Washing powder  is a synthetic powdery synthetic detergent for washing. Washing powder refers to household cleaning products.

In 2010, Russia produced almost 1 million tons of washing powder. A quarter of this volume was exported to Kazakhstan, Ukraine and Belarus. Exports of detergents exceed imports; powder consumption by Russians is less than 6 kg per capita. The share of washing powders for automatic washing on the market exceeds the share of powders for hand washing and is constantly growing: according to estimates by AC Nielsen, in 2007 the proportion of powders for automatic washing was around 70%, and by the end of 2010 - more than 80%.

It should be borne in mind that since 2010 in Russia the share of washing powders in the market of detergents has been gradually falling, since washing gels are becoming more common, the production of which consumes less electricity and which does not require ballast salts.

Technology for the production of washing powders

Raw materials

Modern washing powders contain a mixture of anionic and nonionic surfactants, soda, sodium silicate (adds alkalinity to the powder and binds dust to granules), as well as ballast from salts as a diluent (usually sodium sulfate (about 40% of the composition of non-concentrated washing powder with a dosage of 150 d. for one wash in a washing machine) or, less commonly, sodium chloride) in an amount of not more than 5% -10%.

Washing powders may also contain other components: cationic surfactants, chemical and optical brighteners, perfumes, substances for binding calcium and magnesium ions: (sodium tripolyphosphate) zeolites, citrates, Trilon B). Also, the composition of the powder may include enzymes, soap, colored additives to give a beautiful color to the powder itself, substances that prevent the sedimentation of contamination on the surface. To keep the pH of the washing powder solution within the specified limits, appropriate additives, most often citric acid, can be included in its composition.

Phosphates in the composition of the washing powder eliminate the water hardness, thereby enhancing the action of surfactants and increasing the effectiveness of the washing powder. Phosphates have been banned for use in many countries since 1983. In the CIS countries, phosphates are still used without restrictions in the production of washing powders. Only in Ukraine has the law adopted a program for restricting the use of phosphates since 2014. Phosphate-free washing powders have gained great popularity in Western countries, both due to restrictions on the use of phosphates and due to voluntary concern for the environment.

In a detergent intended for automatic washing, there are substances that inhibit foaming.

Since the raw material is in a loose state, then from a container intended for the transport of bulk solids, the raw material is transferred directly to special tanks. Such tanks can be of huge capacity. Their task is to store raw materials so that they do not lose their physical properties and flowability. Conditions are created with a suitable percentage of moisture and a suitable temperature regime.

Description of the process + video

Powder production technology requires the use of, in addition to bulk raw materials, also liquid. These are sulfuric acid and alkaline liquids. Such raw materials are delivered to the factory in specially designed tanks. Pipelines are connected to them and, using the injection process, which is provided by pumps, liquids are transferred to special tanks. There are also special aids, without which production is impossible, they are fed directly by labor directly to the hopper. There is at this stage specialized control over everything that happens. The dosage and selection of the necessary substances for the next production process is controlled by software.

The selected components for the formulation enter the tank for the dosage process. Liquid soda is first mixed with sulfonic acid. When the mixing step has taken place, other liquid as well as solid formulation components are added to the dosing tank. The necessary mixing takes place in it so that the necessary homogeneous mass is obtained. It turns out a solution that should be passed through a special magnetic filter. After that, the contents fall into the holding tank. The solution is in a state of calm for some time, and after that, it is delivered to the homogenization stage. Vasya may still be in a solution of various kinds to the end of the insoluble matter. It is important at this stage to eliminate particles that have an inhomogeneous concentration. At the end of this stage, the solution will have the uniformity that is required for the further course of the production process.

Further, the substance passes to spraying and drying. From below, hot air is supplied. It is formed directly in the air-heating equipment, which works on the principle of a furnace. It is intended for drying. The dried mixture leaves the dryer in the form of powder on a conveyor belt stretching from it. In this process, the formation of volatile gases, which must be trapped and removed. Therefore, there is a cyclone type separator on top. It captures gases that urgently need to be removed. These gases are no longer needed. Because they have a fulfilled status. Powder separator is collected and sent to the tower. Powder leaves the tower with a moisture content of about seven ten percent and is sent to the pipeline. In it, the powder is supplied pneumatically. Further, the resulting powder is accumulated using compressed air. The deposition process, as well as the separation process. At this stage, some kind of future powder is obtained. Dust that occurs is captured using a cyclone separator. The powder is also aged and the temperature decreases. Also, water passes from an ionic state to a crystalline one.

Next is the addition of excipients. They are usually in solid loose and liquid state. The process of loading excipients into tanks takes place with the help of the physical strength of plant employees. Accumulation takes place in storage tanks. Of these, a portion is taken automatically, according to the specified standards in the software, with the help of dosing pumps and the auxiliary components get into the mixer.

Video what production looks like:

At each stage of the production of washing powder, automatic control takes place. Using the loaded parameters of the formulation of the preparation of washing powder in the software, it is possible to achieve the most accurate execution of all important operations and a clear dosage of the components for the production of washing powder.

Man has always strived for cleanliness, starting from ancient times, when people rinsed their clothes in rivers, and to the present day, when in most cases cars take over this duty.

Of course, initially no one knew about detergents in their modern sense, they used exclusively natural products and water. Soap later appeared, and in 1876 the first in the world history production of washing powder was created. The manufacturer was the German factory Henkel & Cie, led by Fritz Henkel.

Our days: the powder market in Russia

Many years have passed since then, and the number of manufacturers has increased to hundreds of thousands around the world. Among them, of course, there are leaders. And in our country they are foreign companies that occupy up to 80% of the entire Russian market.

Domestic large manufacturers of washing powder in Russia have a small share - about 10%. The remaining 10% is held by small firms and is ideal for newcomers wanting to occupy their niche in this segment of detergents.

Of course, it is not easy to fight the giants of the market, which have also long won the trust of most consumers. However, to win over some of them is quite possible. To do this, you need to prove yourself on the best side according to three main criteria: efficiency, safety and accessibility. And about how to establish a business for the manufacture of powder, you will learn from this article.

The range of basic questions on the organization of powder production

The production of washing powder is a rather complicated process from the point of view of technology, therefore it requires a competent approach. This is due to the large variety of chemicals used to create it. Due to the multicomponent and the correct combination of elements, the ability of a detergent to effectively remove impurities is provided, without affecting the quality of the fabric. Thus, the main issues that need to be carefully thought out and properly organized are the technology and equipment for the production of washing powder. In addition, it is necessary:

• choose a suitable room for the workshop / plant;
• collect the necessary permits;
• determine the market and think over a marketing strategy.

Technology: how and from what to produce

The composition of the washing powder is characterized by a variety of components. Almost all the products on the market are made from the same chemicals, and the difference is due to a combination of various ingredients in certain proportions, which directly affects the quality of the finished product.

