JP5888648B2 - Method for producing temperature-sensitive adhesive - Google Patents

Description

  The present invention relates to a thermosensitive adhesive whose adhesive strength is reduced at a predetermined temperature and a method for producing the same.

  The temperature-sensitive adhesive contains a side chain crystalline polymer as a main component, and when cooled to a temperature lower than the melting point of the side chain crystalline polymer, the side chain crystalline polymer is crystallized to cause adhesive force. It is a pressure-sensitive adhesive that decreases. In the conventional temperature-sensitive adhesive, the monomer constituting the side chain crystalline polymer is usually polymerized by free radical polymerization.

  However, in free radical polymerization, side reactions such as a recombination reaction occur, so that the side chain crystalline polymer is unlikely to have a high molecular weight, its molecular weight distribution (Mw / Mn) tends to be wide, and the monomer tends to remain. Such a temperature-sensitive pressure-sensitive adhesive containing a side-chain crystalline polymer may have insufficient cohesive force and insufficient heat resistance.

  On the other hand, as a method for solving the problems caused by free radical polymerization, atom transfer radical polymerization (hereinafter referred to as “ATRP”), which is one of living radical polymerizations, is known. The present applicant has developed the temperature-sensitive adhesive described in Patent Document 1 by adopting this ATRP. According to this temperature-sensitive adhesive, the monomers constituting the side chain crystalline polymer are polymerized by ATRP, so that the molecular weight distribution and molecular weight distribution (Mw / Mn) of the side chain crystalline polymer can be narrowed. Although possible, the reaction time was long and there were problems with productivity.

JP 2004-2684 A

  An object of the present invention is to provide a temperature-sensitive pressure-sensitive adhesive which has a high molecular weight and contains a side chain crystalline polymer having a narrow molecular weight distribution (Mw / Mn), and which can be easily produced, and a method for producing the same. .

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means having the following constitution and have completed the present invention.
(1) A temperature-sensitive adhesive containing a side-chain crystalline polymer, the adhesive strength of which decreases at a temperature lower than the melting point of the side-chain crystalline polymer, wherein the side-chain crystalline polymer is side-chain crystalline. A temperature-sensitive adhesive comprising a polymer obtained by polymerizing monomers constituting a polymer by atom transfer radical polymerization under pressure.
(2) The temperature-sensitive adhesive according to (1), wherein the side chain crystalline polymer has a weight average molecular weight (Mw) of 1 million or more and a molecular weight distribution (Mw / Mn) of 5 or less.
(3) A method for producing a temperature-sensitive pressure-sensitive adhesive containing a side-chain crystalline polymer and having reduced adhesive strength at a temperature lower than the melting point of the side-chain crystalline polymer, and constituting the side-chain crystalline polymer A method for producing a temperature-sensitive adhesive, wherein a monomer is polymerized by atom transfer radical polymerization under pressure.

  According to the present invention, the contained side chain crystalline polymer has a high molecular weight and has an effect that the molecular weight distribution (Mw / Mn) is narrow and the production is easy.

  The temperature-sensitive adhesive of the present invention contains a side chain crystalline polymer. The side chain crystalline polymer is a polymer that is crystallized at a temperature lower than the melting point and exhibits phase flow at a temperature higher than the melting point. That is, the side chain crystalline polymer is a polymer that reversibly causes a crystalline state and a fluid state in response to a temperature change.

  The temperature-sensitive adhesive of the present invention contains a side-chain crystalline polymer in such a ratio that the adhesive strength decreases when the side-chain crystalline polymer is crystallized at a temperature below the melting point. That is, the temperature-sensitive adhesive of the present invention contains a side chain crystalline polymer as a main component. This makes it possible to reversibly control the adhesive force by heat. That is, when the temperature-sensitive adhesive is peeled from the adherend, if the temperature-sensitive adhesive is cooled to a temperature below the melting point of the side-chain crystalline polymer, the side-chain crystalline polymer is crystallized. Adhesive strength decreases. In addition, if the temperature-sensitive adhesive is heated to a temperature equal to or higher than the melting point of the side chain crystalline polymer, the adhesive strength is restored by the fluidity of the side chain crystalline polymer, so that it can be used repeatedly.

  The melting point means a temperature at which a specific portion of the polymer that is initially aligned in an ordered arrangement becomes disordered by an equilibrium process, and is measured using a differential thermal scanning calorimeter (DSC) at 10 ° C./min. It is a value obtained by measuring with. As melting | fusing point, it is preferable that it is 20 degreeC or more, and it is more preferable that it is 20-60 degreeC. The melting point can be arbitrarily set to a predetermined value by changing the composition of the side chain crystalline polymer.

