage exceeds 10% (all pigments and fillers). Not suitable for high-gloss OEM intermediate coating.

The following are three commonly used midcoat formulations:

A

One-component thermoplastic acrylic self-drying intermediate coating (using acrylic acid and nitrocellulose) is usually used as intermediate coating for repair. Self-drying 1HR can be polished, smooth and shiny.

Medium size preparation: P/B = 80/20, S = 70%.

Thermoplastic acrylic resin 28

Domestic anatase titanium dioxide (A 10 1) 30

Ultrafine talcum powder (1250 mesh) 15

Hollow Beads (Hainawei Company) 10

Fumed silica (as precipitant) 1

BYK-P- 104 0.50

Ethylene glycol ether acetate 5

Xylene to 100

Domestic high pigment carbon black was mixed into water ash, and the amount of titanium dioxide added was five thousandths. After adding it, grind it or draw it together.

Then color it with black paste.

The high-speed disperser disperses evenly, sanding 1-2 times, and controlling fineness.

Preparation of nitrocellulose solution (s = 21%);

1/2 s nitrocellulose (containing 30% alcohol) 30

Butyl acetate 70

After soaking in 12HR, stir evenly at low speed, and let stand overnight before use. (stored in galvanized bucket)

Matching paints are as follows:

Medium size (P/B = 80/20, S = 70%) 42

Thermoplastic acrylic resin (S = 50%) 22

1/2s nitrocellulose solution (S = 2 1%) 20

Butyl acetate 10

Xylene to 100

Acrylic self-drying intermediate coating (S = 45%), viscosity about 150-250S (coating -4/25℃). The diluent may be a two-component system diluent (II)

Toluene/butyl acetate/ethylene glycol ether acetate = 50/35/ 15), and flash paint thinner (xylene) can also be used at low temperature.

/butyl acetate = 50/50), because it is a nitric acid system, the amount of strong solvent in the diluent must be >: 40%.

Thermoplastic acrylic acid and nitrocellulose are completely miscible in nitric acid system, so it is necessary to determine the compatibility when choosing other thermoplastic acrylic acids to replace them. The determination method is as follows:

50/50 thermoplastic acrylic acid and nitrocellulose (solid ratio) are mixed, diluted with butyl acetate until the mixed solution is transparent, coated on a transparent glass plate, and dried at 60-80 ~ C. When it is completely transparent, it indicates good compatibility.

B

Two-component acrylic polyurethane intermediate paint (using TDI adduct as curing agent, drying at 60℃/ 1hr or white drying for 24HR and then polishing)

Acrylic resin adopts low hydroxyl resin, such as Deqian 2050, Bayer A-405 and medium hydroxyl toughness resin, such as Guan Xu Additives Factory 450).

There are many curing agents for TDI adducts, such as Bayer L-75 and Deqian DL-75. The solid content of most domestic varieties is about 50%, which needs to be tested. TDI curing agent has high viscosity and must be diluted before use. Medium light, luster 40~60%.

Dilute DL-75 to 50% for later use:

L-75(S=75%) 66.6

Ethyl carbamate anhydrous butyl acetate 33.4

Medium size preparation: P/B = 80/20, S = 70%.

Acrylic resin (Guan Xu Additive Factory 450) (S = 55%) 25

Domestic anatase titanium dioxide (A 10 1) 35

Ultrafine talcum powder (1250 mesh) 9

Hollow Beads (Hainawei Company) 12

Carbon black (domestic high pigment carbon black) 0. 15

BYK-P- 104 0.56

Ethylene glycol ether acetate 5

Xylene to 100

The high-speed disperser disperses evenly, sanding 1-2 times, and controlling fineness.

Matching painting:

Medium size (P/B = 80/20, S = 70%) 52

Acrylic resin (Guan Xu Additive Factory 450) (S = 55%) 35

BYK-358 0.5

Butyl acetate 5

Xylene to 100

Acrylic polyurethane intermediate coating (S 2 55%), viscosity about 60-90S (coating -4/25℃).

