2-Methyl-1,3-propanediol (MPO) introduction and application

About:

Methylpropylene glycol is a colorless transparent liquid with low viscosity. Miscible with water, methanol, ethanol, butanol, propylene glycol, propylene glycol

monomethyl ether, tetrahydrofuran, acetone, carbonate lactone, styrene, insoluble in cyclohexane, hexane, toluene, xylene. At about -54℃, the viscosity increases

and the crystallization is not obvious.

Applications:

Methyl propylene glycol can be used in the manufacture of unsaturated polyester, liquid saturated polyester, thermoplastic polyester resin (PET and PBT

modification), alkyd resin, polyurethane resin, double ester type plasticizers, lubricants, etc. Also used in cosmetics, pharmaceuticals and so on. The obtained

polymer has the characteristics of low viscosity, low melting point, low temperature resistance and weather resistance.

In the field of polyurethane, it is used to produce polyester polyols with low crystallization, and can be used as chain extender. The application fields are synthetic

leather paste, polyurethane coating, polyurethane adhesive for food flexible packaging composite.

Preparation:

In industry, propylene oxide is isomerized to produce allyl alcohol, and then through hydroformylation reaction, methyl propylene glycol is synthesized.

Synthesis of new diols (2-methyl-1, 3-propanediol), 2006

ARCO Chemical Company of the United States: MPO was first introduced to the chemical industry in 1990 as a new diol synthesis block.

MPO has a unique molecular structure and quickly became the first choice for polyester manufacturers and urea-formaldehyde coating producers in many ways

Gradually replacing the traditional diol products such as diethylene glycol, neopentylene glycol (NPG), 1, 4-butanediol (1, 4-BDO), 1, 3-butanediol (1, 3-BG), 1, 3-

propanediol (1, 3-PDO), and hexadiol (HDO), which are widely used in polyester at present.

At present, MPO is mainly used in the following areas:

(1) unsaturated polyester resin

The high boiling point and full primary hydroxyl group of MPO can shorten the esterification reaction time, increase the production efficiency of the reactor, and

greatly reduce the formation of acid-catalyzed reaction byproducts. The resin obtained is very light in color.

Using MPO instead of propylene glycol (PG) or neopentanediol, it was found that unsaturated polyesters using MPO had higher tensile and bending properties,

higher elongation, lower modulus and lower thermal deformation temperature than those using the latter two. In addition, compared with PG polyester, MPO

polyester is not easily hydrolyzed.

This advantage enables the corresponding polyester products to be widely used in the manufacturing process of shipbuilding, sanitary ware and other FRP

products.

Advantages:

① Low crystalline resin, prevent curing, good resistance to boiling water, hot and cold water properties.

② Good coordination

Cons:

More reactive than neopentyl glycol, to prevent low fumarate formation.

(2) Powder coating:

Powder coatings, as one of the main development directions and key products of green coatings, are developing in the direction of thin coating, low temperature

curing, non-toxic curing agents and auxiliaries, high temperature resistance, weather resistance, corrosion resistance, non-metallic materials, traditional powder

coatings modification, etc.

Polyester powder coating has strong adhesion, high hardness, impact resistance, weather resistance, and its key performance parameter glass transition

temperature (Tg) is expected to be above 50℃ to ensure good storage stability without agglomeration.

MPO based polyester powder coatings have the necessary glass transition temperature (Tg) to provide excellent storage stability; Low viscosity enhances its fluidity

and uniformity, good corrosion resistance and moisture resistance; Moreover, the flexible characteristics of MPO shaped the toughness of the paint.

(3) Coil steel coating

MPO used in coil steel coatings has 0-T bending flexibility, high hardness, good solvent compatibility, no turbidity precipitation phenomenon, excellent stain

resistance and durability.

PE-2186 polyester, a coating for coil steel using MPO, has high weather resistance, while ordinary polyester has low weather resistance.

Advantages:

① Wide coordination, strengthen the hardness of the coating without losing its flexibility, improve the rust prevention ability, and make the appearance luster

lasting.

② is cheaper than hexanediol, and replacing 1, 6-hexanediol can effectively reduce the cost

(4) Polyurethane coatings/water-based polyester

MPO plays a decisive role in the processing and performance characteristics of polyester and polyurethane polymers.