  The side chain crystalline polymer is composed of a polymer obtained by polymerizing a monomer constituting the side chain crystalline polymer (hereinafter sometimes referred to as “monomer”). Examples of the monomer include (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, and a polar monomer.

  Examples of the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms include 16 to 22 carbon atoms such as cetyl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate, and behenyl (meth) acrylate. (Meth) acrylate having a linear alkyl group of, for example, (meth) acrylate having an alkyl group having 1 to 6 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate Hexyl (meth) acrylate and the like, and as the polar monomer, for example, ethylenically unsaturated monomer having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid; 2-hydroxyethyl (Meth) acrylate, 2-hydride Kishipuropiru (meth) acrylate, 2-hydroxyhexyl (meth) ethylenically unsaturated monomers having a hydroxyl group such as acrylate and the like, which may be used alone or in combination.

  As a polymerization ratio of the monomer, 30 to 100 parts by weight of a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, and 0 to 70 parts by weight of a (meth) acrylate having an alkyl group having 1 to 6 carbon atoms. The polar monomer is preferably 0 to 10 parts by weight.

  Polymerization of the monomer is performed by ATRP. ATRP is one of the living radical polymerizations as described above. According to ATRP, a polymer having a high molecular weight and a narrow molecular weight distribution can be obtained. Various shapes of polymers such as block copolymers and star polymers can be synthesized by applying plural types of monomers, selecting an initiator, and the like.

  ATRP is performed by adding an initiator and a catalyst to the monomer. Examples of the initiator include organic halides. Examples of the organic halide include organic halides having a highly reactive carbon-halogen bond, carbonyl compounds having a halogen atom at the α-position, and halogen atoms at the benzyl-position. Specifically, there may be mentioned, for example, methyl 2-bromo (or chloro) propionate, ethyl 2-bromo (or chloro) propionate, methyl 2-bromo (or chloro) -2-methylpropionate, Examples include 2-bromo (or chloro) -2-methylpropionate ethyl, 1-bromo (or chloro) ethylbenzene, and the like. The addition amount of the initiator is suitably about 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the total amount of monomers in terms of solid content.

  Examples of the catalyst include a transition metal complex. Examples of the transition metal complex include a metal complex having a group 7 element, 8 group, 9 group, 10 group, or 11 group element as a central metal. Preferred examples include 0-valent or monovalent copper, divalent ruthenium, divalent iron, divalent nickel complexes, and the like. Among these, copper complexes are preferable. Specific examples of the monovalent copper compound include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide and the like. The addition amount of the catalyst is suitably about 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the total amount of monomers in terms of solid content.

  When a copper compound is used as a catalyst, it is preferable to further add a ligand (ligand) in order to enhance the catalytic activity. Examples of the ligand include 2,2′-bipyridyl and derivatives thereof, 1,10-phenanthroline and derivatives thereof, tetramethylethylenediamine, pentamethyldiethyleneamine, hexamethyl (2-aminoethyl) amine, and tris (2-dimethylamino). And polyamines such as ethyl) amine, mercaptan derivatives, and trifluorate derivatives. The addition amount of the ligand is suitably about 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the total amount of monomers in terms of solid content.

  When a ruthenium compound is used as a catalyst, it is preferable to further add aluminum alkoxides or the like as an activator. As the catalyst, for example, a divalent iron bistriphenylphosphine complex, a divalent nickel bistriphenylphosphine complex, a divalent nickel bistributylphosphine complex, and the like are also suitable.

  ATRP can be carried out without solvent or in a solvent. Examples of the solvent include hydrocarbons such as benzene, toluene and heptane; ethers such as diethyl ether and tetrahydrofuran; halogenated hydrocarbons such as methylene chloride and chloroform; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Alcohols such as ethanol, 2-propanol, isopropanol, n-butyl alcohol, t-butyl alcohol; nitriles such as acetonitrile, propionitrile, benzonitrile; acetates such as ethyl acetate and butyl acetate; ethylene carbonate, etc. Carbonates; dimethylacetamide and the like. These may be used alone or in combination of two or more.

  When ATRP is carried out in a solvent, the solid concentration is preferably about 10 to 50% by weight. Further, when ATRP is carried out in a solvent, it is preferable to isolate the polymer from the solvent by adding the polymerization solution after completion of the reaction to a large amount of solvent and filtering and drying the resulting precipitate. . The precipitation may be repeated a plurality of times to increase the purity of the polymer. Examples of the solvent used for the precipitation include the same solvents as those exemplified above for the ATRP solvent. Among these, a solvent that can be precipitated may be arbitrarily selected in consideration of the solvent used for ATRP. The precipitate is preferably dried under reduced pressure.

