High Performance water-based resins for all your graphic arts applications
Do you need help to synthesise high quality water based resins for specialty Graphic Arts GA flexographic inks & OPV´s?
Resyner offers synthesis consultancy on a wide range of emulsions for graphic arts flexographic applications.
This study evaluates the performance properties of the most important emulsions for Graphic Arts of Resyner Technologies, which are characterized by offering high added value performance, such as glycol ether free, alkyl phenol ethoxylate (APE) free, very low residual monomers, broad FDA compliance (Food and Drug Administration), etc.
Resyner Technologies consulting services include flexographic packaging inks and innerliners for tobacco metallised paper, overprint varnishes (OPV´s), tissue & detergent inks, food packaging, corrugated, film & aluminium printing, among others.
This study correlates the most important physical-chemical polymer properties such as polymer composition, glass transition temperature (Tg), acidity, and molecular weight to the most important application properties pertaining to specific end markets such as gloss, adhesion, dry & wet crinkle resistance on difficult substrates, water, grease, chemical resistance, and heat resistance.
INTRODUCTION
Most waterborne graphic arts polymers are either low molecular weight resins made in a solution polymerization process, or emulsions, which incorporate low molecular weight resins as raw materials. In either case, the chain of manufacturing processes leading to most waterborne inks begins with a process called solution polymerization. In solution polymerization, a solvent is required to produce the “solution”. After polymerization, most of the residual solvent is removed. However, because 100% removal is impossible, all solution polymers contain some level of residual solvent. In terms of converting and packaging fields, most low molecular weight graphic arts polymers are polymerized in a glycol-ether solvent, and therefore contain residual glycol ether. Analytical testing shows these products, as shipped to the ink maker, generally contain glycol ethers at levels between 2% and 7% of the dry weight of the actual polymer. Studies proved that some glycol ethers may cause DNA lesions that could explain the spontaneous abortions, the malformations and the testicular cancers observed in exposed individuals to this type of substances. Some glycol ethers are also highly odorous and may migrate from printed packaging inks, affecting food flavor.
During polymerization, monomers are reacted to form a polymer. However, because chemical reactions are not 100% efficient, some monomers are not converted into polymers. These unconverted materials, known as residuals, are organic materials (VOCs) which can evaporate. These residual monomers can then migrate into packaged products, tainting aroma and taste. For these reasons, glycol ether and residual monomers are proving unacceptable to many packaged – goods marketers.
The Food and Drug Administration (FDA) sets limits on materials that come in contact with foods and administers regulations. When print on packaging can come in contact with food, or the package contains a printed insert, the ink’s components must be recognized as safe, either as a direct food additive or as an indirect additive, introduced by contact with the food. Therefore FDA compliance is a must for packaging inks polymers.
Chemically referred to as "environmental estrogens", Alkylphenol ethoxylates (APEs) are suspected of causing birth defects in both humans and wildlife through disruption of the endocrine system. Given the reported concerns factors of APE products, there is a growing trend towards the use of APE-free polymers in printing inks.
This presentation emphasizes a sample of Resyner Technologies emulsion polymerisation consulting offer to resin manufacturers interested in producing emulsions, dispersions and resin solutions for water based Graphic Arts flexo inks & OPV´s - a portfolio of high performance products which are glycol ether free, alkyl phenol ethoxylate (APE) free, have very low residuals, and broad FDA compliance.
Resyner Technologies products covered in our synthetic consulting services are designed to cover the specific needs of a large number of water based graphic arts end application markets. Among those, there are certain segments that are almost exclusively water-based, including folding cartons, multi-wall bags, and corrugated products, both pre-printed and post-printed. Another sector where water-based is replacing solvent-based systems is printing on flexible substrates (e.g. films; polyethylene, polypropylene, polyester, PVC, etc) in applications such as shopping bags, grocery sacks and food packaging. Resyner Technologies glycol ether free polymers offer packagers the advantage of using human and environmentally safe, stable and low flammability products.
Another packaging application sector where solvent based systems are used traditionally and water based usage is witnessing a considerable growth, is heat resistant and sealable inks and coatings applications. Our polymers offer the heat resistance and sealability that is required in markets like pouches, lidding, paper plate, and bakery over wraps.
