KR20070010393A - Development of pressure sensitive adhesives with nano particle - Google Patents

Abstract

Provided is a water latex adhesive composition, which contains no volatile organic solvent and toxic component, is a harmless and environment-friendly product by applying a harmless inorganic flame retardant to a water adhesive, and thus hardly generates toxic gas upon firing. The water latex adhesive composition has a core-shell structure, wherein the core is aluminum hydroxide and magnesium hydroxide nano particle surface-treated with a silane coupling agent or a titanate coupling agent, and the shell is an adhesive layer formed of a copolymer of at least two acrylate monomers. The nanoparticles are produced by dry or wet grinding aluminum hydroxide and magnesium hydroxide using a mortar, a homogenizer, a ball mill, a roll mill, a sand mill, a dyno mill, and an ultrasonic grinder, etc.

Description

Environment-friendly aqueous latex flame retardant adhesive using inorganic nanoparticles {Development of pressure sensitive adhesives with nano particle}

Due to the recent devastation caused by large fires, the preference and interest for flame retardant products have been amplified. As reported in various media, the cause of death is known to be the cause of asphyxiation due to toxic gas more than that caused by flame. Currently, research on various flame retardants has been actively conducted at home and abroad, but there is still a problem that a halogen-based flame retardant which is still excellent in performance is mainly used. Korean Patent Publication No. 1999-0036727 discloses a flame retardant using aluminum hydroxide and magnesium hydroxide, and Korean Patent Publication No. 2002-0003925 also discloses a flame retardant resin composition composed of silicon oxide, aluminum oxide, iron oxide, calcium oxide, magnesium oxide, and the like. In addition, U.S. Patent No. 4,532,287 also introduces flame retardants using aluminum hydroxide and magnesium hydroxide, but when using most inorganic flame retardants, the content of 50 to 200% of the resin is required to secure the same flame retardant performance as halogen flame retardants. Done. Therefore, the basic physical properties of the resin is falling, there is a problem that also falls inherent in the resin. In Japanese Patent 2001-339131 and Japanese Patent 2001-339132, conventional flame retardant adhesives have excellent flame retardant performance, but they are poisonous gas and phosphine gas which are harmful to human body when burning by using flame-retardant adhesive made of halogen adhesive and phosphorus compound harmful to human body. May occur. Therefore, in the present invention, by dispersing the metal hydroxide which is a non-halogen flame retardant into nanoparticles to secure the maximum effect with a minimum flame retardant content.

In the present invention, while developing an aqueous emulsion adhesive that can replace the harmful components such as volatile organic solvents and formaldehyde appearing in the conventional solvent-type pressure-sensitive adhesive, at the same time, the polymer and the fire caused by the recent social problems In order to solve the toxicity problem of resins, it is possible to provide eco-friendly aqueous nano inorganic flame retardant adhesive which has low toxicity and flame retardancy by emulsification polymerization using inorganic flame retardant into nano particles to maintain the properties of low toxicity and excellent adhesive to human body. will be.

The present invention provides water-based pressure sensitive adhesives and a method for imparting flame retardancy.

Conventional pressure-sensitive adhesives have been mainly used solvent-based pressure-sensitive adhesive (solvent-based). However, there is a growing interest in the construction of air pollution inside the building and the demand for eco-friendly products is increasing. In addition, due to the recent devastation caused by large fires, the preference and interest for flame-retardant products have been amplified.