  ATRP is preferably performed in an inert atmosphere, for example, in an inert gas atmosphere such as argon gas or nitrogen gas, or in a state where oxygen is lyophilized to remove oxygen from the reaction system.

  The reaction temperature of ATRP is preferably 0 to 200 ° C, more preferably 40 to 150 ° C.

  Here, in the present invention, the above-described ATRP is performed under pressure. Thereby, the reaction time of ATRP can be shortened compared with the case of performing under normal pressure, ie, 1 atmosphere (atm). The reason for this is that when ATRP is performed under pressure, the distance between adjacent monomers decreases, and as a result, the monomers are easily brought into contact with each other and the polymerization reaction is promoted. It is assumed that

  The pressurization condition is not particularly limited as long as the pressure is higher than 1 atm. However, a high pressure is preferable in order to reliably reduce the reaction time of ATRP. Specifically, the pressure is preferably 2000 atmospheres or more, more preferably 4000 atmospheres or more, and further preferably 6000 atmospheres or more. In addition, since a very high pressure is industrially difficult, about 10,000 atmospheres is appropriate as an upper limit of the pressure.

  The reaction time of ATRP performed under pressure is usually about 1 to 30 hours.

  When the monomer is polymerized by ATRP under pressure, the side chain crystalline polymer can be made high molecular weight and the molecular weight distribution (Mw / Mn) can be narrowed while shortening the reaction time. More specifically, the weight average molecular weight (Mw) of the side chain crystalline polymer can be 1 million or more, preferably 1.5 million or more, and the molecular weight distribution (Mw / Mn) is 5 or less. Can be.

  In addition, as an upper limit of the weight average molecular weight (Mw) of a side chain crystalline polymer, about 2 million is suitable. The weight average molecular weight (Mw) is a value obtained by measuring a polymer constituting the side chain crystalline polymer by gel permeation chromatography (GPC) and converting the obtained measurement value into polystyrene. The molecular weight distribution (Mw / Mn) is a value calculated from the formula: weight average molecular weight (Mw) / number average molecular weight (Mn). The number average molecular weight (Mn) is a value obtained by converting the measured value of GPC to polystyrene as in the case of the weight average molecular weight (Mw).

  The usage form of the above-described temperature-sensitive adhesive of the present invention is not particularly limited, and may be used by directly applying to the adherend, for example, or may be a baseless sheet-like form, You may use it with the form of an adhesive sheet.

  Moreover, the temperature sensitive adhesive of this invention can also be used with the form of an adhesive tape. In this case, what is necessary is just to provide the adhesive layer which consists of a thermosensitive adhesive of this invention in the at least single side | surface of a base film.

  As a constituent material of the base film, for example, polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, polyvinyl chloride, etc. Synthetic resins are mentioned.

  The base film may be either a single layer or a multilayer and its thickness is usually about 5 to 500 μm. The base film can be subjected to surface treatment such as corona discharge treatment, plasma treatment, blast treatment, chemical etching treatment, primer treatment, etc., in order to improve the adhesion to the pressure-sensitive adhesive layer.

  In order to provide the pressure-sensitive adhesive layer on at least one side of the base film, a coating solution obtained by adding the temperature-sensitive adhesive of the present invention to a solvent may be applied to at least one side of the base film with a coater or the like and dried. . Various additives such as a crosslinking agent, a tackifier, a plasticizer, an anti-aging agent, and an ultraviolet absorber can be added to the coating solution. Examples of the coater include a knife coater, a roll coater, a calendar coater, a comma coater, a gravure coater, and a rod coater.

  It is preferable to provide a release film on the surface of the pressure-sensitive adhesive sheet or the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape. Examples of the release film include those obtained by applying a release agent such as silicone to the surface of a film made of polyethylene terephthalate or the like.

  The use of the above-described temperature-sensitive adhesive of the present invention is not particularly limited, and for example, it can be suitably used as an adhesive in a field where heat resistance or the like is required.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example. In the following description, “part” means part by weight.

  First, 43 parts by weight of behenyl acrylate manufactured by NOF Corporation, 54 parts by weight of methyl acrylate manufactured by Nippon Shokubai Co., Ltd., and 3 parts by weight of 2-hydroxyethyl acrylate manufactured by Nippon Shokubai Co., Ltd. were mixed to form a monomer mixture. Obtained. The initiator, catalyst and ligand were then added to the monomer mixture. The composition and addition amount of the added initiator, catalyst and ligand are as follows.

