Archive for category: Industry News

Acrylate pressure sensitive adhesive is the most widely used pressure sensitive adhesive at present

Acrylate pressure sensitive adhesive is the most widely used pressure sensitive adhesive at present, it is the copolymer of an acrylate monomer and another ethylene monomer. Compared with other pressure sensitive adhesives has the following characteristics: almost no need to add antioxidants excellent weather resistance and heat resistance; No phase separation and migration phenomenon, good transparency, and good oil resistance; It has no effect on the skin and is suitable for medical use.

Acrylic emulsion pressure sensitive adhesive has the characteristics of a simple formula, good weather resistance, wide bonding range, and low toxicity, so in recent years, it has been widely used in many fields, from the current practical application of pressure sensitive adhesive comprehensive view, to prepare high strength, good heat resistance pressure sensitive adhesive, simply use one type of resin, difficult to obtain good results, must be modified. Polyacrylate pressure sensitive adhesives are widely used for their excellent bonding properties, chemical stability, non-toxicity, harmless and low cost. However, in order to achieve a better improvement effect, it is very important to select the right functional resin and develop the environment-friendly acrylic emulsion pressure sensitive adhesive with good bonding properties.

In most of the existing solvent polymerization methods for environmental pollution, relatively speaking, emulsion polymerization is a larger trend. Both at home and abroad attach great importance to the emulsion polymerization technology and the development of emulsion adhesive new products, its output increases year by year, the quality is constantly improving, the variety is increasing day by day, and the production process is gradually improving. For acrylate adhesive, the monomer is the base material formed by polymer, different monomer gives different properties of polymer products including hardness, tensile strength, elasticity, adhesion and softness, and other different functions, and determines the physical and mechanical properties of emulsion and latex film.

The glass transition temperature is an important index to reflect the softness and brittleness of the polymer. The higher the glass transition temperature of the homopolymer is called the hard monomer, which can provide the hardness and tensile strength of the copolymer resin. In contrast, the soft monomer refers to the lower glass transition temperature of the homopolymer, which gives the resin certain flexibility and extensibility when participating in resin copolymerization.

The preparation of water-based pressure sensitive acrylate adhesive with high solid content has been one of the research hotspots at home and abroad.

Pressure sensitive adhesive refers to a kind of adhesive that can be bonded with the adhesive under external pressure. At present, it is widely used in sealing belts, labels, protective tape and decorative plates, and other industries. With the development of industry, the application market of adhesives for self-adhesive labels is more and more extensive, and the varieties are increasing. The commonly used adhesives are solvent-based, water-based, and hot-melt. At present, the amount of solvent-based products is relatively large, which uses toluene, benzene, and other volatile organic compounds as solvents.

These solvents will directly volatilize into the atmosphere in the process of use, which will pollute the environment and endanger workers’ health. Therefore, in recent years, domestic government departments at all levels have constantly strengthened the supervision of organic exhaust emissions and restricted the use of volatile organic compounds. And the residual solvent in the sticker label is harmful to human health. At present, water-resistant white (no white after soaking in water for a long time) self-adhesive labels are used in food and beverage packaging. Some need to be refrigerated for a long time (contact with condensate), and bottle labels need to be pasteurized (high temperature and high humidity).

These kinds of labels still use toxic and harmful oil-based pressure sensitive adhesive, and the transformation of adhesive from solvent type to water-based type and non-solvent type has become inevitable. The peeling strength of pressure-sensitive adhesive mainly depends on the adhesion force of the polymer and colloid on the bonding surface. The holding viscosity is mainly determined by cohesion, and cohesion and cohesion affect each other. At the same time, there should be a proper balance between cohesion and holding viscosity. Traditional pressure-sensitive adhesive products have poor cohesion, poor adaptability to substrates of different polarities, and poor temperature resistance, resulting in defects in the adhesion and weather resistance of products, especially water-based system products.

The application market of adhesives for peeling self-adhesive labels is becoming more and more extensive. Currently, the existing adhesives are solvent-based and hot melt. Among them, the mainstream two-component solvent-based pressure-sensitive adhesive used by peeling self-adhesive has environmental protection problems and a large number of organic volatilization. Must be in 2  used up within 3 hours after adding curing agent, use not convenient. In the market, the water-based pressure-sensitive adhesive is mainly acrylic emulsion pressure sensitive adhesive, which has the advantages of a simple preparation process, low cost, safety, and non-toxic, as a typical green product, more and more favored by the market.

