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Additives for plastic coatings“Surface Control Agents―Leveling, Slip, Anti-Scratch and Anti-Stain”

1. Introduction
Plastics are flexible and light materials and they are widely used forvarious products such as cellular phones and laptops. However, someplastic properties like hardness, color and gloss are often insufficient tomeet the market's demands. That's the reason why plastic coatings areneeded.
In general, isocyanate cure coatings and UV cure coatings are used forplastics. Coating films are classified to three types, primers, base coats
and top coats. For plastics, top coats are especially important. For
example, we carry around cellular phones and use them for a long time.
Of course we care about appearance and colors of cellular phones.
Therefore top coats need to have durable and beautiful surfaces, andthen leveling, slip, anti-scratch and anti-stain properties are generallyrequested for top coats of plastic coatings.

SOFTBANK MOBILE corp.

In this document, we would like to introduce our additives which
provide these various required properties.

2. Leveling, slip, anti-scratch and anti-stain properties for clear top coats
1) Additives for plastic coatings
Isocyanate cure coatings and UV cure coatings are often used for plastics as clear top coats.
There is wide variety of resins, and various needs such as improvement of leveling, anti-scratch
and anti-stain properties. Therefore, we have to select the appropriate additives to fulfill therequirements for each type of resin.
First, we would like to introduce our surface control agents as follows:
Acrylic /Vinyl Polymer TypeFeatures: Slightly reducing the surface tension of coatings
Improving the levelingLess trouble with poor adhesion, cratering, cissing, and foaming etc
Excellent recoatability (excellent printing properties)
Fig1( CH2CH )n( CH2C=OCH )nRO
Polyacrylate

PolyvinylR
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R = Alkyl, Polyether,
Silicone …
Homopolymer/ Copolymer

2/6

Silicone Type (Polysiloxane / Modified Polysiloxane)
Features: Significantly reducing surface tension of coatings
Improving the leveling
Providing slip, anti-scratch and anti-cratering properties
Small dosage
Fig2SiSiOOSiSiOxPolyether-modified
polysiloxane

yO

EOO

Pendant structuremPOOnR

Table2. Type of additive
Product

Chemical type

SPL-70, SPL-71

Acrylic / Vinyl Polymer with Silicone

SPL-80Acrylic-Silicone Copolymer

SPL-90, SPL-91
SPL-92, SPL-93, SPL-94

Silicone

Advantage
Good Balance ofLeveling and Slip
Recoatability(Printing property)
Slip / Anti-Scratch

Surface tension order
Silicone ≦ Acrylic / Vinyl polymer with Silicone ＜ Acrylic-Silicone copolymer
SPL-93≦SPL-92＜SPL-91＜SPL-94＜SPL-90＜SPL-70＜SPL-71＜SPL-80
Low

Surface tension

HighGenerally, additives which reduce surface tension significantly (like silicone type) need only small
amounts of dosage and can impart slip, anti-scratch and anti-cratering properties very well.
However this kind of additives may inhibit the inter coat adhesion.
On contrary, additives which reduce surface tension slightly (like acrylic/vinyl polymer type) havemild effects and tend not to cause problems such as inter coat adhesion, cratering and foaming.
We offer a wide range of additives to meet the various needs in various resin systems.

Copyright 2011. Kusumoto Chemicals, Ltd. All right Reserved.

3/61) Improvement of leveling
Isocyanate cure coatings are also called 2KPU coatings. "2K" means two-component (2Komponent in German) and "PU" stands for polyurethane. In this coating system, films areformed by the reaction of a polyisocyanate with a polyol. Since isocyanate cure coatings are toughand look thick, the coatings are used for base coats and top coats of plastics.
Below you can find the leveling test result of our additives in a 2KPU coating.
We adjusted the solid content of different kinds of leveling additives to 0.05% and applied thepaint by air spray. Then we evaluated leveling improvement by checking the coating film
reflected images of fluorescent light tubes. A flat and smooth surface gives sharp images.
The results are as follows:
Table3. Effect of leveling additives
AdditiveBlank
SPL-80SPL-93

