KR102498638B1 - Manufacturing method of an acrylic polymer and an acrylic polymer - Google Patents

Abstract

This application relates to a method for preparing an acrylic polymer and an acrylic polymer. The method of the present application can produce an acrylic polymer having a specific molecular weight, polydispersity index and conversion rate. The method of the present application can prepare an acrylic polymer capable of minimizing the content of unreacted monomers remaining when further polymerized by irradiation with active energy rays or the like. Since the acrylic polymer of the present application has a specific molecular weight, polydispersity index and conversion rate and the content of unreacted monomers is minimized, it is particularly suitable for the optical pressure-sensitive adhesive (or adhesive) field.

Description

Manufacturing method of an acrylic polymer and an acrylic polymer

This application relates to a method for producing an acrylic polymer and an acrylic polymer.

Various types of polymers are applied to Optical Clear Adhesive (hereinafter also referred to as “OCA”). Among them, an acrylic polymer is applied as a main material of an optical pressure-sensitive adhesive. In particular, in the case of an acrylic polymer, the polymer must have a low molecular weight, for example, a weight average molecular weight (Mw, hereinafter also referred to as molecular weight) of about 100,000 g/mol for optical use. It is known to be suitable as an adhesive.

In general, acrylic polymers are prepared by applying heat or irradiating active energy rays such as ultraviolet rays to a monomer mixture containing one or more acrylic monomers. In order to lower the molecular weight of the acrylic polymer, a molecular weight regulator, which is a compound capable of suppressing polymerization between monomers constituting the polymer, is generally introduced. However, in order for the acrylic polymer to have a desired molecular weight, it is inevitable to increase the amount of the molecular weight regulator. However, when the amount of the molecular weight modifier is increased, the molecular weight modifier remains in excess even after the polymer is produced. However, the remaining molecular weight modifier becomes the main cause of product defects when the adhesive product is manufactured by applying the polymer thereafter. Therefore, it is necessary to minimize the content of the residual molecular weight modifier after preparing the acrylic polymer.

In the present application, one object is to prepare an acrylic polymer having a low molecular weight, for example, a weight average molecular weight of around 100,000 g / mol while minimizing the amount and residual amount of the molecular weight modifier.

In the present application, another object is to prepare an acrylic polymer capable of minimizing the content of residual unreacted monomers.

In this application, the term “acrylic, acryl-based” may mean that the main component constituting the material is a compound derived from acrylic acid ester and/or methacrylic acid ester. That is, the acrylic monomer or polymer mentioned in this application may mean a monomer or polymer derived from acrylate or methacrylate. In addition, in this application, the term polymer is used as a meaning including a homopolymer and a copolymer.

In this application, when a component is referred to as a main component, it may mean that the proportion of the component is approximately 50% by weight or more based on the total weight of the subject including the component. The ratio may be, in another example, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more or 90% by weight or more, It may be approximately 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less by weight.

This application relates to a method for producing an acrylic polymer. In particular, according to the method of the present application, an acrylic polymer having a low molecular weight can be prepared while minimizing the amount of the molecular weight modifier.

In this application, the term “low molecular weight” may mean that the weight average molecular weight of a polymer (a concept encompassing copolymers, oligomers, etc.) is 110,000 g/mol or less. In another example, the molecular weight may be 100,000 g / mol or less, 99,000 g / mol or less, 98,000 g / mol or less, 97,000 g / mol or less, 96,000 g / mol or less, or 95,000 g / mol or less, , The lower limit is not particularly limited, but may be 70,000 g/mol or more, 75,000 g/mol or more, 80,000 g/mol or more, 85,000 g/mol or more, or 90,000 g/mol or more. In the above, the weight average molecular weight may be a standard polystyrene conversion value using gel permeation chromatography (GPC).

The manufacturing method of the present application may be to use a batch reactor. In this application, the term “batch reactor” is a reactor of the opposite concept to a continuous reactor, in which reactants and/or products enter and/or exit a system not continuously. may mean a reactor. As batch reactors, various types are known, ranging from small vessels such as beakers to large-sized reactors, and in this application, all known batch reactors are applicable.

As will be described later, the acrylic polymer prepared in a continuous reactor has a relatively high polydiversity index (PDI). For example, the polydispersity index of an acrylic polymer prepared in a continuous reactor may exceed 3. A polymer having a high polydispersity index has an excessively high viscosity even at the same molecular weight compared to a polymer having a low polydispersity index, and thus, a manufacturing process of an adhesive product using the polymer, such as a coating process, has a difficult problem. Therefore, acrylic polymers prepared in a continuous reactor are not suitable for optical applications, for example, as optical adhesives.

