1.Preface —————————————————————————————————————————————————

Pharmaceutical clean room, also called clean plant, is a space for human activities where the air cleanliness reaches a specified level. The function is to control the pollution of living particles(for example, unicellular algae, fungus, protozoon, bacteria, virus,etc.) and particles(dust particles). Floor production has been a basic requirement in drug industry since the implementation of GMP in the pharmaceutical industry. GMP requires that the clean room floor should be made of hard materials, good integrity, smooth and flat, non-cracking,wear-resistant and impact resistance, not easy to accumulate static electricity, easy to clean and disinfect, and corrosion-resistant materials. Cracking and moistureproofing of the ground should be paid attention to during use, especially in large area. At present, the widely used floor materials in Chinese pharmaceutical industries mainly include inelastic ground, coated ground and elastic ground, etc. The following mainly introduces some commonly used floor materials and the control points in construction process. 

 2.Terrazzo floor ———————————————————————————————————————————————

Terrazzo floor is a kind of inelastic floor, which has the characteristic of good integrity, good mechanical strength, wear resistance, heavy pressure resistance, anti-static and easy to clean. However if we observe terrazzo surface microscopically(as shown in figure 1), though the surface is polished, microbes and dust particles may hide in the gap, so the floor need to be waxed after polishing. Terrazzo usually uses in the workshop which cleanliness level is low (one hundred thousand class clean area), such as solid preparation workshop, raw material medicine (refining, baking, packaging) workshop.

Due to the elasticity lack of terrazzo floor, when the concrete base layer cracks, it will spread to the surface, so the management should be strengthened during construction. Terrazzo’s main structure is shown the figure 2. Construction process of terrazzo mainly includes basic treatment→leveling layer construction→fixing dividing strip→plastering terrazzo surface→polishing→waxing.

 Common defects and construction control points of terrazzo in the construction process —————————————————————

2.1 Ground hollowing

The main reason is that the terrazzo has many layers on the ground, different times, different materials, and the improper handling, which may affect the bonding and cause hollowing, especially the large-area hollow with cracks will greatly affect the life of the terrazzo. Hollow is mainly manifested in: the insufficient bonding between the surface layer and the base layer causes hollow. The insufficient bonding between the surface layer and the leveling layer causes hollow.
The main reason is that the basic layer is not cleaned enough, such as ash, residue and other additions, which all can affect the bonding of two layer. It can be seen that the cleaning of basic layer must be careful, which is an important factor affecting the bonding.

2.2 Dividing strip breaking  
    Dividing strip should use copper and glass strip. But under the heavy pressure or expansion and contraction, glass strip will break at the same time and cause microbes grow inside. So the dividing strips in clean room usually use copper. The main reason of dividing strip breaking is that the height of the dividing strip itself is inconsistent and the surface layer is uneven. Therefore the elevation should be adjusted when installing dividing strip, and the error should be corrected in time.

2.3 Surface powdered after waxing  
    The purpose of waxing is to make the terrazzo floor brighter, smoother and more beautiful, and is easy to maintain and clean because of a thin wax on the surface at the same time. When waxing, the improper surface treatment will cause powdering, which will seriously affect the cleanliness of the workshop. The main reason of causing powdering is that surface layer is not dry completely and the fine stone powder on the surface is not cleaned. In order to remove the surface residual cement mortar and fine stone powder, before waxing, we can evenly sprinkle 10% oxalic acid solution on the surface, then lightly rub it with oilstone, and then rinse it off with water, after the ground is dry, waxing can be carried out.

 3.Epoxy self-leveling floor ——————————————————————————————————————————

Epoxy self-leveling coating use epoxy resin as coating film-forming material, and through adding curing agent, non-volatile reactive diluent, additives, pigments and fillers to make a solvent-free high-performance coating.

