JP2013116935A - Adhesive composition and adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive tape that has excellent adhesive strength and retentivity under room temperature and under high temperature even if a crosslinking agent is not used.SOLUTION: An adhesive composition that contains an acrylic copolymer as a base component, wherein the acrylic copolymer contains as monomer components: a (meth)acrylate monomer (a); a polar group-containing monomer (b); and a monomer (c) in which the glass transition temperature of homopolymer is 20°C or more. The content of the polar group-containing monomer (b) is 5 mass% of the monomer components that forms the acrylic copolymer. With the adhesive composition, an adhesive tape can be achieved which has excellent adhesive strength and retentivity under room temperature and under high temperature even if a crosslinking agent is not used.

Description

  The present invention relates to a pressure-sensitive adhesive composition that provides a pressure-sensitive adhesive tape that can be suitably attached to an adherend and fixed between articles without using a crosslinking agent.

Adhesive tape is a bonding means with excellent workability and high bonding reliability. It is used to fix parts in various industrial fields such as OA equipment, IT / home appliances, automobiles, temporarily fix parts, and label to display product information. Used for applications. Typical characteristics necessary for securing adhesion reliability include heat resistance and peeling resistance. In order to secure these, it is necessary to improve the cohesive strength of the pressure-sensitive adhesive. Generally, a cross-linked pressure-sensitive adhesive composition is used.
On the other hand, when focusing on the production process of adhesive tape, it is required to eliminate the aging process from the viewpoint of production efficiency with respect to the aging process after coating and drying the adhesive composition containing the crosslinking agent. ing.

  As the non-crosslinked adhesive composition, for example, an adhesive composition using a block copolymer composed of a polymer block having a high glass transition temperature such as styrene and an acrylic polymer block is disclosed ( Patent Document 1). It is disclosed that the pressure-sensitive adhesive composition satisfies adhesive force and cohesive force without being subjected to crosslinking treatment, and can realize good adhesive properties at room temperature. However, the pressure-sensitive adhesive composition has insufficient characteristics relating to heat resistance and peeling resistance, and further improvement of the characteristics has been demanded.

JP 2003-096421 A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition having an excellent adhesive force at a high temperature and a high holding power without using a crosslinking agent.

In the present invention, an adhesive composition mainly comprising an acrylic copolymer,
The acrylic copolymer contains, as a monomer component, a (meth) acrylate monomer (a), a polar group-containing monomer (b), and a monomer (c) having a glass transition temperature of 20 ° C. or higher as a homopolymer. A high temperature adhesive force and a high holding force can be realized by the pressure-sensitive adhesive composition in which the content of the group-containing monomer (b) is 5% by mass in the monomer component constituting the acrylic copolymer.

  According to the pressure-sensitive adhesive composition of the present invention, a suitable adhesive force can be realized at room temperature without using a cross-linking agent, and it has a suitable holding force due to an excellent cohesive force. Moreover, since excellent adhesive force and holding force can be realized even at high temperatures, it can be suitably applied to various label applications and component fixing applications.

[Acrylic copolymer]
The acrylic copolymer used in the pressure-sensitive adhesive composition of the present invention has, as a monomer component, a glass transition temperature of (meth) acrylate monomer (a), polar group-containing monomer (b), and homopolymer of 20 ° C. or higher. The pressure-sensitive adhesive composition contains the monomer (c) and the content of the polar group-containing monomer (b) is 5% by mass or more in the monomer component constituting the acrylic copolymer.

  As the (meth) acrylate monomer (a), a (meth) acrylate monomer used in a general acrylic pressure-sensitive adhesive composition can be used as appropriate, for example, a (meth) acrylate having an acryloyl group having 1 to 14 carbon atoms. Can be used. Specifically, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) ) Acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (Meth) acrylate, n-tetradecyl (meth) acrylate, etc. can be illustrated. As the (meth) acrylate monomer (a), a polar group-containing monomer (b) described later and a monomer not corresponding to the monomer (c) having a glass transition temperature of 20 ° C. or higher are preferably used. .

  Especially, it is preferable to use the (meth) acrylate monomer whose glass transition temperature of a homopolymer is 0 degrees C or less, More preferably, it is -20 degrees C or less, More preferably, it is -60 to -30 degreeC. A (meth) acrylate monomer having a glass transition temperature in the above range is preferable because suitable adhesiveness can be easily secured. The glass transition temperature of the homopolymer can be referred to the glass transition temperature disclosed in POLYMER HANDBOOK (THIRD EDTION, J. BRANDRUP and EH IMMERGUT, A WILEY-INTERSCIENCE PUBLICATION, 1989).

  Among the above (meth) acrylate monomers (a), n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isooctyl acrylate are preferable because they can easily realize particularly suitable adhesive force. Furthermore, n-butyl (meth) acrylate can be particularly preferably used because it easily achieves a particularly excellent high-temperature adhesive force, and 2-ethylhexyl (meth) acrylate easily secures an adhesive force at low temperatures.