The method of the present application includes at least a step of introducing a monomer mixture including a specific component into the batch reactor and thermally polymerizing the introduced mixture. In addition, the method of the present application can prepare an acrylic polymer having a conversion rate, a weight average molecular weight, and a polydispersity index within a specific range by setting the composition and reaction conditions of the monomer mixture to a specific range. These acrylic polymers have the advantage of being particularly suitable for optical applications.

In the method of the present application, a solvent-free monomer mixture is introduced into the batch reactor. In the above, the non-solvent type monomer mixture is used as a meaning including the case where the solvent used in the known solution polymerization method is not applied, or even if the solvent is applied, the amount of the solvent is extremely small. That is, the polymerization method for preparing the acrylic polymer in the present application may be bulk polymerization.

Since the method of the present application applies a solvent-free monomer mixture that does not substantially contain a solvent, the polymerizable component included in the mixture may consist of only specific monomers. In the above, the polymerizable component may mean a component involved in a polymerization reaction.

For example, the polymerizable component may be composed of one or more acrylic monomers. In this application, the term “acrylic monomer” is used to refer to both methacrylate or acrylate monomers, as described above.

The type of acrylic monomer is not particularly limited. For example, if the acrylic component has a glass transition temperature within a specific range or is less than or equal to a specific value so that a mixture or composition containing the acrylic component can exhibit predetermined adhesion or adhesive properties when cured or polymerized, known acrylic monomers can be applied. can

In one example, the acrylic monomer may include an alkyl (meth)acrylate monomer and a polar functional group-containing monomer.

As the alkyl (meth)acrylate monomer, an alkyl (meth)acrylate monomer having an alkyl group having 1 or more carbon atoms, for example, an alkyl group having 1 to 20 carbon atoms, in consideration of the cohesive force, glass transition temperature, and adhesiveness of the acrylic polymer, may be used. can In another example, the number of carbon atoms of the alkyl group may be 3 or more, 4 or more, or 6 or more, and may be 16 or less, 12 or less, or 8 or less. The alkyl group may mean chain-type alkyl or cyclic alkyl such as straight-chain or branched-chain alkyl. In addition, the alkyl group may be substituted with an arbitrary atom (eg, oxygen, nitrogen, or halogen atom) or an arbitrary substituent.

Examples of the alkyl (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. rate, t-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl Monomers such as (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate and tetradecyl (meth)acrylate can be exemplified. Specifically, it may be advantageous in terms of securing physical properties to apply 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-butyl acrylate, or a combination thereof as the alkyl (meth)acrylate monomer.

When an alkyl (meth)acrylate monomer and a polar functional group-containing monomer are used as the acrylic monomer, the alkyl (meth)acrylate monomer may be included as a main component. Similarly, the description of the main component is the same as described above.

The polar functional group-containing monomer may mean a monomer having a hydroxy group or a carboxy group as a polar functional group or containing nitrogen. When securing suitable physical properties and considering application to various optical products, it is appropriate to apply at least one of a hydroxy group-containing monomer and a nitrogen-containing monomer as a polar functional group-containing monomer. More preferably, it is appropriate to apply at least one of a hydroxy group-containing alkyl (meth)acrylate monomer and a nitrogen-containing monomer as the polar functional group-containing monomer.

As the hydroxy group-containing alkyl (meth)acrylate monomer, a hydroxyalkyl (meth)acrylate monomer having a hydroxyalkyl group having 2 to 6 carbon atoms may be used. Examples of such monomers include hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate or 6-hydroxyhexyl (meth)acrylate. can

As the nitrogen-containing monomer, acrylamide-based monomers can be exemplified. As these monomers, (meth)acrylamide, N,N-dimethyl acrylamide (DMAA) or N,N-diethyl acrylamide (N,N-diethyl acrylamide, DEAA) are applied. can do.

The ratio of these polar functional group-containing monomers may also be appropriately adjusted. For example, the ratio of the polar functional group-containing monomer may be in the range of 10 parts by weight to 50 parts by weight based on 100 parts by weight of the alkyl (meth)acrylate monomer. The ratio may be, in another example, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more, and 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, or 30 parts by weight or less.