In general, as a flame retardant to be contained, halogen-based flame retardants having high performance are used, but there are problems of fumes during combustion, generation of toxic substances, and disposal of a compound containing a flame retardant. Accordingly, inorganic metal hydroxides, phosphate esters, ammonium polyphosphate, red phosphorus and the like are known as flame retardants that can replace toxic flame retardants used as flame retardants. However, phosphate esters and polyammonium phosphates are less flame retardant than conventional brominated flame retardants. In addition, since the phosphorus-based flame retardant acts as a plasticizer in the resin, extreme softening of the pressure-sensitive adhesive and migration of the flame retardant to the surface of the pressure-sensitive adhesive may occur, thereby lowering the adhesive force and not maintaining sufficient holding power. Red phosphorus is often added as an aid for improving the effect of phosphorus-based flame retardant, but there is a problem of generating phosphine gas during combustion. On the other hand, when using an inorganic metal hydroxide as a flame retardant, it is necessary to add a large amount of inorganic metal hydroxide in order to obtain the same flame retardancy as bromine-based flame retardant. Thereby, the performance of an adhesive, such as adhesive force, a holding force, and a wrinkle of an adhesive, is brought. In addition, the addition of the inorganic metal hydroxide loses the flexibility of the pressure-sensitive adhesive, there is a problem that the adhesion to the adherend is also lowered. Hydroxide is prepared from nanoparticles to prepare an aqueous emulsion pressure-sensitive adhesive using an acrylic base monomer.

 The reaction system of emulsion polymerization consists of a monomer, a dispersion medium, a surfactant active substance (surfactant; micelle generating substance; soap) and an initiator dissolved in the dispersion medium. Emulsion polymerization is maintained in a good state of fluidity of the reaction solution by the dispersion medium, it is easy to remove the reaction solution and can produce a polymer having a high molecular weight at a high polymerization rate. In order to have elasticity as rubber, most synthetic rubbers are produced by emulsion polymerization since high molecular weight polymers with many entanglements between molecules are required.

Among the components of the emulsion polymerization, there is water. The role of water in the emulsion polymerization is very large and important, so the physical properties of the prepared emulsion largely depend on the quality of the water. Water is a dispersion medium of the material to be emulsified, which facilitates heat transfer during polymerization, and also acts as a solvent such as an emulsifier, a monomer and an initiator. In addition, the viscosity of the emulsion is adjusted. A relatively high solid content and low viscosity is one of the great advantages of the emulsion.

The final properties and properties of the emulsion as monomers depend on the choice of monomers. Glass transition temperature, heat of polymerization, specific heat, solubility in water, type and content of polymerization inhibitor, purity (content of impurity), boiling point and freezing point are important points to be considered in the selection of monomer and design of reactor.

The monomers commonly used in emulsion polymerization can be classified into the following chemical compositions. Hydrocarbons, Vinyl Esters, Acrylics, Polymerizable Acids and Anhydrides, Esters for Copolymerization, Ally Derivatives

 It can be divided into vinyl ethers and nitrogen-containing monomers.

In terms of pressure-sensitive adhesives and sealants, about 126,000 tons of acrylate esters are used in pressure-sensitive adhesives, sealants, and coatings. About 70-80% are used in water-soluble emulsions and 20-30% in solvent-based formulations. . In Korea, it is estimated to be about 20,000 tons, and the conversion to water-based adhesives continues to lead to the consumption of general-purpose acrylate esters with an average annual growth rate of 6.5% and an increase of 2-Ethylhexyl acrylate (EHA) from 1997 to 2002. It seems to account for most of the esters.

Acrylic polymers are made by emulsion polymerization and are pressure sensitive

(pressure-sensitive) Used as a base material for adhesives in tapes, labels and other decorative and functional pressure sensitive products.

The sticky nature of the long chain acrylates can make adhesives of various compositions. These polymers can be made with a variety of acrylic and methacrylic esters. The main composition is 2-EHA, Butyl acrylate (BA), Ethyl acetate (EA), and small amounts of methyl methacrylate (MMA), Vinyl acetate, Vinyl chloride and Styrene can be used as comonomers. 2-EHA and BA are the main esters of acrylic pressure-sensitive adhesives, and they provide transparency, color stability, yellowing resistance due to ultraviolet rays and weather. Pressure sensitive adhesives are mainly used in applications of transparent substrates such as polyester films, vinyl and cellulose acetate. General purpose acrylate esters are widely used in magic tapes, plastic tapes, labels, adhesives, and other products such as bricks and floor tiles for home decoration. Acrylic emulsion is easy to apply, adheres well to all surfaces, cleans the adhered parts cleanly and quickly dries, allowing for immediate coating. In addition, it can be mixed with silicon in consideration of physical properties and cost. Main alkyl methacrylate monomers used in pressure sensitive adhesives, for example ethyl methacrylate, methyl methacrylate.