Leveling
155Anti-cratering
155Slip
115
Excellent : 5 Poor :1

In the 2KPU coating, SPL-80 and SPL-93 showed excellent leveling and anti-cratering effects.
(Table2 & Photo 1)
SPL-80, an acrylic-silicone copolymer, doesn’t contain free-silicone. So SPL-80 could achieve
excellent leveling and anti-cratering effect without a recoatability problem. On the other hand,the silicone based product SPL-93 imparted excellent slip properties to the coating. (Table 2)

Photo1. Leveling improvement

BLANK

SPL-80

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SPL-93

4/63) Slip and anti-scratch properties
Plastics have excellent formability, but the surfaces are soft and get scratched easily. So UV hardcoatings such as urethane acrylate are often applied to plastics for surface protection. UV hardcoatings have a good scratch resistance, but the anti-scratch properties can be improved withadditives. An additive which provides excellent slip property can reduce the friction resistance ofa coating film and prevent the film surface from getting scratched. You can feel the slip effect byrubbing a film with a cloth.
UV coatings composed of urethane acrylate resins are quite hard. The hardness of the film isusually over 5H in pencil hardness test. Thus we used a rubbing meter with steel wool toevaluate the scratch resistance. (Photo 2)
Generally, we can find scratches on films which are rubbed about 50 times by a rubbing meter,with some silicone based additives, scratches will not be observed even after 150 times rubbing.
Photo2

Steel wool #0000

Rubbing meter (Suga test instruments Co., Ltd.)The pictures (Photo 3) show how the scratch resistance can be improved by an additive.
We prepared two films of a 2KPU coating, one didn’t contain any additive and the othercontained 0.5% SPL-92 which is a silicone based surface control agent. Those films were rubbed
1000 times by a rubbing meter with gauze.
2KPU films are softer than UV coatings. As shown in the picture, there were a lot of scratches
observed on the Blank film. The film with SPL-92 didn't get scratched much. Moreover, the valueof 20°gloss of the SPL-92 film was higher than the Blank.
Photo3. Anti-scratch

20o GlossBlank
82.2

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SPL-9290.85/64) Anti-stain and easy-cleaning properties
Recently, touch panels are widely used for smart phones, computers and vending machines etc.
Like touch panels, there are a lot of products which are required to have anti-stick (anti-stain /anti-fingerprint) properties and easy-cleaning properties. A smooth and slippery surface is also
important.
To meet these requirements, some additives which have a low surface tension are used. There
are two types of this kind of product, the silicone-based type and fluorine-based type. We would
like to introduce a silicone-based product here.
As shown in the pictures (Photo 4), a line drawn by a marker pen on the film which contains asilicone-based product is easily wiped off with a dry gauze.
Photo4 Easy-cleaning

wipe withgauze

Keeping this kind of effects is also important. There are some common silicone products whichhave excellent slip, anti-stain and easy-cleaning properties at first. However, repeated wiping,touching and cleaning removes the silicones from the film surfaces and the effect will not last. Aproduct which can react with the resin keeps the effect for a long time since it is fixed on the film
surface.
This is an evaluating method of an easy-cleaning effect and durability. (Fig 3)First, wipe half of the film 50 times with an IPA wetted gauze. Then draw a line on the film witha marker pen. Finally, wipe the line on the film with dry gauze and compare the IPA Wiping Partto the No Wiping Part.
Fig3.
Evaluation methodof easy-cleaningand durability

Glass plate
IPA wet gauzeFilm

Wipe

IPA wiping

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No wiping6/6LS-280 is a hydroxy-functional silicone leveling and slip agent. The features are excellent slip,anti-stain, anti-slip and easy-cleaning properties. We evaluated LS-280 in a 2KPU coating andcompared it with the Blank and the non-reactive silicone product (Conventional product).
Additive dosages are 0.03% solid.
The marker line on the Blank film was never erased. The non-reactive conventional product lostthe easy-cleaning effect after IPA wiping. LS-280 showed an excellent easy-cleaning effectwhether wiped or not. (Photo 5)
Photo5. Easy-cleaning properties and durability
IPA wiping

No wiping

BlankIPA wiping

No wiping

LS-280

IPA wiping

No wiping

Conventional productAs mentioned in the document, many properties such as leveling, slip, anti-scratch and anti-stain
are required for plastic coatings. And we offer a wide range of additives to meet your various
needs in various resin systems.

Copyright 2011. Kusumoto Chemicals, Ltd. All right Reserved.