On how to properly select the percentage depends on how effectively the powder will remove stains, whether it will gently affect the quality of tissues, their color, etc. In this matter, the role of a chemist is great. Therefore, make sure that your production has a competent and experienced specialist.

The chemical composition of washing powder: a list of ingredients

As for the main components, most of the washing powders contain the following substances:

• surface-active - separate dirt from tissue (synthetic substances, soap);
• binding - eliminate water hardness, provide softness of fabrics, prevent scale formation in the washing machine (phosphates or, if it is phosphate-free washing powders, zeolites);
• bleaching - due to the oxygen content they give freshness to tissues, remove vegetable stains on clothes (sodium perborate, etc.);
• lipases - break down fatty contaminants, amylases - starch, alkaline proteases - protein;
• antiresorbents - prevent re-contamination of tissues during washing, keeping the removed contaminants in the solution;
• auxiliary - give freshness to linen, neutralize an unpleasant smell when washing.

Thus, in today's powder industry, as a rule, synthetic substances are used - frozen. If the detergent is intended for washing children's things, then soap shavings are usually added to its composition. It is absolutely harmless and environmentally friendly.

If the powder is intended for use in a washing machine, antifoam agents are a must. These substances inhibit the formation of foam during washing. Recently, phosphate-free washing powders in which phosphates are replaced by zeolites, citrates and other harmless components are becoming more widespread. The result is a product that is completely safe for the environment and humans.

Raw materials for the manufacture of washing powder

Raw materials for powder production are not cheap, but quite affordable. The chemical industry is well developed in our country and it is not so difficult to find domestic suppliers for a plant starting its work. If we talk about cost, then on average the price tag for Russia is as follows (per kilogram):

• sulfanol powder - about 100 rubles;
• surfactants - 80 rubles;
• soap shavings - 45 rubles.

Naturally, these are only the main components. There are many others, additional ones, which will also have to be purchased. However, the cost of one pack (500 grams) as a result of their combination will be low.

Production Process: Powder Preparation Steps

We talked about the lineup. But what is the technology for the production of washing powder? The success of the final result will depend on its proper organization. As mentioned earlier, the most important difference between products from different manufacturers is not the components used, but their combination. It determines the successful (or not so) composition of the powder and determines its quality characteristics. For example, some components enhance each other's action, while others reduce it. The process of developing the composition should be carried out in conjunction with competent chemists.

If we talk about the sequence of actions in the manufacture of the powder, then it is as follows:

1. The paste obtained by sulfonation of acibenzene combines with other heat-resistant ingredients.
2. The resulting mass is sprayed through the nozzles of the spray drying tower.
3. The droplets dried by hot air turn into powder granules.
4. Further, the powder mass is mixed with non-heat-resistant ingredients (perborate, enzymes, etc.).
5. As a result of all these processes, detergent is obtained, which is sent to the packaging.

Powder production itself is a fairly understandable and well-defined process. The main thing is to successfully develop the composition of the detergent.

Powder Manufacturing Technology

In the manufacture of powders, like any drug лекар specialists perform professional actions in a strictly established sequence:

conduct a pharmaceutical examination of the prescription;

choose the best technology option taking into account the mass and physico-chemical properties of the incoming components;

calculate the mass of prescription ingredients for all doses and determine the weighting of the powders (mass of one dose);

perform preparatory operations;

conduct the actual process;

control the quality of the drug at the stages of manufacture, the finished product and when the patient is dispensed.

Pharmaceutical examination prescription.Examination of the prescription of any dosage form, including powders are carried out according to the following scheme:

checking component compatibility;

checking the compliance of the mass of narcotic substance written in the recipe with the rate of one-time leave for one recipe;

verification of doses of substances of lists A and B in powders for the enteral route of administration.

Incompatible ingredient combinationsin powders are less common than in dosage forms with a liquid dispersion medium.

There are cases of wetting of the powder mixture as a result of: increased hygroscopicity of the starting ingredients and their mixtures; water evolution from crystalline hydrates during grinding or as a result of a chemical reaction in a mixture that was previously wetted due to its high hygroscopicity.

These phenomena lead to a violation of the flowability and uniformity of the powders. However, in a humid environment, chemical interactions are possible.

There may be a loss of activity of drugs (antibiotics, vitamins, enzymes) under the influence of salts of heavy metals and other factors.

It is possible to melt the powders at the eutectic point (a sharp decrease in the melting temperature of the powder mixture compared to the melting temperature of the starting components). Sometimes the formation of a eutectic mixture (melting of powders) is advisable. It can be used as an auxiliary fluid to grind some powdered substances. The eutectic mixture should be prescribed as a dosage form, for example, drops for dentistry.

Incompatibility must be prevented, and difficulties can be resolved in one of the following ways:

by isolating the substance that causes difficulty or causing incompatibility from the prescription (except for substances on list A and B) and dispensing it separately, but in the same dosage form (biopharmaceutical aspect);

introducing an adsorbent (as agreed with the doctor) - starch, aerosil (oxyl), etc .;

using substances dried to constant weight;

replacing (as agreed with the doctor) a pharmacological analogue.

Checking the correspondence of the mass of narcotic substance written in the recipe to the rate of one-time leave for one recipe.At this stage, the mass written out at the entire dose is compared with standard indicators. In case of exceeding the norm of dispensing (without corresponding marks on the prescription), the number of dispensed doses is reduced without changing the concentration of all substances and the ratio of ingredients in the recipe.

Reduce the number of doses so that the total mass of the accounting substance at all doses does not exceed the mass allowed for a one-time dispensing according to one recipe.

Verification of doses of substances of list A and B in powders for enteral administration.Single and daily doses are checked taking into account the patient's age, route of administration and method of prescribing the drug.

If the substance is not in the table of children's doses, then the doses are checked according to the note to the table of higher doses for adults. It also provides instructions for checking the doses of drugs prescribed to patients over the age of 60.

With the distribution method of prescribing the mass of substances indicated in the prescription ͵ correspond to a single dose, therefore, during verification, the prescribed dose (single) is compared with the highest single dose specified in the regulatory document.

The daily dose is calculated by multiplying the single dose by the number of doses per day, and compared with the highest daily dose specified in the regulatory document.

With the separation method of prescribing, a single dose is first determined by dividing the total mass of the substance prescribed in the recipe by the number of doses, and then similar to the distribution method.

In case of overstatement of single and daily doses in the absence of special doctor’s notes, the mass of substances is recounted based on the half of the dose indicated in the Global Fund as the highest.

After the conclusion about the possibility of manufacturing the drug draw up the main label.

Calculations of the masses of ingredients and powder weighing.Considering that a powder mixture is prepared at all doses at the same time, and then the number of prescribed doses is dosed from the total mixture, it is necessary to calculate the total weight of each ingredient. With the separation method of prescribing, the mass of each substance in the recipe is indicated in all doses. With the distribution method, you

the masses of single doses written in the recipe are multiplied by the number of doses.