, Propyl methacrylate, butyl methacrylate, pentyl methacrylate

(pentylmetacrylate), hexyl methacrylate (hexylmetacrylate), 2-ethylhexyl methacrylate (2-ethylhexylmethacrylate), octyl methacrylate

(octylmetacrylate), iso-octylmetacylate, nonyl methacrylate, nonylmetacrylate, isononoylametacylate, decyl methacrylate, lauryl methacrylate

(laurylmetacrylate), stearyl methacrylate (stearylmetacrlyate) and the like are typical.

Another component is an emulsifier, which is an important component in the emulsion polymerization process. The properties of the surfactant, which acts to stabilize the function of the emulsifier and the latex, are due to its unique chemical duality, that is, hydrophilic and hydrophilic in the same molecular structure. Surfactants perform three functions when used in emulsion polymerization processes. First, the interfacial tension between monomer and liquid phase is lowered to make stable dispersion, dissolution and emulsification of reaction phase and continuous phase. Secondly, micelle formation provides the micelle reaction site for polymerization. Finally, the emulsion of unreacted monomers and the growing polymer particles are stabilized and ultimately the polymer latex emulsion is stabilized.

It also serves to protect monomer droplets to stabilize the monomer source. As the reaction proceeds gradually, the particles become larger and the size of the monomer droplets becomes smaller, causing the emulsifier to migrate from the monomer particles to the particle surface. Emulsifiers are both hydrophilic and lipophilic and should be used with caution because excessive use can reduce their resistance to water and oil. It may also cause deterioration in wear resistance and air bubbles. Emulsifiers can be divided into nonionic, anionic, cationic and amphoteric or zwitterionic. Anionic and nonionic are commonly used in emulsion polymerization. Cationic and zwitterionic properties are used in extremely limited cases. Types of emulsifiers are classified as chemical compositions and shown in Table 29.

Nonionicity is inferior to anionic in emulsifying effect and also produces larger particles. Therefore, in the emulsion polymerization, anionic emulsifiers are used a lot. Even with the same emulsifier, the higher the concentration, the smaller the particles. Another important emulsifier role is lowering of surface tension and interfacial tension. Substances that are coated on the subject, such as paint, require low interfacial tension because they evenly coat the subject. The side effects of emulsifiers in emulsions and blended paints improve freeze storage, mechanical stability, and stability to electrolytes.

In many cases, anionic and nonionic are used together, where anionic is used as a primary emulsifier and nonionic is often used as a secondary emulsifier. In order to increase the stability of the particles produced, there are many cases of post addition of an emulsifier after the reaction. Anionic species include Fatty Acids, Sulfates, Sulfated fatty alcohols, Sulfates of ethoxylated alcohols, Sulfated natural oils and esters, Sulfonates, Sulfonated aromatic and condensed ring compounds,

Aliphatic chain sulfonates, Phosphates, Fluorochemicals, etc., and nonionics include Polyethylene Oxides, Alkyl ethers, Alkylaryl ethers, Fatty acid esters, Alkylamines, Polyol Esters, Glycerine, Sorbitane, Sugar. Cationics are Amines, Quaternary Ammoniums, Amphoteric Carboxylates, Betain,

Aminocarboxylates and Sulfonates.

Next, as an initiator, decomposition of the initiator generates free radicals that cause a reaction. Water-soluble substances are mainly used for emulsion polymerization. Persulfate salts and hydrogen peroxide are commonly used, especially sodium, potassium and ammonium persulfates. Table 30 shows the solubility of the two persulfate salts in water. The initiator is decomposed by heat or reducing agent. In the case of persulfate, ionic radicals are produced as in the following equation (1).