In addition to the above components, the acrylic monomer may further include other types of acrylic monomers distinguished from these. In particular, as will be described later, in the method of the present application, since an acrylic polymer is prepared through thermal polymerization and then further photopolymerized to improve a form more suitable for application to the final product, a (meth)acrylate monomer having a functional group suitable for photopolymerization may be additionally applied. That is, the acrylic polymer may further include a monomer containing a photoreactive functional group. Monomers containing such photoreactive functional groups include benzophenone-based (meth)acrylate monomers. Examples of the benzophenone-based (meth)acrylate monomer include Bensophenone methacrylate (BPMA), 6-(4-benzoylphenoxy)hexyl (meth)acrylate or benzophenone acrylate, From the viewpoint of forming a cross-linked structure, it is suitable to apply benzophenone methacrylate. In particular, in the case of benzophenone (meth)acrylate, since it is composed of an unsaturated functional group (ex. carbon = carbon double bond) and benzophenone, in the process of forming an acrylic polymer, the double bond included therein is released, and the acrylic monomer and Since it is polymerizable, it is possible to form a linear acrylic polymer, wherein benzophenone as a photopolymerization initiating component can constitute a side chain of a repeating unit of the acrylic polymer. Therefore, as will be described later, when the acrylic polymer is irradiated with active energy rays such as ultraviolet rays, crosslinking between the acrylic polymers may be achieved in the process of recovering hydrogen from the acrylic monomer having a hydrogen donating group. Crosslinking of such a linear polymer has an advantage suitable for improving the optical properties of the acrylic polymer.

The monomer mixture contains the polymerizable component as a main component. The meaning of the main component is as described above.

As described above, the acrylic polymer prepared according to the method of the present application is a low molecular weight polymer of 11 g/mol or less. Therefore, from the viewpoint of preventing an increase in the molecular weight of the polymer due to overpolymerization of the polymerizable component, the monomer mixture further includes a molecular weight regulator. The molecular weight modifier is a compound not involved in the polymerization reaction, and may refer to a material that increases or decreases the molecular weight of a polymerization product without affecting the polymerization rate.

As the molecular weight modifier, mercaptans such as t-dodecyl mercaptan or n-dodecyl mercaptan, terpenes of dipentene or t-terpene, chloroform, halogenated hydrocarbons of carbon tetrachloride, or pentaerythritol tetrakis 3-mercapto propionate or the like may be used, but is not limited thereto. In general, a mercaptan having a thiol group (-SH) is used as the molecular weight modifier.

As described above, since the molecular weight modifier is not a component involved in the polymerization reaction, if it remains in the acrylic polymer, it causes defects during post-curing or post-polymerization (by irradiation of active energy such as ultraviolet rays). Therefore, it is necessary to appropriately control the amount of the molecular weight modifier.

In the method of the present application, the content of the molecular weight modifier is adjusted within an appropriate range. Specifically, the monomer mixture includes a molecular weight modifier in a ratio ranging from 0.15 parts by weight to 0.35 parts by weight based on 100 parts by weight of the polymerizable component. When the ratio of the molecular weight modifier is less than the above range, an acrylic polymer having a desired molecular weight cannot be obtained. In addition, when the ratio of the molecular weight modifier exceeds the above range, the molecular weight modifier remains even after the polymerization is completed, resulting in product defects. In another example, the ratio may be in the range of 0.15 parts by weight to 0.3 parts by weight, 0.2 parts by weight to 0.35 parts by weight, or 0.2 parts by weight to 0.3 parts by weight.

After the monomer mixture having the adjusted composition is introduced into a batch reactor, a step of thermally polymerizing the monomer mixture is performed. Since the polymerization reaction of the acrylic monomer proceeds as thermal polymerization, the starting temperature of the reaction is also appropriately controlled. For example, the starting temperature of the thermal polymerization is 75°C or higher. When the reaction initiation temperature does not reach the above temperature, the acrylic polymer of the desired molecular weight cannot be produced, or the amount of the molecular weight modifier is excessively increased, resulting in an increase in the content of remaining unreacted monomers, thereby adversely affecting physical properties. The reaction initiation temperature, in another example, may be 80 °C or higher, 81 °C or higher, or 82 °C or higher, and may be 90 °C or lower, 88 °C or lower, 86 °C or lower, 85 °C or lower, or 84 °C or lower.

In the above, the reaction initiation temperature may refer to a temperature at which a polymerization reaction of an acrylic monomer into a polymer is initiated. The starting temperature may mean a temperature at which the reactor is set using a known heater, and specifically, may mean a temperature of the reactor set before introducing the monomer mixture into the reactor. In addition, since polymerization of acrylic monomers is usually an exothermic reaction, the reaction initiation temperature may be used as a concept different from the temperature during the polymerization of acrylic monomers.

