Wetting Agent in Coagulant

Manufacturer: We are having problems of wetting with our coagulant resulting in uneven latex coating and thin spots of our products. We are using Triton X100. Can you trouble shoot for us?

John Woon (Senior Latex Consultant): Triton X100 is a good wetting agent but it tends to foam which might lead to weaknesses in the final products.

You should evaluate Teric 320 (Ethoxylates of long chain aliphatic alcohols with 16 moles of ethylene oxide) or the more expensive Surfynol TG from Air Products which has the least tendency to foam. Some manufacturers are adding a small level of Surfynol TG in the coagulant tank to prevent the formation and foam and air bubbles.

Another possible reason for your problem could be the wrong choice of coagulant temperature. All wetting agents used in coagulant are normally non-ionic surfactants which have a unique property – they become less soluble in water when the temperature increases. The temperature at which they become insoluble (i.e. becoming cloudy) is termed the “Cloud Point”.

Whatever wetting agent you are using, you must know the cloud point. You can determine the cloud point by doing the following:

After you have dissolved calcium nitrate in the water, add the wetting agent and mix for about 15 to 20 minutes. Do not add the detack powder.

Introduce this into a beaker and heat it on a hot plate with a magnetic stirrer. Put a thermometer in the beaker to monitor the rise in temperature while the coagulant is being heated and stirred. Once the solution becomes cloudy, take note and record the temperature. This would be the “cloud point” of your coagulant.

When the solution is allowed to cool down, it would become clear again once the temperature falls below the “cloud point”.

It is important due to the following two reason:

Assuming the “cloud point” of your coagulant is 60ºC and the actual temperature of your coagulant in your dipping line is 62ºC, the coagulant would perform as if there is no wetting agent since the wetting agent has become insoluble and therefore lost its function as a wetting agent.

Please refer to Page 20 to Page 25 of my separate report to you.

Hope this would help.

Latex Compounds for Back-Sizing of Woven Carpets

Manufacturer: We are using natural rubber latex compounds for Back Sizing (back coating) of woven carpets. Please suggest some tests we should carry out to ensure consistency in coating quality.

John Woon (Senior Latex Consultant): Your latex compounds should be designed to have the following properties:

1) Constant solid content
2) Consistent viscosity. However it should not be too thixotropic.
3) Should be free from too much bubbles otherwise areas where the bubbles burst would be left uncoated.
4) The surface tension should be low enough to give good wetting property to allow it to penetrate to lock the individual tufts while "strike through" due to too much wicking is prevented.
5) The compound must have sufficient mechanical stability to withstand transportation, mixing and pumping.

I suggest carry out the following tests:

1) Total Solid Content
2) pH
3) Viscosity including measurement of thixotropy
4) MST (Mechanical Stability Time)
5) Coagulum Content
6) Surface Tension

India Overtakes U.S. As Second Largest Consumer of NR

India has overtaken the recession-hit U.S. as the second largest consumer of natural rubber, clocking a 6.8 percent growth in 2009-10. India's consumption of rubber rose to 930,565 metric tons in 2009-10 from 811,720 metric tons. The United States lost the No. 2 position after its consumption plummeted by 34 percent on account of the economic slowdown. China is the world's largest rubber consumer. During 2008-09, the consumption of natural rubber by the U.S. was 1,041,000 metric tons, which fell to 687,000 metric tons in 2009-10 on account of recessionary trends. In India, the consumption of rubber by the automotive tire sector in 2009-10 climbed by 13.5 percent in comparison to 2008-09.

Malaysian Rubber Sector to Recapture Its Bounce

Malaysia is poised to remain competitive on the global front via revitalised strategies and action plans under the newly launched Malaysian Rubber Industry (MRI) Strategies 2010-2020 and Malaysian Rubber Board (MRB) Strategies 2010-2020.
 
By 2020, Malaysia is targeting for rubber productivity to hit 1.8 tonnes per ha per year, total production of about 1.8 million tonnes, total rubber planted area of 1.2 million ha and tappable area of one million ha.
Plantation Industries and Commodities Minister Tan Sri Bernard Dompok said the formulation of the domestic rubber industry strategy to reposition the sector and sustain its competitiveness was timely given the highly challenging global environment.

Both the midstream and downstream sectors would focus on improving market share through value-addition and diversification initiatives, including sustaining the growth of the Standard Malaysian Rubber (SMR) market and creating the market for speciality rubber and value-added production.

