Frequently asked questions

This collection of frequently asked questions (FAQ) provides brief answers to many common questions about wet wipe preservation.

 

Advices for formulators of wet wipes

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Why do wet wipes need preservatives?
 

Wet tissues are an excellent environment for the growth of bacteria, yeasts and moulds.

Environmental requirements, e.g. from the detergent directive to use only biodegradable detergents, increase the susceptibility of the wet tissues to microbial growth.

The demands for flushable wipes and the increased use of natural fibres make mould growth more likely with its easily visible staining .

To ensure product and consumer safety, the addition of preservatives is necessary.

Which parameters influence the performance of the preservative?
 

1. Formulation of the wet tissue liquid
2. Type of nonwoven
3. Quality of raw materials
4. Quality of nonwoven
5. Type of preservative
6. Amount of liquid per tissue
7. Production process
8. Distribution of the wet wipe liquid onto the wipe

Solution versus emulsion?
 

Solutions are clear liquids:
1. Easy to produce
2. Contain in general high amounts of water
3. Cheap
4. Limited skin care properties
5. Solutions must be preserved with water-soluble actives
6. Good physical stability
7. Easy to produce
8. Only one interface » liquid / solid


Emulsions are mixtures of two or more immiscible liquids:
1. The basic color of emulsions is white
2. Water insoluble emollients can be incorporated
3. Excellent skin care properties are possible
4. Emulsions can be preserved with limited water soluble systems
5. Stability must be checked carefully
6. One more interface » oil / water
7. Migration of preservatives into the oil phase might occur
8. Special equipment necessary
9. Single layer wetting is preferred

Can the type of nonwoven be changed without revalidating the preservation?
 

If anything is changed in the formulation, in the raw material quality, in the production process or in the batch size, the change has to be analysed to see if it has an influence on the microbial stability of the formulation.

The type of nonwoven can have a dramatic influence on the efficiency of the preservative system. If the type or even the supplier of the substrate is changed a revalidation is recommended.

influence of nonwoven
Can the raw material supplier be changed without revalidating the preservation?
 

If anything is changed in the formulation, in the raw material quality, in the production process or in the batch size, the change has to be analysed to see if it has an influence on the microbial stability of the formulation.

The same INCI name does not necessarily mean the same compatibility. Often impurities can lead to more incompatibilities than the chemical itself. For example the change from carbomer in powder form to a liquid form has shown dramatic effects. The liquid material contained sulphite impurities generated from the polymerisation process. These impurities destroyed the Isothiazolinone content used in the preservation system of the end product. Also sulphonates based on the production process can contain high amounts of sulphite. The different pH values of raw materials have to be adjusted in the finished product.  Otherwise the stability can be influenced or pH value can get out of the active pH range of the preservative actives.

Which influence has the pH value on the effectiveness of the preservation?
 

Attention should be paid to the pH value when preservatives based on organic acids are used. Only the free acids act as preservatives, the efficiency is increased by reducing the pH value. In all cases the pH value of the finished product must be checked at the end of the production process, and if necessary adjusted.

Are there special procedures to check the pH of wet wipe liquids?
 

The pH value has not only be checked in the wet tissue liquid, but in a liquid squeezed from the tissue.
Particularly airlaid showed a severe influence to the pH.

Which influence has the production process on the effectiveness of the preservation?
 

If anything is changed in the formulation, in the raw material quality, in the production process or in the batch size, the change has to be analysed to see if it has an influence on the microbial stability of the formulation. Especially the distribution of the wet wipe liquid onto the wipe and the amount of liquid per tissue are important. Variation in weight of impregnated wipe depends on the method of manufacture.

Which influence has the use of raw materials from sustainable / natural sources?
 

1.Biodegradable ingredients need better protection » e.g. sugar-based surfactants
2.Flushable wipes need special attention
3.Natural fibres, like cotton or celluloses, are changing the typical product-spoiling microorganisms » e.g. Trichoderma viride is a typical cellulose-degrading mould » challenge testing has to be adapted
4.Natural fibres might carry a higher microbial load

Are there microbiological standard specifications for nonwoven?
 

A total germ count specification ≤ 100 cfu/g nonwoven is accepted for the production of cosmetic wipes.
This is based on the recommendations:
"THE SCCS'S NOTES OF GUIDANCE FOR THE TESTING OF COSMETIC INGREDIENTS AND THEIR SAFETY EVALUATION - 8TH REVISION"

4-4.2 Quantitative and qualitative limits
It is generally accepted that for cosmetics classified in Category 1, the total viable count for aerobic mesophyllic microorganisms should not exceed 102 cfu/g.
Category 1 : Products specifically intended for children under 3 years, to be used in the eye area and on mucous membranes.

How to test the germ count in nonwoven?
 

A possible method is:
1. Extract 10 g nonwoven in 100 ml buffer solution in a stomacher
2. Filter the buffer solution (0.45 µm)
3. Wash twice with buffer solution and once with sterile water
4. Place the filter on agar plates
5. Evaluate after incubation

Are there guidelines for the quality of nonwoven used for wet wipes?
 

Yes, the "Guidelines for evaluating sanitary papers (German BfR)"

Pre-moistened sanitary product
The impregnating liquids used in the manufacture of such products are subject to the Cosmetics Regulation.

The impregnated materials must comply with:
Recommendation XXXVI "Paper and paperboard (including cardboard) as food-contact materials".

What are the possible sources of formaldehyde in wet wipes?
 

