KR20080043926A - High solid pressure-sensitive adhesive, fabrication method of that, and the second product using that - Google Patents

Abstract

A high solid pressure-sensitive adhesive is provided to ensure good adhesion due to high shear strength and peel strength, to facilitate a coating work due to low viscosity, and to consume less drying energy due to high solid content. A method for preparing a high solid pressure-sensitive adhesive having a bi-modal or multi-modal particle size distribution includes the steps of: (i) adding at least two monomers and an emulsifier to water to prepare a pre-emulsion; (ii) dividing the pre-emulsion into a first pre-emulsion fraction and a second pre-emulsion fraction, and adding an additional emulsifier to the second pre-emulsion fraction; (iii) charging water, an initiator, seed polymer latex, and a part of the first pre-emulsion fraction into a reactor, stirring the materials, and raising the temperature of the reactor to predetermined temperature; (iv) controlling the temperature of the reactor, and performing stirring while charging the first pre-emulsion fraction and an initiator into the reactor continuously; (v) controlling the temperature of the reactor, and performing stirring while charging the second pre-emulsion fraction and an initiator into the reactor continuously; (vi) controlling the temperature of the reactor, and adding an initiator for the final reaction to treat the residual monomer; and (vii) cooling and filtering the prepared polymer emulsion.

Description

High Solid Pressure-sensitive Adhesive, Fabrication Method of That, and the Second Product using that}

1 is a diagram illustrating the emulsion according to the size distribution of the particles.

Figure 2 is a batch structure of particles of single modal and bimodal in high solid emulsion.

U.S. Pat. No. RE24,906

U.S. Pat. No. 4,925,908

U.S. Pat. No. 5,278,227

U.S. Pat. No. 3,637,563

U.S. Pat. No. 6,048,611

U.S. Pat. No. 6,707,356

The present invention relates to a special purpose acrylic polymer latex, and more specifically, it has high shear strength and peel strength, good adhesion, low viscosity, easy coating work, high solid content, low dry energy and transport. And it relates to a high-solid PSA adhesive easy to store, a production method thereof, and a secondary product using the same.

PSA (Pressure-Sensitive Adhesive) adhesive is also called pressure-sensitive adhesive. It is not permanently bonded after adhesion, so it can be reapplied after it is adhered once. The adhesive used is typical. Such adhesives are generally prepared by dissolving a tacky polymer material in a solution or emulsion state using a dispersion medium such as water or an organic solvent. Among such pressure-sensitive adhesives, solids having a high content of 60% or more of the total pressure-sensitive adhesive volume are generally referred to as high solid adhesives. Usually, the pressure-sensitive adhesive is coated on a synthetic resin film or paper such as vinyl and used in the form of an adhesive tape.

Common pressure sensitive adhesives are single or two or more monomers (called monomers or monomers, and a mixture of two or more monomers is called a comonomer). Polymerization (polymerization, polymerization of monomers) or copolymerization (Co-Polymerization, polymerization of comonomers) To prepare a polymer (polymer of monomer) or copolymer (polymer of comonomer). In the present specification, unless specifically indicated, monomers and comonomers are collectively referred to as monomers, polymers and copolymers are collectively referred to as polymers, and polymerization and copolymerization are collectively referred to as polymerization.

The acrylic copolymer for pressure sensitive adhesives is described in U.S. Patent U.S. Pat. No. Since the introduction of RE24,906 (Ulrich), it has been used a lot. Initially, a solution polymerization method using an organic solvent was used to make such a co-polymerizing composition. In the process of polymerization, post-processing such as coating, and final use of coated products, organic solvents volatilize to release harmful substances to the human body.

In order to solve this problem, a method of polymerization in an aqueous solution introduced by reference in the present invention has been developed. In general, since the polymerization method using an aqueous solution uses water as a dispersion medium, the reaction heat generated during the reaction can be easily controlled and has an environmentally advantageous advantage.

U.S. Patent U.S. invented by Avery Dennison Corp. of the United States. Pat. Nos. 4,925,908 and 5,278,227 describe emulsion copolymerization methods of acrylic monomers for pressure-sensitive adhesives using aqueous solutions, but neither patent mentions high-solid emulsion polymers.

Emulsion polymerization techniques using aqueous solutions, despite the remarkable advantages mentioned above, require about five times the energy required to dry the water used as a dispersion medium from the coated adhesive material, compared to using organic solvents. In addition, a large amount of water contained in the diluted adhesive composition has been a problem in storage and transportation by increasing the volume and weight. In order to alleviate these problems, there has been an interest in a process for making emulsion compositions high-solids ”. However, in most cases, in order to achieve high solids in order to increase the viscosity, but the result is a difficult coating work in the post-process, the manufacturing cost of the secondary product was raised.

US patent U.S. filed by Celanese, USA. Pat. No. In 3,637,563, a pre-emulsion of an irreversible-emulsion type in which water is present inside an acrylic comonomer in a high monomer-to-water ratio is prepared, and the pre-emulsion is continuously introduced into the polymerization reactor. A method of forming a solid acrylic polymer emulsion is presented. However, there is no mention in this invention of a seed emulsion polymerization process in which the polymerization reaction takes place effectively.

United States patent US Pat. No. 6,048,611 discusses the use of functional emulsifiers in preemulsions of monomers and water as a method of copolymerizing high solid acrylic emulsions, and is described in US Pat. No. 6,707,356 mentions a two-step method of supplying a certain amount of pre-emulsion to make a high solid acrylic copolymer emulsion. Nevertheless, neither of the above two inventions mentions a seed emulsion polymerization which proceeds with the polymerization using acrylic seed polymer latex or another kind of seed polymer latex.

