Description

N-MethylformamideTypical Properties

N-Methylformamide Usage

This product is an important organic chemical raw material and intermediate, and it is a good organic solvent. It is used to synthesize high-efficiency and low-toxic single-method, double-milk and so on. Used as a reaction solvent and a purified solvent for organic synthesis. Also widely used in medicine, dyes, spices and electrolysis, electroplating industry.

1. Chemical Synthesis: N-Methylformamide is often employed as a solvent in the synthesis of pharmaceuticals, agrochemicals, and various organic compounds. It is particularly useful in reactions that involve the formation of amides and other nitrogen-containing compounds.

2. Polymer Industry: It is used in the production of polymers, such as polyurethanes and polyacrylonitrile. In the manufacture of certain fibers and resins, N-Methylformamide serves as a solvent and a reaction medium.

3. Pharmaceuticals: The chemical is utilized in the pharmaceutical industry for the synthesis of active pharmaceutical ingredients (APIs) and other intermediates. It facilitates reactions that involve the introduction of amide groups into molecules.

4. Textile Processing: N-Methylformamide is employed in the textile industry as a solvent for spinning fibers, particularly in the production of synthetic fibers like acrylic and modacrylic.

N-Methylformamide Packaging

1kg/bpttle, 200kg/drum

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What is the effect of catalyst on foaming?

Polyether, as the main raw material, reacts with isocyanate to generate urethane, which is the skeleton reaction of foam products. In the case of the same functionality, the molecular weight increases, the tensile strength, elongation and resilience of the foam increases, and the reaction activity of the same kind of polyether decreases; in the case of the same equivalent value (molecular weight/functionality), the functionality increases, the reaction is relatively accelerated, and the cross-linking degree of the generated urethane improves, and the hardness of the foam is increased, and the elongation rate decreases. The average off-energy of polyol should be above 2.5, if the average off-energy is too low, the foam body has poor recovery after pressure.

If the dosage of polyether is high, it is equivalent to the reduction of other raw materials (TDI, water, catalyst, etc.), which is easy to cause the foam products to crack or collapse. If the dosage of polyether is small, the foam products are hard, the elasticity is reduced, and the handfeel is bad. 1、Foaming agent

Generally in the manufacture of density greater than 21 polyurethane block foam, only use water (chemical blowing agent) as a blowing agent, in the low-density formulations or ultra-soft formulations before the use of methylene chloride (MC) and other low-boiling point compounds (physical blowing agent) as an auxiliary blowing agent. The auxiliary blowing agent will reduce the density and hardness of the foam, and the curing will be slowed down due to the absorption of part of the reaction heat by its gasification, which requires an increase in the catalyst dosage. Due to the absorption of heat, the danger of core burning is avoided. Foaming ability can be reflected by foaming index (number of water or water equivalents used for 100 parts of polyether): m—amount of foaming agent Foaming index IF=m(water)+m(F-11)/10+m(MC.)/9(100 parts of polyether) Water as a foaming agent reacts with isocyanate to generate urea bond and release a large amount of CO2 and heat, which is a chain growth reaction. The amount of water is more, the density of foam decreases, the hardness increases, at the same time, the pillars of bubble holes become smaller and weaker, which reduces the carrying capacity and is easy to collapse the bubble and crack the bubble. The amount of TDI consumed increases, more heat is released, and it is easy to burn the heart. If the amount of water exceeds 5.0 parts, a physical foaming agent must be added to absorb some of the heat to avoid the occurrence of core burning. Less water, the amount of catalyst is reduced accordingly, but the density increases ‘’F’

2、Toluene diisocyanate

General soft foam with TDI80/20, 2, 4 and 2, 6 isomers of the mixture. Available cooling method to prepare T100 that is pure 2,4 TDI. TDI dosage = (8.68 + m water × 9.67) × TDI index. TDI index is generally 110-120. Isocyanate index increases in a certain range, then the foam hardness increases, but reaches a certain point after the hardness is no longer a significant increase in the tear strength, tensile strength and elongation decreases, the foam formation of large holes, the closed-cell rise, the The resilience decreases, the surface is sticky for a long time, the maturing time is long, causing core burning. Low isocyanate index will cause foam cracks, poor resilience, poor strength, compression permanent deformation is larger, and the surface has a moist feeling.