Some test-magazines like ÖKO Test devaluate product containing formaldehyde. Their formaldehyde determination is based on an acid steam distillation, reaction with acetylacetone (2,4-pentanedione) and photometric determination. Under this strong conditions many compounds may split formaldehyde.
For cosmetic products an official testing method for free formaldehyde exists (Directive 82/434/EEC)
THE RULES GOVERNING COSMETIC PRODUCTS IN THE EUROPEAN UNION / IV. IDENTIFICATION AND DETERMINATION OF FREE FORMALDEHYDE. This method allows to detect free formaldehyde beside formaldehyde donors.

Possible sources:
1.Formaldehyde in nonwoven:
Recommendation XXXVI BfR: “No more than 1.0 mg formaldehyde / m2 must be detectable in the extract of the finished product”.
For a nonwoven 50 g/m² this is 100 mg formaldehyde per 50 g - which means up to 2000 ppm formaldehyde in the nonwoven.
Sources of formaldehyde in nonwoven:
• Sizing agents
• Precipitating and fixing agents
• Retention agents
• Dispersion and flouting agent
• Slimicides
• Preservatives
• Wet strength agents
This explains why some wipes are microbial stable although the wet wipe liquid fails in the challenge test.

2.Formaldehyde donors as preservative:
• Benzylhemiformal
• Diazolidinyl Urea
• Dimethyl Oxazolidine
• DMDM Hydantoin
• 7- Ethylbicyclooxazolidine
• Hexetidine
• Imidazolidinyl Urea
• Methenamine
• Quaternium-15
• Sodium Hydroxymethylglycinat

3.Preservatives which may split formaldehyde under harsh analytical conditions:
• 5-Bromo-5-nitro-1,3-dioxane
• 2-Bromo-2-nitropropane-1,3-diol

4.Other compounds which may split formaldehyde under harsh analytical conditions:
• Perfume compounds e.g. dimethyl acetals

5.Compounds which can form formaldehyde by oxidation with air:
• Polyethylenglycol
• Alkyl polyethylene glycol ethers

Are there special hints for antimicrobial wipes based on cationic actives?
 

Nonwoven fabrics are used for disposable antimicrobial wipes that are capable of disinfecting hard surfaces.

Cellulose based fibres (e.g. cotton, rayon, viscose) should not be used for this application, the quaternary ammonium surfactants used to disinfect hard surfaces readily adsorb onto cellulose fibers, and thus are not released onto the contaminated surface.

Polyester and polypropylene based fibres neither adsorb nor absorb quaternary ammonium surfactants.

 

Production hygiene

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Which products do you recommend for production hygiene?
 

Our standard recommendation for basic cleaning and disinfection is grotanol® SR 2. Also grotanol® SR 1 is recommendable for basic cleaning and disinfection, especially if biofilms have to be removed.

For regular disinfection grotanol® 3025 is recommended.

What are the differences between grotanol® SR 1 and grotanol® SR 2?
 
differences SR 1 / SR 2
In which cycle grotanol® SR 1 / grotanol® SR 2 should be used?
 


To remove biofilms you only have to apply it once.

The formation of new biofilms has to be prevented with a regular hygiene concept.

Generally, we recommend a regular system cleaning every 6 – 12 months.

How is grotanol® SR 1 / grotanol® SR 2 applied?
 
  • Use a 1 – 3 % aqueous dilution of grotanol® SR 1 / use a 0.25 – 0.75 % aqueous dilution of grotanol® SR 2.
  • Pump it through the pipes, filters and vessels to guarantee a mechanical effect.
  • High pressure units or a simple brush can support the cleaning.
  • Contact time at least 6 hours.
Are there any restrictions regarding the material compatibility of grotanol® SR 1?
 

In general, grotanol® SR 1 dilutions have a good material compatibility, but avoid contact with aluminium.

grotanol® SR 2 is totally corrosion inhibited and can be used without limitation.

How can a disinfectant dilution be prepared?
 

• The easiest way is to prepare a stock solution in a container (e.g. an old euxyl® container).

• E.g. for a 1 % dilution: add 10 kg grotanol® 3025 to 1 m3 of water.

• A solution of grotanol® 3025 is stable for several months.

Which use concentration of grotanol® 3025 is recommend for disinfection?
 

The normal use concentration is 0.5 % - 1.0 % in water.

How to disinfect e.g. a production vessel?
 

Add 0.5 % - 1.0 % grotanol® 3025 to the last rinsing water. Fill pipes, pumps and filters with the disinfection solution.

How to disinfect a filling line?
 

Fill some bottles of product (in case of a wet wipe production line some wet wipe packages) with the disinfectant solution (grotanol® 3025 0.5 % - 1.0 % in water).

Keep the system under disinfectant solution until it has to be used again.

Is rinsing necessary after disinfection?
 

Generally we do not recommend rinsing with water if production is not started immediately after disinfection. If the water is unpreserved there is a high risk of recontamination.

Normally, rinsing with water is not necessary, because grotanol® 3025 contains only actives which are permitted as cosmetic preservatives.

Nevertheless, we suggest to perform compatibility tests. E.g. proteins can cause discolorations in the presence of only small amounts of grotanol® 3025. In these cases it is necessary to rinse, but this is only allowed directly before using the equipment.

Can grotanol® 3025 solutions be left in the production facilities for a longer period of time?
 

Yes, grotanol® 3025 has an excellent material compatibility. It will be stable and will preserve the facilities over a longer period.

» Different to chlorine, this is corrosive and stable for only a short time.

Can a solution of grotanol® 3025 / grotanol® SR 1 / grotanol® SR 2 be drained?
 

All products are biodegradable in a sufficient dilution rate (below use concentration).

As a general guideline: a 1 : 20 dilution of the applied disinfectant solution is sufficient to dump into a biological waste water treatment.

Can a preserved product be kept in a vessel / filling line overnight?
 

Yes, of course. It is protected against microbial growth.