KR100940707B1 - Method for Preparing Starch-Acryl Copolymer Using Emulsifier-Free Emulsion Polymerization - Google Patents

Abstract

The present invention relates to a method for preparing a starch-acrylic copolymer useful as a base resin of a pressure-sensitive adhesive used in the display field such as a polarizing plate, using starch together with an acrylic compound and emulsion-polymerized under an emulsifier-free environment-friendly adhesive properties (eg For example, wettability to the adherend) and optical properties (for example, light transmittance) have excellent advantages.

Acrylic, starch, pressure-sensitive adhesive, polarizing plate, light transmission, wettability, emulsion polymerization

Description

Method for preparing starch-acrylic copolymer using emulsion-free emulsion polymerization {Method for Preparing Starch-Acryl Copolymer Using Emulsifier-Free Emulsion Polymerization}

The present invention relates to a method for preparing a starch-acrylic copolymer using an emulsion-free emulsion polymerization. More specifically, the present invention relates to a method for producing a starch-acrylic copolymer for pressure-sensitive adhesive, which uses starch together with an acrylic compound as a monomer and is emulsion-polymerized under an emulsifier-free, which is environmentally friendly and excellent in adhesive and optical properties.

In general, a liquid crystal display includes a liquid crystal cell and a polarizing plate, and an adhesive is used to coalesce it. Pressure sensitive adhesives (PSAs) are also called pressure sensitive adhesives in the sense of being tacky at room temperature and being adhered by a small pressure within a short time.

Typically, a display polarizing plate is composed of a base film, a transparent protective film or the like in which an iodine compound or a dichroic polarizing material (dye) is oriented as a polarizer. At this time, the transparent protective film is made of hydrophilic triacetyl cellulose (TAC) material, and laminated on both sides of the lipophilic polyvinyl alcohol (PVA) film as a base material so as not to change the physical properties according to the direction. In order to apply a thin adhesive (for example, 30 μm) on such a transparent protective film, a release film is attached to one side of the adhesive layer. Then, when the flat plate is to be attached to the liquid crystal cell, the release film is removed and attached to the liquid crystal cell by the exposed adhesive layer.

However, in the process of applying the pressure-sensitive adhesive to the polarizing plate, the pressing marks or the foreign matter may be mixed on the pressure-sensitive adhesive layer by sheet loading and rolls. As such, when foreign matters are mixed or pressed, not only light refraction or reflection but also light leakage may occur to increase a defective rate. At present, attempts have been made to develop an adhesive having excellent permeability and cohesion while preventing light leakage.

As a base resin of an adhesive, copolymers, such as a silicone type, an acryl type, and a polyurethane type, are used widely. Among them, the acrylic pressure sensitive adhesive is known to be excellent in transparency and cohesion, and to easily control viscosity or molecular weight. Due to these advantages, the acrylic pressure-sensitive adhesive is not only suitable for display, but also versatile because the spreadability can be adjusted through the viscosity and the amount of the solvent so as to be easily applied on the film. In particular, in the case of a pressure-sensitive adhesive for display, the spreadability to the adherend should be excellent and no refraction or scattering to light should occur. In addition, foreign matters should not be generated as much as possible, and resistance to heat and light should be ensured even after preparing the adhesive.

In general, the acrylic pressure-sensitive adhesive may be prepared by various methods, such as solution polymerization, bulk polymerization, emulsion polymerization. In the case of bulk polymerization, the heat of reaction is difficult to control and the viscosity is too high, which is disadvantageous in terms of productivity. In the case of solution polymerization, although excellent transparency and viscosity and molecular weight can be controlled, the increase in production cost and the harmfulness to the human body are problematic. In the case of emulsion polymerization, since the fluidity of the reaction solution is maintained in a good state by the dispersion medium, it is easy to remove the heat of reaction, and polymers having high molecular weight can be produced at a high polymerization rate. Although having, there is a problem that does not satisfy the physical properties required as a pressure-sensitive adhesive for display such as a polarizing plate or a polarizing film. This can be prepared by the emulsion polymerization method, but because the emulsifier acts as an impurity is not suitable for the polarizing plate, because it has a milky white color to induce reflection and refraction of light.

