Archive for the ‘Finishing/Converting’ Category

Yeast & Mold Standard

December 1, 2017

Reul asks,

We recently had a batch of doublewall boxes held at the port because it was mishandled by the shippers and delayed for about two weeks. The dry container van was stored at the Customs Yard. Maybe the two weeks of exposure to cyclic condition, high humidity at night time and occasional rainfall may have resulted in a favorable condition for spore to develop into molds.

Do you know a standard or allowance of presence of yeast/molds in a corrugated box? We have this analysis of 1500 CFU from the swab test conducted on the samples coming from a certain batch of corrugated boxes that we produce.

This has been a concern for us since one of our customers complained the boxes they received had some dusty matter on its surfaces. We sent samples to an independent lab for microbial analysis and it was confirm to have that reading mentioned above. Is this value alarming?

That’s a tough question. We have no threshold count for molds and yeasts. It would not come with the containerboard except where the relative humidity or liquid water is present with the spores. Certainly the conditions you described could have had an impact on the condition of the boxes and the growth of molds if spores were present. Depending on what the contents are and what the end user environment is these conditions could very well be unacceptable.

— Ralph


Hot Melt Glue Separation

December 1, 2017

Mike asks,

I have a customer that runs case make up units using a solid set hot melt. As of late we have an issue with the appearance of the seal on the bottom of the carton. When we are using light weight single ply liners the customer is not seeing fibre pull when breaking the bottom flaps apart to check for a bond. They are now considering this test to be a fail. Even though we can do a shake test and it passes. When pulling the cartons apart by hand the strength feels the same if you have fibre pull or not. When we are not seeing fibre pull what you see is the hot melt glue lines on each flap that is stuck to the paper so it looks like the glue came apart in the middle.

Anyway, is there is a tool that we can measure the bond strength on the bottom of a carton?

If glue is remaining on both flaps and is not separating from the paperboard, then the bond between the paperboard and the glue would appear to be good. If we take a lesson from the corrugator, too much glue can be as bad as too little glue. Too much and you risk shear within the glue itself. I’m not positive if the same ‘holds’ true (pun intended) in hot melt. I know too much hot melt can cause a variety of problems, but I’m not sure if shear within the glue is one of them. I’ve reached out to some of my industry contacts and I’m awaiting their input. I’ll update this post as when received.

I’m not sure if here is an official measuring device. However, I would think that if the box was to hold, say 25 pounds, you could get 25 pounds of weights at the local sporting goods store, place them in the bottom of the box and then somehow suspend the box so the full weight was on the bottom flaps. Perhaps do a few jerk tests where you would quickly lift the box with the weights in it. This would simulate the additional forces of acceleration. If it supports the weight, perhaps your customer would accept this as proof that the bond is sufficient to hold the prescribed weight. Be careful when you are testing.

Okay readers, has anyone else seen this type of separation with hot melt? Do you have any experience or suggestions to pass along?

— Ralph

Regulations on box storage for food related boxes

November 17, 2017

Tim asks,

Ralph, are you aware of any regulations regarding the storage of secondary packaging for food related boxes? We make secondary packaging for a customer and they received some of our boxes that were covered with stink bugs. Apparently there was a small hole in the wall, which we have repaired, where the boxes were stored. Being that they are secondary boxes it does not required us to be AIB certified.

Those little insects get everywhere! There should not be any regulations for reasonable storage of secondary packaging. Below is a link for recommended practices for the storage of corrugated.

I would also suggest that you walk through 21 CFR 110 for the “Current Good Manufacturing Practice in Manufacturing, Packing, or Holding Human Food.”  You may also consider an overview of the Food Safety Modernization Act.

However, regardless of whether there are regulations or not, your customers don’t want any little six-legged stowaways in their shipments. Perhaps you could bag or stretch wrap the entire pallet to protect against further infiltration or contamination from dust or other elements that me be present in the atmosphere.

– Ralph

Peeling white liner issue

October 24, 2017

Khuram asks,

We are experiencing a peel off issue with white 135gsm test liner. This issue is random and the top layer of white liner gets peeled off in the cross direction during conversion. (See the picture below for examples.) We have our own vertically integrated board mill which is providing this white test liner and as far as ply bond strength is concerned we have tested it different lots (using method TAPPI-569) and its average values are >250J/m2.

This issue can have several root causes.

One is that the ink is too tacky and it is pulling the white fibre from the brown base sheet.  It can also be that the ink is drying on the printing plate or otherwise not releasing properly from the plate.

Second is that there could be a poor bond between the white fibre top sheet and the brown base sheet.  This is usually caused by poor fibre developing during the pulping process.  It could also be an issue of poor water drainage in the board making segment.  There could be a contaminated water system, or there may not have been enough starch between the two layers to hold them together.

Sometimes closure tapes can be used in the box plant to predict the ply separation.

So there are a few things that you can look at. Let’s toss this out to our followers and see what they have experienced and information they can offer.

— Ralph