MPO dimers and trimers are very important molecular chain extenders and reaction thinners in polyurethane products.

The high solid polyester resin synthesized by MPO as a functional monomer has good fullness and satisfactory performance index.

Advantages:

The construction solid content of amino paint was obviously increased and the environmental pollution was reduced. It can be applied to the painting of cars, buses

and construction machinery.

(5) Polyurethane adhesive, food packaging

MPO based polyester coatings and adhesives are liquid rather than solid, showing extensive solvent compatibility, minimal delamination, and a wide range of paint

design capabilities.

MPO also improves the flexibility of the binder and provides conditions for the generation of more ductile coatings and adhesives. MPO also has excellent moisture,

stain resistance and weather resistance, and can be used as a raw material for synthetic polyurethane adhesives and food packaging materials.

Advantages:

The smell is small, and the smell in use is better than that of neopentyl glycol; Wide coordination.

(6) Plasticizer

MPO/ adipic acid type plasticizer is soluble in PVC and has low temperature brittleness, so it can be used in refrigerator gaskets and cable insulation.

Advantages:

It is cheaper than 1-3-butanediol and saves costs by replacing 1-3-butanediol.

(7) Daily necessities

MPO can be used as neutralizer, emollient, emulsifier and moisturizer because of its transparent appearance, low odor, low toxicity, low volatility, excellent skin

feeling, good aroma enhancement and antibacterial properties, hydration and solubilization. It is used in daily life products such as cosmetics, and it can make the

retention of the aroma longer. Therefore, MPO as a carrier solvent will be more widely used.

MPO can replace propylene glycol, 1-3-butanediol, propylene glycol, dipropylene glycol, pentanediol, used in the production of deodorant, antiperspirant, hair care

lotion, sunscreen, skin care products, lipstick, nail polish, etc.

Advantages:

No smell, antibacterial, feel good, non-toxic, moisturizing

(8) Ink

MPO is mainly used as a moisturizing agent in ink, reducing the formation of volatilization and precipitation of organic matter, increasing the fluidity of ink, thereby

avoiding the blockage of the print head nozzle, and significantly improving the printing effect. It can be printed on various media such as fibrous paper, resin paper

and even translucent film.

For thermal inkjet printers, the drying time of the ink can also be shortened. MPO can be a good substitute for diethylene glycol.

Domestic and foreign research:

Since the discovery of MPO’s important use in the 1990s, the source of MPO has been mainly recycled as a by-product of 1-4-butanediol. The United States Arco

company first uses propylene oxide isomerization to obtain allyl alcohol, and then uses allyl alcohol as the main raw material, through hydroformylation reaction to

obtain a mixture of 1-4-butanediol, MPO and n-propyl alcohol (formylation reagent is syngas CO/H2 or formaldehyde), after separation, the above three products

are obtained.

At present, the maximum selectivity of MPO prepared by this method is only about 35%. To improve the selectivity of MPO, the hydroformylation catalyst whose

main product is MPO with branched chain structure must be screened. There are almost no relevant research reports at home and abroad, which makes the

research too difficult and unreliable.

 

In addition, about the synthesis method of MPO, there are some reports abroad:

① Using diethyl 2-methylmalonate as raw material. In the first stage, boran-tetrahydrofuran was used as catalyst and tetrahydroyvean as solvent. In the second

stage citric acid was used as catalyst and water as solvent. The total yield of MPO was 87%.

The advantages of this route: single raw material, simple route, good selectivity. Disadvantages: The raw materials and catalysts used are expensive, and are only

suitable for laboratory preparation, not suitable for industrial production.

② The synthesis route using calcium sulfate as catalyst.

Advantages of this route: The process is very simple. Disadvantages: The raw material used is uncommon and expensive and the yield is not very good. Therefore,

there is no large number of reports, and it is only suitable for laboratory preparation, and is not suitable for industrialization.

③ The synthesis route using 2-methyl-3-hydroxypropanal as raw material and nickel as catalyst.

The advantages of this route: the route is simple and the application is mature, and the selectivity is very good. Disadvantages: poor stability of raw materials, not

easy to get, can only be a step to achieve industrialization, can not become a complete and reasonable synthesis route.