Therefore, most of the acrylic pressure-sensitive adhesive for display is manufactured by a solution polymerization method, and at this time, a crosslinking agent is used to secure cohesion.

In this regard, US Pat. No. 7,160,611 discloses a method for manufacturing an adhesive for an optical film such as a liquid crystal display (LCD), a CRT, a PDP, and the like. According to the patent, the base resin of the pressure-sensitive adhesive is polymerized by an acrylic copolymer having an acrylate monomer having a hydroxyl group, a carboxyl group, a sulfone group, a phosphoric acid group, or the like by a solution polymerization method or a bulk polymerization method in the presence of a polyfunctional isocyanate crosslinking agent. Are manufactured.

Japanese Patent Laid-Open No. 8-32782 discloses a method for producing an acrylic copolymer for pressure-sensitive adhesive by solution polymerization of an acrylic acid alkyl ester and 10 to 20% by weight of an amide group-containing polymerizable monomer in the presence of a radical polymerization catalyst. . At this time, as the crosslinking agent, polyisocyanate compounds such as aliphatic diisocyanate and aromatic diisocyanate, melamine compounds such as trimethylolmelamine, diamine compounds and the like can be used.

Japanese Patent Laid-Open No. 14-309208 discloses a method for producing a pressure-sensitive adhesive useful for attaching a liquid crystal cell and a polarizing film. The main component copolymer is a polyalkylene glycol modified acrylate or polycaprolactone modified having a hydroxyl group in a molecule. An acrylic acid alkyl ester having an acrylate and an alkyl group having 4 to 12 carbon atoms is used as a monomer, and is prepared by solution polymerization using an isocyanate crosslinking agent, a melamine crosslinking agent, an epoxy crosslinking agent or the like as a crosslinking agent.

Korean Patent No. 528807 discloses a solution polymerization method in which an alkyl (meth) acrylate is dissolved in a solvent (ethyl acetate) as a base monomer and a toluene diisocyanate (TDI) adduct of trimethylolpropane is used as a crosslinking agent. According to the said patent, the polymer manufactured as mentioned above can be applied to the adhesive for polarizing plates.

However, in the case of the above-described prior art, in particular, the solution polymerization method, since it is difficult to meet the requirements due to the recent surge in raw material prices and human hazards, it is urgent to develop an adhesive which can be manufactured in a more economical and environmentally friendly way. It is true.

On the other hand, starch, an environmentally friendly material, is widely distributed in nature as a storage carbohydrate of plants, and is a resource that can be reproduced through cultivation. Commercially, starch is produced from corn, waxy corn, sweet potato, potato, sorghum and tapioca. Starch is a polymerized form of hundreds to thousands of glucose and is composed of amylose and amylopectin depending on the binding. However, starch has a lower mechanical property and lower processability than synthetic polymers, so it is difficult to be practically applied to starch, and there is a limit to wide application.

The present inventors have continuously studied a method of producing an acrylic copolymer for pressure-sensitive adhesives, which is suitable for a display and the like, and found that starch, which has been conventionally limited in application with an acrylic compound, is used for polymerization and does not use an emulsifier. A friendly emulsion polymerization method was developed, and it was found that the prepared starch-acrylic copolymer for pressure-sensitive adhesive exhibited excellent properties in adhesive strength, wettability, optical properties, and the like, and thus could be effectively applied to applications such as displays.

Accordingly, it is an object of the present invention to provide a method for producing a starch-acrylic copolymer for pressure-sensitive adhesive that can improve environmental friendliness and economy.

Another object of the present invention is to provide a method for producing a starch-acrylic copolymer for pressure-sensitive adhesive, which adopts an emulsion polymerization method without using an emulsifier and generally improves physical properties such as adhesive strength, wettability, and optical properties.

Still another object of the present invention is to provide a pressure-sensitive adhesive comprising the starch-acryl copolymer prepared above.

Still another object of the present invention is to provide a polarizing plate to which an adhesive including a starch-acrylic copolymer is applied.

According to the first aspect of the invention,

a) gelatinizing starch; And

b) adding an acrylic compound-containing monomer to the starch gelatin solution in a ratio of 1: 1 to 1: 9 (weight ratio of starch: acrylic compound-containing monomer) to perform emulsion polymerization under the presence of an initiator and under an emulsifier-free condition. ;

Provided is a starch-acrylic copolymer production method comprising a.