In this application, since the polymerization reaction of acrylic monomers to acrylic polymers proceeds through thermal polymerization, a thermal polymerization initiator is introduced in the thermal polymerization step of the monomer mixture. On the other hand, the thermal polymerization initiator may be added together with the acrylic monomer and the molecular weight modifier included in the monomer mixture, or the monomer mixture is first introduced into the reactor, the reaction temperature is set to the above-mentioned temperature, and then the reaction is performed. It may be added in such a way that an appropriate amount is added at the time of initiation. That is, the thermal polymerization reaction may proceed while the thermal polymerization initiator is added. However, as described above, since the monomer mixture does not separately include a solvent in the method of the present application, the temperature of the reactor may rapidly increase depending on the reaction rate of the polymerization reaction. In addition, the physical properties of the desired acrylic polymer may vary depending on the amount of the thermal polymerization initiator applied. Therefore, from the viewpoint of securing the desired physical properties of the acrylic polymer and preventing safety problems in the polymerization reaction, it is necessary to properly control the amount and number of times of use of the thermal polymerization initiator.

For example, the thermal polymerization initiator is introduced into the reactor at a ratio of 0.005 parts by weight to 0.015 parts by weight based on 100 parts by weight of the polymerizable component per cycle. In another example, the ratio may be 0.006 parts by weight or more, 0.0065 parts by weight or more, 0.007 parts by weight or more, or 0.0075 parts by weight or more, 0.015 parts by weight or less, 0.0145 parts by weight or less, 0.014 parts by weight or less, 0.0135 parts by weight or less, 0.013 parts by weight or less. It may be less than 0.0125 parts by weight or less than 0.0125 parts by weight. The thermal polymerization initiator is added 5 or more times in the above ratio. Specifically, the thermal polymerization initiator may be added at a number within the range of 5 to 6 times.

Therefore, the total content of the thermal polymerization initiator added in the thermal polymerization step may be in the range of 0.025 parts by weight to 0.1 parts by weight based on 100 parts by weight of the polymerizable component. The number of inputs may also be appropriately adjusted within a range that satisfies the above total amount ratio.

Examples of the thermal polymerization initiator include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Wako (product)), 2,2-azobis- 2,4-dimethylvaleronitrile (V-65, Wako (product)), 2,2-azobisisobutyronitrile (V-60, Wako (product)) or 2,2-azobis-2-methyl azo-based initiators such as butyronitrile (V-59, Wako (product)); Dipropyl peroxydicarbonate (Peroyl NPP, NOF (product)), diisopropyl peroxy dicarbonate (Peroyl IPP, NOF (product)), bis-4-butylcyclohexyl peroxy dicarbonate (Peroyl TCP, NOF (product) )), diethoxyethyl peroxy dicarbonate (Peroyl EEP, NOF (first)), diethoxyhexyl peroxy dicarbonate (Peroyl OPP, NOF (first)), hexyl peroxy dicarbonate (Perhexyl ND, NOF (first)) ), dimethoxybutyl peroxy dicarbonate (Peroyl MBP, NOF (product)), bis (3-methoxy-3-methoxybutyl) peroxy dicarbonate (Peroyl SOP, NOF (product)), hexyl peroxy pival Perhexyl PV, NOF (product), amyl peroxy pivalate (Luperox 546M75, Atofina (product)), butyl peroxy pivalate (Perbutyl, NOF (product)), or trimethylhexanoyl peroxide (Peroyl 355, NOF a peroxyester compound such as (a)); Dimethyl hydroxybutyl peroxaneodecanoate (Luperox 610M75, Atofina (product)), amyl peroxy neodecanoate (Luperox 546M75, Atofina (product)) or butyl peroxy neodecanoate (Luperox 10M75, Atofina (product) a peroxy dicarbonate compound such as ))); acyl peroxides such as 3,5,5-trimethylhexanoyl peroxide, lauryl peroxide or dibenzoyl peroxide; ketone peroxide; dialkyl peroxide; peroxy ketals; Alternatively, one or two or more such peroxide initiators such as hydroperoxide may be used. In terms of securing the physical properties of the acrylic polymer desired in the present application, it may be appropriate to apply an azo-based initiator in the above.

