Novel Light Stabilizers for Coatings...Copyrights reserved by Everlight Chemical Industrial Corp,...

Sep. 2019

Novel Light Stabilizers for Waterborne UV-Curable

Coatings

Copyrights reserved by Everlight Chemical Industrial Corp, 2019

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Why Should We Use Light Stabilizers forWaterborne UV-Curable Coating?

Degradation

Coatings

Chalking

Color change

Cracking

Delamination


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Damage from UV light

UV-A400nm-320nm : 88%Polymer Degradation

Skin Suntan

UV-B320nm-280nm

9%Polymer

DegradationSkin Sunburn

UV-C<280nm

3%The ozone

layer blocking


Polymer Stabilization

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O2

X X*hv R.RH

O2

O21

ROO.

ROOH RHRH

X is chromophore

RO.

UVA

HALS

Antioxidants


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Conventional UV-curing system

Photoinitiator Light Stabilizer

UV Light

Need UV light to generate

free radical for curing

Absorb UV light and terminate

free radical to prevent

degradation

Reduce line speed

Increase cost


The criteria for UV package in UV-curable system

• Not competing with UV energy.

• High compatibility with UV-curable resins.

• No effect on initial color.

• No interference with production speed.

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The Novel Light Stabilizers for Waterborne UV-Curable Systems

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NLS = Novel Light Stabilizers

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16Min. energy to reach curing need (J/cm2)

3% NLS

2% NLS

1% NLS

Blank

NLS is not affecting curing speed for UV-curable coatings


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Dispersion test in Waterborne UV Curable Resin

(10g UVA/100g Waterborne Polyurethane UV Resin)

filter

Traditional UV Absorbers:Difficult to Disperse in Waterborne Systems

Fail


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Dispersion test in Waterborne UV Curable Resin

filter

The Novel Light Stabilizers for Waterborne UV-Curable Systems

PASS

(10g UVA/100g Waterborne Polyurethane UV Resin)


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Customers usually run into two problems when using UVAs

in the waterborne UV-curable coating

1. Difficult to Disperse in Waterborne Systems

2. Conflict of UVA and Initiator in UV-curable Systems


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New Light Stabilizers forWaterborne UV-Curable Coating


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Model Formulation

Materials Characteristic Structure

Waterborne UV-

Curable Resin

Polyurethane Dispersion

( for water-based system ) ---

Photo-initiator

50% α-Hydroxyketone

+ +

50% Benzophenone

Table 1 Compositions of waterborne UV model formulation

Ingredients Characteristic

AUVA

(for Water-based system)

NLS Formulation of novel light stabilizers

BHALS

(for Water-based system)

Table 2 Classification of light stabilizers


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Table 3 Details of screening design with different light stabilizers and test results

RUN Pattern A NLS B DFT

The min. energy to

reach curing need

(J/cm2)

1 ++-- 1% 1% 0 15 0.108

2 --+- 0 0 1% 15 0.123

3 -++- 0 1% 1% 15 0.123

4 +-+- 1% 0 1% 15 0.197

5 -+-- 0 1% 0 15 0.071

6 ---- 0 0 0 15 0.071

7 +++- 1% 1% 1% 15 0.197

8 +--+ 1% 0 0 15 0.108

9 ++-+ 1% 1% 0 50 0.057

10 --++ 0 0 1% 50 0.063

11 -+++ 0 1% 1% 50 0.063

12 +-++ 1% 0 1% 50 0.065

13 -+-+ 0 1% 0 50 0.051

14 ---+ 0 0 0 50 0.051

15 ++++ 1% 1% 1% 50 0.065

16 +--+ 1% 0 0 50 0.057

Screen Design of Light Stabilizers for Waterborne UV-Curable Coatings

Curing condition: 1x150w/cm2 (High pressure Hg lamp)


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Table 4 Parameter Estimates

Influence of Waterborne UV Absorber

Term Estimate Std Error t Ratio Prob>|t|

Intercept 0.1179286 0.006255 18.85 <.0001

A 0.02975 0.004584 6.49 0.0013

NLS 8.327e-17 0.004584 0.00 1.0000

(A-0.5)*(NLS-0.5) -8.67e-18 0.009168 -0.00 1.0000

B 0.04025 0.004584 8.78 0.0003

(A-0.5)*(B-0.5) 0.0165 0.009168 1.80 0.1318

(NLS-0.5)*(B-0.5) 1.735e-18 0.009168 0.00 1.0000

DFT -0.001879 0.000131 -14.34 <.0001

(A-0.5)*(DFT-32.5) -0.001471 0.000262 -5.62 0.0025

(NLS-0.5)*(DFT-32.5) -1.74e-17 0.000262 -0.00 1.0000

(B-0.5)*(DFT-32.5) -0.001729 0.000262 -6.60 0.0012

For W-UVA, the Influence of curing energy was about 10.1%


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For W-HALS, the Influence of curing energy was about 18.6%