The film-forming process of epoxy self-level coating is a kind of chemical film-forming method. First coating the soluble low molecular weight epoxy resin on the surface of the substrate, then intermolecular reactions cause further increase in molecular weight or cross-linking to form a tough paint film. Epoxy self-leveling not only has the advantages of terrazzo floor, but also has the advantages of more corrosion resistance, wear resistance, and easier cleaning, which can meet the requirements of higher cleanliness levels, so it is mostly used in class 10000 and class 100 clean rooms. Epoxy self-leveling is accepted by many pharmaceutical industries domestic and aboard now and always used in water injection workshop, freeze-dried powder injection workshop and biological product workshop.
The construction of epoxy self-leveling coating is relatively mature, it mainly includes basic layer inspection and treatment→brush primer→putty repair→scrape the surface layer→waxing maintenance→construction and acceptance. (figure 3)

 Construction point and technology control of epoxy self-leveling —————————————————————————————

3.1 Basic layer handling

The foundation of epoxy self-leveling floor is cement ground. The original cement ground is full of holes, and these holes contain water and alkaline substance, so we need a pretreatment for the ground before construction, otherwise epoxy self-leveling floor will cause blistering, whitening, cracking, and even peeling. The basic layer specification and index after polishing processing should meet the following index:   

The moisture content of the basic layer has a great influence on the coating . If the moisture content is too high, bubbles will appear (Figure 4). Therefore, it is recommended to add a moisture-proof layer under the floor during the base construction.

Cement ground will shrink to a certain amount during the coagulation process, so it is inevitable that a considerable number of cracks will occur. For the cracks which is not occurred from hollow problem, simply cut a V-shaped groove in the direction of the cracks and fill it with epoxy grout, paste a layer of glass fiber cloth on the surface, and finally fill it with epoxy grout. That’s can meet the construction requirements. If the cement ground occurs serious ground hollowing problem, straightly cutting the ground and filling the hollow with cement, solving hollow fundamentally. 

3.2 Construction environment

Construction environment has a great influence on the quality of epoxy self-leveling, the construction environment temperature should be above 10℃, amine curing agents are usually used in floor coating, the reaction between epoxy group and amine group is very slow below 10℃, basically no reaction below 5℃. And the surface temperature of the primer should be more than 3℃ higher than the environmental dew point. If this condition is not met, on the one hand, the surface of substrate is easy to condense, resulting in poor adhesion of the back coating. On the other hand, after painting, there is a water film on the condensation on the surface before paint film is dry, causing surface defect. Especially for finishes, in this situation, water vapor easily reacts with the amine curing agent in the paint, causing some defects such as low gloss of coating film surface, foggy, whitish, sticky, oily, low hardness, which greatly reduce the effect of surface decoration and cause rework in severe cases.        

3.3Construction of finishing coat

Finishing coat should not only consider the leveling property but also ensure the uniformity of the filler during construction. Theoretically, the lower the viscosity or the thicker the coating of the finishing coat, the better the leveling property. We can use an appropriate amount of solvent to improve the leveling of the finishing coat, but during the process of construction, the filler of the finishing coat gradually decreases, which causes low surface hardness and poor wear resistance. Therefore, it is important to choose a suitable curing agent. Ordinary curing agents cannot fully meet the requirements of the product. Generally, they are compounded with modified curing agents, and no free amine is precipitated during the curing process. At present, widely used curing agents in epoxy resin floor are polyamide curing agent and modified aliphatic amine curing agent. 

3.4 Using time after construction

Due to different seasons, the normal use time after construction is different. Winter: walkable for 3 days, light load for 6 days, normal use for 10 days; Spring and autumn: walkable for 1 days, light load for 4 days, normal use for 7 days; Summer: walkable for 18 hours, light load for 2 days, normal use for 5 days. 

 4.Plastic floor ———————————————————————————————————————————————

Comparing with other flooring, the characteristics of plastic floor are good fire resistance, good sound absorption, impact resistance, slightly elastic, reduce fatigue on long-time stand operation work, but the cost is more expensive, pharmaceutical industries can choose appropriately according to their own process requirements. Generally used plastic floor materials are vinyl plastic board, PVC soft board, PVC semi-rigid board and polyurethane floor coating. Main process of elastic ground construction includes basic treatment → snapping the line → trial paving → brushing the base glue → paving the plastic floor → paving the plastic skirting board → polishing and waxing.

The construction process of plastic floor is relatively simple. The defects and reasons that are easy to produce during the construction process are as follows:

Analysis of the defects and causes of plastic floor in the construction process

 5. Summery —————————————————————————————————————————————————

During the use of the ground, it must not only meet the process requirements of the clean room, but also need to be durable. This is directly related to the model selection of floor materials and quality monitoring in construction process. At present, there are no perfect ground materials in China can meet all requirements. Pharmaceutical companies should make a comprehensive consideration in GMP requirements, process specificity, using life of materials, whether the construction is simple or not, price, source, construction technology level, etc. Making a reasonable choice, construction and use according to the differences of materials performance.   

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