The total mass of the powder mixture is obtained by summing the total masses of each of the ingredients.

The weight - the mass of the powder mixture at one time (the mass of one powder) - is determined by dividing the total mass of the powder mixture by the number of doses prescribed. With the distribution method of writing out the weighting should be determined more simply - by summing up single doses of all the ingredients written out in the recipe.

All calculations are performed on the reverse side of the written control passport (PPC). The front side of the PPK is made out of memory, after the manufacture of the total mass (before weighing into doses). PPC for all dosage forms is filled out in Latin in the order of adding the ingredients, indicating the weight of each substance in all doses (including excipients, solid and liquid), indicating the total weight of the powder mixture and the number of doses. Sign in the manufacture and pass on the packaging (dosing).

Private rules.The calculations have their own specific features in the manufacture of powders containing substances prescribed in a total mass at all doses of less than 0.05 g; extracts (belladonna, etc.
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), difficult to grind substances; antibiotics and using semi-finished products.

Calculations in the manufacture of powders using trituration.Trituration is a powdered mixture of a poisonous or potent substance with an indifferent excipient (usually with milk sugar) in the ratios 1: 10 or 1: 100. The 1: 10 trituration contains 1 part of the active substance and 9 parts of the filler, and 1: 100 - respectively - 1 part of the drug and 99 parts of the excipient.

Triturations in pharmacies are made by a pharmacist-technologist for a period of up to 1 month. Qualitative and quantitative analysis of triturations is carried out by a pharmacist-analyst immediately after manufacture and with an interval of 15 days, after preliminary mixing the whole mass of trituration with a pestle in a mortar to avoid delamination of the mixture.

In accordance with the State Pharmacopoeia Monograph, triturations are used if 0.05 g or less is prescribed for all doses of a toxic or potent, sometimes mild, substance (in medicines for children). On BP-1 scales, it is possible to weigh 0.02 g (minimum load) with an objectively larger weighing error, which is unacceptable for substances of lists A and B.

The choice of diluting trituration (1: 10 or 1: 100) depends on the mass of a toxic or potent substance at all doses:

0, 01-0, 05 g - trituration 1: 10;

less than 0,01 g - 1: 100 trituration.

When performing calculations related to the use of trituration, two cases should be taken into account.

1. In the recipe is written out with a x and r.
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In this case, in order not to increase the amount of excipients, the total sugar mass should be reduced by the sugar mass in the taken trituration, since it contains 9 or 99 parts of sugar. In cases where the mass of the drug substance in trituration is extremely small and practically does not affect the size of the suspension, the sugar mass can be reduced by subtracting the mass of the entire trituration.

The weighting in this case will correspond to the recipe.

2. There is no sugar in the recipe. In this case, the mass of trituration sugar always goes above the prescribed mass of powders; the weight does not correspond to the recipe; it increases by the mass of trituration of a single dose.

Calculations in the manufacture of powders containing extracts.Plant extracts are concentrated extracts from medicinal plant materials. According to the consistency, they are distinguished: extracts are thick, liquid and dry. In the manufacture of powders, belladonna extracts are most often used.

The pharmaceutical industry produces the following types of belladonna extracts:

thick (1: 1) (extractum spissum) containing 100% of the active substance in terms of pa hyoscyamine;

dry (1: 2) (extracum siccum), in which 50% of the active substance and 50% of the filler (dextrin) added to reduce the hygroscopicity of the extract.

If there is no dry extract in the pharmacy for the convenience of working from the belladonna thick extract, its solution (extractum solutum) is made in a ratio of 1: 2 according to the GF ʼʼExtracts статьи article:

thick extract ................................................ .. 100 pieces

solvent................................................. ... 100 parts

For the manufacture of a solution of a thick extract using a solvent of the following composition:

purified water (basic solvent) .. 60 parts

glycerin (solubilizer) ........................... 30 parts

ethanol (cosolvent and preservative) ...................... 10 parts

The mass of extract described in the recipe always corresponds to the thick extract. For this reason, in the manufacture of powders using a dry extract, it is taken in double quantity relative to the mass of the thick extract written in the recipe; in this case, the weight increase.

The solution of the thick extract by weight is also taken in a double amount relative to the weight of the thick extract written in the recipe ͵ as in the case of dry belladonna extract (0.1 g of thick belladonna extract is contained in 0.2 g of the solution of this extract).

The solution is usually dosed in drops. The vial of the thick extract solution is provided with a calibrated droplet meter. On the label of the bottle indicate: the number of drops corresponding to 0.1 g of a solution of a thick extract; the number of drops of a solution of a thick extract͵ corresponding to 0.1 g of a thick extract:

Extractum Belladonnae solutum (1: 2)

0.1 g of a thick extract solution - 3.5 drops of a solution 0.1 g of a thick extract - 7 drops of a solution

The shelf life of a solution of thick belladonna extract is not more than 15 days.

Calculations in the manufacture of powders with difficult to grind substances.If the mass of the hard-to-grind substance is less than 1.0 at the entire dose, to obtain the optimal dispersion and uniform distribution of the substance in the total mass of the powder mixture, the amount of volatile liquid is taken taking into account the solubility of the hard-to-grind substance in it.

With large masses of the substance, 5-10 drops of volatile liquid per 1 используют are used. Boric acid, salicylic acid, sodium tetraborate, streptocide can be crushed without adding auxiliary liquid, but the grinding process will be longer and more laborious. The withdrawn amount of volatile liquid should be indicated in the PPC after a difficult to grind substance, but volatile liquid is not included as a substance in the total mass of the powder and in the suspension, ски volatiles during the manufacturing process.

Calculations in the manufacture of powders containing antibiotics.For calculations in the manufacture of complex powders with antibiotics, it should be borne in mind that the activity of many antibiotics is expressed in units of action (U). The relationship between the UNIT and the mass is established using a private article of the pharmacopeia for this antibiotic. For example, if it is extremely important to take 300,000 IU of benzylpenicillin sodium salt in all doses of the powder, then this will correspond to 0.18 g (100,000 IU \u003d 0.059 \u003d 0.06).

Calculations in the manufacture of powders using semi-finished products.To increase labor productivity in pharmacies use semi-finished products. These are special intra-pharmacy blanks consisting of medicinal and auxiliary substances (trituration) or a mixture of two or more substances mixed in the same proportions as those most often found in recipes. Their nomenclature is determined by the often repeated prescription of a particular pharmacy, in some cases it is approved by the current control and analytical service or regulatory documents.

The use of convenience foods speeds up the manufacturing process of the drug by reducing the number of weighings. In pharmacies

in accordance with regulatory documents, semi-finished products of the following composition are made:

zinc oxide, talc - equally;

zinc oxide, talc, starch - equally (shelf life of semi-finished products made from both prescriptions - 30 days at 25 ° C);

dibazole, papaverine hydrochloride - equally;

diphenhydramine 0.03 g; sugar 0.225 g;

acetylsalicylic acid, phenacetin - equally;

phytin, calcium glycerophosphate - equally;

ascorbic acid 0.1 g; glucose 0.5 g;

riboflavin, thiamine bromide - equally.