According to the second aspect of the present invention, there is provided an adhesive comprising a starch-acrylic copolymer prepared according to the above-described method.

According to the third aspect of the present invention, a polarizing plate to which the pressure-sensitive adhesive is applied is provided.

In the method for preparing a starch-acryl copolymer according to the present invention, starch is used together with an acrylic compound for polymerization and the optical properties of the emulsifier are reduced by minimizing impurities without using a separate emulsifier in the emulsion polymerization process. For example, milky white expression, low light transmittance, etc.) can be effectively suppressed. In addition, compared to the solution polymerization, which is relatively complicated in the manufacturing process and difficult to manage, the economical efficiency can be improved, and the wettability is excellent, and adhesive properties such as no peel-off and glass transfer do not occur. If applied, the failure rate can be lowered. Moreover, since the use of starch has the advantage of improving the environmental friendliness, the application is expected as an adhesive for not only display materials such as polarizing plates but also other electronic component materials.

The present invention can all be achieved by the following description.

According to the present invention, the emulsion polymerization method that has caused various problems in the conventional application of the base resin of the pressure-sensitive adhesive for polarizing plate (or polarizing film) is adopted. At this time, by polymerizing without using an emulsifier, it is possible to effectively suppress the problem of impurities due to the unreacted substance of the emulsifier, especially the emulsifier. The copolymer prepared as described above has good optical properties including transparency and light transmittance, and is excellent in adhesive properties because of its strong cohesive force. In addition, compared to the solution polymerization produced in the two-component form, since the emulsion polymerization is produced in a one-component form, the production process is efficient and the impact on the rise in raw material prices is relatively insignificant.

In this invention, the component used for manufacture of a starch-acryl copolymer is as follows.

Starch

In the present invention, conventionally available starch may be utilized as starch used with an acrylic monomer. As described above, the starch may be divided into, for example, corn starch, tapioca starch, potato starch, sweet potato starch, wheat starch and the like, but is not limited thereto. However, instead of using an emulsifier that affects optical properties such as transparency during emulsion polymerization, it is preferable to use modified starch. Specifically, one or more selected from the group consisting of etherified starch, esterified starch, oxidized starch, oxidized ester starch, oxidized ether starch, acid treated starch and enzyme treated starch can be used, more preferably oxidized starch, Etherified starch and the like can be used.

As the etherified starch, hydroxy propyl starch, hydroxy ethyl starch, carboxy methyl starch, cyanoethyl starch or amphoteric starch may be used, and preferably low viscosity ether starch or amphoteric oxidized starch may be used. Starch acetate or maleic acid starch may be used as the ester starch, and preferably low viscosity ester starch may be used. As the starch oxide, hydrogen peroxide oxide starch or hypochlorous acid starch may be used.

Acrylic compound

In the present invention, the acryl-based compound used as the monomer broadly refers to a compound containing a vinyl group, it is sufficient to use those commonly known in the art and are not limited to a specific kind. For example, an alkyl acrylate, a vinyl cyanide compound, an amide type vinyl compound, a hydroxyl group containing vinyl compound, and a bifunctional vinyl monomer are mentioned, These can be used individually or in combination.

As the alkyl acrylate, one or two or more selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl acrylate, 2-ethyl hexyl acrylate, butyl acrylate and butyl methacrylate can be used. . The vinyl cyanide compound may be acrylonitrile, methacrylonitrile or a mixture thereof. The amide vinyl compound is acrylamide, methacrylamide, N-methyrol acrylamide, diacetone acrylamide, itaconeamide, methylene diacrylamide, diethyl acrylamide, dimethyl methacrylamide and diethyl methacrylamide One or two or more may be selected from the group which consists of these. The hydroxy group-containing vinyl compound is selected from the group consisting of 2-hydroxy ethyl acrylate, 2-hydroxy ethyl methacrylate, 3-hydroxy propyl acrylate and 3-hydroxy propyl methacrylate. Can be used. As the bifunctional vinyl monomer, one or two or more selected from the group consisting of divinyl benzene, diallyl benzene and divinylsulfonic acid may be used.