In the present application, when the thermal polymerization initiator is added after the monomer mixture is introduced into the reactor, the thermal polymerization initiator is introduced into the reactor in the form of a solution dissolved in a known organic solvent, for example, a solvent such as ethyl acetate. may be When the thermal polymerization initiator is introduced in the form of a solution, the concentration of the thermal polymerization initiator in the solution may be, for example, 0.5% by weight to 2% by weight. On the other hand, even if the thermal polymerization initiator is added to the reactor in the form of a solution, the input amount of the thermal polymerization initiator is not as large as described above. Amounts may also be trace amounts. Therefore, even if the thermal polymerization initiator is added in the form of a solution, the polymerization reaction of the acrylic monomer may be regarded as a bulk polymerization reaction without using a solvent.

The method of the present application may further include photopolymerizing the monomer mixture. For example, after thermal polymerization of the monomer mixture proceeds to some extent, photopolymerization may further proceed. Specifically, when the conversion rate of the acrylic monomer to the polymer described later may be within a specific range or when the temperature of the reactor reaches a specific temperature, the thermal polymerization reaction may be terminated, and then the photopolymerization reaction may be further proceeded. The method of photopolymerization is not particularly limited, and photopolymerization may proceed through electron beam irradiation, visible light irradiation, or ultraviolet light irradiation. Generally, photopolymerization proceeds through ultraviolet irradiation.

Meanwhile, as described above, when the monomer mixture further includes a monomer containing a photoreactive functional group, physical properties of the acrylic polymer may be further improved through such a photopolymerization reaction.

In addition, in this photopolymerization process, the photopolymerization initiator is added to the monomer mixture in which the thermal polymerization reaction proceeds to a certain extent, for example, the conversion rate of the acrylic monomer to the polymer is within a specific range, for example, in the range of 70% to 80%. may additionally be included.

As the photopolymerization initiator, a benzoin-based, hydroxy ketone-based, amino ketone-based, or phosphine oxide-based photopolymerization initiator may be used, and specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin Isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylanino acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylaceto Phenone, 2-hydroxy-2-methyl-1-phenylpropan-1one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane -1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichloro Benzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, acetophenone dimethylketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1-[4-( 1-methylvinyl)phenyl]propanone] and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, etc. may be exemplified, but are not limited thereto.

The ratio of the photopolymerization initiator is not particularly limited, and may be freely added within a range that does not particularly affect the physical properties of the final product. For example, the photopolymerization initiator may be in the range of 0.01 part by weight to 10 parts by weight based on 100 parts by weight of the polymerizable component (eg, the total amount before inputting into the reactor) in the initial monomer mixture. In another example, the ratio may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, 0.2 parts by weight or more, 0.25 parts by weight or more, or 0.3 parts by weight or more, 5 parts by weight or less, 3 parts by weight or less, It may be 1 part by weight or less, 0.75 parts by weight or less, or 0.5 parts by weight or less.

The method may further include, for example, a step of diluting with a monomer for dilution so that the acrylic polymer has an appropriate solid content and an appropriate modulus change. The type of monomer for dilution is known, and, for example, the same or different components as the aforementioned polymerizable component may be applied.

This application also relates to acrylic polymers. For example, the acrylic polymer of the present application may be prepared by the method described above. Accordingly, the acrylic polymer of the present application may have a specific range of physical properties, and the acrylic polymer satisfying these physical properties is particularly suitable for application as a pressure-sensitive adhesive or adhesive, particularly an optical pressure-sensitive adhesive or optical adhesive.

Since the acrylic polymer of the present application is prepared by the above-described method, the acrylic copolymer is a reaction product of a mixture including a polymerizable component composed of one or more acrylic monomers, a molecular weight modifier, and a thermal polymerization initiator. Hereinafter, in the description of the acrylic polymer of the present application, contents overlapping with those described in the above method will be omitted.

The acrylic polymer of the present application has a molecular weight, specifically a weight average molecular weight, within a specific range. Specifically, the acrylic polymer of the present application has a molecular weight of 110,000 (g/mol) or less. In some cases, these polymers are also referred to as low molecular weight acrylic polymers. Such a low molecular weight acrylic polymer has a relatively high solid content at the same viscosity than a polymer having a higher molecular weight. Such a polymer can impart a rapid modulus change depending on temperature. For example, the acrylic polymer of the present application has a soft property at a high temperature, for example, within a temperature range of 40 ° C to 50 ° C, and when applied to a member having steps, it can sufficiently fill the gaps between the steps. In addition, the acrylic polymer of the present application has the advantage of being easy to cut because it has a somewhat hard property at room temperature, for example, within the range of 20 °C to 30 °C. From the viewpoint of ensuring durability of the adhesive film to which the acrylic polymer is applied, the weight average molecular weight of the polymer may, in another example, be 107,000 or less or 105,000 or less, 70,000 or more, 75,000 or more, 80,000 or more, It could be over 85,000 or over 90,000. The unit of molecular weight is g/mol unless otherwise specified.