3、Catalyst

Amine: generally use A33 its role is to promote the reaction of isocyanate and water, adjust the foam density, bubble opening rate, etc., mainly to promote the foaming reaction. Amine more: the foam products appear split, the foam has holes or bubble eyes Amine less: the foam shrinkage, closed-cell, issued by the bottom of the foam products thick. Tin: generally use stannous octoate T-9; T-19 is a gel reaction catalyst with high catalytic activity, mainly to promote gel reaction, i.e. late reaction. Tin more: gelling fast, viscosity increases, poor resilience, poor permeability, resulting in closed hole phenomenon. If appropriately increase its dosage can get loose good open-cell foam, further increase the dosage to make the foam gradually become tight, so that shrinkage, closed-cell. Tin less: insufficient gel, the foaming process causes splitting. There is cracking at the edge or top, and dehiscence, burr phenomenon. Reducing the amine or increasing the tin can increase the polymer bubble film wall strength when gassing occurs in large quantities, thus reducing hollowing or cracking. Whether a polyurethane foam has a desirable open or closed cell structure depends primarily on the balance between the rate of gel reaction and the rate of gas] expansion during foam formation. This balance can be achieved by adjusting the type and amount of tertiary amine catalyst and foam stabilising and other additives in the formulation.

4、Foam stabiliser (silicone oil)

Foam stabiliser is a kind of surfactant, which can make the polyurea well dispersed in the foaming system, play the role of ‘physical cross-linking point’, and can obviously improve the early viscosity of the foam mixture to avoid cracking foam. On the one hand, it has emulsification effect, so that the foam material components of the mutual solubility between the enhancement, on the other hand, after adding silicone surfactant can reduce the surface tension of the liquid r, gas dispersion needs to increase the free energy to reduce the air dispersed in the raw materials in the stirring and mixing process is more likely to become nucleated, to help the generation of small bubbles, adjust the size of the foam pores, control the structure of the pores to improve the stability of the foaming; prevent the bubble holes from deflating, rupture, and avoid cracking. It can adjust the size of foam pores, control the structure of foam pores, and improve the stability of foaming; prevent the foam pores from deflating and rupturing, make the foam wall elastic, and control the pore size and uniformity of foam. It stabilises the foam at the early stage of foaming, prevents the foam from bubbling in the middle of foaming, and makes the foam holes connected at the late stage of foaming. Generally speaking, the more foaming agent and POP dosage, the more silicone oil dosage. More dosage: make the late foam wall elasticity increase, should not rupture, bubble hole fine. Cause closed cell. Low dosage: foam rupture, after the rise of the collapse of the bubble, pore size is larger, easy and bubble.

5、Temperature influence

The foaming reaction of polyurethane is accelerated with the rise of material temperature, which will cause the danger of core burning and fire in the sensitive formula. General control of polyol and isocyanate components of the temperature remains unchanged. When foaming foam density decreases material temperature increases accordingly. The same formula, material temperature is the same summer temperature, reaction speed accelerated, resulting in a decrease in foam density, hardness, elongation increased, mechanical strength increased. In summer, the TDI index can be increased appropriately to correct the decline in hardness.

6、Effect of air humidity

The humidity increases, due to the isocyanate-based part of the foam reacts with the moisture in the air, resulting in a decrease in hardness, so the TDI dosage can be increased appropriately when foaming. When it is too large, it will cause the maturing temperature to be too high to cause heartburn.

7, the influence of atmospheric pressure

The same formula, foaming at high altitude, the density of foam products is small. Note:

(1) In the process of foam formation, gel reaction and foaming reaction occur at the same time, but there is competition between the reactions, and generally the speed of foaming reaction is greater than the speed of gel reaction. Gel reaction — the formation reaction of carbamate, (reaction with -OH) Foaming reaction — refers to the reaction with the participation of water, generating urea and producing bubbles

2) Nucleating agent – a substance that causes the formation of bubbles, such as microscopic solid particles and liquids in the system. Foam stabiliser or originally dissolved in the material of the fine bubbles, etc.; including air or nitrogen dissolved in polyols and isocyanates, carbon dioxide, foam stabiliser, carbon black and other fillers. But the gas in the material to produce more bubbles; stabilisation and the more generated bubble holes will be finer. The number of bubbles formed in the foaming system and the size of the bubble holes in the foam depends on the role of the addition of nucleating agents; more nucleating agents, more bubbles, small bubble holes. When the temperature rises, the gas solubility in the liquid decreases, thus more bubbles are formed or the previous start grows. Longer emulsion time favours the growth of large bubbles. Increasing the amount of catalyst can shorten the emulsion time, and fine-cell foam can be obtained due to the competing reactions of gel reaction and bubble formation.

3) Whether the foam has a desirable open or closed cell structure depends mainly on whether the gelation rate and gas expansion rate during foam formation are in balance. This balance can be achieved by adjusting the type and dosage of tertiary amine catalysts and additives such as foam stabilisers in the formulation.