The masses of ingredients for all doses of powders are calculated according to general rules. The mass of the semi-finished product is equal to the sum of the masses of the individual components. The weight of the semi-finished product is recorded in the control panel ая noting the components with a curly bracket.

Preparatory measures. At this stage, the technologist must choose the right instruments, materials and equipment. For weighing use manual scales (BP, HSR), tariff, electronic, etc.
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Scales are selected based on the weighed sample, taking into account the minimum and maximum permissible load of the balance.

To grind medicinal and auxiliary substances, porcelain mortars with a pestle and unglazed inner surface are used. Industry produces mortars of seven numbers.

To grind poisonous substances, as well as substances that irritate the mucous membranes, special mortars with covers are used or ordinary mortars are covered with cardboard or plastic circles with a hole for the pestle. At the same time, the respiratory organs should be protected with a multilayer gauze cloth, and when grinding arsenic dioxide, salicylic acid, iodine and other irritating substances, the eyes must be covered with protective glasses. The mortar and pestle are selected in appropriate sizes so that the volume of the mortar is filled by no more than 20%.

Apply other means of mechanization of the technological process: tissue shredders (RT-1, RT-2); Islamgulov apparatus, coffee mills; batchers (TK-3, DPR-2, DVA-1, 5, DP-2, etc.
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), celluloid plates (scrapers), scoops for dosing.

Packaging material (paper capsules, cellophane, bottles, plastic film, gelatin capsules) is selected taking into account the physicochemical properties of the ingredients. Paper capsules (simple) are used for packaging powders with non-hygroscopic and non-volatile substances.

Waxed and waxed capsules are used for packing powders with hygroscopic substances (absorbing

mi moisture), eroded (losing moisture); changing under the influence of atmospheric oxygen and carbon dioxide. Powders with volatile, odorous substances, as well as substances that dissolve in wax and paraffin are packaged in parchment capsules and cellophane.

As directed by a physician, powders with substances that have coloring, irritating properties are released in hard gelatin capsules. For packaging powders containing iodine, potassium permanganate and some other substances with oxidizing properties, dark glass bottles with a stopper are selected from materials resistant to oxidizing agents.

For the design, they select the appropriate warning labels: “Baby”, “Handle with care”, “Keep in a cool place”, which are placed on the packaging after manufacture. In the case of the presence in the recipe of a substance of list A and a narcotic package, the package is sealed, sealing wax, a thread for tying the package, and a signature are prepared hollow.

General information on the properties of the components of the powders.In the manufacture of complex powders, it is extremely important to take into account such properties of medicinal and auxiliary substances as the size and shape of crystals, solubility in ethanol, ability to adsorb (including coloring ability), ability to spray; volatility, odor, etc.

Substances with coloring properties (riboflavin, furatsilin, ethacridine lactate, potassium permanganate, methylene blue, brilliant green, iodine), as well as odorous and volatile substances (thymol, menthol, camphor, essential oils) are stored in special cabinets; they are dosed and crushed at a specially designated workplace, using separate scales, mortars, devices for grinding and packaging, since these substances give a strong specific smell or severely pollute the equipment, and with careless work, and surrounding objects.

It should be remembered that not all substances that are colored are coloring. So, the dermolith, copper sulfate, sulfur, dry extracts do not belong to the colorants, since they do not have a strongly expressed sorption ability.

During the manufacture and storage of powders, it is extremely important to consider that some substances: analgin, antipyrine, dry extracts (for example, belladonna extract), dibazole, ammonium chloride, diphenhydramine, glucose, potassium acetate, potassium iodide, calcium chloride, burnt alum and others substances absorb water vapor from the air. Powders lose their flowability, and the possibility of chemical processes increases in a humid environment. Many substances in a humid environment are oxidized by atmospheric oxygen (ascorbic acid, etc.
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).

Some substances lose crystallization water, i.e., they erode (sodium sulfate, magnesium sulfate, zinc sulfate, glucose, alum, calcium gluconate and lactate, codeine, caffeine, rutin, theophylline and other crystalline hydrates).

A number of substances absorb carbon dioxide (magnesium oxide, zinc oxide, barbamil, sodium barbital, aminophylline, temisal, etc.
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).

It is worth saying that for some substances it is not possible to obtain a particle size corresponding to the GF indication without the use of special grinding techniques. For example, substances such as sulfur, butadione, terpin hydrate during electrification are electrified and sprayed when they are removed from the walls of the mortar with a celluloid plate, they are ground in a mixture with other substances or liquids prescribed in the recipe.

Hard materials (menthol, thymol, camphor, iodine) are crushed in the presence of volatile solvents - ethanol or, in extreme cases, ether. These liquids easily penetrate into micro-cracks of crystals, having a proppant effect, contribute to grinding. After evaporation of the liquid, fine powder is formed.

If the amount of volatile liquid is taken into account the solubility of the substance and ground in the presence of other substances, without waiting for the complete evaporation of ethanol, you can get very small particles.

Phenyl salicylate, streptocide, sodium tetraborate, boric acid, salicylic acid can also be classified as difficult to grind substances.

Substances such as bismuth basic nitrate, zinc oxide, xeroform, phytin, and quinine salts are pressed together and adhere to the walls of the mortar during grinding; therefore, they need to be crushed without much effort. Antibiotics (penicillins, erythromycin, griseofulvin, etc.) should not be crushed excessively.
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).

Dyes should be introduced into the composition of the powders in such a way as to avoid direct and prolonged contact with the grinding surfaces of the equipment.

To avoid wetting the powder mixture, some substances (alum, sodium sulfate, magnesium sulfate, and some others) are expediently used dried.

In powders intended for subsequent dissolution, substances containing crystallization water are used.

In accordance with the instructions of the Global Fund, substances prescribed in a mass of less than 0.05 g for all doses (especially for substances of lists A and B) are used in the form of trituration - a mixture with milk sugar or other excipient approved for medical use. Milk sugar is the most suitable substance for this for the following reasons:

mixtures with milk sugar do not stratify for a long time, since its density is close to the density of many salts of alkaloids and nitrogenous bases;

milk sugar is less hygroscopic and trituration does not lose flowability during storage for 1 month;

it is the most indifferent excipient.

In the manufacture of powders with dry extracts (for example, belladonna extract), their high hygroscopicity should be remembered. It is unacceptable for a long time to keep the trouser-voice with the dry extract open, powders should be prepared quickly and pack the powders in waxed or waxed capsules.

