Sodium hypophosphite

The two CAS numbers of sodium hypophosphite are 10039-56-2(monohydrate) and 7681-53-0(anhydrous),the molecular formula is NaH2PO2.H2O,anhydrous sodium hypophosphite  is easy to absorb moisture and caking, the nature is unstable, there is no manufacturer at present. Sodium hypophosphate structural formula phosphorus valence is +1, is normal salt rather than acid salt, solubility in water at room temperature is about 150g /ml, good water solubility, decomposition temperature is about 200℃, is the main raw materials of electroless nickel plating, aluminum hypophosphate, aluminum diethyl phosphite,calcium hypophosphate,zinc hypophosphate, manganese hypophosphate, potassium hypophosphate, the price is closely related to yellow phosphorus.

Basic information

English name: sodium hypophosphite; Sodium Hypophosphate; disodium hypophosphite; SHPP

CAS No. : 10039-56-2/7681-53-0

Executive Standard: HG/T3253-2000

Molecular formula NaH2PO2. H2O

H.S code: 28351000.00

Molecular weight: 105.99

EINECSentry number: 231-669-9

Melting point: 100℃

Density: 1.388 g/cm3

Toxicity: LD50:4000mg/kg (rat oral); 4720mg/kg (rabbit transdermal)

LC50:9400mg/m3, 2 hours (for mouse inhalation)

Solubility: Insoluble in propanol, insoluble in ethanol, easily soluble in water

Stability: reducing agent, stable at room temperature, reacts violently with strong oxidants

Decomposition temperature: 200℃

Appearance: white transparent quicksand-like crystal

Chemical mechanism

1, The valence  of phosphorus is +1, with strong reducibility,  which can reduce metal ions in electroless plating and reduce Ni2+, Cu2+, Zn2+, etc. into a metal state so that  play a role in corrosion prevention. Sodium hypophosphite reduces nickel ions to metal nickel, so  Ni-P alloy coating is obtained on the plating part with a catalytic surface. The oxidation-reduction mechanism can be explained by the following chemical reaction: 3NaH2PO2+3H2O+NiSO4 -- 3NaH2PO3+H2SO4+2H2+Ni

2, Sodium hypophosphite +1 valence P has the ability to capture electrons, anti-oxidation effect is significant, is a green preservative.

3, It can react with a variety of metal salts or alkaline reaction generate to hypophosphate,  aluminum hypophosphate, aluminum diethyl phosphonate, one of the raw materials for the  production of halogen-free flame retardants calcium hypophosphate.

Production process and method

1, proportioning feed

Feed the lime, liquid alkali and water according to the weight ratio. The ratio is lime: liquid alkali: water = 1:3.6:16, pump into the reactor; steam will drive out the air out of reaction vessel by stirring,after the slurry temperature to 40-50℃, then add yellow phosphorus immediately.

2, reaction

The reaction vessel immediately begins to react after adding yellow phosphorus, because it is an  exothermic reaction, the temperature will continue to rise up to 95-98℃, in the reaction process, continue to output phosphine gas, keep the pressure in the reaction vessle is always less than 0.05Mpa,  90-120 minutes after the reaction ends until no phosphine gas production.

3, filtration

After the end of the reaction, the material is hydraulically pumped into the diaphragm press filter for  filtration, removing the calcium phosphite CaHPO3 and excess calcium hydroxide Ca(OH)2 precipitates generated during the reaction process, and the aqueous solution containing sodium hypophosphate is transported to the next process.

4, the first concentration

The material liquid after removing the impurities and filtering is directly transported to the primary concentrator by the pump.  Under the vacuum of negative 0.04 -0.08Mpa, 0.1-0.4Mpa steam is heated and concentrated until the material concentration is 25 -30Be, and the material is transported to the alkali vessel.

5 Adjustment

Add soda ash in the alkali vessel, use carbonic acid to eradicate excess calcium  ions in the material, filter with the  plate frame, remove calcium carbonate  precipitation, transfer the material liquid to the acid adjusting  kettle, use 5- 10%  hypophosphate H3PO2 to neutralize the excess sodium hydroxide NaOH in the material liquid, adjust to the PH value of the material liquid is neutral, filter again, filtrate stored in the storage tank, to be reconcentrated.

6, the second concentration

When the vacuum is negative 0.04-0.08Mpa, the material is sucked into the concentration vessle and heated and concentrated with 0.1-0.4Mpa steam until the material concentration is 48-48.5Be.

7, cool and crystallize

Put the concentrated material into the crystallization vessel, under the condition of continuous stirring, with jacket cooling water slowly cool the 98℃ material in the vessel between 8-10 hours to 40-45℃to, in the cooling process, when the material temperature drops to 72 -74℃, there is a small amount of sodium hypophosphite fine crystalline particles produced, with the extension of time and the further reduction of temperature, These crystalline particles gradually increase and grow.

8, centrifugal packaging

The crystallizing vessel cooling to the specified temperature of the material, into the centrifuge to dry, sodium hypophosphite products directly into the plastic inner bag or bucket, accurate weighing, net weight: 25Kg/ bag, tighten the inner bag, the outer bag with a baler to seal.

Use

1, Chemical plating, plating reducing agent. Nickel, copper, gold, zinc and other metal ions can be reduced to a metallic state under certain conditions, so it is often used in the surface treatment of metals and plastics.

2.It is the raw material of organic phosphine water treatment agent.

3,It is the production of aluminum hypophosphate, aluminum diethylphosphonate flame retardant,manganese hypophosphate, calcium hypophosphate, potassium hypophosphate   and other inorganic salt raw materials.

4, It is a mild, harmless antioxidant, heat stabilizer, foreign in food production and processing as a preservative.

5,It is used as a chain transfer agent in polycarboxylic acid superplasticizer, it is convenient to use, odorless and better environmental performance than suspending white block,mercaptopropionic acid and thioglycolic acid.

sodium hypophosphite GHS

【Prevention】

Do not breathe dust or fume.

Wash hands thoroughly after handling

No eating, drinking or smoking when using this product.

【Incident Response】

 IF SWALLOWED: Rinse mouth. induce vomiting.

SKIN OR HAIR:Remove/take off immediately all contaminated clothing. Rinse skin with water/shower. Wash contaminated clothing before reuse.

IF INHALED: Remove to fresh air and keep the rest in position comfortable for breathing.

Immediately call a POISON CENTER or doctor.

IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.

Using water spray, carbon dioxide and dry powder when in a fire disaster

【Storage】

General（mechanical）room ventilation is considered satisfactory in enclosed spaces.

【Disposal Considerations】

Dispose will be in accordance with local, regional, national, and international disposal regulation.

Packaging

Net weight 25Kg, 500Kg, 1000kg

The production process of sodium hypophosphite monohydrate is relatively simple, but the quality of yellow phosphorus has a great impact on the quality and grade of sodium hypophosphite. Sodium hypophosphite in contact with the air for a long time will slowly absorb moisture, and can react with oxidants to produce sodium phosphite or sodium phosphate. It will also react with aluminum sulfate, aluminum chloride, calcium chloride, zinc sulfate, etc. Therefore, these influencing factors should be fully considered in the production process and formulation design of chemical electroplating and flame retardants.