The pressure-sensitive adhesives prepared by the above method are all single-modal (single-modal) polymers having a uniform particle size of the polymer, and are limited in increasing the content of solids. There is a problem that the coating operation is difficult to increase.

The requirements to be provided as an excellent PSA adhesive are environmentally friendly, high shear strength and peel strength, excellent adhesion, low viscosity, easy coating work, low moisture content and high solid content, which requires less drying energy and storage. And easy to carry. In addition, the surface energy of the pressure-sensitive adhesive is low, the adhesion strength is good to the HDPE (High Density Poly Ethylene), a polyolefin-based plastic, and the adhesive part should not be dried or partially peeled off after adhesion.

The present invention is to realize the above technical problem, adopting an environmentally friendly acrylic polymer emulsion adhesive composition with high shear strength and peel strength, and the particle distribution of the emulsion is bi-modal (Bi-Modal, double particle distribution) or multi-modal ( Multi-Modal (Multi-Modal Distribution) to realize PSA pressure-sensitive adhesives with very high solids content and very low viscosity and low surface energy.

 The present invention relates to an acrylic high solid emulsion adhesive, which is easy to be applied as an adhesive, and has good adhesive properties due to high shear strength and peel strength, and is prepared by the seed emulsion copolymerization method, which is a high solid emulsion having a high content of solid content. The distribution of particles has a bimodal or multimodal form.

The shape of the particle distribution in the polymer emulsion has a great influence on the moisture content, and has a great influence on the solid content ratio. As shown in (a) of FIG. 1, a single modal (b) and a single particle having a substantially uniform particle distribution are shown in FIG. Bimodal is composed of two sizes of different particle distribution as shown, and multi-modal consisting of three or more sizes of different particle distribution as shown in (c).

The aqueous polymer emulsion has a spherical shape in which hydrophobic groups of the polymer particles are concentrated in the center and hydrophilic groups are radially directed to the outside. When the particles have a uniform single modal shape, as shown in FIG. , There is a certain space between the particles, and there are a large number of water molecules as a dispersion medium there is a high moisture content and low solid content ratio, if excessively high solid content ratio polymer particles are in close contact with each other The viscosity increases sharply.

On the other hand, in the case of bi-modal or multi-modal, as shown in (b) of FIG. 2, small polymer particles are distributed among the large polymer particles, thereby reducing the space where water molecules can exist, and thus water content is low. And the proportion of solids is high. In such a case, the proportion of solids can be increased without increasing the viscosity.

The size of the polymer particles is greatly affected by the type of monomer used in the polymerization and the amount of the emulsifier used in the polymerization. The present invention is to implement a bimodal or multimodal polymer latex emulsion by varying the size of the polymer particles, adopting a two-step seed emulsion copolymerization method, each having a different amount of emulsifier.

Seed emulsion polymerization is a method in which the polymerization is effectively performed by injecting a polymer having completed polymerization (called a seed polymer) together with the monomers at the initial stage of the polymerization of the monomers. The polymer seeds used in the seed emulsion polymerization determine the surface energy and adhesion properties of the entire polymer with the choice of polymerization method.

The preemulsion copolymerization method is a method widely used in the polymer polymerization process, and water, two or more types of monomers, and an emulsifier, which is a surfactant, are put in a container at a predetermined ratio and stirred to make a preemulsion monomer. It is a method of producing a polymer by causing a polymerization reaction by adding together an initiator as a catalyst.

The present invention is an acrylic emulsion PSA adhesive polymerized using an acrylic monomer as a main material, and is prepared by a two-step seed emulsion copolymerization method. The seed polymer is a copolymer having a low glass transition temperature (Tg, hereinafter indicated as isooctyl acrylate). Acrylate ester monomer, a vinyl ester monomer having a high Tg such as vinyl acetate, and a polar acrylic monomer such as acrylic acid are continuously added together with other reaction additives to cause copolymerization.

Acrylic emulsion PSA pressure-sensitive adhesive of the present invention, the two-step seed polymer is prepared by the preemulsion seed copolymerization method, which method (1) to make the seed polymer by the conventional preemulsion copolymerization method, (2) the seed polymer is a preemulsion monomer The copolymer is supplied to the reactor together with the first fraction of and the copolymerization is performed. (3) The second fraction of the preemulsion monomer is continuously added to form a final latex. The polymer latex thus prepared has a solid content of 65% or more. A high solid, low viscosity latex composition having a viscosity of 300-15,000 cP and a bimodal particle size distribution may be used as a PSA adhesive.

The PSA pressure-sensitive adhesive of the present invention is composed of solids having a bimodal or multimodal particle size distribution of 40 to 70% by weight and water of 30 to 60%. Here, a solid component is a polymer copolymerized with the following component ratios, and a component ratio is a weight ratio.

(1) 35 to 85% of C ₄ to C ₁₂ alkyl acrylate esters or mixtures thereof

(2) 0 to 35% vinyl ester, C ₁ to C ₄ (meth) acrylic acid ester, styrene or a mixture thereof

(3) 1 to 35% of C ₈ Monomers which are dicarboxylic acid diesters each having an alkyl group of an ester of C ₁₆ to C ₁₆

(4) polar monomers copolymerizable with 0.5 to 10% of the components of (1) to (3) above

(5) 0 to 10% seed polymer

(6) 0.01 to 1% of initiator

(7) 0-1% chain transfer agent

(8) 0 to 5% multifunctional crosslinking agent

In the above, the component ratio of (5) to (8) is the weight ratio with respect to the total monomer which combined (1)-(4), and the component ratio of (1)-(4) is the monomer of (1)-(4) It is a weight ratio with respect to the sum of the seed polymers of (5). A component ratio of 0% in the composition ratio means that the component may not be used in some cases.