Acrylic emulsion pressure sensitive adhesive due to water as the medium, the drying speed is slow, especially for some pressure sensitive adhesive products with a large amount of glue, the coating drying problem is particularly prominent, therefore, in the application of acrylic emulsion pressure sensitive adhesive, it is necessary to improve its solid content to solve the problem of slow drying and high coating energy consumption.

Traditional emulsion between 30  50% solid content and high solid content emulsion generally refers to the solid content in 54  62% of polymer emulsion, emulsion, high solid content emulsion more traditional prominent advantage is that its dry film speed, transportation, and storage cost is greatly reduced and the environmental pollution and small, This makes high solid content emulsion in reducing cost and emulsion performance has a great advantage, therefore, the high solid content emulsion has broad application and development prospects. However, when the solid content of the emulsion exceeds 50%, the viscosity of the emulsion system will rise sharply with the increase of the solid content in the emulsion polymerization.

The increase of the viscosity will lead to problems of monomer mixing, reaction heat transfer, and so on in the emulsion polymerization system so that the emulsion polymerization cannot be carried out stably and a large number of condensates will appear, which is not conducive to production. It even leads to synthesis failure or serious accidents such as burst polymerization. At present, the solid content of pressure sensitive adhesive on the market is below 50%. Therefore, the preparation of water-based pressure sensitive acrylate adhesive with high solid content has been one of the research hotspots at home and abroad.

Preparation method of acrylic pressure sensitive tape with high temperature resistance mesh 2

The utility model relates to a high temperature resistant mesh acrylic pressure sensitive tape, which comprises a mesh release film and a modified acrylic pressure sensitive adhesive coated on the surface of the mesh release film. Wherein, the composition of the modified acrylic pressure sensitive adhesive is calculated by weight, including 20 of butyl acrylate, acrylic   2 ethyl caproic ester 18,  2  hydroxyl ethyl acrylate 15, eight aniline propyl cage half as many poly siloxanes 6. 5 copies of tungsten, acrylic amide acid scandium powder 4. 2, initiator 1. 2, the first solvent 6 and 14-second solvent.

Wherein, the mesh release film is a PET material release film; The first solvent and the second solvent composition are the same, are toluene; The initiator is azobisisobutyronitrile.

Among them, the preparation method of the acrylamide scandium tungstate powder is S1. Preparation of amino-modified scandium tungstate powder: The scandium tungstate powder and 30% hydrogen peroxide aqueous solution were mixed, dispersed evenly, and heated to boiling, reflux condensation, and stirring for 8h. After natural cooling, solid particles were filtered out by vacuum, washed three times, and then vacuum dried to obtain hydroxyl-modified scandium tungstate powder. Among them, the weight ratio of scandium tungstate powder to hydrogen peroxide solution is 1:10;

The hydroxy-modified scandium tungstate powder was mixed with 60% ethanol aqueous solution, dispersed evenly, and the amino silane coupling agent KH792 was added. After stirring at 25℃ for 8h, the temperature was heated to boiling, and the reflux condensation was stirred for 5h. After natural cooling, the solid particles were filtered out by vacuum, washed three times, and then vacuum dried to obtain the amino-modified scandium tungstate powder.  Among them, the weight ratio of hydroxy-modified scandium tungstate powder, amino silane coupling agent KH792 and ethanol aqueous solution is 1:0.06:6.

S2. Preparation of scandium acrylamide tungstate: the amino-modified scandium tungstate powder is dispersed in tetrahydrofuran solvent, constantly stirring until uniform, then heating up to 40℃, add acrylic anhydride drop by drop, under the condition of shade, heat preservation stirring for 15h, remove the unreacted acrylic anhydride and tetrahydrofuran solvent, scandium acrylamide tungstate powder obtained; Among them, the weight ratio of amino-modified scandium tungstate powder, acrylic anhydride, and tetrahydrofuran solvent is 1:3:4:15.

The preparation method of the above high temperature resistant mesh acrylic pressure sensitive tape includes the following steps:

Step 1: Prepare complex modified scandium tungstate mixture: The powder of scandium acrylamide tungstate was dispersed in the first solvent, octa aniline propyl cage polysesquisiloxane was added, ultrasonic uniformity, and then at 25℃, at the speed of 800r/m for 18h, the complex modified scandium tungstate mixture was obtained.

Step 2: Prepare modified acrylic pressure sensitive adhesive: Butyl acrylate and acrylic acid   2 ethyl caproic ester, ethyl 2  hydroxyl acrylic  mixed into the second solvent, stir to dissolve, straight ventilation with nitrogen gas as shielding gas, with half of the initiator, heating up to 60 ℃, stir at a speed of 100 r/m after 1 h, adding the other half of the initiator, At the same time, the compound modified scandium tungstate mixture was added drop by drop within 30min, and then the temperature was raised to 70℃, and the temperature was kept and stirred at the speed of 200r/m for 4h. After the reaction, the modified acrylic pressure sensitive adhesive was obtained by natural cooling.