For the chemical resistance required in certain markets, such as wall covering, flooring, household products, tissues and wipes, Resyner Technologies offers products with improved chemical resistance complying with DIN646 (standard for resistance to specific chemicals). Additionally, Resyner Technologies offers products with superior oil and grease resistance for the food wrapping applications.
A growing trend in the folding carton market is the requirement for an increase in the gloss levels of water based systems to compete with the UV technology. This represents a technical challenge due to the technical limitations related to the lower solids of WB systems in comparison to UV. Nevertheless, the further increase of gloss that Resyner Technologies products offer, provide converters with the opportunity to comply with the market needs. On the other hand, the corrugated inks market leans towards economical systems. This market requires low resin solids systems (cost) balancing up with good press runnability (transfer and resolubility during printing) as well as good pigment binding of the printed ink.
|
PROPERTIES
|
EMULSIONS |
COLLOIDAL DISPERSIONS |
SOLUTION RESINS |
|
|
NON-RHEOLOGY CONTROLLED EMULSIONS |
RHEOLOGY CONTROLLED RC EMULSIONS |
|||
|
Molecular weight (Mw) |
200.000 -1.000.000
|
200.000 -1.000.000
|
20.000-200.000 |
<20.000 |
|
AN (mg KOH/g) average |
<10-20 |
50-100 |
30-100 |
100-200 or higher |
|
Tg (ºC) |
Broad range |
Broad range |
Broad range |
Broad range |
|
Resolubility |
Fair |
Fair-good |
Good |
Excellent |
|
Water resistance |
Excellent |
Good |
Fair |
Fair |
|
Chemical resistance |
Excellent |
Good |
Fair |
Fair |
|
Flow & Levelling |
Fair |
Fair-good |
Good |
Very good |
|
Transfer |
Fair |
Fair-good |
Good |
Very good |
|
Pigment wetting |
Fair |
Fair-good |
Good |
Very good |
Table 1. Performance properties of various types of resins technologies.
Table 1 compares the performance properties of the three main water based polymer types. Typically, styrene acrylic emulsions are used for GA applications. Generally, they exhibit low acid numbers and high molecular weights (Mw). Emulsions are organized into two basic categories: rheology controlled RC and non-rheology controlled emulsions, depending on the type of surfactant (emulsifier) used to stabilize the emulsions.
On one hand, Rheology Controlled RC emulsions commonly use high acidic low molecular weight Mw resins as main emulsifier (also named as support). This support stabilizes the emulsion particles during and after polymerization, as well as, additionally confer resolubility, transfer, leveling and press cleaning during application, due to its hydrophilic nature.
Non-rheology controlled or standard emulsions commonly use standard emulsifiers (e.g. APE, and recently some new APE free ones) to stabilize the emulsion particles. Since these systems do not usually contain acidic groups they tend to exhibit better chemical resistance properties than Rheology Controlled RC emulsions. Adversely, they tend to have poor resolubility, transfer, leveling and press cleaning.
Solution resins, which normally refer to solutions of solid resins in water at basic pH, are characterized by having excellent pigment grinding performance, transfer, resolubility, leveling, press cleaning, etc. Their compositions are mainly based on high acidic low Mw styrene acrylic monomer compositions. Mainly, the high acidity and low Mw are responsible for the performance properties stated previously.
Colloidal dispersions have acid numbers and molecular weights intermediate to emulsions and solution resins. Indeed, their performance characteristics are also between both product types. Upon neutralization dispersions become clear solutions due to their hydrophilic nature and their water solubility at basic pH.
EXPERIMENTAL
HEUCOSPERSE™ -BS 9590 (water based pigment blue 15:3 paste) was used as pigment paste for making the starting point water based flexographic ink formulations. The emulsions (letdowns) were added to the pigment pastes at 65/25 ratio for making the water flexo inks. The inks were formulated and diluted to application viscosity of c.20 seconds in Ford cup # 4 at 25ºC and applied on several absorbent (coated paper) and non absorbent substrates (films and aluminum).
The inks were applied with a K bar # 2, at approximately 12 microns wet, on oriented polypropylene (OPP), low density polyethylene (LDPE), polyethylene terephthalate (PET), aluminum (Al) and on a standard coated paper.