The alkyl acrylate ester monomers of C ₄ to C ₁₂ in (1) above are n-butyl acrylate, amyl acrylate, hexyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, dode Can be selected from the group consisting of real acrylates, and mixtures thereof, of which is preferably selected from the group consisting of isooctyl acrylate, n-butyl acrylate, and mixtures thereof, for reasons of effect and usefulness of the final properties. .

The vinyl ester of (2) is a monomer having a high Tg, selected from the group consisting of vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, It may be selected from C ₁ to C ₄ alkyl ester (meth) crylic acid, such as isobutyl methacrylate, or the like, or from styrene and mixtures thereof. Among these, it is preferable to use vinyl acetate in terms of usability.

As polar copolymerization monomer of (4), acrylic acid, methacrylic acid, itaconic acid, hydroxy alkyl acrylate, styrene sulfonic acid, maleic acid, fumaric acid, citraconic acid, acrylamide, modified acrylamide, N- N-vinyl lactams such as vinylpyrrolidone, N-vinyl caprolactam, acrylonitrile, dimethylamino ethyl methacrylate and mixtures thereof, among which acrylic acid and methacryl in terms of physical properties and usability of the polymer It is preferable to select from the group of an acid, acrylamide, modified acrylamide, and the like.

As an emulsifier used in the production of the seed polymer, a small amount of copolymerized ionic surfactant is used to achieve pressure-sensitive adhesive properties and low viscosity and to obtain a more stable emulsion copolymer. Good results for stable initiation and particle formation can be obtained when 0.1 to 0.5%, more precisely 0.2 to 0.3%, of functional anionic surfactant is added to the seed latex, where the content of surfactant is determined by the total monomers in the seed latex. The weight ratio of surfactant to.

As an emulsifier used for polymerization of a comonomer, it is preferable to use several surfactant, and an anionic surfactant is the best. In particular, a mixture of anionic surfactants and nonionic surfactants can be used to obtain good emulsion particle formation and stable latex. The composition ratio of the anionic surfactant in the anion and nonionic mixture is preferably 20 to 95% (based on the weight ratio), and the optimum ratio is 70 to 90%.

The surfactant can be selected from the group consisting of anionic surfactants such as polyhydric alcohol sulfates, alkyl benzene sulfonates, polyoxyethylene alkylphenol ether sulfates, dialkyl sulfosacsinates. Nonionic surfactants are such as block copolymers of alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene / polyoxypropylene.

The seed polymer of (5) was manufactured by the general copolymerization method with the component except (5) in the said composition ratio.

As an initiator (6), a water-soluble free radical polymerization initiator can be used. Useful initiators include peroxide and peroxydisulfate, and water-soluble initiators include hydroperoxide, t-butyl hydroperoxide, potassium persulfate, ammonium persulfate, sodium persulfate and mixtures thereof. It is used in combination with a reducing agent such as sodium bisulfate, sodium formaldehyde sulfoxylate to make up a redox initiator system. The amount of initiator is used 0.1 to 0.2% by weight of the monomer.

The chain transfer agent of (7) may not be used, and may be selected from carbon tetrabromide, mercaptan alcohol, and mixtures thereof, and carbon tetrabromide, isooctyl thioglycolate and mixtures thereof good.

The crosslinking agent of (8) may not be used, but diacrylate, triacrylate, tetraacrylate, 1,6-hexanediol diacrylate, poly (ethylene glycol) diacrylate, polyurethane di Groups composed of polyfunctional acryl such as acrylate, trimetholpropane triacrylate, and polyfunctional allyl mixtures such as 4-acryloxybenzophenone, divinyl benzene, diallyl maleate and allyl methacrylate, and the like. Among them, 1,6-hexanediol diacrylic lake (HDDA), tetraethylene glycol diacrylate, 4-acryloxybenzophenone and mixtures thereof are preferable.

The seed polymer used above refers to a copolymer latex made by emulsion copolymerization, and is a polymer latex prepared by copolymerizing constituents excluding the seed polymer of (5) among the above-mentioned PSA pressure-sensitive adhesive components. The seed polymer is not limited in kind, but may be selected from the group consisting of ethylene vinyl acetate (EVA) copolymerized latex, and as commercialized products, Air Products' AirPlex 401, 420, 426. This is useful, and Airprex 401 and 420 have low surface energy and good adhesion performance.

PSA pressure-sensitive adhesive of the present invention is prepared by the method of pre-emulsion seed copolymerization of acrylic comonomer, specific examples thereof are as follows.

In one embodiment, the acrylic copolymer seeds are first placed in a reactor, and a pre-emulsion monomer primary input is placed in the reactor and polymerized. Subsequently, a second input of preemulsion monomer is further added to the reactor. The monomer of the second input is a preemulsion monomer in which 2 to 4 times more emulsifier is added than the first input. In this way, in the first step, seed particles grow in a water-soluble state in which the emulsifier is insufficient, and in the second step, new particles are produced in a water-rich state in which the emulsifier is rich. As a result, latex has a bimodal or multimodal particle size distribution, and has a low viscosity in a high solid state with a high solid content ratio.

In the multimodal particle size distribution, the larger particle size is larger than 0.8 micron in diameter under the influence of seed particles, and the small particle size is 0.1 due to the formation of a new particle due to the rich emulsifier effect in the aqueous state. Distributed between ˜0.5 microns.

