Carrier Starch Standards

December 17, 2014

Ruel asks,

Is there a standard testing method for a modified carrier starch? Just like the caustic sensitivity for the pearl starch. I am looking for such test for our basis of acceptance for carrier starch samples. What we have now is just the pilot mixing/formulation at the lab and get the gel point and viscosity of the resulting mixture. However, I believe this can be misleading in some cases, because we may be getting our desired gel point and viscosity at the lab but not be able to determine the other important character of the adhesive which is the green bond.

Ruel –

Roman Skuratowicz from Ingredion Incorporated contributed the information below. I hope this provide the information you were looking for.

— Ralph.

There are a variety of different modified starches used in the industry, and many are distinct from each other. There are viscosity adjusted starches (both stabilized and not stabilized), high amylose starches, non-corn starches, derivatized starches, and custom mixtures. Depending on the type of modified starch used, one of several viscosity, fluidity, or rheology tests would be used for quality control. These are run on the starch similar to the alkali sensitivity and viscosity analyses currently used for unmodified starch. There is no specific test to determine modified starch performance in an adhesive, as the performance is subject to formulation, application conditions, and desired performance attributes.

What has traditionally been done in the field is running a production trial with the modified carrier starch formulated by the adhesive supplier, thus giving them an opportunity to demonstrate product performance as well as their formulation proficiency. Performance is measured by machine speed, bond strength, and quality of board against total consumption (application level) of adhesive. There is no standard method that can predict all of these attributes and conditions.

Ideal moisture content to prevent score cracking on doublewall

December 5, 2014

John asks:

Could you tell me the acceptable level of moister in 90# liners after they have been converted? We have an issue with 600# B/C converted boxes that crack at the scores. Our customer will not accept them and the corrugator that supplies us states that they have to apply enough heat to acquire the correct bond and that sometimes that allows the liner to crack. They say that they ran a moisture test and the moisture is 6.48%, but it does not affect the strength of the container. Is this correct?

Interesting that you bring this question forward now as I am creating a white paper on warp, bonding, and paper and board moistures.

However for a more immediate answer I would ask your supplier three questions. First , how they measure combined board moisture? Second, I would ask what their moisture targets are and if they experience any variations in the containerboards they purchase? Finally, I would ask what their pin adhesion values? Your sheet supplier, especially if it is an integrated, should be able to provide an internal expert on scoring to visit you operation.

Corrugators operate on a delicate balance between running an ideal seven percent combined board moisture and achieving the proper bond. Combiners with the proper process controls can control paper temperatures through the manufacturing phase, but cannot measure moisture with economically available controls.

Once you know what moisture contact you are working with, I would suggest that you contact one of the industry suppliers of creasing profiles to see if they can help you determine the best profiles given the moisture content of the combined board.

— Ralph

Tearing Glue Joints

October 31, 2014

Will asks;

We have recently had a slew of customer concerns in regards to glue joints. Our customers are saying that it is “tearing too easily.” This is for both hot melt and soft white glued boxes, (generally larger boxes that are NOT run through a flexo folder, but rather a Bahmuller or similar piece of equipment). Is there any way to baseline what poundage a glue joint should hold? Does it depend on what liner the board has and what material it is? If so how do you recommend measuring it?

Thank you for the question. First let me point you to an AICC resource, Key Characteristics of Linerboard and Medium and Their Impact on Combined Corrugated Board.  In that brochure you will learn what linerboard physical properties impact glue joint adhesion. Have you reviewed the FBA Handbook?  There is also a TAPPI Test Method for testing adhesives used in glue lap joints.

The strength of the glue bond is dependent on board moisture, relative humidity, slide angle, fibre type, surface strength and internal bond.

The type and location of the fibre tear, rather than an actual physical property value, will provide better information for identifying the source of the issue. Do you have any pictures to share? Is this a recycled linerboard?  Do you have any Dennison wax pick strips? Do you have containerboard mill specifications from the paper suppliers?

Where I am headed is that while it may be the adhesive, the environment, the process, the amount of coverage, it is usually a board and liner issue. Can you provide more information that will help us dig further into the issue?

Detecting Metal in Corrugated Boxes

October 29, 2014

Rich asks;

I have a food customer who must send product through a metal detector to ensure there is no metal in the food. Intermittently the detector has gone off and when they send my corrugated box through without product it still goes off leaving them to the conclusion that there is metal in the boxes. We are using recycled liners and the mill has essentially let us know that they cannot 100% guarantee that there will be no metal imbedded in the fibres of the box. The mill also provided me with a document from the FBA essentially saying that during the paper making process there is the slight possibility of small metal fibres getting into the paper. Is this consistent with how you understand it to be? Do we have any other options for guiding our customer and ensuring there will not be a chance of metal in the box? Is there a way to prescreen the boxes to determine which ones may have a trace of metal in them before I ship them? Is there a way to test the boxes to determine where the metal exactly is?

I must concur with the position of the FBA and the nature of the 140 domestic paper machines that manufacture containerboard. I have attended enough TAPPI CORBOTEC meetings over my 31 years to know that this concern comes up at every meeting three times a year.  Even the sophistication levels at the different recycled mills vary in their ability to remove metals from the recovered fibre.

The sensitivity levels of different detectors vary as well and the food industry is going to be using a very sensitive detector. Remember, they are looking for the tiniest pieces of metal in food. So a piece of metal that is likely to trip the detector they are using may not trip a more standard detector. You might have passed another packer’s inspection process depending on their equipment and sensitivity settings. The only sure way to prescreen your boxes to your customers’ spec may be to have the same metal detection system and sensitivity settings as your customer is using.

As far as pinpointing the location of the metal in the box, I do not currently know of a way to determine the exact location of the metal IN the board. I would think that this would require some type of probe detector that would be extremely sensitive and have a very narrow scan range. I would also believe the process would probably be quite time consuming and costly.

I don’t know how sensitive the wand type scanners that security firms use are. If you’ve traveled through an airport you’ll know that these can detect something as small as a staple in a paper… when they want too. If you could locate one of those it might be worth trying to see if it would pinpoint the offending contaminant. I wouldn’t suggest asking the TSA though. They don’t tend to have a sense of humor.

Another possible means for pinpointing the metal in the box or sheet would be x-ray. This too will most likely be expensive and time consuming.

However, from past experience if there is metal in your box, it will most likely be found in the medium.

— Ralph


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