Step 3: Prepare high temperature resistant mesh acrylic pressure-sensitive tape: cut the mesh release film and lay it on a flat surface, and use the machine to coat the modified acrylic adhesive on the top, and dry it in the oven at 100 ℃ for 5min to obtain high temperature resistant mesh acrylic pressure sensitive tape.

Preparation method of a water-based polyacrylate block copolymer pressure sensitive adhesive 4

In this example, the water-based polyacrylate block copolymer pressure sensitive adhesive, the pressure sensitive adhesive solid content of 55% is water-based polyacrylate-block copolymer, water-based polyacrylate block copolymer multi-block structure, including hard monomer: voice methacrylate tablets 15kg, acrylamide 5kg; Soft monomer: butyl acrylate 50kg, isooctyl acrylate 25kg; Functional monomers: hydroxyethyl methyl acrylate 2kg; Crosslinking monomer, N  hydroxymethyl acrylamide 1 kg, acetoacetic acid ethyl methacrylate, 2 kg.

The preparation method of the above water-based polyacrylate block copolymer pressure sensitive adhesive includes the following steps:

• S1, 1.2kg sodium dodecyl sulfate was dissolved in 81.82kg deionized water to obtain the aqueous phase, 0.12kg octadecyl alcohol, and 0.15kg trithiocarbonate (Z group is alkyl, the R group is isopropyl) were dissolved in the soft monomer successively and then added to the aqueous phase. After mixing evenly, the pH of the mixture was adjusted to 10. Then the mixture was dispersed ultrasonically for 30min to obtain the soft monomer pre-emulsion.
• S2, add the soft monomer pre-emulsion into the reactor, add 0.1 kg sodium persulfate, stir evenly, and heat the reaction solution to 75℃ for polymerization;
• S3, after polymerization for 2 hours, hard monomers, functional monomers, and crosslinked monomers were added, stirred evenly and block copolymerization was initiated at 75℃.
• For S4, after copolymerization for 2 hours, adding 0.025kg sodium persulfate, and holding temperature at 80℃ for 2 hours, discharge, to obtain water polyacrylate block copolymer pressure sensitive adhesive;

When using, the pressure sensitive adhesive emulsion is directly coated on the PET base film of 50μm, the thickness is 10μm, and the PET base film is placed in the oven at 125℃ and baked for 3min.

Pressure-sensitive adhesive, also known as pressure-sensitive adhesive, is a kind of adhesive with pressure sensitivity, which refers to a little pressure that can be bonded with the adhesive, with the rapid development of the economy, the pressure-sensitive adhesive has been widely used in all walks of life, in some special construction, industrial fields, need high-temperature tape. At present, most of the high-temperature resistant adhesive on the market uses solvent-based silicone pressure-sensitive adhesive, which is obtained by the copolymerization of silicone rubber and MQ resin. In the coating-drying process, it will be further crosslinked. Its unique structure and strong silico-oxygen bond energy give silicone pressure-sensitive adhesive good heat resistance.

The acrylic pressure-sensitive adhesive has a wide range of adhesion, adjustable performance, and good weather resistance, accounting for about 80% of the pressure-sensitive adhesive industry dosage, but the acrylic pressure-sensitive adhesive is made of soft monomer synthesis, the glass transition temperature of monomer is low, will become soft and lose strength at high temperature, this structure is poor in heat resistance, limiting its application in the field of high-temperature resistance. In the prior art, it is disclosed that the cross-linking degree of soft and hard monomers, inorganic fillers, and modified compounds will improve the high-temperature resistance. However, the pressure-sensitive adhesive formed in this way has low initial viscosity and peeling force, and the problem of residual glue or ghost will be generated in the use process, and the application value is greatly reduced.

Currently available is a water-based acrylic pressure-sensitive adhesive consisting of the following raw materials: Acrylic monomer 65 ~ 95, functional monomer 2 ~ 6, internal crosslinking monomer 0.5 ~ 5, liquid epoxy resin 2 ~ 20, emulsifier 0.3 ~ 2, initiator 0 ~ 1, reducing agent 0 ~ 0, wetting agent 0 ~ 1, defoamer 0 ~ 0 5 parts, 100 parts deionized water; Described for butyl acrylate emulsifier- acrylic block polymers.