As a specific method of causing a polymerization reaction in which an emulsifier is added, a preemulsion is prepared by mixing half of the total amount of the emulsifier with the entire amount of the monomer. 50% of the total amount of the preemulsion in this state is first introduced into the reactor to cause a polymerization reaction in which the emulsifier is insufficient, and the remaining half of the emulsifier is added to the preemulsion monomer containing the remaining 50% of the emulsifier. It is added to add to the reactor to cause the polymerization of the emulsifier-rich step.

In another method, 60% of the total amount of the preemulsion monomer containing 1/2 of the total emulsifier is first introduced into the reactor as the first input, and the remaining 40% of the total amount of the emulsifier is added to the second input preemulsion monomer. The remaining 1/2 of the emulsifier is mixed and introduced into the reactor to cause the polymerization reaction of the emulsifier-rich step.

Alternatively, a preemulsion is made by mixing 1/3 of the total amount of the emulsifier with the total amount of comonomer. From this, 50% of the total preemulsion monomer is taken as the first input and fed into the reactor which is an emulsifier deficiency stage, and the remaining pre-emulsion monomer is mixed with the remaining emulsifier, which is 2/3 of the total amount of the emulsifier, and introduced into the reactor where the emulsifier is rich. do.

The final polymer PSA pressure-sensitive adhesive prepared through the above process is composed of 50 to 70% solids and 30 to 50% water by weight. It is important to minimize the amount of water in order to improve the productivity of the process of producing secondary products by applying this adhesive to the film, to minimize the transportation and storage costs, and to save energy when drying the latex. It is good to make up 65% solids and 35-45% water.

The aqueous solution polymer emulsion PSA pressure-sensitive adhesive of the present invention is produced by continuously introducing a pre-emulsion mixture such as water, acrylate, vinyl monomer, ionic / nonionic surfactant, chain transfer agent, crosslinking agent into the reactor to cause seed emulsion polymerization to occur, The emulsion is stirred and heated under nitrogen treatment and a proportion of the initiator is used for temperature control. The reaction mixture is heated with stirring until the reaction is complete.

The PSA pressure-sensitive adhesive which is the aqueous acrylic polymer emulsion thus prepared is coated on paper, vinyl film, etc. to a certain thickness and dried at 60 to 110 ° C. to prepare a secondary product such as a packaging tape, an adhesive tape, and the like.

The PSA pressure-sensitive adhesive has high molecular weight (1,000,000 or more), high solids content (60 to 70% by weight), and low viscosity. The glass transition temperature (Tg) of the polymer, such as a pressure-sensitive adhesive, is determined by the composition of the comonomer. The lower the temperature, the better the pressure-sensitive adhesive can be used even at low temperatures. The glass transition temperature of the copolymer copolymerized with different monomers is determined according to Fox's law, which is calculated by Equation 1 below.

In Equation 1, Tgi is the Tg of each monomer, absolute temperature, and w _i is the weight ratio of each monomer. If the type and weight ratio of the monomers are well selected, even if some monomers having a Tg of 25 ° C. are used, the Tg of the adhesive can be lower than -50 ° C., and a product without problems in winter can be produced in Korea.

PSA pressure-sensitive adhesive of the present invention can be usefully used in places where it is difficult to use a solvent-type adhesive such as weather-seal tape, medical tape, label. In particular, it can also be used for materials with low surface energy, such as materials containing polypropylene, polyethylene, fluorochemicals and the like.

The method of making the adhesive coating sheet which is a secondary product using the PSA adhesive of this invention can use a conventional method. In a new adhesive coating sheet manufacturing method, the present adhesive is coated on a release liner, the adhesive coated release liner is dried, and the substrate is laminated thereon. As the substrate, paper, polypropylene, polyurethane, polyethylene, FBC, polyester, cellulose acetate, a plastic film such as ethyl cellulose, and a metal thin plate are used. The adhesive coated sheet thus laminated the substrate can be rolled with a roll to simplify the use. When using this adhesive coating sheet, the release liner that is easily peeled off can be removed.

The secondary coating thus prepared adhesive coating sheet may be used as a label, a tape, a sign plate, a cover, an indication mark.

In the secondary product, if the release liner is also laminated on the top surface instead of the substrate, the adhesive layer can be used as a transfer tape (commonly referred to as a double-sided tape) that glues two objects together.

In order to evaluate the shear strength and peel strength of the present invention PSA pressure-sensitive adhesive, the method specified by the American Society for Testing and Materials (ASTM) and the PSA tape committee of the United States (Test method for pressure-sensitive tapes, eighth edition, August 1985, Pressure The test was conducted according to Sensitive Tape Council, Glenview, III.

Peel strength test was performed in accordance with ASTM P3330-78 PSTC-1 (11/75), measuring the force required to remove the coated adhesive sheet from the test plate at a specific angle and peeling rate, the coating sheet width 100mm ( 1 dm.) Assessed by force, the unit is N / dm.

Shear strength was performed in accordance with ASTM D3654-78, PSTC-7, to measure the cohesive force or the internal strength of the adhesive. This allows the adhesive strip to be attached to the surface of the standard plate 1 inch each horizontally and vertically, and is placed vertically with a weight of 1 kg after a certain amount of time has elapsed. To measure.

Hereinafter will be shown the experimental results of each embodiment of the PSA pressure-sensitive adhesive of the present invention. Abbreviations of the names of the monomers and other additives used in the examples are as follows.