④ Synthesis was carried out with the catalyst code-named 75-17-2.

Advantages of this route: The route is simple and very selective. Cons: Ingredients are uncommon and expensive…

It is reasonable and feasible to prepare MPO from isobutylene by chlorination, hydrolysis and hydrogenation, and this route has the advantages of simple steps,

low raw materials and easy realization. Therefore, this paper decided to use this route to study the synthesis process of MPO……

Advances in application of 2-methyl-1, 3-propanediol, 2005

2-methyl-1 ‚ 3-propylene glycol (MPO) is a colorless, transparent, low toxicity and low viscosity liquid diol. Its application in polyester resin, plasticizer, white

electrical paint, ink, personal care products, transparent resin crafts and other fields. Especially the application of COPET in high-tech products such as island fiber

has attracted attention, and the excellent property of island fiber exceeds that of natural fiber. At present, all the MPO used in China is imported.

Structural properties of 1, 2-methyl-1, 3-propanediol

The melting point of MPO with unique methyl branch chain is very low, so the product prepared from it has the characteristics of low melting point and low

viscosity. Moreover, the presence of methyl branch chain prevents the polyester chain from overlapping, which effectively inhibits the crystallization of the

polyester.

MPO has higher hydroxyl value than more than 5 carbon diols, less materials, low cost and good compatibility with solvents, and more kinds of dibasic acids can be

selected for polyester preparation. In addition, the nonlinear carbon chain polyester structure increases the compatibility of the resin with the styrene monomer.

2, MPO in resin application…

2.4 High solid polyester resin

The prominent disadvantage of polyol monomer NPG, which is widely used in polyester coatings, is the long reaction time. Easy to form crystalline resin, so that

the coating transparency is poor; And because NPG is a solid at room temperature, in order to facilitate pumping, 10% water needs to be added, but it must be

removed before esterification, which extends the reaction time and increases the operating cost.

Liquid MPO has a fast esterification speed and a short esterification time. If the acid value (KOH) reaches 10mg/g, it only takes 190min, while NPG requires

270min. Compared with NPG, the high solid polyester coating is transparent, high hardness and has excellent impact strength and adhesion. Good resistance to

dirt, moisture and weather.

The high solid polyester resin synthesized by using functional monomer MPO has a good fullness, which significantly increases the construction solid content of

amino baking enamel and reduces the pollution to the environment. Applied to car, bus and construction machinery painting….

2.6 Modifiers of polyethylene terephthalate (PET)

Because PET is easy to crystallize, it is opaque in fog. The common improvement method is to add phthalic acid to the main material terephthalic acid in the

polymerization process for esterification polymerization.

MPO can be used as an effective PET crystallization modifier: the branched chain structure of MPO can change the thermal properties and crystallization

characteristics of polyester resin. The modified resin can display different and controllable application characteristics after blowing or drawing. However, the unit

price of phthalic acid is high, and MPO modified PET bottles can effectively reduce the cost.

MPO has methyl branch chains, which can break the symmetry and mutual arrangement of polymer molecules after polymerization into PET. If the molecules inside

the PET fiber are more disordered after processing, the result is faster and easier to lock the dye onto the PET fiber.

Therefore, the PET fiber is easy to dye, low extensibility and better strength….

4. Application of MPO in personal care products

Due to the appearance of MPO transparent, low toxicity, low volatility, excellent skin feeling, good antibacterial and hydration, MPO can be used as soap substitute,

neutralizer, emollient, emulsifier and moisturizer in cosmetics and personal care products, balanced adjustment of the overall polar and non-polar additives of the

solution, so that hydrophilic/oleophilic amphoterics can coexist. Thus maintaining the stability, transparency and homogeneity of the overall composition; It also

makes the aroma last longer. Therefore, MPO as a carrier solvent will be more widely used. And it reduces the need for oils and strong flavors, helping to reduce

costs.

In deodorant, it also has a desticking effect, and is an economic alternative to high performance alcohols such as propylene glycol, 1-3-butanediol, glycerol,

diethylene glycol, sorbitol, and pentanediol.