Preferably, butyl acrylate, methyl methacrylate, 2-ethyl hexyl acrylate or a combination thereof, more preferably butyl acrylate, 2-ethyl hexyl acrylate or a combination thereof can be used.

Meanwhile, a vinyl silicon compound such as vinyl trichloro silane, vinyl trimethoxy silane, or a combination thereof may be optionally added to the acrylic compound to be used as a monomer.

In the present invention, the acrylic compound-containing monomer is used such that the weight ratio of starch: acrylic compound-containing monomer is about 1: 1 to 1: 9. If the amount of the acrylic compound-containing monomer used is too small, there is a problem in that the initial adhesive strength is lowered and the flexibility of the film is lowered. In the case where the acrylic compound-containing monomer is used, polymerization is difficult without using an emulsifier. Therefore, it is preferable to maintain the above-described mixing ratio, more preferably about 1: 2 to 1: 5.

Unsaturated carboxylic acid compound

According to the present invention, the acrylic compound-containing monomer may be an acrylic compound alone, but may further include an unsaturated carboxylic acid compound in the acrylic compound as a monomer in order to improve the adhesive strength and mechanical stability of the copolymer. . In this case, the unsaturated carboxylic acid compound may be introduced into the reaction system separately or mixed with the acrylic compound. However, when used in an excessively large amount, since the viscosity of the copolymer rises and handling is difficult, the unsaturated carboxylic acid compound may be added up to 20 to 100 parts by weight of the acrylic compound (the combination when the acrylic compound and the vinyl silicon compound are combined). It is preferable to further include by weight. Although such unsaturated carboxylic acid compound is not particularly limited, there are typically monocarboxylic acid, dicarboxylic acid, dicarboxylic acid anhydride, and the like, and one or two or more thereof can be selected and used. Preferred examples of the unsaturated carboxylic acid compound are acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid or a combination thereof, more preferably acrylic acid, methacrylic acid, maleic acid or a combination thereof.

Initiator

In the present invention, an initiator is preferably used for the copolymerization reaction of the acrylic compound-containing monomer and starch. As such an initiator, an initiator commonly used in the emulsion polymerization reaction may be used. Specifically, an organic peroxide compound, an inorganic peroxide compound, a persulfate compound, cerium ammonium, a redox-based initiator, or a combination thereof may be used. Preferred examples of the persulfate compound may be potassium persulfate or ammonium persulfate, the redox-based initiator may be first ammonium sulfate, ascorbic acid or sodium bisulfite, and the cerium ammonium is ammonium diacetate Can be. Preferably, the initiator is a persulfate compound or cerium ammonium. In case of less initiator, emulsion polymerization takes place and the reaction time is longer. On the other hand, when an excessive amount of the initiator is added, browning of the starch-acryl copolymer may be caused to be discolored, and a problem may occur in that the adhesive force decreases as the molecular weight decreases. In view of the above points, it is preferably about 0.01 to 10 parts by weight, more preferably about 0.2 to 5 parts by weight based on 100 parts by weight of the total of the starch and the acrylic compound-containing monomer.

Chain transfer agent

According to the present invention, in the preparation of the starch-vinyl copolymer, a chain transfer agent may be optionally used to adjust the molecular weight of the copolymer, and is preferably added to the monomer mixture. As the chain transfer agent, conventional chain transfer agents such as n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer, and the like can be used, but are not limited to specific types.

The chain transfer agent may be used in an amount of preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the starch, starch, and the acrylic compound-containing monomer in total. When the chain transfer agent is used too much, the molecular weight is also lowered, so that the phenomenon that the adhesive force is lowered, it is preferable to use properly within the above range.

According to the invention, the starch is first gelatinized. At this time, as the dispersion medium, preferably water, more preferably distilled water or deionized water is used. For the gelatinization of starch, a batch-cooking method which proceeds at atmospheric pressure and a jet-cooking method which proceeds at high temperature and high pressure may be optionally used, and preferably an intermittent method is used. The gelatinization temperature of the intermittent method is preferably about 50 to 120 ° C, more preferably about 70 to 105 ° C. In addition, the amount of the dispersion medium is appropriately adjusted so that the amount of starch is preferably about 2 to 30% by weight, more preferably about 5 to 20% by weight, based on the gelatinous liquid.