The acrylic polymer of the present application has a polydispersity index of 3 or less. In the case of an acrylic polymer exceeding the above range, the viscosity is excessively high even under the condition of the same molecular weight, and when the viscosity is high, there is a problem in that it is difficult to coat a solution such as a composition containing the polymer. On the other hand, in the case of an acrylic polymer that satisfies the range of the polydispersity index described above, there is an advantage in that a uniform coating surface can be formed with little variation in thickness when a solution containing the acrylic polymer is coated. In particular, such a polydispersity index is a unique characteristic of a polymer that cannot be achieved by a method other than the present application, for example, a method for producing an acrylic polymer using a continuous polymerization reactor. The polydispersity index, in another example, may be in the range of 2 to 2.5. The meaning of the polydispersity index may be applied as it is commonly used in the art, and may mean, for example, the ratio (Mw/Mn) of the weight average molecular weight (Mw) and number average molecular weight (Mn) of a polymer. The method for measuring the polydispersity index follows the method mentioned in Examples to be described later.

The acrylic polymer of the present application has a degree of reaction of acrylic monomers to the polymer, for example, a conversion rate within a specific range, for example, a range of 70% to 80%. That is, the acrylic polymer satisfies the following formula 1:

[Equation 1]

0.7 ≤ (A/B) ≤ 0.8

In Equation 1, A is the weight of the acrylic polymer after drying at 150 °C for 50 minutes, and B is the weight of the acrylic polymer before drying.

When the conversion rate of the acrylic polymer does not satisfy the above range, that is, when the A / B value in Equation 1 is less than 0.7, the content of the molecular weight modifier remaining in the monomer mixture increases, so in the additional photopolymerization process, unreacted monomers content will increase. In addition, when the A/B value in Equation 1 exceeds 0.8, there is a problem in that the reaction components are not smoothly mixed in the reactor. In another example, the value of A/B in Equation 1 may be 0.71 or more, 0.72 or more, 0.73 or more, 0.74 or more, or 0.75 or more, and may be 0.79 or less.

An acrylic polymer having the above-mentioned properties can be achieved, in particular, by the above-mentioned production method. That is, by using a batch reactor as a reactor applied to the polymerization reaction of acrylic monomers to acrylic polymers, and controlling the reaction initiation temperature, the content of the molecular weight modifier, the amount and number of additions of the thermal polymerization initiator, etc. in the above-described manner, , polydispersity index and conversion rate are within a specific range, and an acrylic polymer particularly suitable for application as an optical pressure-sensitive adhesive (or adhesive) can be prepared.

As described above, since photopolymerization may also proceed following thermal polymerization into the acrylic polymer of the present application, the mixture forming the acrylic polymer may further include a photopolymerization initiator. That is, in another example, the acrylic polymer may be a reaction product of a mixture including a polymerizable component composed of one or more acrylic monomers, a molecular weight regulator, a thermal polymerization initiator, and a photopolymerization initiator.

In another example, from the viewpoint of preventing the change over time of the acrylic monomer (excessive increase in the degree of curing over time) and maintaining the appearance of the final product, the residual monomer of the acrylic polymer that can be prepared by further proceeding with photopolymerization It is appropriate that the content is adjusted. The residual monomer content of the acrylic polymer may be, for example, 4% by weight or less. That is, the acrylic polymer may satisfy Equation 2 below:

[Equation 2]

(1-A/B)≤0.04

In Equation 2, A and B are as described in Equation 1 above.

The lower limit of the value of Equation 2 is not particularly limited because the closer to 0, the better. In another example, the value of Equation 2 may be 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, or 0.015 or less.

Acrylic polymers satisfying the above characteristics have an advantage that they are particularly suitable for application to pressure-sensitive adhesives or adhesives that require optical transparency.

This application also relates to a pressure-sensitive adhesive composition, adhesive composition, pressure-sensitive adhesive layer or adhesive layer.

The pressure-sensitive adhesive composition or adhesive composition includes the aforementioned acrylic polymer. In addition, other components required to exhibit the adhesive or adhesive function may be applied to the pressure-sensitive adhesive composition or the adhesive composition without limitation.