Many powders strongly “dust” with stirring, pouring. The ability to spray is due to the magnitude of the adhesion forces between the particles and is highly dependent on the moisture content of the powder. For this reason, hydrophobic substances (for example, talc) are often sprayed more easily than hydrophilic ones.

The ability to spray is characterized by a bulk (or bulk) mass of a substance, i.e., a mass of 1 cm 1 in a dry-air state under conditions of free filling (not to be confused with density). The smaller the bulk (bulk) mass of a substance, the higher its ability to spray. For example, bulk (bulk) mass increases in the series: magnesium carbonate< магния оксид < глюкоза < < кислота ацетилсалициловая < фенацетин < стрептоцид < каль­ция карбонат < кальция глицерофосфат < сахар < висмута нитрат основной. Плотность порошка не характеризует его способность рас­пыляться. К примеру, магния оксид, несмотря на большую плотность (3, 65 г/см 3), легко распыляется (объемная масса - 0, 387 г/см 3).

All of these properties are extremely important to consider when choosing the best technology, packaging material, ensuring appropriate storage conditions.

The powder manufacturing process includes the following stages: preliminary grinding (dispersing) of the substance with the smallest relative loss in the pores of the grinding equipment; sequential grinding and mixing; dosing; packaging; design (marking).

Powder manufacturing technology.Grinding and mixing.Grinding is called the process of reducing particle size, leading to an increase in the specific surface of the crushed substance.

The grinding stage is very important. It is necessary to achieve uniformity of complex powders when mixing the ingredients (the more particles obtained in the grinding process, the better they are distributed in the total mass of the powder mixture); increase dosing accuracy; strengthening the pharmacological effect.

A measure of the fragmentation of any dispersed system can be: the transverse particle size (for spherical particles, this is the diameter, for cubic particles, the edge of the cube); the reciprocal of the transverse particle size, called dispersion.

The dispersion of powders (particle size) significantly affects the speed and strength of the pharmacological effect ͵ the uniformity of the mixture and the accuracy of dosing. The higher the dispersion of the powder (the smaller the particle size), the easier they are to dissolve, absorb faster, and increase the speed and strength of the pharmacological effect. With high monodispersity (approximately the same size and shape of the particles), powder mixtures do not exfoliate longer and are more accurately dosed.

The size of the crystals of drugs produced by industry varies from 0.07 to I mm. Moreover, in each case, it is necessary to achieve the optimal degree of grinding.

The degree of grinding is the ratio of the linear or volumetric size of the largest particles of a powdery substance before grinding to the size of the largest particles after grinding. Medicinal substances are crystalline or amorphous. When grinding crystalline substances, a certain mechanical force is extremely important, amorphous substances are crushed more easily or do not require preliminary grinding at all.

When grinding substances, two processes occur: separation of particles and enlargement of small particles under the influence of mutual attraction, due to the high value of free surface energy of the ground mass (Gibbs energy). Free surface energy is the sum of unbalanced molecular forces located on the surface of a given substance. The more the substance is crushed, the more its specific surface becomes, the higher the value of free surface energy. Mathematically, the process of changing free surface energy should be expressed as follows:

∆G \u003d ∆ Ss,

where ∆G  - change in free surface energy; ∆S- change in the free surface; s  - interfacial tension coefficient.

At the first stages of grinding, the process of separation of particles prevails over the process of their enlargement. In this case, an increase in free surface energy is observed. However, it cannot increase indefinitely. In accordance with the laws of thermodynamics, free surface energy (to stabilize the state

systems) seeks to a minimum (G min).For this reason, at a certain stage of grinding, the speed of the reverse process (enlargement of particles) begins to increase, then the processes of separation and enlargement of particles acquire the same speed, a state of dynamic equilibrium is established, and further grinding becomes inappropriate.

In the event that a greater degree of grinding is necessary than that which was achieved at the time of equilibrium, special technological methods are used:

substances are ground separately, and then in the presence of other solids (sucrose, lactose, etc.
  Posted on ref.rf
), it should be borne in mind the possibility of solid-phase interactions in the joint grinding of certain substances with a partial or complete loss of pharmacological activity;

liquids are added to facilitate grinding, for example, volatile (ethanol, ether). The liquid not only saturates the free surface, reducing free surface energy, but also, penetrating microcracks, increases them, weakens bonds between particles, and has a wedging effect. When grinding substances in the presence of a liquid, particles with a size of 0, 1-5 microns can be obtained, especially when using the process of recrystallization (recrystallization) of a substance from a solution in the form of a finely divided powder.

High values \u200b\u200bof free surface energy are both positive and negative. For this reason, we should always talk about optimal (rather than maximum) dispersion, which is extremely important to ensure the extremely important pharmacological effect. As positive high values \u200b\u200bof free energy, one can consider an increase in the rate of absorption, absorption of skin secretions (sweat) and purulent wound contents (powder), rapid dissolution, enveloping effect, etc. As negative values, a decrease in some cases of pharmacological activity by following reasons:

violation of the structure of substances, hydrolytic destruction of the drug substance;

a decrease in the stability of a substance in contact with gastrointestinal enzymes with a sharply increasing contact surface of a finely divided substance with biological fluids;

too fast elimination of the substance from the body;

increased toxicity, the appearance of a side effect (increased speed and completeness of absorption of the substance).

The desire of the system to reduce the value of free surface energy can be accompanied by: adsorption of moisture and gases from air; aggregation of particles, conglomerates are formed (sulfur, salicylic, acetylsalicylic acid, streptocide, butadion

and etc.
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); adsorption of substances on the walls of grinding devices; oxidation by oxygen of air.

For grinding solid medicinal substances in pharmacies, volume and surface grinding are used.

Volumetric grinding includes two operations: crushing and impact.
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When crushing, the force is directed perpendicular to the crushed substance, the force increases gradually, the crushed body is deformed in its entirety, and when the internal stress in it exceeds the tensile strength, the body is destroyed. Pieces of different shapes and sizes are obtained.

Upon impact, the force is directed perpendicular to the crushed body, acts instantly. It turns out the product is large, uneven. In the manufacture of powders, this effect cannot be limited, in addition, this technique is not allowed to be used in porcelain mortars.

Surface grinding. When grinding, the force is directed perpendicularly and tangentially to the crushed body. The body is crushed simultaneously under the action of several forces (compressive, tensile, shear). Particles taken from the surface layers are smaller and of the same size.

Medicinal and auxiliary substances are crushed for a certain time based on their mass, physico-chemical properties and taking into account the size of the mortar. The optimum load for grinding powders in mortars should be considered a load not exceeding 1/20 of the working volume of the mortar. If the maximum load is exceeded, the specific surface of the powders sharply decreases, and it becomes difficult to achieve uniformity of the mixture.

When grinding, the mortar is pressed to the table with the left hand or fixedly fixed with a mortar holder of various designs. In the process of grinding, the mass is 2-3 times collected in the center of the mortar using a celluloid plate (scraper). The optimum grinding time in the mortar is 2 - 3 minutes.