At this time, if the viscosity exceeds a certain level, it is possible to optionally add starch degrading enzyme to the gelatin solution. The starch dehydrogenase is preferably used within a maximum of 2 parts by weight based on 100 parts by weight of starch. When the starch dehydrogenase is added, the reaction is preferably performed at about 60 to 120 ° C, more preferably at about 70 to 105 ° C, preferably about 5 to 120 minutes, more preferably about 30 to 60 minutes.

According to a preferred embodiment of the present invention, when the viscosity of the starch gelatin solution is 20 cps (50 ° C., based on 10% by weight), the polymerization reaction may be performed with the subsequent acrylic compound-containing monomer without using starch enzyme. On the other hand, in the case of having a viscosity exceeding 20 cps, the reaction may be performed after adding about 0.0001 to 2 parts by weight of starch degrading enzyme with respect to 100 parts by weight of starch, followed by subsequent polymerization.

On the other hand, the starch degrading enzyme is not limited to a specific kind as an enzyme having ordinary starch degrading capacity, preferably alpha-amylase can be used. The alpha-amylase is a conventional alpha-amylase, preferably all of mesophilic alpha-amylase exhibiting the highest activity in the range of about 60 to 80 ° C., and high temperature alpha-amylase exhibiting the highest activity at about 90 to 105 ° C. have.

After preparing the gelatinized liquid of starch, the acrylic compound-containing monomer is added in the above-described mixed weight ratio to perform emulsion polymerization under the presence of the initiator and under the condition of no emulsifier. At this time, it is preferable to advance the reaction while dropping the acrylic compound-containing monomer and the initiator separately or in a mixed form.

According to a preferred aspect of the present invention, the polymerization may be performed at about 50 to 110 ° C., more preferably at about 60 to 95 ° C. for about 30 to 360 minutes, more preferably about 60 to 300 minutes. . In the polymerization process, for example, the reaction proceeds with dropwise addition, and then optionally aged for about 20 to 120 minutes at about 50 to 110 ℃, more preferably about 60 to 95 ℃ to improve the stability of the polymer And the amount of residual monomer can be minimized. After performing the polymerization reaction, the reaction may be finally cooled to about 40 ° C. or less. In some cases, the polymerization reaction may be repeated two or more times to minimize residual monomers.

As a result of the polymerization reaction, the starch-acrylic copolymer is obtained in the form of an emulsion, where the solids content of the copolymer is about 10 to 50% by weight, more preferably about 15 to 40% by weight. In addition, the viscosity of the starch-acrylic copolymer in emulsion form is preferably in the range of about 10 to 10,000 cps (25 ° C.), more preferably about 200 to 3000 cps. In this case, in some cases, a chain transfer agent may be used in the polymerization process to adjust the viscosity to a desirable viscosity range.

The starch-acrylic copolymer prepared according to the present invention is contained in an adhesive, and the characteristics (ie, wettability, light transmittance, bubble generation, glass transfer, etc.) required for applying the adhesive to a display field such as a polarizing plate or a polarizing film and Satisfy related properties. In order to prepare the pressure-sensitive adhesive, various optional additive components, for example, silane coupling agents such as amino, epoxy, acrylic and vinyl resins, crosslinking agents such as isocyanates, resins, epoxy resins, urea resins, and the like, may be used alone or in combination. Can be used.

The adhesive containing the said starch-acryl copolymer is useful as an optical adhesive, especially as an adhesive which adhere | attaches the polarizing film and the glass substrate of a liquid crystal cell. In particular, the wettability with respect to a large area polarizing plate and a liquid crystal cell is excellent. In addition, since the pot life is longer than the solvent-based pressure-sensitive adhesive, workability is excellent in industrial use. In relation to the properties of the pressure-sensitive adhesive, for example, the light transmittance is about 70% or more, more preferably about 80% or more, and the peel strength is about 60 kgf / cm ² or more.

On the other hand, in the present invention, the polarizing plate comprises a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive on at least one side of the polarizing film, such a polarizing film or polarizing element constituting the polarizing plate is a known type without particular limitation to the present invention According to the pressure-sensitive adhesive may be applied. At this time, the thickness of the typical adhesive layer is about 5 to 500 μm, preferably about 30 to 150 μm.