The ratio of 50% DL-75 curing agent is (5: 1), and the two-component system diluent (xylene/butyl acetate/ethylene glycol ether acetic acid

Ester = 50/35/ 15). If low hydroxyl resin (Deqian 2050, Bayer A-405) is used, the ratio of (intermediate coating: curing agent) is (8: 1). When the primer is not completely dry, it is easy to bite when spraying the topcoat, and the topcoat can only be sprayed after drying at 60℃/0.5 hour or self-drying 1.2 hours ... The performance of both components is better than that of thermoplastic nitric acid intermediate coating. No desiccant is needed, otherwise the construction time will be less than 4 hours. If self-drying is too slow in cold weather, 0.2% desiccant (1% xylene solution) can be added.

C

Polyester amino intermediate paint: (alkyd amino intermediate paint)

OEM midcoat containing polyester amino group has excellent stone impact resistance, and (344/582) aminoalkyd is used under low requirements.

Basic system. Generally, the coatings in the OEM baking varnish are high gloss (60-80% gloss), which requires high toughness and hardness, and the acrylic amino system is difficult to meet the requirements, so polyester amino is usually selected.

Medium size preparation: P/B = 80/20, S = 80%.

Polyester resin (300 polyester) (S = 60%) 27

Domestic anatase titanium dioxide (A 10 1) 40

Ultrafine talcum powder (1250 mesh) 6

Hollow Beads (Hainawei Company) 18

Carbon black (domestic high pigment carbon black) 0.2

BYK-P- 104 0.7

Ethylene glycol butyl ether 5

Xylene to 100

The high-speed disperser disperses evenly, sanding 1-2 times, and controlling fineness.

Matching painting:

300 polyester medium size (P/B = 80/20, S = 80%) 45

300 polyester fiber (s = 60%) 33

5386 amino groups (s = 60%) 15

BYK-3 10 0.2

BYK-358 0.5

Ethylene glycol butyl ether 2

Butanol 3

Xylene to 100

Polyester primer coating (S = 65%), viscosity about 60-90S (coating at -4/25℃), drying 120- 140℃/0.5 hr, diluent xylene/150 aromatic hydrocarbon/butanol/ethylene glycol butyl ether (. Leveling agent BYK-3 10 and BYK-358 shall not be added (on the premise of ensuring leveling).

The production ratio of (344/582) alkyd amino intermediate coating is similar to that of polyester intermediate coating:

Medium size preparation: P/B = 80/20, S = 80%.

Alkyd resin (modified by 344-2 soybean oil from Xinhua Factory) (S = 55%) 30

Domestic anatase titanium dioxide (A 10 1) 40

Ultrafine talcum powder (1250 mesh) 6

Hollow Beads (Hainawei Company) 6

Precipitated barium sulfate 5

Carbon black (domestic high pigment carbon black) 0.2

BYK-P- 104 0.7

Butanol 5

Xylene to 100

The high-speed disperser disperses evenly, sanding 1-2 times, and controlling fineness.

Matching painting:

344-2 Medium size (P/B = 80/20, S = 80%) 43

344-2 polyester fiber (S = 55%) 3 1

582 amino groups (s = 60%) 13.5

Butanol 5

Xylene to 100

Alkyd amino intermediate paint (S=60%), viscosity about 60-90S (coated at -4/25℃), dried at130-140℃/0.5h, and xylene/150 aromatic hydrocarbon/butanol/ethylene glycol butyl ether was used. Alkyd resin has good leveling performance, so leveling agent BYK-3 10 and BYK-358 can be omitted.

Alkyd primer is not resistant to excessive baking. Repeated high temperature baking will precipitate the modified oil, which will affect the performance of paint film and interlayer adhesion.

The storage stability of the coating during baking must be determined: after 7 days storage at 60℃, the viscosity will not increase by more than 40%.