<Composition of initiator, catalyst and ligand>
Initiator: Ethyl 2-bromo-2-methylisobutylate (EBB)
Catalyst: Cuprous bromide (CuBr)
Ligand: tris (2-dimethylaminoethyl) amine (Me ₆ TREN)

<Addition amount of initiator, catalyst and ligand>
Initiator: 0.3 parts by weight with respect to 100 parts by weight of total monomer in terms of solid content Catalyst: 0.4 parts by weight with respect to 100 parts by weight of total amount of monomer in terms of solid content Ligand: monomer in terms of solid content 1.0 part by weight per 100 parts by weight of total

  Next, the monomer mixture to which the initiator, the catalyst and the ligand are added is adjusted with a mixed solvent of ethyl acetate: heptane = 7: 3 (weight ratio) so that the solid concentration becomes 30% by weight, and the mixed solution is prepared. Obtained. Then, nitrogen gas was blown into the mixed solution to sufficiently remove oxygen in the mixed solution, and then the monomer was polymerized by ATRP under pressure. The pressurizing conditions are as follows.

<Pressurizing conditions>
Pressure: 6000 atmospheres Reaction temperature: 60 ° C
Reaction time: 24 hours Pressurizer: A high-pressure reactor manufactured by Hikari Kouhiki Co., Ltd. was used.
Others: Monomers and the like are accommodated in a polyethylene resin raw material container, and after this raw material container is accommodated in a Teflon (registered trademark) high pressure reaction vessel provided in the pressurizing device, the outer periphery of the high pressure reaction vessel is By pressurizing, the monomer in the raw material container was pressurized.

  After completion of the reaction, the polymerization solution was added to a large amount of 2-propanol, and the resulting precipitate was filtered and dried under reduced pressure to isolate the produced copolymer. About the obtained copolymer, the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and melting | fusing point were measured. Each measurement method is shown below, and the results are shown in Table 1.

<Method for measuring weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)>
The weight average molecular weight (Mw) was obtained by measuring the copolymer with GPC and converting the obtained measurement value into polystyrene. The molecular weight distribution (Mw / Mn) was calculated by applying the weight average molecular weight (Mw) and the number average molecular weight (Mn) to the formula: weight average molecular weight (Mw) / number average molecular weight (Mn). In addition, the number average molecular weight (Mn) used for calculation of molecular weight distribution (Mw / Mn) was obtained by converting the measured value of GPC into polystyrene as with the weight average molecular weight (Mw). The monomer conversion was calculated by a nuclear magnetic resonance apparatus, and the theoretical molecular weight was calculated from the ratio of the monomer and the initiator.

<Measuring method of melting point>
The copolymer was obtained by measuring by DSC under measurement conditions of 10 ° C./min.

[Comparative example]
45 parts of behenyl acrylate manufactured by NOF Co., 50 parts of methyl acrylate manufactured by Nippon Shokubai Co., Ltd., 5 parts of acrylic acid, and 0.2 part of initiator “Perbutyl ND” manufactured by NOF Co., Ltd. In addition to 230 parts of ethyl, they were mixed and stirred at 55 ° C. for 4 hours under 1 atm. These monomers were polymerized by free radical polymerization to obtain a copolymer.

  About the obtained copolymer, it carried out similarly to the Example, and measured the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and melting | fusing point. The results are shown in Table 1.

  As is clear from Table 1, the copolymer of the example, that is, the side chain crystalline polymer, has a higher molecular weight than the side chain crystalline polymer of Comparative Example 1 by conventional free radical polymerization and has a molecular weight distribution (Mw). / Mn) is also narrow. Further, the side chain crystalline polymers of the examples were easy to manufacture because the reaction time was as short as 24 hours as ATRP. Therefore, the temperature-sensitive adhesive containing the side chain crystalline polymer of the examples is excellent in productivity and can be expected to have high heat resistance.

Claims (1)

A method for producing a temperature-sensitive adhesive comprising a side-chain crystalline polymer, wherein the adhesive strength is reduced at a temperature below the melting point of the side-chain crystalline polymer,
The side chain crystalline polymer has a weight average molecular weight (Mw) of 1 million or more, and a molecular weight distribution (Mw / Mn) of 5 or less;
The monomer constituting the side chain crystalline polymer includes a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, a (meth) acrylate having a C 1-6 alkyl group, and a polar monomer, A method for producing a temperature-sensitive adhesive, wherein a monomer is polymerized by atom transfer radical polymerization under pressure.