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硼酸分类侵蚀胶粘剂的选择

来源：林中祥胶粘剂技术信息网2011年07月27日

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Borate Classifications Erode Adhesive Options

On 18 June 2010 the European Chemical Agency added boric acid and borax to the candidate list of ‘substances of very high concern for authorisation.¹ That decision came because they are considered as substances Carcinogenic, Mutagenic or Toxic to Reproduction (CMR) as category 1B reproductive toxins in Europes Classification, Labelling and Packaging (CLP) regulations.² Thanks to their CMR status, since December 2010 preparations containing 5.5 per cent or more of free boric acid or 4.5 percent or more of anhydrous borax must be labelled: "May damage fertility. May damage the unborn child"³. From June 1 2015, that labelling will have to include the "exploding chest" pictogram for target organ toxicity⁴.

Figure 1: The "exploding chest" pictogram for targeted organ toxicity, which formulations containing more than 5.5 per cent boric acid, or more than 4.5 per cent anhydrous borax, will have to show by June 1 2015.

However, even at levels down to 0.1 per cent boric acid by weight formulators must be prepared to provide users with details of their inclusion on request in Europe, due to their entry on the "substances of very high concern" (SVHC) candidate list.⁵ Companies were also obliged to let the European Chemical Agency know if they were producing or importing articles containing boric acid or borax at this concentration prior to June 1 2011. Furthermore, if they do not gain authorisation for use, these borates could ultimately be removed from the market.

Boric acid and borax are widely used in the adhesive industry, where customers are often highly sensitive to any such classification or labelling. For example, although starches can be good adhesives by themselves, for many applications the wet tack they provide is too low.⁶ Adding borax, also known as disodium tetraborate, makes the starch into a more highly branched and higher molecular weight polymer. This gives the adhesive increased viscosity, quicker tack and better fluid properties that help corrugated board production, winding tubular products like kitchen and toilet roll, laminated paper board and carton sealing adhesives.

Type of adhesive	Typical application	Borate role	Effects if borates were not available
Borated dextrins	Tube winding toilet/kitchen paper/metal foils	Raise viscosity and tackiness of the adhesives, increase molecular weight	Lower viscosity would slow production and higher costs potentially leading to replacing this renewable adhesive with petrochemical products
Caseins	Labelling glass bottles	Gelling agent/humectant/plasticiser/ biocide for casein adhesives	More preservatives would be needed, potentially making products more allergenic and less biodegradable.
Starches & derivatives	Glass bottle labelling, paper making, wallpaper paste	Crosslink to increase viscosity and stability giving "jelly like" shear sensitive rheology.	Lower viscosity would mean more adhesive is needed, raising costs potentially leading to replacing this renewable adhesive with petrochemical products
Polyvinyl alcohol	Paper articles, corrugated board, tubes	Gelling agent, crosslink to increase viscosity, tack and stability, reduce use of preservatives and biocides	Machine outputs would be much reduced and more of the adhesive would have to be applied to the substrate.
Magnesium phosphate technology	Adhesives grouts and repair products	Allow to products to be sold in liquid form, the main format in certain regions (e.g. the UK)	Would have to be sold in powder form and to be mixed with water at home, which is less convenient, especially for professionals.

Table 1: Use of borates in adhesive preparations and applications

In these cases, borax can comprise up to 10 per cent of an adhesive by weight - more than enough for off-putting labels to be needed. However, many applications use significantly less than this, and because in most situations the adhesives are not used by consumers, the final adhesive only makes up a very small proportion of the weight of the end product. Nevertheless, were borates to be banned completely and no replacement found, the net result would likely be significantly lowered throughput. This would make these renewable starch adhesives less competitive compared with petrochemical-derived rivals. One company estimates that its turnover would fall by ? million annually because it can no longer make these adhesives.

Boric acid can sometimes be used interchangeably with borax, an