PE: Polyethylene

SS: Stainless Steel

NP-1040: Nonyl Polyethoxy Alcohol, Nonionic Surfactant (Southeast Chemical, Korea)

960SN: sodium salt of nonyl polyethoxy sulfate, anionic surfactant (Encross)

SVS: sodium vinyl sulfonate, emulsifier (Japan Asahi Kasei Fine Chemical)

AA: acrylic acid

BAM: Butyl Acrylate Monomer

DOF: Dioctyl fumarate

2-EHA: 2-ethylhexyl acrylate

EVA: Ethylene Vinyl Acetate Copolymer

HDDA: Hexanediol diacrylate, crosslinking agent

KPS: potassium persulfate, initiator

MAA: Methacrylic acid

SPP: Sodium Pyrophosphate, Electrolyte

VAC: Vinyl Acetate

<Example 1>

In this example, to prepare a preemulsion polymer, water, anionic and nonionic surfactants, and monomer mixtures are prepared according to the preemulsion component ratios of Table 1. The emulsion is stirred at 120 rpm to form a preemulsion. The pre-emulsion thus prepared is divided into two parts and divided into first and second parts, wherein the first part is for emulsion polymerization in a state in which an emulsifier is insufficient, and the second part is in the same preemulsion as in the first part of Table 2. Only an additional emulsifier is added so that the emulsifier is for emulsion polymerization in an excessive state.

Table 1. Preemulsion Component Ratios

Preemulsion total 617.03 308.52 (the first minute) 308.52 + 49.04 (secondary) Water (ionized) 100.00 50 50 + 15 960 N 14.88 7.44 7.44 + 29.75 NP-1040 2.15 1.08 1.08 + 4.29 DOF 150 75 75 VAC 125 62.5 62.5 2-EHA 215 107.5 107.5 AA 5 2.5 2.5 MAA 5 2.5 2.5

Table 2. Additional Emulsifier Solutions in Secondary Preemulsions

Emulsifier solution 49.04 Water (ionized) 15 960 N 29.75 NP-1040 4.29

The reactor was equipped with a reflux condenser, a stirrer, a thermometer, and a nitrogen input device, and the reactor was first charged according to the initial input component ratio of the following Table 3. Then, the reactor was heated to 75 ° C. while stirring at 50 rpm under a nitrogen atmosphere. . As the seed polymer used herein, one made by the procedure of Comparative Example 1 described later was used.

Table 3. Reactor Initial Charge Component Ratios

ingredient Weight (g) Total input volume in initial reactor 149.9 Water (ionized) 50.0 Seed Polymer (59% Solids) 33.9 Preemulsion (A) 66.0

When the temperature of the reactor reaches 75 ° C, 36.375 g of an aqueous solution of 3.78% KPS is added as an initial initiator, purge nitrogen for 5 minutes, close the valve, and observe an exotherm for 15 to 20 minutes.

When the temperature of the reactor is stable, primary copolymerization is performed by adding a primary preemulsion. This first copolymerization reaction is to continuously drop the preemulsion and the starting material into the reactor prepared as described above at a rate of 2.5 g / min and 0.32 g / min, respectively, until the primary preemulsion is completely added. Continue for 2 hours.

When the first copolymerization is completed as described above, the temperature of the reactor is increased to 80 ° C., and the stirring speed is increased to 120 to 130 rpm. Then, the remaining second fraction of the preemulsion is introduced into the reactor for 2 hours in the same manner as the first copolymerization. This process is a polymerization stage rich in emulsifier.

The initiator used for the primary and secondary copolymerization was prepared as in Table 4 below.

Table 4. Initiator solution for continuous feed

KPS solution (for continued supply) 77.232 Water (ionized) 75.40 KPS 1.382 Sodium bicarbonate (buffer) 0.45 Catalyst solution feed rate (g / min) 0.32

After all the preemulsion was charged, the temperature of the reactor was raised to 85 ° C. And the initiator for final reaction is thrown in order to process a residual monomer. The remaining monomer treatment takes approximately 1 hour, but it can be seen from the smell whether the monomer remains. In this way, when all remaining monomers are processed, superposition | polymerization is complete | finished.

Residual monomer treatment initiator is prepared as shown in Table 5.

Table 5. Initiator solution for remaining monomer treatment

KPS solution (for finishing reaction supply) 5.25 Water (ionized) 5.0 KPS 0.25

After all the polymerization process as described above, the temperature of the reactor is cooled to room temperature. Then, the polymer latex prepared by polymerization is filtered using a 50 micron filter cloth. In this way, it can be seen that the amount of particles larger than 50 microns is 100 ppm or less. The polymer latex has a solid content of 60%, a viscosity of 500 cP (Brookfield Viscometer # 3 spindle / 30 rpm), and a particle size distribution of the latex with bimodal, with one peak at 0.8 microns and the other at 7 microns. Appeared.

Comparative Example

This comparative example is a monomer of the same component as Example 1 of this invention, compared with the adhesive which is this invention, and polymerizes a polymer by the conventional copolymerization method. Therefore, the seed polymer was not used in the polymerization process, and the total amount of the preemulsion was polymerized in one polymerization step without dividing the polymerization degree into two steps.

The component ratio of the preemulsion of this comparative example is shown in Table 6.

Table 6. Preemulsion component ratio of the comparative example

Preemulsion total 666.07 Water (ionized) 115 960 SN 44.63 NP-1040 6.44 DOF 150 VAC 125 2-EHA 215 AA 5 MAA 5

The composition ratio of the reactor initial feed of this comparative example is shown in Table 7.

Table 7. Reactor Initial Charge Component Ratios

ingredient Weight (g) Total inputs from initial reactor 151.73 Water (ionized) 75.0 SVS (25% aqueous solution) 4.0 960 SN 0.36 Preemulsion (A) 66.0 KPS (3.78% aqueous solution) 36.37

The composition ratio of the initiator for continuous supply of this comparative example is shown in Table 8.