The ink applications were dried at 70ºC for 20 seconds. The tape adhesion was measured with a tape immediately and after 24 hours on different substrates. The wet and dry crinkle resistance was measured after 24 hours by crinkling the films between the fingers (under tap water for the wet crinkle). The scratch or mar resistance and gloss of the inks on coated paper were measured with the nail. The chemical resistance to different chemical was measured with the drop test for 60 seconds.
RESULTS & DISCUSSION
This study evaluated the performance of the most important products for Graphic Arts "GA" of Resyner Technologies, which product number reflects their softening or more precisely, their glass transition temperature "Tg". Note: E refers to Emulsion, CR to Chemical Resistance, HA to High Acidity, CD to Colloidad Dispersion in the coding of the products. Examples: Resyncryl GA-E+100 is a Graphic Arts Emulsion with Tg 100ºC. Resyncryl GA-E-25 is a Graphic Arts Emulsion with Tg of -(minus) 25ºC.
Table 2 describes the general product properties, such as solids, Tg, Acid number (AN), pH, minimum film forming temperature (MFFT), viscosity, neutralizer type, etc., as well as several general previously tested characteristics like, transfer, resolubility, press cleaning.
|
Resyncryl GA
|
E+100 |
E+20 |
E-30 |
E+45 |
E-25 |
E-15 |
E+35 |
E+35CR |
CD1 |
CD2HA |
|
Description |
RC styrene acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
RC acrylic emulsion |
Acrylic colloidal dispersion |
Acrylic colloidal dispersion |
|
Solid content (%) |
45 |
45 |
45 |
45 |
45 |
45 |
45 |
45 |
35 |
35 |
|
Tg (ºC) |
100 |
20 |
-30 |
45 |
-25 |
-15 |
35 |
35 |
35 |
5 |
|
MFFT (ºC) |
>70 |
<10 |
<10 |
<50 |
<10 |
<10 |
<10 |
<50 |
<10 |
<10 |
|
Mw (g/mol) |
>200k |
>200k |
>200k |
>200k |
>200k |
>200k |
>200k |
>200k |
>20k |
>20k |
|
Acid Number (mg KOH/g) |
50 |
50 |
85 |
20 |
75 |
50 |
<20 |
<20 |
>100 |
>200 |
|
PH |
8-9 |
8-9 |
8-9 |
8-9 |
8-9 |
8-9 |
8-9 |
8-9 |
5-7 |
8-9 |
|
Brookfield viscosity at 25°C (mPas) |
<1500 |
<1500 |
<1500 |
<1500 |
<1500 |
<1500 |
<1500 |
<1500 |
<1500 |
<5000 |
|
Grinding vehicle |
No |
No |
No |
No |
No |
No |
No |
No |
Yes |
Yes |
|
Transfer- resolubility |
Fair-good |
Fair-good |
Good |
Fair |
Fair-good |
Fair-good |
Fair |
Fair |
Good |
Good |
|
Press cleaning |
Good |
Good |
Good |
Fair |
Good |
Good |
Fair |
Fair |
Good |
Good |
|
Glycol ether free |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Alcohol free |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
FDA clearance |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Table 2. General properties of Graphic Arts product portfolio of Resyner Technologies.
As commented previously, most products are alcohol, glycol ether and APE free. Additionally, the exhibit a broad FDA clearance being suitable for food contact applications.