There are features in the manufacture of various types of powders.

In the manufacture of simple powders, the physicochemical properties of medicinal substances and the method of their use are taken into account. Always grind the following substances before vacation:

coarse-grained substances in metered powders (potassium chloride, sodium bromide, bromocamphor, acetylsalicylic acid) - to avoid mechanical injury and irritation of the mucous membranes;

substances intended for powders;

fine crystalline substances, hardly soluble in water and the secrets of the gastrointestinal tract.

Simple powders are released unmilled:

from medicinal substances intended for the manufacture of solutions (potassium permanganate, alum, sodium tetraborate, magnesium sulfate);

highly dispersed, easily atomized substances (talc, lycopodium, xeroform, pancreatin, magnesium oxide);

fine crystalline substances, readily soluble in the secrets of the gastrointestinal tract (analgin, glucose).

In the manufacture of complex powders, sequential grinding and mixing is always preceded by the stage of preliminary grinding of the substance, ĸᴏᴛᴏᴩᴏᴇ the least is lost in the pores of the grinding equipment, that is, the substance with the lowest relative loss.

Xeroforms, salicylic acid, bismuth basic nitrate, barbamyl, spazmolitin, amidopyrine, butadion, zinc oxide, benzoic acid, acetylsalicylic acid are strongly lost in the pores of the mortar. Glucose, ascorbic acid, calcium carbonate, calcium lactate, sodium bicarbonate, codeine, codeine phosphate, resorcinol, antipyrine, tannin are little lost in the pores of the mortar.

Optimally, if a small relative loss of the substance, which is preliminarily ground, is combined with its greater indifference and larger crystal size. After preliminary grinding, the substance, as a rule, is poured onto a capsule and then a sequential grinding and mixing process is carried out.

The values \u200b\u200bof the absolute and relative loss of certain substances during grinding in mortar No. 1 are given in the GF reference table. With increasing mortar size, the loss of substance increases in proportion to the coefficient of the working surface of the mortar.

Given that in a pharmacy, the grinding and mixing of ingredients is carried out, as a rule, in one mortar, to simplify the calculations work surface coefficients  can not be used.

The absolute loss of a substance in a mortar should be correlated with its weight written in the recipe, i.e. it is extremely important to calculate the relative loss of substance,%, during grinding.

P% \u003d (K / M) ´100%

where TO-relative loss coefficient, that is, the value of the relative loss of the substance after grinding 1,0 g of the substance in mortar No. 1; M- the total mass of the medicinal substance according to the recipe, ᴦ.

For example, when grinding ascorbic acid in mortar No. 1, the absolute loss of substance will be 12 mg (0.012 g). If the mass of ascorbic acid at the whole dose is 0.2 g, then the relative loss of substance will be:

P% \u003d (0.012 / 0.2) ´100% \u003d 6%

If the total mass of ascorbic acid at the entire dose is 2.0 g, and the absolute loss of the substance remains unchanged, then the relative loss will decrease:

P% \u003d (0.012 / 2.0) ´100% \u003d 0.6%

It follows that the smaller the mass of the substance is ground in a mortar, the greater its relative loss. For this reason, poisonous, potent and other substances prescribed in small quantities are not the first to be ground in a mortar. If sugar is prescribed in the recipe, then it is ground first and the relative loss of substances is not calculated. Calculations of the relative losses of substances written out in equal amounts are not carried out, it is enough to compare the magnitudes of the absolute losses.

If there is no loss in the table of one or more substances of the prescription, the sequence of grinding and mixing the ingredients of complex powders will depend on the following indicators:

the presence of difficult to grind substance;

the ratio of ingredients (values \u200b\u200bof the prescribed masses);

physico-chemical properties of the prescribed substances (the nature of the crystals, the ability to adsorption, consistency, ability to spray).

The sequence of grinding and mixing depends on the properties of the components of the powder. Grinding and mixing should be carried out with a minimum expenditure of time, energy, minimal loss of medicinal substances. We consider two cases.

1. There is a hard-to-grind substance in the recipe. In this case, it is ground first. Pre-grinding another substance is not practical. Hard-to-grind material is ground with a volatile solvent (or dissolved in it). When volatile liquid (ethanol or ether) is added, the substance rubbed into the pores of the grinding apparatus (mortar) will be washed out of them and, in turn, will complicate the process of dissolving the hardly ground substance and its subsequent recrystallization from solution.

If the mass of the hard-to-grind substance is more than 1.0 g, add 10 drops of volatile liquid to 1.0 g of the substance. In this case, partial dissolution with subsequent recrystallization is observed, but to a greater extent, the liquid, penetrating the microcracks of the crystals and exerting a wedging effect, provides grinding. After evaporation of the liquid, fine powder is formed. The decrease in the amount of auxiliary liquid in this case is also due to the fact that camphor, menthol, thymol are volatile substances and, with an increase in the time of ethanol evaporation, can themselves be largely lost.

Other prescription ingredients are added to the solution, without waiting for the complete evaporation of the liquid. At the same time difficult to grind substances

Powder manufacturing technology - concept and types. Classification and features of the category "Powder Manufacturing Technology" 2017, 2018.

Powders - solid LF for internal and external use, consisting of one or more ground substances and having the property of flowability.

Powders are isolated simple (boric acid, potassium permanganate, magnesium sulfate) and complex (licorice powder, Karlovy Vary artificial salt, powders - for children, amicazole, galmanin).

Classification:

1. for internal use (LF from solid individual dry particles of various degrees of grinding, with the property of flowability):

M. B. colorants, flavorings;

2. for external use (LF from solid individual dry particles of various degrees of grinding, with the property of flowability):

M. B. single and multi-dose;

3. effervescent:

M. B. single and multi-dose;

· For dissolution in water;

4. for inhalation:

M. B. single and multi-dose;

· For their more effective use of DV, b. in a mixture with a carrier;

· Used with an inhaler;

5. for the preparation of injectable drugs and infusions (sterile solids placed in appropriate containers and, when appropriate sterile fluid is added, forming a clear and particle-free solution or uniform suspension) (often lyophilized powders);

6. nasal (for insertion into the nasal cavity by means of a suitable device);

7. powders and granules for the preparation of syrups, solutions, suspensions.

Requirements:

The crushing of DV and auxiliary;

Flowability;

Stability;

Uniformity of the content of active ingredients (for single-dose powders for internal use with a content of active ingredients less than 2 mg or 2℅ of the total mass;

Mass uniformity (for single-dose powders for internal use; if OSDV was performed, it is not used).

Powder Production Scheme

BP1.2. Staff training

TP1. Grinding → Loss

TP2. Screening → Loss

TP3. Mixing → Loss

TP4. Screening → Loss

TP5. Dosing → Loss

TP6. Standardization

Shredding   - the process of mechanical division of solids into parts, resulting in increased surface area, degree of dispersion, which ultimately leads to an increase in biological effects.