The present invention can be more clearly understood by the following examples, which are only intended to illustrate the present invention and are not intended to limit the scope of the invention.

In this Example and Comparative Example, a solution-polymerized acrylic pressure-sensitive adhesive or emulsifier was used by measuring light transmittance, peel-off, bubble generation, glass transfer, and peel strength of the starch-acrylic copolymer-containing pressure-sensitive adhesive. It was compared with the pressure-sensitive adhesive prepared. The evaluation method is as follows:

1) Light transmittance

The light transmittance is measured in the visible range by coating a 100 μm adhesive on a glass substrate (50 mm × 50 mm × 5 mm).

2) Peel-off Evaluation

A pressure-sensitive adhesive having a thickness of 30 μm is formed on the polarizer, and then a protective film and a release film are attached to both surfaces of the polarizer. The polarizing plate of the laminated structure is cut to a size of 25mm x 75mm to be laminated on a glass substrate, and left for 48 hours at 80 ℃ to observe the occurrence of peeling on the glass substrate.

3) Bubble generation

The pressure-sensitive adhesive is applied to the polarizing plate at a thickness of 30 μm, and then a protective film and a release film are attached to both surfaces of the polarizing plate. The polarizing plate was cut to a size of 25 mm x 75 mm and laminated on a glass substrate, and left for 48 hours at 80 ° C. to observe whether bubbles were generated in the glass substrate.

4) Glass Transfer

The pressure-sensitive adhesive film is coated on the polarizing plate with a thickness of 30 μm, and then a protective film and a release film are attached to both surfaces of the polarizing plate. The polarizing plate was cut to a size of 25 mm x 75 mm and laminated on a glass substrate, left for 48 hours at 25 ° C. for desorption from the glass substrate, and then observed in the glass substrate.

5) Contact angle measurement

The adhesive is coated with a glass substrate (50mm × 50mm × 5mm) at 100μm using CAA (Contact Angle Analysis) .Then, the contact angle is measured 9 times by dropping water to predict the relative wetting power and the surface tension of the adhesive. Can be. That is, when the surface tension of the pressure-sensitive adhesive is lower than the surface tension of the adherend, the contact angle is lowered because the wettability is excellent, whereas when the surface tension of the pressure-sensitive adhesive is higher than the surface tension of the adherend, the contact angle is high due to poor wettability. As such, when the pressure-sensitive adhesive exhibits a low contact angle, the pressure-sensitive adhesive is well coated and spreads over a larger area than when the pressure-sensitive adhesive has a high contact angle.

6) Peel strength

The PET film is used to cut the width and length to 25 mm and 250 mm, respectively. The surface of the test plate is lightly ground with water-resistant abrasive paper and then washed thoroughly with isopropyl alcohol. The pressure-sensitive adhesive was cast to the test piece at 30 μm on the washed test plate, and then dried under 120 ° C. conditions, and then reciprocated once with a 2 kg manual pressing roller. After 20 minutes, measure at a rate of 300 ± 30 mm / min at room temperature using a 180 ° peel test instrument.

Example  One

Into a 1,000 ml four-necked reactor equipped with a stirrer, a reflux cooler, a nitrogen inlet, and a separating funnel, 46 g of oxidized starch (trade name: Sunsize C3010, Samyang Genex) and 400 g of distilled water were put in a water bath at a temperature of 90 ° C. The starch was gelatinized by stirring for 1 hour in a water bath). After 1 hour, the temperature of the bath was lowered to room temperature. Sunsize C3010 is a low viscosity corn starch with a viscosity of 10 cps at 50 ° C. and 10% solution.

Nitrogen gas was added to the reactor for emulsion polymerization, and the temperature of the reactor containing the starch gelatinized solution was raised to 80 ° C., followed by 299.8 g of 2-ethylhexyl acrylate, 63.0 g of methyl methacrylate, and unsaturated carbohydrate, which are acrylic monomers. An initiator solution in which 2.0 g of ammonium persulfate was dissolved in 20 g of water and a monomer mixture containing 7.2 g of acrylic acid as a main acid monomer was added dropwise for 3 hours. After dropping of the monomer mixture and the initiator solution was completed, the mixture was aged for 1 hour. After aging was completed, the reactor was cooled to 40 ° C, and 6.0 g of ammonia water was added to adjust the pH of the starch-acrylic copolymer solution to 7.0.