Intercept 0.1179286 0.006255 18.85 <.0001

A 0.02975 0.004584 6.49 0.0013

NLS 8.327e-17 0.004584 0.00 1.0000

(A-0.5)*(NLS-0.5) -8.67e-18 0.009168 -0.00 1.0000

B 0.04025 0.004584 8.78 0.0003

(A-0.5)*(B-0.5) 0.0165 0.009168 1.80 0.1318

(NLS-0.5)*(B-0.5) 1.735e-18 0.009168 0.00 1.0000

DFT -0.001879 0.000131 -14.34 <.0001

(A-0.5)*(DFT-32.5) -0.001471 0.000262 -5.62 0.0025

(NLS-0.5)*(DFT-32.5) -1.74e-17 0.000262 -0.00 1.0000

(B-0.5)*(DFT-32.5) -0.001729 0.000262 -6.60 0.0012

Influence of Waterborne HALS


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For NLS, the Influence of curing energy was about 0%



Intercept 0.1179286 0.006255 18.85 <.0001

A 0.02975 0.004584 6.49 0.0013

NLS 8.327e-17 0.004584 0.00 1.0000

(A-0.5)*(NLS-0.5) -8.67e-18 0.009168 -0.00 1.0000

B 0.04025 0.004584 8.78 0.0003

(A-0.5)*(B-0.5) 0.0165 0.009168 1.80 0.1318

(NLS-0.5)*(B-0.5) 1.735e-18 0.009168 0.00 1.0000

DFT -0.001879 0.000131 -14.34 <.0001

(A-0.5)*(DFT-32.5) -0.001471 0.000262 -5.62 0.0025

(NLS-0.5)*(DFT-32.5) -1.74e-17 0.000262 -0.00 1.0000

(B-0.5)*(DFT-32.5) -0.001729 0.000262 -6.60 0.0012

Influence of NLS (Novel Light Stabilizer)


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Novel Light StabilizerThe correlation between concentration and

film thickness


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w% DFT(μm ) 365nm(T%) 380nm(T%) △Y

0 10 82.5 89 6.5

0 30 71 81.3 7.6

0 50 68.4 79.2 8.4

0 140 52.3 62.1 12.4

1 10 68.7 80.5 3.1

1 30 39 62.5 4.5

1 50 33.5 57.4 5.4

1 140 2.89 19.2 6.7

3 10 50.2 74 1.8

3 30 12 37.1 2.5

3 50 7.86 33 3.2

3 140 1.67 18 3.7

5 10 24.6 55.1 0.8

5 30 6.7 31.6 1.3

5 50 0.7 11.5 1.9

5 140 0.09 6.88 2.2

Two Factors:

NLS2(w%)、DFT (μm )

w% 0 1 3 5

DFT(μm) 10 30 50 140

Test Model ：340nm Light on for 120hrs

Four Levels：

Coated on glass

From the table above, the 5% concentration and 140μm DFT gives the strongest UV-filtration, but the 5% concentration with 10 μm DFT gives the best yellowing color change.


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%9.2012974

2.10512813

%5.6212974

2.10518218

T

EDFTDFTDFT

T

ENLSNLSNLS

SS

MSSS

SS

MSSS

Influence of NLS(w%) with DFT in 365nm

At 365nm, the influence on the concentration of NLS is more important than film thickness.


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%4.2711351

9913213

%7.4711351

9915509

T

EDFTDFTDFT

T

ENLSNLSNLS

SS

MSSS

SS

MSSS

Influence of NLS(w%) with DFT in 380nm

At 380nm, the influence on the concentration of NLS is more important than film thickness.


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%7.74.148

559.0109.12

%8.764.148

559.0157.114

T

EDFTDFTDFT

T

ENLSNLSNLS

SS

MSSS

SS

MSSS

Influence of NLS(w%) with DFT in Yellowness

At yellowness , the influence on the concentration of NLS is more important than film thickness.


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Combining 3 factors in 120hrs weathering study (Optimal Prediction Profilerer)

The optimal combination is 5% conc. In 140μm DFT as the best result.


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Response surface methodology (RSM) (NLS vs. DFT vs. 365nm)


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Response surface methodology (RSM) (NLS vs. DFT vs. 380nm)


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Response surface methodology (RSM) (NLS vs. DFT vs. ΔY)


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Enhanced Color Retention of Waterborne UV-Curable Clear Coatings

0 1 2 3 4 5 6 7 8

Delta Yellowness Index (△YI)

Blank

1% NLS

3% NLS

Resin：Waterborne UV-curable clear coatingExposure Time : 120 hours Test Methods ：ASTM G154-1 (Q-U-V with UVB-340 light bulb)

After Test

Before Test3% NLSBlank

ΔY=7.5 ΔY=1.8

Dosage:

NLS is 1% and 3% on solid content


Conclusions

1. For WUVA, the effect factor of curing energy is about 10.1%.

2. For WHALS, the effect factor for curing energy is about 18.6% and it’s higher than UVA.

3. For NLS, the effect of curing energy was about 0%


Conclusions

4. NLS can be used directly and homogenously disperses very well in waterborne UV curable coating.

5. Test data showed that NLS in the waterborne clear UV curable coating did not influence with curing speed.


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