Methyl acrylate (MA) is the fourth most-used of the basic acrylic esters for production of acrylic and vinyl-acrylic resins, surpassed only by butyl acrylate, ethyl acrylate and 2-ethylhexylacrylate. As the lowest-molecular weight member of the homologous acrylic ester family, MA also finds uses as a starting material for the synthesis of other acrylates and derivatives ( these often involve transesterification reactions, or “Michael Additions” to the acrylic double-bond).
The relative sizes of the alkyl acrylate homologs are shown in the chart below. The other category includes propyl and isobutyl acrylate, and more. The current global market size for MA is about $350 million.
Formulators use copolymers of MA a in paints and coatings, adhesives and sealants, and inks, but not to the extent to BA or 2-ethylhexylacrylate. We see MA monomer more generally used in special applications such as films, fibers, and rheology modifiers. Derivatives produced where MA is a reaction intermediate include 2-dimethylaminoethyl acrylate (via transesterification) and amphoteric surfactants (via Michael Additions). Industry segments for MA include coatings, adhesives and sealants, thermoplastic resins, chemical synthesis, and additives.
Attributes of Methyl Acrylate
MA is often used in a copolymer to achieve a desired balance of hardness, tack, flexibility, and strength properties. When used as a comonomer in polymerization with other (meth)acrylic and vinyl monomers, MA offers the following attributes in the associated copolymer:
- With a homopolymer Tg of +10 °C, MA can increase the hardness and strength, and reduce tact vs. the homologous acrylates.
- Good water resistance.
- Excellent UV, sunlight, weathering resistance, and transparency
- Excellent copolymerization characteristics with other (meth)acrylates and vinyl acetate monomer.
- Commodity economics and excellent availability.
- Higher polarity which increases adhesion to more polar surfaces.
- With acrylonitrile, MA is used to reduce the crystallinity and melting point via copolymerization.
Take a look at the rich diversity of applications for methyl acrylate in homo- and copolymers below.
Poly(methyl acrylate) (PMA) and poly(methyl methacrylate) (PMMA) differ significantly in properties. With a Tg of +10 °C, PMA is a soft, tough, rubbery material at room temperature. PMMA, with a Tg of 105 °C (atactic), is a strong, hard, clear plastic material often used as shatter-resistant glassing. These differences portray a general trend between polyacrylates and polymethacrylates.
Poly(methyl acrylate) and poly(ethyl acrylate) (PEA) are used in blends to achieve the required hardness, extensibility, and strength for appropriate end-uses. PEA with a Tg of -28°C is considerably softer than PMA. Both are formulated with a broad range of adhesive properties, from low tack and adhesion to high tack and good surface bonding properties. PMA is often copolymerized with a low level of a crosslinking monomer to improve property retention.
PMA is partially hydrolyzed to produce so-called “gum thickeners” used as rheology modifiers. These sodium polyacrylate thickeners effectively thicken compounded coatings and adhesive systems based on SBR, VAEs, and natural rubber lattices. They are used in hard-to-stabilize emulsions and dispersions. Application areas include coatings, precoats, foam coatings, and adhesives used in the carpet industry.
Styrene-acrylonitrile (SAN) copolymers have been grafted onto polyacrylates such as PMA to improve properties such as toughness, rigidity, and thermal stability. These ASA terpolymers are used in the automotive, packaging, building, and construction industries.
Ethylene-Methyl Acrylate (EMA) Copolymers
Formulators produce EMA copolymers by reacting ethylene and methyl acrylate via a free-radical copolymerization in a high-pressure autoclave process. The general level of MA in the copolymer varies from about 16 to 25 percent. The content of MA is dependent on the end-use application. Articles intended for contact with food, in compliance with 21CFR 177.1340, require MA contents to be below 25%.
Demand for EMA copolymers is increasing based on film and adhesive applications that require properties such as adhesive and cohesive strength, adhesion to polyolefins and polyesters in multi-layer film applications, low temperature performance and heat resistance. Typical markets are extrusion coatings, coextrusion, blow molding, injection molding, and compounding. Packaging and automotive industries are anticipated to increase their demand for EMA copolymers based on their requirements for flexibility, low heat-sealing temperatures, low temperature performance, and adhesion in multilayer film constructions. Recycling of packaging materials is another market driver for the use of thermoplastic EMA copolymer films and tie-layer resins. At higher MA contents, EMA resins are utilized in hot-melt adhesives to achieve softness, flexibility, and polarity for adhesion to polar surfaces.
Methyl Acrylate-(Meth)acrylic Acid Copolymers
Formulators prepare methyl acrylate-acrylic acid or methacrylic acid copolymers by copolymerization or by simultaneous hydrolysis and polymerization of methyl acrylate. The emulsion polymerization route is preferred due to the ease of reaction control and the high molecular weights, affording hydrophilic copolymers in an easier-to-handle latex form.