Example  2

In a 1,000 ml four-necked reactor equipped with a stirrer, a reflux cooler, a nitrogen inlet, and a separating funnel, 140 g of oxidized starch (trade name: Sunsize C3060, Samyang Genex), 600 g of distilled water, 0.04 g of enzyme (Termamyl 120L, Novo, Denmark) The starch was gelatinized by stirring for 1 hour in a water bath with the temperature set at 90 ° C. Sunsize C3060 is a low viscosity corn starch with a viscosity of 80 cps at 50 ° C. and 10% solution.

Nitrogen gas was added to the reactor for emulsion polymerization, and the temperature of the reactor containing the starch liquor was lowered to 80 ° C., followed by 120.0 g of 2-ethylhexyl acrylate, 50.0 g of butyl acrylate, and 30.0 methyl methacrylate. 3 g of an initiator solution in which 3.0 g of ammonium persulfate was dissolved in a monomer mixture of 3.6 g of acrylic acid as an unsaturated carboxylic acid monomer and 30 g of water was added dropwise thereto. After the dropping of the monomer mixture and the initiator solution was completed, it was aged for 1 hour. After the completion of aging, 0.396 g of t-butyl hydroxy peroxide (Lancaster, UK) was dissolved in 20 g of water with an organic initiator, added to the reactor, and further reaction was performed for 30 minutes to remove residual monomer. After the reaction was completed, the reactor was cooled to 40 ° C. and 4.0 g of ammonia water was added to adjust the pH of the starch-acrylic copolymer solution to 7.0.

Comparative example  1 to 3

Solution polymerization was carried out to prepare a base resin of an acrylic pressure-sensitive adhesive. In order to reflux nitrogen gas to the reactor and control the temperature control and the exothermic reaction, a cooling device and a thermometer were installed in the reaction port. 109 g of ethyl acetate solvent was injected, and 25 g of 2-ethyl hexyl acrylate, 50 g of butyl acrylate, 3.5 g of acrylic acid, and 0.075 g of BPO (benzoyl peroxide) were added thereto, followed by 6 hours 30 at 80 ° C. The reaction was carried out by stirring for minutes.

To 100 g of the acrylic copolymer resin prepared as described above, 0.5, 1.0, 1.5 g of isocyanate-based curing agents and 1.0 g of methacrylic oxypropyl trimethoxy silane, which is a silane coupling agent, were uniformly mixed to prepare an acrylic adhesive liquid.

Comparative example  4

Oxide starch (trade name: Gencote C3005, Samyang Genex) 175 g, distilled water 600 g, and enzyme (Termamyl 120L, Novo, Denmark) 0.18 g in a 1,000 ml four-necked reactor equipped with a stirrer, reflux cooler, nitrogen inlet, and separatory funnel. Was added, and the starch was gelatinized by stirring for 1 hour in a water bath at which the temperature was set at 90 ° C. Gencoat C3005 is a low viscosity corn starch with a viscosity of 8 cps at 50 ° C., 10% solution.

Nitrogen gas was added to the reactor for emulsion polymerization, and the temperature of the reactor containing the starch gelatinized solution was lowered to 80 ° C., and then 18.0 g of sodium docecyl benzene sulfonate was added as an emulsifier and stirred for 30 minutes. . A monomer mixture prepared by mixing 121.0 g of styrene, 95.0 g of butyl acrylate, 16.8 g of methyl methacrylate, and 7.2 g of an acrylic acid which is an unsaturated carboxylic acid monomer, and an initiator in which 2.9 g of ammonium persulfate was dissolved in 29 g of water. The solution was added dropwise for 3 hours 30 minutes. After the dropping of the monomer mixture and the initiator solution was completed, it was aged for 1 hour. After the completion of aging, 0.396 g of t-butyl hydroxy peroxide (Lancaster, UK) as an organic initiator was dissolved in 20 g of water and added to the reactor, followed by additional reaction for 30 minutes to remove residual monomer. After the reaction was completed, the reactor was cooled to 40 ° C., and 6.0 g of ammonia water was added to adjust the pH of the starch-acrylic polymer solution to 7.0.