^- O ₃ S-O-O-SO ₃ ^-   → 2SO ₄ ^- K _d            (One)

The resulting radicals react with the monomers to initiate polymerization, the polymerization rate depending on the decomposition constant (k _d ) of the initiator. The decomposition constant depends on the efficiency of the initiator, solubility, temperature, concentration, half-life (t _1/2 ), polymerization inhibitor in the monomer, impurities, and the like, and also depends on the presence or absence of a reducing agent or an activator. Half life (half life) of the performance of the initiator indicates the time that half of the initiator decomposes at a constant temperature, an initiator having a half-life of 0.5 to 20 hours for emulsion polymerization with a material that is not too fast or slow. The efficiency of the initiator is that the initiator decomposes to form radicals. The usefulness of the azo compound initiator, which is useful, is close to 1.0. However, the peroxide has a high reactivity with other substances, and the radicals participating in the actual polymerization are 0.3 to 0.6. The efficiency of the degree is shown. The efficiency of persulfate is high so that the number of radicals produced at pH 10 of 0.01MK ₂ S ₂ O ₈ is 8.4 × 10 ¹² radicals / ml.sec at 50 ℃, 1.8 × 10 ¹⁴ at 70 ℃, 2.5 × 10 at 90 ℃ ¹⁵ pieces and an activation energy in the range of 50-90 degreeC are 33.5 Kcal / mol. Table 4 shows the activation energies, decomposition rates, and half-lives of the various initiators. Most use sole initiators, but more than one initiator may be used. For example, (NH ₄ ) ₂ S ₂ O ₄ is used as the polymerization initiator, and another initiator may be used, such as a reducing agent, in order to remove unreacted monomers.

Decomposition of the initiator produces free radicals that cause the reaction. Water-soluble substances are mainly used for emulsion polymerization. Persulfate salts and hydrogen peroxide are commonly used, especially sodium, potassium and ammonium persulfates. Initiators that can be used include Azobisisobutyronitrile, t-Butyl peroixde, Cumyl peroxide, Acetyl peroxide, Benzoyl peroxide, Lauroyl peroxide, t-Butyl hydroperoixde, t-Butyl peracetate, Diisopropyl peroxydicarbonate, t-Butyl perbenzoate, and the like.

As a surface treatment method of the inorganic particles, 20 ml of toluene was added to a 250 ml 2-neck round flask equipped with a reflux condenser. Subsequently, nano-sized aluminum hydroxide particles (or magnesium hydroxide particles) are placed in a reactor and stirred under argon gas substitution. Excess silane coupling agent (γ-MPS: 3- (trimethoxysilyl) propyl methacrylate) is added to the reactor and stirred at room temperature to react. The reaction proceeded under argon gas substitution at room temperature.

The solid content of eco-friendly flame retardant used is about 30 ~ 60%. If the solid content is too low, it is difficult to uniformly indicate the thickness of the pressure-sensitive adhesive coating, and in the case of solid content, the viscosity may increase, thereby causing problems such as deterioration of coating properties.

The inorganic nano low toxicity aqueous adhesive made in the present invention is applicable to various films. In particular, it is possible to secure flame retardancy by applying to interior film and interior film composed of PVC and polyolefin. It is also applicable to paper and various films.

By measuring the adhesive force, the test piece was cut out to have a butterfly having a length of 25 mm and a length of 250 mm. A tensile tester (AMETEK EZ 250) was used as a test device. The test plate (adhesive) should be STS 304 (SUS 304) or acrylic plate (PMMA). Then, the test piece is attached to the test plate using a 2Kg compression roller and left for a predetermined time (1 hour, 24 hours) in a standard state, and the force measured while peeling at a speed of 300 mm / min using a tensile tester is obtained.