Methyl acrylate-methacrylic acid copolymers are highly efficient thickeners and rheology modifiers for aqueous systems like acrylic emulsions, natural rubber latex, SBR emulsions, and more. The increased thickening viscosities achieved starting with starting low viscosity methyl acrylate-methacrylic acid copolymer (60:40 -45:55 ratios) emulsions cannot be attained with copolymers based on the higher ester acrylic homologs. The MA-co-MAA systems are prepared as a low viscosity emulsion that changes to a high viscosity by simply adjusting the pH above the neutral point and through association with other co-dispersed polymers.
The uniquely higher viscosities with the methyl acrylate copolymers are due to the greater water solubility of the methyl ester and high associative compatibility. The low viscosities of the starting MA-co-MMA allow for easier storage and handling versus other thickeners. Initial viscosities of less than 100 cps in a latex can be elevated to well above 10,000 cps by raising the pH above neutral.
A new generation of Alkali-Swellable (Soluble) Emulsions called ASE rheology modifiers are copolymers of methacrylic acid and methyl acrylate or higher homolog acrylates. They mimic the characteristics of cellulose rheology modifiers, but ASE rheology modifiers are easier to use and lower in cost. A rich diversity of rheological characteristics has been obtained by changing the ratio of acrylic ester and methacrylic acid, by utilizing the various alkyl acrylate esters in the copolymer and modifying the molecular weight of the copolymers. ASE rheology modifiers build high viscosities at very low shear rates after pH adjustment but are highly shear-thinning. Applications include paints, caulks, sealers, mastics and other aqueous construction materials.
Methyl Acrylate-Acrylonitrile Copolymers
Formulators also incorporate methyl acrylate in acrylonitrile (AN) polymers in order to allow melt processability and fiber-spinning operations. They have also produced random copolymers of AN and MA by free-radical solution and suspension techniques. Levels of up to 15 percent MA monomer decrease the melting point and crystallinity of the copolymers and increase the melt stability and processing. These copolymers are used commercially as precursors for so-called “PAN-based” carbon fibers.
A melt-processable, impact modified copolymer of MA and AN at a level of about 60-75 percent AN was developed as an oxygen barrier resin for packaging applications. Nitrile rubber (NBR) modified MA-AN copolymers were produced by graft copolymerization of the two monomers in the presence of 8-10 wt. percent of NBR. At AN:MA ratios of ~75:25 percent, the impact modified resin complies with 21CFR177.1480 for food contact use. They are used in extruded sheets and thermoformed trays.
Safety, Handling and Polymerization Principles for MA
Methyl acrylate hazards include skin sensitization, eye irritation, inhalation, flammability, and the potential for uncontrolled and rapid polymerization. However, the chemical industry has handled MA safely for more than 80 years and when properly inhibited, MA is stable under the recommended storage conditions.
The following principles must drive the handling and polymerization of MA.
- Use and maintain proper inhibitor levels, as inhibitors are consumed over time.
- MA must never be handled or stored under an inert atmosphere, as the the presence of oxygen is required for the inhibitor to function effectively.
- Observe the recommended storage time and temperatures to prevent depletion of the inhibitor, below 35°C (95°F) and preferably below 30°C (86°F).
- Use proper MOCs and keep tanks, reactors, and piping thoroughly clean
- Prevent contact with amines, strong acids, alkalis, silica, alumina, oxidizing agents, UV, and initiators, which can cause spontaneous polymerization.
- Direct contact can cause irritation of the eyes, skin, nose, and throat.
Gantrade’s Safety Data Sheet for MA contains up-to-date information on all concerns relevant to safety, handling, storage, and industrial hygiene. Refer to the Safety Data Sheet for methyl acrylate for information regarding all handling aspects.
Methyl Acrylate Sales Specifications
If you are looking to purchase high-purity MA, Gantrade Corporation markets this monomer in 20 MT (44,000 lbs.) ISO Tanks and in 200 Kg.(441 lbs.) factory-sealed drums for industrial use only.
The purity of our MA is greater than 99.5 percent. Gantrade’s BA contains 15 ± 5 ppm of MEHQ inhibitor. Take a look at Gantrade’s BA sales specifications in the chart below.
|Purity, wt. %||GC||≥ 99.5|
|Color||ASTM D 1209||≤ 10|
|Water, PPM||ASTM D 1364||≤ 500|
|Acidity||ASTM D 1613||≤ 50|
|Inhibitor Level, MEHQ, ppm||ASTM D 3125||15 ± 2|
|Sp. Gravity (20/4°C)||ASTM D 1298||0.953-0.958|
At Gantrade Corporation, we offer a broad line of high-quality acrylic and vinyl monomers, supported by knowledgeable professionals. Contact us today to discuss your needs for MA and other chemical products.