Shredding Goals:

· To achieve uniform mixing of all components;

· To eliminate large aggregates, clumping and sticking together materials;

· To increase biological and technological effects.

Shredding Methods  (depending on the physicochemical properties of the material being ground):

· Crushing (mechanical force is applied from above);

· Hit (jerked on top);

· Abrasion (progressively from above and from the side);

· Splitting (above and below suddenly);

· Sawing (progressively angled teeth);

· Cutting (jerked on top);

Cracking.

If the material hard and brittlethen use methods of crushing and impact; hard and sticky  - crushing and sawing; for brittle and medium hard  - blow, cracking, abrasion; for viscous and medium hardness  - abrasion, sawing, abrasion and shock.

The initial drug is crushed to the optimum degree of grinding, depending on the purpose of the finished product (crystalline substances for the manufacture of solutions - 0.2-0.3 mm, powder - 0.09-0.093 mm, if the degree of grinding is not specified - not more than 0.160 mm). Some materials (waxes, resins, gums, solid fats) are crushed with cooling to increase the fragility of the material, some (camphor, boric acid) with the addition of alcohol or ether.

Grinding machines (grinders) are classified into:

1) Mills (fine and ultrafine grinding) and crushers (large, medium and fine grinding).

2) Machines for pre-grinding and ashina for final grinding.

3) By the grinding method:

Cutting and sawing action (grass, root cutters, machines with circular knives);

Cracking and crushing action (jaw crushers);

Crushing action (roller crushers);

Abrasive-crushing action (disc mills, Excelsior);

Impact type (hammer, jet mills, disintegrators, dismembrators);

Shock-abrasive action (ball and drum mills);

Colloidal shredders (vibro and jet mills).

Screening   aims to separate the crushed material into fractions with the same particle diameter.

Screening machines are divided into:

Braided sieves and stamped;

Swing, drum and vibration (inertial, gigration, electrovibration) sieves.

Mixing   - a mechanical process that ensures the distribution of particles of one solid material among particles of another or other materials.

The following principles are used in the factory technology of powders:

If substances of lists A or B are included in the powder in small quantities, then they are preliminarily crushed

List A or B substances are mixed with excipients (lactose monohydrate)

The substance prescribed in a very small amount is pre-dissolved, the powder mass is sprayed, mixed, dried

Mixing starts with the least-prescribed component

Faucets: lobed, screw, “drunk barrel”.

Dosage   is carried out for a given volume corresponding to a specific mass of powder with dispensers of various designs: screw, chamber vacuum.

For packaging   multi-dose powders use polymer containers; single-dose powders use paper bags.

Collection   - a mixture of several types of crushed, less often whole LRS, sometimes with impurities of salts, essential oils, etc.

Classification:

1) Simple and complex

2) Non and metered

3) Non and pressed

4) According to the method of application: for internal, external, inhalation use

Production Scheme

BP1 → BP1.1. Room preparation

BP1.2. Staff training

BP1.3. Equipment Preparation

BP1.4. Farm preparation. substances auxiliary substances

TP1. Grinding → Loss

TP2. Screening → Loss

TP3. Mixing → Loss

TP4. Addition of essential oils and salts (not always)

TP5. Dosing (not always) → loss

TP6. Standardization

At shredding   LRS should take into account the localization of DV and the orthological and anatomical structure (for example, belladonna leaf veins are poorly powdered, it is impossible to discard them, but it is necessary to achieve maximum grinding, since there are most alkaloids there). LRS should be crushed without residue, because the distribution of DW in the plant tissues is uneven. Typically, LRS is also dried to a residual moisture content of 6-8%.

In the collections for the preparation of infusions and decoctions, the degree of grinding is established: leaves, flowers, herbs no more than 5 mm (bearberry no more than 1 mm); stems, bark, roots, rhizomes of not more than 3 mm; fruits and seeds no more than 0.5 mm. In collections for baths, poultices and emollients, the degree of grinding is 2 mm.

For milling, DM-400 jaw and hammer crushers, dismembrators and disintegrators using chipping, grinding, impact (rhubarb, soapwort, eleutherococcus, chaga, viburnum bark, rhizome of zamani, fern), grass and root cutters (plantain leaf, rhizome) are used valerian).

At the introduction of salts they are dissolved in a minimum volume of water, the collection from the spray gun is sprayed with the resulting saturated solution, then it is dried in an oven at 40-60 ° C. If a significant amount of salt is included in the collection, then one of the herbal ingredients of the collection (preferably with mucous substances) is selected, it is moistened with water, sprinkled with salt powder, and dried. Hygroscopic raw materials are added to the collection in the last turn, after spraying and drying. Essential oils dissolved in alcohol 1:10, spray collection, dried. After drying, the collection mass should equal to the mass of all ingredients, excluding solvent.

Fees pack   in boxes lined with parchment paper, or in a double paper bag of 50, 100, 150, 200 g. The composition and method of preparation are indicated on the package.

9. Characterization of tablets. Types of tablets, technological requirements for them. Quality control. Auxiliary characteristics

Tablet - a solid dosed LF containing in its composition 1 dose or more active in - c, obtained by direct pelletizing of auxiliary and active iv or using granulation.

T. There are various shapes (flat, flat-cylindrical, doubly convex, etc.), of different diameters (4-25 mm, if the diameter is greater than 9 - there is a risk on the surface (notch), the height must be 30-40% of the diameter )

Classification: A) as intended.

1. For oral use: DV are released in the oral cavity (sublingual T, T for sucking, buccal, for biting, for chewing, for a dental hole); T for swallowing (DV released in the stomach; in the small intestine; T with a modified release rate); effervescent T and T for diagnostic purposes.

2. For introduction into the body cavity (vaginal, rectal)

3. For extraintestinal use: T for the preparation of RDI, T for implantation.

B) Depending on the presence of the shell: coated and uncoated.

C) depending on the dose of DV: mite is the minimum dose of DV for a minimally pronounced therapeutic effect, semi is average, forte is the maximum dosage for a large therapeutic effect.

Technological requirements.

1. Flowability - the ability of a powdery mass to precipitate out of a container or flow under its own gravity and thereby ensure uniform filling of the matrix channel.

2. Compressibility - the ability of a tabletted powder to take and maintain a specific shape and size of a tablet under the influence of pressure.

3. Bulk mass - the mass of a unit volume of free bulk powder material.

4. Relative density - characterizes the density of the particles in the powder and represents the ratio of the density of the powder to the density of the compact material and is expressed in%.

5. Porosity - the amount of free space between the powder particles. It is determined based on the values \u200b\u200bof bulk and true density.

Quality control.