Table 8. Component ratios of initiator for continuous feeding

KPS aqueous solution (for continuous supply) 77.232 Water (ionized) 75.40 KPS 1.382 Sodium bicarbonate (buffer) 0.45 Catalyst solution feed rate (g / min) 0.32

The component ratio of the initiator for finishing reactions of this comparative example is shown in Table 9.

Table 9. Component ratios of initiator for finishing reaction

KPS solution (for finishing reaction supply) 5.25 Water (ionized) 5.0 KPS 0.25

The polymer emulsion latex prepared as in this comparative example showed a single modal having a solid content of 60%, a particle size distribution of 0.2 micron, and a viscosity of 54,000 cP. Was used.

Peel strength and shear strength of the PSA adhesive prepared in Example 1 and Comparative Example were measured and the results are shown in Table 10 below. Peel strength was performed on SUS plate, high density polyethylene plate, and glass plate.

Table 10. Mechanical Performance Comparison of Pressure Sensitive Adhesives of the Invention and Conventional Adhesives

division Peel Strength (180 °, gf / in) Shear strength (60 ℃) Material SUS # 304 HDPE Glass time 20 minutes 24 hours 4 Weeks 20 minutes 24 hours 4 Weeks 20 minutes 24 hours 4 Weeks 24 hours Example 1 1500 1800 1800 1200 1300 1300 1400 1700 1700 60min < Comparative Example 1520 1810 1820 1210 1300 1300 1400 1650 1680 60min <

As can be seen in Table 10, the PSA adhesive of the present invention can be seen that there is no inferior in terms of mechanical performance compared to the PSA adhesive prepared by the conventional method.

<Example 2>

Example 2 is different from Example 1 as shown in Tables 11 to 15 only in the proportion of the composition, the preparation method was the same as in Example 1.

Table 11. Preemulsion Component Ratio of Example 2

Pre-emulsion 702.10 351.05 (1st) 351.05 + 59.8 (2nd) Water (ionized) 185.00 92.5 92.5 + 25 960 N 15.0 7.5 7.5 + 30.5 NP-1040 2.1 1.05 1.05 + 4.3 BAM 181.35 90.67 90.67 DOF 9.8 4.9 4.9 VAC 50 25 25 2-EHA 239.05 119.53 119.53 MAA 9.8 4.9 4.9 HDDA 10 5 5

Table 12. Additional Additive Emulsifiers in Secondary Preemulsions

Emulsifier solution 59.8 Water (ionized) 25 960 N 30.5 NP-1040 4.3

Table 13. Reactor Initial Charge Component Ratios

ingredient Weight (g) First dose in reactor 140.68 Water (ionized) 72.0 Seed Latex (52.7% Solids) 33.5 Preemulsion (A) 35.18

Initial input initiator: 34.87 g of KPS 3.21% aqueous solution

Table 14. Initiator solution for continuous feed

KPS solution (for continued supply) 34.875 Water (ionized) 33.75 KPS 1.125 Sodium bicarbonate (buffer) 0.3 Catalyst solution feed rate (g / min) 0.15

Table 15. Initiator solution for remaining monomer treatment

KPS solution (for finishing reaction supply) 5.25 Water (ionized) 5.0 KPS 0.25

The PSA pressure-sensitive adhesive prepared according to the present example had a solid content ratio of 61.5%, a viscosity measured by a Brookfield viscometer of 1400 cP, and confirmed to have a bimodal particle distribution.

For the PSA adhesive of this example, the adhesive performance was evaluated on PE and stainless steel plates. The test piece was coated with a pressure-sensitive adhesive on a silicone release paper and dried for 3 minutes at 100 ℃ in an oven. Then, a separate substrate having a thickness of 80 microns was laminated thereon. The base material was previously coated with a primer on the adhesive side, and the coating weight of the adhesive was measured to be 25 ± 1 g / m 2 after drying. Peel strength and shear strength were measured for this PSA adhesive at 180 degrees. The peel strength is above 450 g _f / inch, PE surface on the stainless steel plate was found to be 350g _f / inch. And when peeling a base material from the stainless steel plate or PE surface, it was confirmed that the surface of a base material peels cleanly without leaving a residue.

<Example 3>

Example 3 is different from Example 1 as shown in Tables 16 to 20 only in the proportion of the composition, and the preparation method was the same as in Example 1. However, EVA was used as the seed polymer latex introduced into the reactor.

Table 16. Preemulsion Component Ratios

Pre-emulsion 617.10 308.55 (1st) 308.55 + 59.8 (secondary) Water (ionized) 100.00 50 50 + 25 960 N 15.0 7.5 7.5 + 30.5 NP-1040 2.1 1.05 1.05 + 4.3 BAM 181.34 90.67 90.67 DOF 9.8 4.9 4.9 VAC 50 25 25 2-EHA 239.06 119.53 119.53 MAA 9.8 4.9 4.9 HDDA 10 5 5

Table 17. Additional Additive Emulsifiers in Secondary Preemulsions

Emulsifier solution 59.8 Water (ionized) 25 960 N 30.5 NP-1040 4.3

Table 18. Reactor Initial Charge Component Ratios

ingredient Weight (g) First dose in reactor 149.5 Water (ionized) 50.0 EVA 401 Latex Seed 33.5 Preemulsion (A) 66.0

Initial input initiator: 34.87 g of KPS 3.21% aqueous solution

Table 19. Initiator solution for continuous feed

KPS solution (for continued supply) 34.875 Water (ionized) 33.75 KPS 1,125 Sodium bicarbonate (buffer) 0.3 Catalyst solution feed rate (g / min) 0.15

Table 20. Initiator solution for remaining monomer treatment

KPS solution (for finishing reaction supply) 5.25 Water (ionized) 5.0 KPS 0.25

<Example 4>

In Example 4, the proportion of the composition was the same as that in Example 3, the amount of the pre-emulsion for one-step reaction was 1/3, and the amount of the two-step reaction preemulsion was 2/3. . Their specific component ratios are as follows Tables 21-25.