  The content of the (meth) acrylate monomer (a) in the acrylic copolymer is preferably 25% by mass or more, and preferably 40 to 85% by mass, in the monomer component constituting the acrylic copolymer. Is more preferable, and it is still more preferable to set it as 50-70 mass%. It becomes easy to implement | achieve suitable adhesiveness by making content of a (meth) acrylate monomer (a) into the said range.

  In the present invention, by using together the polar group-containing monomer (b) as a monomer component constituting the acrylic copolymer, it is possible to ensure excellent cohesion, excellent adhesion at high temperatures, and high holding power. Can be realized. Examples of polar group-containing monomers include vinyl monomers having a polar group such as a hydroxyl group, a carboxyl group, an amino group, an imino group, or an amide group. It is preferable because it is easy to contribute to improvement of force. Among them, a polar group-containing vinyl monomer that can form a hydrogen bond can be preferably used, and the hydroxyl group-containing vinyl monomer is excellent in adhesion and stability over time of the pressure-sensitive adhesive layer after bonding, and realizes excellent cohesion. It is particularly preferable because it is easy. These polar group-containing monomers may be used in combination as appropriate, and when used together, a hydroxyl group-containing vinyl monomer may be used, and the hydroxyl group-containing monomer and another polar group-containing vinyl monomer may be used in combination. Particularly preferred. In addition, it is preferable to use the monomer which does not correspond to the monomer (c) whose glass transition temperature of the homopolymer mentioned later is 20 degreeC or more as the said polar group containing monomer (b).

  Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl ( (Meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, etc. Can be used. Among these, 2-hydroxyethyl (meth) acrylate can be particularly preferably used.

  As the carboxyl group-containing vinyl monomer, for example, a monomer having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, or the like may be used. it can.

  Examples of amide group-containing vinyl monomers include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N. -Diethyl methacrylamide, N, N'-methylenebisacrylamide, N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, diacetone acrylamide, etc. can be used. Examples of amino group-containing vinyl monomers include Aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and the like can be used.

  As the imino group-containing monomer, for example, cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, itaconimide and the like can be used.

  As content of a polar group containing vinyl monomer, it is 5 mass% or more in the monomer component which comprises an acryl-type block polymer, Preferably it is 5-30 mass%, More preferably, it is 5-25 mass%, More preferably, 8- By setting the content to 20% by mass, the cohesive force of the pressure-sensitive adhesive layer at a high temperature is increased, and excellent high-temperature adhesiveness can be exhibited.

  In the present invention, by using a monomer (c) having a glass transition temperature of 20 ° C. or higher as a monomer component constituting an acrylic copolymer, suitable cohesive force is imparted to the obtained pressure-sensitive adhesive. it can. Examples of the monomer having a homopolymer glass transition temperature of 20 ° C. or higher include tert-butyl (meth) acrylate, methyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, 1-adamantyl (meth) acrylate, 3 , 5-dimethyl-1-adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, styrene and the like can be preferably used, and tert-butyl (meth) acrylate is particularly preferably used. it can.

  The content of the monomer (c) having a glass transition temperature of 20 ° C. or higher in the homopolymer in the acrylic copolymer is preferably 10% by mass or more in the monomer component constituting the acrylic copolymer, It is more preferable to set it as 20-50 mass%, and it is still more preferable to set it as 25-40 mass%. It becomes easy to implement | achieve suitable adhesiveness by making content of the said monomer (c) into the said range.

  In the acrylic copolymer used in the present invention, the glass transition temperature of the (meth) acrylate (a), the polar group-containing monomer (b) and the homopolymer is within the range where the effects of the present invention are achieved. May contain other monomers other than the monomer (c) at 20 ° C. or higher, but when using such other monomers, 30% by mass or less in the monomer component constituting the acrylic copolymer It is preferable to be 10% by mass or less.

  The mass average molecular weight of the acrylic copolymer used in the present invention may be appropriately adjusted according to the use mode in the range of about 10,000 to 2,000,000, and 10,000 to 100,000 from the viewpoint of maintaining good production efficiency. In terms of maintaining good adhesive strength, it is preferably 150,000 or more, more preferably 300,000 or more, and particularly preferably about 450,000 to 1,000,000. Moreover, it is also preferable to set it as 600,000 or more especially when it is desired to ensure the cohesive strength of the adhesive layer. The pressure-sensitive adhesive composition of the present invention can realize high adhesive force and cohesive force due to a high molecular weight having a mass average molecular weight of 150,000 or more.

  The said mass mean molecular weight is standard polystyrene conversion by a gel permeation chromatography (GPC). As an example of measurement conditions, HLC-8220GPC (manufactured by Tosoh Corporation) is used, the column is TSKgel GMHXL (manufactured by Tosoh Corporation), the column temperature is 40 ° C., the eluent is tetrahydrofuran, the flow rate is 1.0 mL / min, and standard polystyrene. Can be measured by using TSK standard polystyrene.