Since the pressure-sensitive adhesive layer (adhesive layer) can be prepared by curing the pressure-sensitive adhesive composition (adhesive composition), it may be a cured product of the composition. The curing method or conditions are not particularly limited.

The method of the present application can produce an acrylic polymer having a specific molecular weight, polydispersity index and conversion rate.

The method of the present application can prepare an acrylic polymer capable of minimizing the content of unreacted monomers remaining when further polymerized by irradiation with active energy rays or the like.

Since the acrylic polymer of the present application has a specific molecular weight, polydispersity index and conversion rate and the content of unreacted monomers is minimized, it is particularly suitable for the optical pressure-sensitive adhesive (or adhesive) field.

Although the present application is specifically described through the following examples, the scope of the present application is not limited by the following examples.

[Experimental Example]

1. Measurement of weight average molecular weight and polydispersity index

The weight average molecular weight and polydispersity index of the acrylic polymers prepared in Examples and Comparative Examples were measured under the following conditions using Gel Permeation Chromatograph (GPC). In the preparation of the calibration curve, the measurement results were converted using standard polystyrene of the Agilent system.

Meter: Agilent GPC (Agilent 1260)

Column: Connect 2 PL Mixed B

Column temperature: 40 °C

Eluent: THF (tetrahydrofuran)

Flow Rate: 1.0 mL/min

Concentration: ~2 mg/mL (100 μL injection)

2. Measurement of conversion rate of acrylic polymer and content of unreacted monomer components

The conversion rate of the acrylic polymer prepared in Examples and Comparative Examples and the content of unreacted monomer components were measured in the following manner.

(1) After taking about 0.5 g of acrylic polymer, prepare a specimen coated on an aluminum dish.

(2) Put the specimen in an oven (Jeotech, OF-12), dry at a temperature of 150 ℃ for about 50 minutes, and then measure the weight of the specimen.

(3) The value obtained by subtracting the weight of the aluminum dish from the weight measured in (1) above is the value obtained by subtracting the weight of the aluminum dish from the weight measured in (2) below in Formula 1 and Formula 2 B. It is measured by substituting into A of General Formula 1 and General Formula 2. Values obtained by multiplying each of the resultant values measured in Formulas 1 and 2 below by 100 and converted into percentages are listed in Table 1 below.

[Formula 1]

(A/B)

[Formula 2]

(1-A/B)

[Production Example]

Example 1

Preparation of acrylic polymers

As polymerizable components, 2-ethylhexyl acrylate (2-EHA), 2-ethylhexyl methacrylate (2-EHMA), hydroxyethyl acrylate (HEA), N,N-dimethyl acrylamide (DMAA), meta Krillamide (MAA) at a weight ratio of 60:18:5:15:2 (2-EHA:2-EHMA:HEA:DMAA:MAA), based on 100 parts by weight of the polymerizable component, as a molecular weight modifier (n-dodecylmercaptan ) 0.2 parts by weight was mixed to prepare a monomer mixture. The monomer mixture was introduced into a 2 L batch reactor in which nitrogen gas was refluxed and a cooling device was installed to facilitate temperature control. Nitrogen gas was then purged for 1 hour to remove oxygen. The temperature of the reactor was then set to about 82 °C. Then, based on 100 parts by weight of the total weight of the polymerizable component, about 0.01 part by weight of a thermal polymerization initiator (V-70, Wako Co., added in the form of a solution diluted in ethyl acetate to a concentration of about 1% by weight) was added to 5 time was put in. As a result of the reaction for about 4 hours, a polymer mixture containing an acrylic polymer having a weight average molecular weight of about 99,000 (g/mol) and a conversion rate of about 75% was prepared.

A photopolymerization initiator (Irgacure 184) was added to the polymer mixture in an amount of 0.3 parts by weight based on 100 parts by weight of the polymerizable component. The polymer mixture was then coated between known release PET substrates to a thickness of about 150 μm. Thereafter, an appropriate amount of ultraviolet light was irradiated using a known ultraviolet coating machine to photopolymerize the acrylic polymer, and as a result, a film having a thickness of about 100 μm was prepared. The content of the monomer component remaining in the film was about 1.4%.

Example 2 and Comparative Examples 1 to 5

An acrylic polymer was prepared in the same manner as in Example 1, except that the temperature of the reactor, the number of additions of the thermal polymerization initiator, and the concentration of the molecular weight modifier were adjusted as shown in Table 2 below. In addition, the evaluation results of the physical properties of the polymer are shown in Table 1.