Sustainability Is What Packaging Adhesive Industry Is Looking For

Developing packaging adhesives can be a thankless task. Despite being the most important end market for adhesives, the effort and ingenuity used to create packaging products can go almost ignored as they are discarded to get to the contents that they protect.
Nevertheless, packaging adhesives have important roles to play in helping ensure that products are supplied in good condition, and are continually improving their ability to do so. Knowing in which area improved performance is most needed can help direct product development.This is what "Special Chem For Adhesives" has found from their recent survey.

1) Around two-thirds of the respondents chose requirements related to sustainability, while only one-third indicated that technical requirements were more important. However, the interest in renewable resources also has a direct business importance as crude oil prices hit 18-month highs in April. Many raw materials used in adhesives are currently expensive, so looking at different, potentially cheaper, sources makes clear economic sense.


2) Biodegradability was the singlemost important sustainability trend, with the focus on this issue almost exclusively in Asia. A ban on most plastic bags in China is seen as a signpost towards legislation that will accelerate the uptake of eco-friendly packaging, while government and industry in Japan are also promoting the use of biodegradable polymers. Compostability is of comparatively little concern to Specialchem4Adhesives readers, and only those based in Europe, perhaps because it could be considered a subcategory of biodegradability.


3) Similarly, the technical interest in lowering additive migration from packaging adhesives is focussed in Europe, and to a lesser extent North America. The European Commission is demanding migration of additives from adhesives be tackled by specific measures to be adopted in the near future. In the US, the Food and Drug Administration has been regulating adhesive additive migration since the 1970s under 21 C.F.R. § 175.105.

4) In adhesive lamination and co-extrusion manufacturing of gas barrier films, the choice of adhesive contributes to how much gas penetrates the final film. While some packaging must let air flow through pharmaceutical packaging and some food applications, for example, demand that the flow rate is reduced to almost 0 cm3/m2/day. Even helping achieve this by laminating other films together is challenging. However manufacturers can also strive to provide an adhesive that is such an efficient barrier by itself that eliminates the need for additional barrier films and coatings.

Lanxess, TSRC to Build Chinese Plant for Nitrile Rubber

Lanxess and Taiwan’s TSRC Corporation will enter into a 50:50 joint venture in China that will produce Nitrile Rubber (NBR) in Nantong, northwest of Shanghai. The €36m plant will have an initial capacity of 30,000 tonnes per year, and is due on stream in early 2012.


The two companies will begin marketing activities in the next few months, in order to build volume. That demand will be supplied from Lanxess plant in La Wantzenau, France until the Nantong plant starts up.

“The partnership is a win-win-combination. It brings together TSRC’s long-history of engineering and production know-how in China with Lanxess' marketing and technical expertise in synthetic rubber,” said TSRC’s CEO Wei-Hua Tu.


TSRC currently operates emulsion styrene-butadiene rubber (ESBR), polybutadiene rubber (BR) and thermoplastic elastomer (TPE) plants in Nantong and is one of the largest synthetic rubber producers in Asia. The products are sold under the tradename Taipol.


TSRC posted sales of USD 700 million in 2009 and currently employs 1,100 people worldwide. In addition to its Nantong site, TSRC has production plants in Shanghai and Jinan in China as well as in Taiwan and Thailand.


Lanxess is the world’s largest producer of synthetic rubber and NBR. Its products sold under the brand names Perbunan, Krynac, Baymod and Nanoprene are part of Lanxess' Technical Rubber Products business unit.

Adhesion to PV Latex Coating

Manufacturer: In a particular application we are using a lightly filled Prevul Latex coating. A second coating based on a blend of synthetic Latices(Acrylic & CSBR) is applied to the first coat after drying. We are finding the adhesion to the Prevul is not very strong, and seems to get weaker after some time. We tried adhesion promoters with limited success. We are seeking advice how to achieve a strong intercoat adhesion, or what type of synthetic polymers form strong bonds with the dried and cured Prevul film.

John Woon (Senior Latex Consultant): This could probably be due to the difference in polarity between NR latex (PV) and acrylic/CSBR. I suggest you try adding a small level of either acrylic or CSBR into the PV before use bearing in mind that there could be some destabilisation of the PV as a result. If this happens, you should pre-stabilise the PV with some surfactants such as the non-ionic surfactants before blending with the synthetic latices.

Do not allow the PV to be too dry before applying the synthetic latex otherwise you would get poor bonding (adhesion).

For other details, please see my separate report on "Adhesion and Cohesion" especially Page 10 to Page 13.

Hope this helps. Do let me know the outcome.