The ball tack shall be taken by cutting the specimen with a butterfly of 10 to 15 mm and a length of 250 mm. As a ball cloud tester, the KPM 202 model of gaseous trade is used, and the auxiliary driving path is 100mm long and 25㎛ thick PET attached to the test piece adhesive surface at a predetermined position. do. The ball used here is made of two kinds of high carbon chrome bearing steel (STB2), whose diameter is from 1 / 32inch to 32 / 32inch, and it is used after cleaning and drying with the material before measurement. In the test method, the inclined plate is fixed at 30 °, the adhesive side is turned upward, the test piece is fixed to the predetermined position on the inclined plate by using adhesive tape, and the PET film is placed on the adhesive side of the specimen so as to be located on the auxiliary runway. After adjusting the ball to be used at the start position, repeat the series of operation by changing the ball size, and find the biggest ball among the balls that stop completely (the ball does not move for more than 5 seconds) in the measuring part. Record 32 times the diameter as the ball number.

As a flame retardant test method, the combustion test apparatus 45 degree micro-burner method which is performed by Korea Fire Protection Corporation was used. Interior sheets can be classified into wallpaper category of Article 3, No. 2 for interior sheets that are currently used for testing, according to the performance test equipment standard of flame retardant products provided by Korea Fire Protection Corporation. Flame retardant test methods are mainly used for combustion test equipment and oxygen index methods. Flame retardant performance criteria of wallpaper-like materials such as interior sheets are within 3 seconds of flame retardancy, within 5 seconds of remnant time, and carbonization area is 30. ㎠, carbonization length should be less than 20cm.

Example 1

 Core-shell emulsion polymerization is dissolved in distilled water by adding 3 w% of nonionic surfactant NP-1060 and 2 w% of anionic surfactant Eu-S133D to the reactor. 10 w% of the surface-modified nano aluminum hydroxide with a silane coupling agent is added to a reactor in which the surfactant is dissolved, and stirred to disperse the particles sufficiently. BA was added 8w%, 2-EHA 30w%, AA 2w%, put into a reactor dispersed 10w% of surface-modified nano aluminum hydroxide (average particle size distribution: 136nm) and emulsified with strong stirring. Transfer the reactor to a thermostat and stir. When the temperature in the reactor reaches 80 ° C, an aqueous solution of ammonium persulfate is added dropwise into the reactor. After dropping the monomers and the initiator, they are aged and the reaction is terminated. The prepared inorganic nano flame-retardant adhesive was coated 40 ~ 60㎛ by the knife coating method on the interior and deco film.

Example 2

 Except for adding BA to 6.4w%, 2-EHA 24w%, AA to 1.6w% and dispersing the surface-modified nano aluminum hydroxide (average particle size distribution: 125 nm) 20w% in the reactor, and emulsifying with strong stirring. Was carried out in the same manner as in Example 1.

Example 3

 6.4w% of BA, 24w% of 2-EHA, 1.6w% of AA were added, and the surface-modified nano aluminum hydroxide (average particle size distribution: 114 nm) was placed in a 30 w% dispersed reactor and emulsified with strong stirring. Was carried out in the same manner as in Example 1.

Example 4

8 w% of BA, 30 w% of 2-EHA, and 2 w% of AA were added, except that the surface-modified nano aluminum hydroxide (average particle size distribution: 105 nm) was placed in a dispersed dispersion reactor and emulsified with strong stirring. It carried out by the same method as Example 1.

Example 5

Except for adding BA to 6.4w%, 2-EHA 24w%, AA to 1.6w%, and dispersing the surface-modified nano aluminum hydroxide (average particle size distribution: 51 nm) 20w% in the reactor, and emulsifying with strong stirring. Was carried out in the same manner as in Example 1.

Example 6

6.4w% of BA, 24w% of 2-EHA, 1.6w% of AA were added, and the surface-modified nano magnesium hydroxide (average particle size distribution: 123 nm) was placed in a dispersed dispersion reactor and emulsified with strong stirring. Was carried out in the same manner as in Example 1.

Example 7

Except for adding BA to 8w%, 2-EHA 30w%, AA to 2w%, and adding 100% by weight of surface-modified nano magnesium hydroxide (average particle size distribution: 56 nm) to a reactor dispersed therein, and emulsifying with strong stirring. It carried out by the same method as Example 1.