The final ink application results are shown in Tables 3 and were ranked as follows: 3 Excellent, 2 Good , 1 Poor
|
Properties Resyncryl GA |
E+100/E+20 6/4 ratio |
E-30 |
E+45 |
E-25 |
E-15 |
E+35 |
E+35CR |
CD1 |
CD2HA |
|
Gloss (60º) of inks applied on coated paper at 20 seconds with K bar #2 |
43 |
45 |
35 |
46 |
44 |
38 |
36 |
38 |
37 |
|
Dry rub resistance, 10 double rubs |
2,5 |
3 |
3 |
2 |
2,5 |
3 |
3 |
3 |
3 |
|
Wet rub resistance on coated paper, 10 double rubs |
2,5 |
3 |
2,5 |
3 |
3 |
3 |
2,5 |
1 |
1,5 |
|
Stability, after 90 days at room temperature |
3 |
3 |
2,5 |
3 |
3 |
2 |
3 |
3 |
2,5 |
|
Scratch resistance |
2,5 |
2,5 |
3 |
2,5 |
2,5 |
3 |
3 |
3 |
3 |
|
Oil resistance@ |
2,5 |
2,5 |
3 |
2 |
2 |
2,5 |
3 |
3 |
3 |
|
Etanol resistance@ |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
1 |
1 |
|
Alkali resistance sodium carbonate at 2%@ |
2 |
2 |
3 |
2 |
2 |
3 |
3 |
1 |
1 |
|
Acid resistance acetic acid at 0.5%@ |
2 |
2 |
3 |
2 |
2 |
3 |
3 |
2 |
2 |
|
Detergent resistance@ |
2 |
2 |
3 |
2 |
2 |
3 |
3 |
1 |
1 |
|
Water resistance @ |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
1 |
2 |
|
Tape adhesion on corona treated OPP initial |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
2,5 |
|
Tape adhesion on corona treated OPP after 24 h |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
2,5 |
|
Tape adhesion on corona treated LDPE initial |
1.5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
2,5 |
|
Tape adhesion on corona treated LDPE after 24 |
1,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
2,5 |
|
Tape adhesion on corona treated PET initial |
2 |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Tape adhesion on corona treated PET after 24 h |
2 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Tape adhesion on Al, initial |
1,5 |
3 |
2 |
3 |
2 |
2,5 |
2 |
3 |
1 |
|
Tape adhesion on Al, after 24 h |
1,5 |
3 |
2,5 |
3 |
2,5 |
2,5 |
2,5 |
3 |
1 |
|
Crinkle resistance on corona treated OPP, after 24 h |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Crinkle resistance on corona treated LDPE, after 24 h |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Crinkle resistance on corona treated PET, after 24 h |
2,5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Crinkle resistance on Al, after 24 h |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
|
Wet Crinkle resistance on corona treated OPP, after 24 h |
2 |
2,5 |
1 |
3 |
2,5 |
2,5 |
2 |
2 |
1,5 |
|
Wet Crinkle resistance on corona treated LDPE, after 24 h |
2 |
3 |
2 |
3 |
3 |
2 |
1,5 |
1 |
2 |
|
Wet Crinkle resistance on corona treated PET, after 24 h |
2 |
3 |
3 |
3 |
3 |
2,5 |
2,5 |
1 |
1,5 |
|
Wet Crinkle resistance on Al, after 24 h |
2,5 |
3 |
2,5 |
3 |
3 |
3 |
2,5 |
1 |
2,5 |
|
Temperature resistance; 140ºC, 2 s, 6 bar |
2,5 |
3 |
2,5 |
3 |
1 |
2,5 |
2,5 |
2 |
3 |
|
Temperature resistance; 200ºC, 2 s, 6 bar |
1 |
3 |
1 |
1 |
1 |
1 |
1 |
1 |
3 |
@ drop test; 1 drop of product applied on the surface for 1 minute
Table 3. Application results of the inks formulated with Resyner Technologies product portfolio
Table 3 shows the gloss of the inks. Generally, emulsions tend to confer higher gloss levels than neutralized colloidal dispersions (e.g. Resyncryl GA-CD1) mainly due to their higher solids at application viscosity, which results in higher film thickness, and consequently in gloss.
Rheology Controlled RC emulsions (e.g. Resyncryl GA-E+100, GA-E+20 and GA-E-30) tend to confer higher gloss levels than non-rheology controlled emulsions (e.g. Resyncryl GA-E+35) due to the support resin, which inherently is glossy due to the high refractive index of styrene monomer.
Most products exhibit reasonable dry rub and scratch resistance upon formulation with polyethylene wax. Most emulsions exhibit good wet rub and water resistance, while the neutralized colloidal system (Resyncryl GA-CD1) and the even higher acidity Resyncryl GA-CD2HA had poor wet rub and water resistance. This is due to their hydrophilic nature, as reflected in their high acid numbers.