Example comparative example One 2 One 2 3 4 5 Reactor temperature (℃) 82 82 62 72 72 82 82 thermal polymerization initiator
Number of inputs (times) 5 6 5 6 7 4 5 Concentration of molecular weight modifier (parts by weight) 0.2 0.3 0.4 0.5 0.5 0.1 0.1 Polymer molecular weight (10,000 g/mol) 9.9 9.5 12 9.5 10.8 9.3 10.5 Polymer Conversion (%) 75 79 72 75 85 68 75 Polydispersity Index (-) 2.9 2.5 2.3 2.2 2.4 3.5 3.7 Residual monomer content (%) 1.40 1.35 4.5 5.21 4.88 1.29 1.13 Parts by weight: based on 100 parts by weight of polymerizable component

[Review]

The physical properties of the acrylic polymer suitable for application as an optical pressure-sensitive adhesive are as follows.

(1) Weight average molecular weight: 110,000 g/mol or less

(2) Conversion rate of acrylic polymer: 70% to 80%

(3) Polydispersity index: 3 or less

(4) Concentration of residual monomer when filmed: 4% or less

In the case of Examples 1 and 2, which are acrylic polymers prepared under the conditions specified in the present application through Table 1, it can be confirmed that all of the above physical properties are satisfied. Therefore, it can be confirmed that the acrylic polymers of Examples 1 and 2 are suitable for application as an optical pressure-sensitive adhesive.

However, in the case of Comparative Examples 1 to 5 relating to acrylic polymers not prepared under the conditions stipulated in the present application, it can be seen that at least one of the above physical properties is not satisfied. Therefore, it can be confirmed that the acrylic polymers of Comparative Examples 1 to 5 are not suitable for application as an optical pressure-sensitive adhesive.

Claims (21)

As a method for producing an acrylic polymer using a batch reactor,
The acrylic polymer is a low molecular weight acrylic polymer having a weight average molecular weight of 110,000 g / mol or less,
The manufacturing method may include introducing a monomer mixture including a polymerizable component composed of one or more acrylic monomers and a molecular weight modifier into the reactor; thermally polymerizing the monomer mixture; And photopolymerizing the monomer mixture,
The onset temperature of the thermal polymerization is 75 ° C or higher,
The thermal polymerization is carried out by adding a thermal polymerization initiator at least 5 times at a ratio within the range of 0.005 parts by weight to 0.015 parts by weight based on 100 parts by weight of the polymerizable component,
The monomer mixture is a method for producing an acrylic polymer comprising a molecular weight modifier in a ratio of 0.15 parts by weight to 0.35 parts by weight based on 100 parts by weight of the polymerizable component. The method for producing an acrylic polymer according to claim 1, wherein the monomer mixture is a non-solvent type monomer mixture. The method for producing an acrylic polymer according to claim 1, wherein the thermal polymerization initiator is an azo compound. The method of claim 1, wherein the molecular weight modifier is a compound containing a thiol group (-SH). The method of claim 1, wherein the thermal polymerization is performed at a temperature in the range of 80 °C to 90 °C. The method of claim 1, wherein the thermal polymerization is performed by adding the thermal polymerization initiator 5 to 6 times at a ratio within the range of 0.0075 parts by weight to 0.0125 parts by weight based on 100 parts by weight of the polymerizable component. The method of claim 6, wherein the thermal polymerization initiator added in the thermal polymerization step is in the range of 0.025 parts by weight to 0.1 parts by weight based on 100 parts by weight of the polymerizable component. The method of claim 1, wherein the monomer mixture comprises a molecular weight modifier in an amount of 0.2 to 0.3 parts by weight based on 100 parts by weight of the polymerizable component. The method of claim 1, wherein the acrylic monomer includes an alkyl (meth)acrylate monomer and a polar functional group-containing monomer. 10. The method of claim 9, wherein the polar functional group-containing monomer is at least one of a hydroxy group-containing alkyl (meth)acrylate monomer and a nitrogen-containing monomer. 10. The method of claim 9, wherein the acrylic monomer further comprises a monomer containing a photoreactive functional group. The method for preparing an acrylic polymer according to claim 11, wherein the monomer containing a photoreactive functional group is a benzophenone-based (meth)acrylate monomer. delete The method of claim 1, wherein the monomer mixture further comprises a photopolymerization initiator. delete delete delete delete delete delete delete