The homogeneity of the DV content in a unit of dosed solid drug is for T with a DV content of 2 mg or less or less than 2% by weight of the tablet. (The content of active substances in each selected unit is 85-15% of the average content of v-va)

Disintegration - the time during which a tablet, immersed in the appropriate liquid breakdown / dissolution, and on the chintz with an average diameter of the holes there are no particles of tablets. (T without a shell - not b. 15 minutes, T for sucking 15-60 minutes, T PO - not b. 30 minutes, T enteric - do not decompose in acid in 120 minutes, in alkalis - not b 60 minutes)

Dissolution (can be used to assess bioavailability) - the number of DV, which under standard conditions for a certain period of time will go into solution from a solid dosed LF. (70-115% of DV from the content specified in the "Composition" section should go into the solution).

Abrasion resistance (for T uncoated). Less than 0.65 g - 20 tablets, 0.65 or more - 10 tablets. At least 99% of the mass should remain after 100 revolutions in the apparatus.

Compressive strength - by measuring the force required to break tablets. (depends on diameter)

Auxiliary Islands.

Cleriches db as low as possible. D. meet the appointment of LF. Maximize your properties. D to ensure the manifestation of the necessary pharmacological action of DV, taking into account their famakokinetics. D. b. technological. Do not have toxic, irritating and allergic effects, do not interact with organic substances, with container materials, with processing equipment. D. have chemical and bacteriological purity. If possible, be affordable.

The role is to provide the necessary mass and volume, contribute to the successful implementation of the process, provide bioavailability of the active ingredient.

From the function performed: lubricating component (hydrophobic), granulating, hydrophilic filler and disintegrating.

From destination: binding  (purified water, starch paste, sugar syrup), loosening  (swelling - starch, pectin; gas-forming - sodium carbonate and bicarbonate; improving wettability and permeability  - starch, lactose), anti-friction  (sliding - starch, talc, aerosil; anti-stick - stearin, talc), fillers  (diluents - glucose, dextrin, mannitol).

10. Comparative characteristics of tablet machines. Double pressing machines.

Cars: skid, intermediate (shoe) and rotor.

Skid - sost from the loading funnel, which moves when the machine is running on special rails. DOS e-you: matrixes and punches. The matrix is \u200b\u200battached to the matrix table and is bounded from below by a lower punch. Pressing is carried out by the upper punch according to the type of impact.

Shoe  - close to sleigh in design and operation. They differ from them by the immobility of the loading funnel. Filling - using a movable shoe. Pressing the upper punch.

Rotary- sost from a matrix table with matrices. Upper and lower punch on press rollers. The hopper is stationary. Pressing occurs simultaneously with the upper and lower punch. (RTM-12; 41; TP-40M, “Drycota”).

“Drycota” - for producing multilayer tablets, for producing coated tablets by compression.

RTM-24D - for receiving facing tablets, consists of two rotary machines connected by a conveying device (the first rotor for receiving the core of the tablet)

The technological process of manufacturing products by powder metallurgy begins with the production of metal powders. A large number of methods for producing powders are known.

The variety of methods used is explained by the fact that the qualitative characteristics of powders and products are largely determined by the method of manufacturing powders. Powder of the same metal, depending on the production method, dramatically changes some of the properties that determine its applicability for a particular purpose.

Powder Properties

In practice, metal powders are characterized by the following properties:

• physical;
• chemical;
• technological.

Physical properties of powders

To the physical properties of powders  usually include the predominant particle shape and particle size distribution of the powder. The shape of the particles mainly depends on the method of preparation and can be spherical, spongy, fragmentation, dendritic, dish-shaped, scaly. The shape of the particles affects the density, strength and uniformity of the compact. The greatest strength of the compacts is given by dendritic particles. In this case, the hardening of the powders during pressing is caused by the action of adhesion forces, particle jamming, interweaving of the protrusions and branching.

The particle size of the powders obtained by various methods ranges from fractions of a micrometer to fractions of a millimeter. To obtain a strong pressing, a powder with a certain particle size and a set of them in size is necessary. In practice, metal powders with particles of the same size are never found.

The particle size distribution of the powder is the relative content of fractions of particles of various sizes. In combination with other properties, it affects the specific pressure during pressing, necessary to achieve the specified mechanical properties of sintered products.

Chemical properties of powders

To the chemical properties of powders  primarily include the content of the base metal, impurities and contaminants. The chemical properties are also affected by the gas content in the bound, adsorbed or dissolved state. The content of the base metal in the powders is not less than 98 - 99%, and such a purity of the powder metals for most sintered products is satisfactory.

Harmful impurities for iron powder are admixtures of silica, aluminum oxides and manganese. These impurities make it difficult to compress the powders and increase the wear of the molds.

The presence in the powders of a significant amount of gases (oxygen, hydrogen, nitrogen, etc.) adsorbed on the surface of the particles, as well as particles that got inside the manufacturing process and as a result of decomposition during heating of impurities, increases the fragility of the powders, makes it difficult to compress, and their intensive release during sintering may cause warping of products. Therefore, powders are sometimes subjected to vacuum treatment to distill gases.

Technological properties of powders

Under the technological properties of powders understand:

• bulk density of the powder;
• fluidity;
• compressibility.

Bulk powder

Bulk powder  - this is the mass of a unit of its volume with free filling. It is determined by the density of the powder material, the size and shape of its particles, the density of the particles and the state of their surface. For example, spherical powders with a smooth surface provide higher bulk density.

Powder fluidity

Powder fluidity  - This is the ability to move under the action of gravity. It is estimated by the expiration time of a certain sample (50 g) through a calibrated hole (diameter 2.5 mm). The fluidity depends on the density of the material, particle size distribution, shape and state of the surface of the particles and affects the performance of automatic presses during pressing, as it determines the time it takes to fill the mold with powder. The fluidity deteriorates when the powder is wetted, its specific surface area and the fraction of the fine fraction increase.

Powder compressibility

Powder compressibility  - this is the ability of a powder, under the influence of an external effort, to acquire and hold a certain shape and size.

Powders of the same chemical composition, but with different physical characteristics, may have different technological properties, which affects the conditions for the further transformation of powders into finished products.
Therefore, the physical, chemical and technological properties of the powders are directly dependent on the method of obtaining the powder.

But not only the qualitative characteristics of the powder are the basis for choosing a method for producing powders. When assessing the method of production of powders, economic issues are very important - the cost of the powder, the size of the investment, the cost of processing the powder into products.

All this necessitated the development and industrial development of a large number of different methods for the production of powders.

Powder Production Methods

All methods for producing powders that are found in modern practice can be divided into two groups:

• mechanical methods;
• physical and chemical.

Mechanical methods for producing powders

By mechanical meanspowders are considered such technological processes in which the source material is crushed as a result of external forces without changing the chemical composition.

Physicochemical methods

TO physicochemical methods  include such technological processes in which powder production is associated with a change in the chemical composition of the feedstock as a result of deep physico-chemical transformations. In this case, the final product (powder), as a rule, differs from the starting material in chemical composition.