Table 21. Preemulsion Component Ratios

Pre-emulsion 617.12 205.67 (1st) 411.45 + 59.8 (2nd) Water (ionized) 100.00 33.3 66.7 + 25 960 N 15.0 5 10 + 30.5 NP-1040 2.1 0.7 1.4 + 4.3 BAM 181.35 60.45 120.90 DOF 9.81 3.27 6.54 VAC 50.01 16.67 33.34 2-EHA 239.05 79.68 159.36 MAA 9.8 3.27 6.54 HDDA 10 3.33 6.67

Table 22. Additional Additive Emulsifiers in Secondary Preemulsions

Emulsifier solution 59.8 Water (ionized) 25 960 N 30.5 NP-1040 4.3

Table 23. Reactor Initial Charge Component Ratios

ingredient Weight (g) First dose in reactor 149.5 Water (ionized) 50.0 EVA 401 Latex Seed 33.5 Preemulsion (A) 66.0

Initial input initiator: 34.87 g of KPS 3.21% aqueous solution

Table 24. Initiator solution for continuous feed

KPS solution (for continued supply) 35.175 Water (ionized) 33.75 KPS 1,125 Sodium bicarbonate (buffer) 0.3 Catalyst solution feed rate (g / min) 0.15

Table 25. Initiator solution for remaining monomer treatment

KPS solution (for finishing reaction supply) 5.25 Water (ionized) 5.0 KPS 0.25

The bimodal particle size distribution prepared in Examples 3 and 4 has a solids content of 65% and a viscosity of 5000 cP, forming one peak at 0.2 microns and another peak at 15 microns Indicated.

The results of testing the peel strength, which is the mechanical performance of the PSA adhesives prepared in Examples 3 and 4, are shown in Table 26 below. As can be seen from the table, the mechanical performance of the two examples is not significantly different, but Example 4 was found to be more superior in adhesive strength than Example 3. And even if the base material was peeled off from the adhesion surface SUS # 304 and the HDPE surface, it was confirmed that no residue remains on the adhesion surface and peels cleanly.

Table 26. Peel Strength of Examples 3 and 4

division Peel Strength (180 °, gf / in) Material SUS # 304 HDPE time 20 minutes 24 hours 4 Weeks 20 minutes 24 hours 4 Weeks Example 3 300 400 400 310 400 410 Example 4 320 400 400 330 420 440

The present invention relates to an acrylic high solid PSA pressure-sensitive adhesive prepared by a two-step preemulsion seed copolymerization method, wherein the size distribution of the particles is in a bimodal or multimodal form.

The PSA pressure-sensitive adhesive having a solid content of 60% prepared by a conventional method with the same raw material and ingredient ratio as the PSA pressure-sensitive adhesive of the present invention is a single modal having a particle size distribution of 0.2 micron and a viscosity of 54,000 cP. On the other hand, the PSA pressure-sensitive adhesive of the present invention has a solid content of 60%, has a very low viscosity of 500 cP, and has a particle size distribution of bimodal form in which one peak is 0.8 micron and the other is 7 micron. Even if the PSA pressure-sensitive adhesive of the present invention increases the solid content to 65%, the viscosity is only 5,000 cP.

PSA pressure-sensitive adhesive of the present invention, while having a very low viscosity, can increase the solid content ratio to 60% or more, thereby reducing transportation and storage costs, and greatly reducing the energy required for drying the pressure-sensitive adhesive when manufacturing secondary products. Because of its low viscosity, it is easy to control the thickness of the coating and easy to apply the coating.

PSA pressure-sensitive adhesive of the present invention has a low surface energy, good adhesion to polyolefin-based plastics (HDPE, High Density Poly Ethylene), and does not cause the adhesive portion to be distorted or curled after adhesion.

Since the emulsion polymerization method used in the present invention uses water as the dispersion medium, the reaction temperature can be easily controlled, and more safe compositions can be obtained in polymerizing the respective particle monomers.

Claims (14)