The stability of the inks was good for most products as reflected in the stability results after 90 days at room temperature. The chemical resistance to oil, ethanol, alkalis, acids and detergent was also tested. As expected, non-rheology controlled emulsions like Resyncryl GA-E+35, GA-E+35CR and GA-E+45 had the best chemical resistance results. Neutralised colloidal dispersions (Resyncryl GA-CD1 and GA-CD2HA) gave the lowest resistance properties due to their inherent hydrophilic nature. These types of products were designed for corrugated ink printing, where chemical resistance is not required but good press runnability and cost effectiveness are desired. Rheology Controlled RC emulsions like Resyncryl GA-E+100, GA-E+20, GA-E-15, GA-E-30 and GA-E-25 have limited chemical resistance mainly due to the resin support, which it is very acidic and consequently susceptible to chemical attack.
Heat resistance was measured at 140 and 200ºC with a heat sealer at 6 bars for 2 seconds. The results reflect that Resyncryl GA-E-30 and GA-CD2HA exhibited the best heat resistance properties among the different systems.
The adhesion properties of the products on OPP, LDPE, PET and aluminium are also compared. The low Tg and medium acidity Rheology Controlled RC emulsions Resyncryl GA-E-25, GA-E-15 and GA-E-30 gave overall good adhesion properties on most films.
The medium-high Tg Rheology Controlled RC emulsions, such as the blend of Resyncryl GA-E+100/GA-E+20 at 6/4 ratio, had worse adhesion properties due to the higher rigidity of the macromolecular backbone. Low Tg emulsions had good overall adhesion properties.
The neutralized colloidal dispersion, Resyncryl GA-CD1, had also good adhesion properties, but reduced wet crinkle resistance under tap water. This is due to its inherent poor water resistance.
Resyncryl GA-E-25 (Tg=-25ºC) had the best wet crinkle resistance among the different products, followed by Resyncryl GA-E-15 (Tg=-15ºC), GA-E-30 (Tg=-30ºC), etc.
Wet crinkle resistance properties are related to a combination of design variables, including adhesion, water resistance, flexibility of the macromolecular backbone, which is related to the softening and to the glass transition temperature "Tg", etc.
Table 5 summarizes the characteristics of the products and their suitability for the most important Graphic Arts applications.
|
LETDOWN: Emulsions or colloidal dispersions |
CHARACTERISTICS |
APPLICATIONS |
|
Resyncryl GA-E-30 |
High gloss, temperature resistance, excellent wet rub resistance, good adhesion on films & aluminium |
High quality water based flexo/gravure printing inks & OPV´s on paper |
|
Resyncryl GA-E+100 |
High gloss & excellent wet rub resistance |
|
|
Resyncryl GA-E+20 |
High gloss & excellent wet rub resistance, good adhesion on aluminium |
|
|
Resyncryl GA-E-25 Resyncryl GA-E-15 Resyncryl GA-E-30 |
High gloss, excellent wet rub resistance, excellent adhesion on films and aluminium |
High quality flexo/gravure printing inks & OPV´s on films & aluminium foil for flexible packaging |
|
Resyncryl GA-E+45 |
Good water & chemical resistance, good adhesion on PVC, PET, etc,… |
Inks for PVC film printing, tissues, napkins. Alkali & detergent resistant inks |
|
Resyncryl GA-E+35 |
Good water and chemical resistance eg detergents, alkalis, etc,... |
Inks for tissues, napkins. Alkali & detergent resistant inks |
|
Resyncryl GA-E+35CR |
Good plasticiser resistance, excellent water and chemical resistance eg detergents, alkalis, oil, etc,... |
Inks & coatings for plastised PVC eg leather & wall paper inks & coatings. Chemical & detergent resistant inks |
|
Resyncryl GA-CD2HA |
Good gloss & hot scuff resistance |
Inks for preprint inks and OPV´s |
|
Resyncryl GA-CD1 |
Good gloss, fair wet & dry rub resistance, excellent holdout, transfer & resolubility, adhesion on PE and aluminium, economics |
Inks for for postprint corrugated applications; Kraft paper, board, polyethylene & aluminium |
Table 5. Summary of product characteristics and applications.
CONCLUSIONS
Resyner Technologies water-based resins portfolio complies with most advanced environmental, health and safety regulations while exhibiting excellent performance properties for a broad variety of GA end applications, including food and tobacco flexographic packaging, where high purity products complying with the most demanding health and safety legislations are required.
Contact us to consult about our emulsion and colloidad synthesis consulting services and your specific performance goals at: info@3Dresyns.com