Example 8

Except for adding BA to 6.4w%, 2-EHA 24w%, AA to 1.6w%, and dispersing the surface-modified nano magnesium hydroxide (average particle size distribution: 52 nm) in 20w% of the reactor and emulsifying with strong stirring. Was carried out in the same manner as in Example 1.

Reaction materials (%) Reaction conditions % Conversion Viscosity (cps) BA 2-EHA AA APS ATH MGH Particle size distribution (nm) Temp. (℃) Time (h) Example-1 8 30 2 0.2 10 - 136 80 3 90 3300 Example-2 6.4 24 1.6 0.2 20 - 125 80 3 92 5800 Example-3 6.4 24 1.6 0.2 30 - 114 80 3 89 8500 Example-4 8 30 2 0.2 10 - 105 80 3 94 3000 Example-5 6.4 24 1.6 0.2 20 - 51 80 3 97 4500 Example-6 6.4 24 1.6 0.2 10 123 80 3 94 5300 Example-7 8 30 2 0.2 - 10 56 80 3 92 4800 Example-8 6.4 24 1.6 0.2 - 20 52 80 3 93 5500

ATH MGH Ignition Time (60sec) Afterglow time (3sec) Remaining time (5sec) Carbonization Length (cm) Bullet area (㎠) Particle Size Distribution (nm) Example 1 10 0 30 × × 9 54 136 Example 2 20 0 34 × × 8 44 125 Example 3 30 0 60 ◎ ◎ 7.5 35 114 Example 4 10 0 44 × × 8 45 105 Example 5 20 0 60 ◎ ◎ 7 38 51 Example 6 25 0 60 ◎ ◎ 6.5 33 46 Example 7 0 10 60 ◎ ◎ 7.5 42 56 Example 8 0 20 60 ◎ ◎ 6.5 35 52

Flame retardant adhesiveness Ball tack ACRYL SUS Early review Early review Example 1 5 1.6 1.8 1.2 1.3 15 Example 2 10 1.4 1.7 1.0 1.3 13 Example 3 15 2.2T5 2.3T1 1.3 2.1 10 Example 4 5 1.1 1.5 1.0 1.7 9 Example 5 10 0.9 1.1 0.8 1.1 11 Example 6 10 1.9 1.9 1.7 3.9 14 Example 7 5 0.8 1.3 1.0 1.5 8 Example 8 10 0.8 1.1 0.8 0.9 10

The present invention is an aqueous latex tm pressure-sensitive adhesive that can dissolve the currently used solvent-based pressure-sensitive adhesives are volatile organic solvents and harmful components to the human body can be said to be environmentally friendly, and fire-retardant problems of polymer materials due to fire has emerged It is an inorganic flame retardant that is harmless to human body and processed to nano size and applied to water-based adhesives.

Claims (5)

Organic-inorganic composite flame-retardant pressure-sensitive adhesive composition comprising a pressure-sensitive adhesive layer composed of a copolymer of two or more acrylate monomers as a core and aluminum hydroxide and magnesium hydroxide nanoparticles surface-treated with a silane coupling agent and a titanate coupling agent. It is known that it improves by surface treatment of an inorganic hydroxide. Examples of surface treatments include hydroxides, which are treated with silicon oil, fatty acids, fatty acid metal salts, silane coupling agents, titanate coupling agents, higher fatty acids, higher fatty acid esters, and the like. Aluminum, magnesium hydroxide flame retardant. The method of claim 1, wherein the nanoparticles are prepared by dry and wet grinding using a bowl, a homogenizer, a ball mill, a roll mill, a sand mill, a dyno mill, an ultrasonic mill, or the like by blocking the aluminum hydroxide and magnesium hydroxide nanoparticles. Inorganic nano flame retardants. In particular, aqueous flame retardant compositions containing 1-40% inorganic nanoparticles in the manufacture of wet nanoparticles. The aqueous acrylic pressure sensitive adhesive according to claim 1, wherein the inorganic nanoparticles are used as cores. The film according to claim 4, wherein the aqueous acrylic pressure-sensitive adhesive having the inorganic nanoparticles as a core is coated on the decor film and the interior film to have flame retardancy.