Pre-emulsion seed copolymerization method of sequentially performing each of the following steps, a method of producing a high-solid acrylic PSA pressure-sensitive adhesive having a bimodal or multi-modal particle size distribution. First step: pre-emulsion preparation step, in which two or more kinds of monomers are added to water together with an emulsifier and stirred to form a preemulsion. Second step: The pre-emulsion is divided into two, the first input and the second input, divided into two, and the second input is added to the second emulsion, the addition of an emulsifier is added, stirring each input, the separation step The third step: the initial input water, the initiator, the already prepared seed polymer latex, and a portion of the first input pre-emulsion of the second step in a predetermined ratio to the reactor in which the polymerization reaction takes place and stirred, the temperature of the reactor is constant Initial polymerization stage to raise temperature to maintain a certain time Fourth step: The first step polymerization step of adjusting the temperature of the reactor, the first step of the pre-emulsion and the initiator while stirring while continuously introducing the initiator into the reactor at a constant flow rate 5th step: 2nd stage polymerization stage with sufficient emulsifier which adjusts the temperature of a reactor and stirs, pre-emulsion secondary content and an initiator are continuously thrown into a reactor by constant flow volume. Step 6: Residual monomer treatment step of adjusting the temperature of the reactor and adding the initiator for the final reaction Step 7: finishing step of cooling and filtering the polymer emulsion prepared by the completion of the polymerization as described above The method of claim 1, wherein the second step, A method in which a half amount of the total emulsifier is mixed with the total amount of the monomer to obtain a preemulsion, the preemulsion is divided into two parts, and the remaining emulsifier 1/2 is added to one of them to make a second input; A half of the total amount of the emulsifier is mixed with the total amount of the monomers to obtain a preemulsion, 40% of the preemulsion is added thereto, and the remaining emulsifier 1/2 is added thereto as a secondary input; And a method of mixing a third of the total amount of emulsifier in the total amount of the monomer to give a preemulsion, dividing the preemulsion into two and adding the remaining emulsifier 2/3 to one of them, as a secondary input; The method of producing a high-solid acrylic PSA pressure-sensitive adhesive, characterized in that any one of the pre-emulsion separation step. The method of claim 1, The third stage is an initial polymerization stage in a nitrogen atmosphere and the temperature of the reactor is maintained at 75 degrees Celsius; The fourth step is a first stage polymerization step wherein the temperature of the reactor is maintained at 75 degrees Celsius, the reaction time is 2 hours; The fifth step is a second polymerization step of maintaining the temperature of the reactor at 80 degrees Celsius, the reaction time is 2 hours; The sixth step is a residual monomer treatment step of maintaining the temperature of the reactor to 85 degrees Celsius, the reaction time is 1 hour; A method of producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that. The method according to any one of claims 1 to 3, The monomer of the first step, based on the total weight of the monomers, Monomers which are 35 to 85% of C ₄ to C ₁₂ alkyl acrylate esters or mixtures thereof; Monomers which are 1 to 35% vinyl esters, C ₁ to C ₄ (meth) acrylic acid esters, styrene or mixtures thereof; 0 to 35% of C ₈ Monomers which are dicarboxylic acid diesters each having an alkyl group of an ester of C ₁₆ to C ₁₆ ; Polar monomers copolymerizable with 0.5 to 10% of the components of (1) to (3); A method of producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that. The method of claim 4, wherein The alkyl acrylate ester monomers of C ₄ to C ₁₂ are n-butyl acrylate, amyl acrylate, hexyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, and mixtures thereof Any one of the furnaces; The vinyl ester is any one of vinyl acetate, vinyl propionate, vinyl butyrate or a mixture thereof; The alkyl ester (meth) acrylic acid of C ₁ to C ₄ is any of methyl methacrylate, ethyl acrylate, ethyl methacrylate, isobutyl methacrylate, and mixtures thereof; The polar copolymer monomers are acrylic acid, methacrylic acid, itaconic acid, hydroxy alkyl acrylate, styrene sulfonic acid, maleic acid, fumaric acid, citraconic acid, acrylamide, modified acrylamide, N-vinylpyrrolidone N-vinyl lactam, such as N-vinyl caprolactam, acrylonitrile, dimethylamino ethyl methacrylate, and mixtures thereof;  A method for producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that. The emulsifier of claim 1, Anionic surfactant groups, which are any of polyhydric alcohol sulfates, alkyl benzene sulfonates, polyoxyethylene alkylphenol ether sulfates, dialkyl sulfosuccinates, and mixtures thereof; Among the nonionic surfactant groups, which are any of alkyl ethers, polyoxyethylene alkylphenol ethers, block copolymers of polyoxyethylene / polyoxypropylene, and mixtures thereof; A method for producing a high-solid acrylic PSA pressure-sensitive adhesive, characterized in that any one selected from an anionic surfactant group and a nonionic surfactant group, and mixed them in a predetermined ratio. The method of claim 1, wherein the initiator, A method for producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that any one of hydroperoxide, t-butyl hydroperoxide, potassium persulfate, ammonium persulfate, sodium persulfate, and mixtures thereof. The method of claim 7, wherein the initiator, A method for producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that it is an initiator constituting a redox initiator system in combination with a reducing agent which is sodium bisulfate or sodium formaldehyde sulfoxylate. The method of claim 1, wherein the fourth step and the fifth step, A method of producing a high solid acrylic PSA pressure-sensitive adhesive, characterized in that the step of selectively adding a chain transfer agent or a crosslinking agent, or both the chain transfer agent and the crosslinking agent into the reactor. 10. The method of claim 9, wherein the chain transfer agent is any one of carbon tetrabromide, mercaptan alcohol, and a mixture thereof. The method of claim 9, wherein the crosslinking agent is Multifunctional acryl including diacrylate, triacrylate, tetraacrylate, 1,6-hexanediol diacrylate, poly (ethylene glycol) diacrylate, polyurethane diacrylate, trimetholpropane triacrylate group; Polyfunctional allyl groups including 4-acryloxybenzophenone, divinyl benzene, diallyl maleate and allyl methacrylate; A method of producing a high solid acrylic PSA acrylic pressure-sensitive adhesive, characterized in that any one or a mixture of two or more selected from. A high solid acrylic PSA pressure sensitive adhesive, wherein the solid content is 40 to 75%, the particle size distribution is bimodal or multimodal, and an aqueous emulsion of polymer latex. A high solid acrylic PSA pressure-sensitive adhesive prepared by the method of claims 1 to 11, having a solid content of 40 to 75%, a particle size distribution of bimodal or multimodal, and an aqueous emulsion of polymer latex. A secondary product of a high solid acrylic PSA pressure-sensitive adhesive prepared by coating the high solid PSA pressure-sensitive adhesive of claim 12 on a base material which is one of paper, a polymer material film, or a metal thin plate.

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