Physical properties of the adhesive solution prepared in Examples and Comparative Examples are shown in Table 1 below.

TABLE 1

Comparison of Properties of Adhesives

Category 성 Physical property Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 0.5 1.0 1.5 - Light transmittance (%) 90 80 85 81 59 35 Peel-off radish radish U radish radish U Bubble outbreak radish radish U U radish radish Glass Warrior radish radish radish radish radish radish Peel strength (kgf / cm ² ) 67 62 65 70 69 60 Contact angle (˚) 75 68 79 74 69 65

As shown in Table 1 above, when the starch-acryl copolymer-containing pressure-sensitive adhesive according to the present invention is compared with the physical properties required for the pressure-sensitive adhesive and the polarizing film pressure-sensitive adhesive of the comparative example, the Example is excellent in light transmittance compared to the comparative example Phenomena such as peel-off, bubble generation, and glass transfer did not occur. In addition, with respect to the contact angle, compared with the pressure-sensitive adhesive using a resin produced by solution polymerization, the wetness (or coating property) to the adherend exhibited at least equivalent physical properties, confirming that there is no problem in terms of application as an actual pressure-sensitive adhesive. .

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of the present invention will be apparent from the appended claims.

Claims (15)

a) gelatinizing starch; And b) adding an acrylic compound-containing monomer to the starch gelatin solution in a ratio of 1: 1 to 1: 9 (weight ratio of starch: acrylic compound-containing monomer) to perform emulsion polymerization under the presence of an initiator and under an emulsifier-free condition. ; Starch-acrylic copolymer manufacturing method comprising a, wherein the acryl-based compound is butyl acrylate, methyl methacrylate, 2-ethyl hexyl acrylate or a combination thereof. The method of claim 1, wherein the acrylic compound-containing monomer in step b) further comprises up to 20 parts by weight of an unsaturated carboxylic acid compound with respect to 100 parts by weight of the acrylic compound, the unsaturated carboxylic acid compound is acrylic acid, methacrylic acid , Maleic acid, fumaric acid, itaconic acid or a combination thereof. The method of claim 1, wherein the initiator is an organic peroxide compound, an inorganic peroxide compound, a persulfate compound, cerium ammonium, a redox-based initiator, or a combination thereof. The method according to claim 1 or 2, wherein the initiator is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total of the starch and the acrylic compound-containing monomer. The starch according to claim 1, wherein the starch is selected from the group consisting of etherified starch, esterified starch, oxidized starch, oxidized ester starch, oxidized ether starch, acid treated starch and enzyme treated starch. -Acrylic copolymer production method. According to claim 1, wherein the step a) is carried out using water as a dispersion medium, the starch-acrylic copolymer manufacturing method, characterized in that the content of the starch is 2 to 30% by weight based on the gelatinous liquid. According to claim 1, When the viscosity of the gelatin solution according to step a) exceeds 20 cps (50 ℃, based on 10% by weight), by adding 0.0001 to 2 parts by weight of starch degrading enzyme per 100 parts by weight of starch Starch-acrylic copolymer production method characterized in that it further comprises the step of reacting. 8. The method according to claim 7, wherein the starch dehydrogenase is alpha-amylase. The starch according to claim 1 or 2, wherein step b) is further performed using a chain transfer agent up to 0.001 to 5 parts by weight based on 100 parts by weight of the total of the starch and the acrylic compound-containing monomer. Acrylic copolymer manufacturing method. The method according to claim 1 or 2, wherein the product obtained in step b) is in the form of an emulsion and has a viscosity (25 ° C.) of 10 to 10,000 cps. The method of claim 1, wherein the emulsion polymerization is performed at 50 to 110 ° C. for 30 to 360 minutes.  2. The method according to claim 1, wherein the product obtained in step b) is in the form of an emulsion and the solids content of the starch-acrylic copolymer is 10 to 50% by weight. delete  A pressure-sensitive adhesive comprising a starch-acrylic copolymer prepared according to claim 1. Polarizing plate to which the pressure-sensitive adhesive according to claim 14 is applied.