  In order to adjust the molecular weight, a chain transfer agent may be used in the polymerization. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

  The acrylic copolymer used in the present invention may be a random polymer or a block polymer as long as it contains the above monomer, but the main monomer is the above (meth) acrylate monomer (a). Polymer block comprising as main components a poly (meth) acrylate block (A) containing a polar group-containing monomer (b) and a monomer (c) having a glass transition temperature of 20 ° C. or higher of the homopolymer. It is preferable to use an acrylic block copolymer containing B) because it can realize particularly high temperature adhesive strength and high holding power.

  The poly (meth) acrylate block (A) is a monomer constituting the poly (meth) acrylate block (A) since the above (meth) acrylate monomer (a) is used as a main monomer component to easily achieve suitable adhesiveness. It is preferable that 50 mass% or more in a component is the said (meth) acrylate monomer (a), and it is more preferable to set it as 80 mass% or more.

  In the poly (meth) acrylate block (A), monomers other than the (meth) acrylate monomer (a) and the polar group-containing monomer (b), for example, the glass transition temperature of the homopolymer is 20 ° C. or higher. The other monomer (c) may be contained. When the poly (meth) acrylate block (A) contains a monomer other than the (meth) acrylate monomer (a) and the polar group-containing monomer (b), the monomer is added to the poly (meth) acrylate block (A ) Is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

  In the polymer block (B), the content of the monomer (c) having a glass transition temperature of 20 ° C. or higher of the homopolymer is 50% by mass or more in the monomer component constituting the poly (meth) acrylate block (B). It is preferable to make it 80% by mass or more.

  In the polymer block (B), a monomer other than the monomer (c) having a glass transition temperature of 20 ° C. or higher, for example, the (meth) acrylate monomer (a) and the polar group-containing monomer (b) Other monomers may be contained, but when the other monomers are contained, it is preferably 30% by mass or less in the monomer component forming the polymer block (B), and 20% by mass or less. More preferably, it is more preferably 10% by mass or less.

  In the acrylic block copolymer used in the present invention, the glass transition temperature measured by the suggested scanning calorimeter (DSC) of the poly (meth) acrylate block (A) is preferably 0 ° C. or lower, and −20 ° C. More preferably, it is -60--30 degreeC. Moreover, it is preferable that the glass transition temperature measured by DSC of a polymer block (B) is 20 degreeC or more, It is more preferable that it is 30 degreeC or more, It is especially preferable that it is 35 degreeC or more. When the glass transition temperature of each polymer block is within this temperature range, it is particularly easy to improve the adhesive strength, high-temperature adhesive strength, and good holding strength of the obtained pressure-sensitive adhesive.

  As for the glass transition temperature of the acrylic copolymer, the onset temperature in the DSC curve measured at a heating rate of 20 ° C./min with a differential scanning calorimeter is defined as the glass transition temperature.

  In the present invention, an acrylic block copolymer having the poly (meth) acrylate block (A) and the polymer block (B), preferably the poly (meth) acrylate block (A) and the polymer block (B). By using an acrylic block copolymer consisting of the above, it is excellent in adhesion to the adherend and cohesive strength of the pressure-sensitive adhesive layer, and can achieve excellent adhesiveness and holding power at room temperature and high temperature, Even if the block copolymer is a block copolymer (AB type block copolymer) of one poly (meth) acrylate block (A) and one polymer block (B), a plurality of poly (meta) ) Block copolymer (ABA type, BAB type, ABAB type, block copolymer in which acrylate block (A) and a plurality of polymer blocks (B) are randomly block-polymerized It may be a BABA type, etc.).

  The content ratio of the poly (meth) acrylate block (A) and the polymer block (B) in the acrylic block polymer is such that (B) is 75 mol% or less with respect to the total of (A) and (B). Preferably, the copolymerization ratio is more preferably 75/25 to 20/80, and particularly preferably 65/35 to 20/80, in terms of a molar ratio represented by (B) / (A). preferable. By setting the block copolymerization ratio within the above range, it becomes easy to suitably express adhesiveness and cohesive force.

  The acrylic copolymer used in the present invention can be produced by radical polymerization reaction of the above acrylic monomer or a mixture of acrylic monomers. When the acrylic copolymer is an acrylic block copolymer, it can be produced by, for example, a living radical polymerization method or a conventionally known radical polymerization method using an azo initiator or a peroxide. Among these, the adoption of the living radical polymerization method does not cause side reactions such as chain transfer reaction and termination reaction in the radical polymerization process, and it can suppress the generation of low molecular weight components, and it is possible to produce an acrylic block polymer with a narrow molecular weight distribution. It is preferable because it can be manufactured.

  Examples of the living radical polymerization method include an atom transfer radical polymerization method (ATRP method), a living radical polymerization method using an organic hetero compound containing a high-frequency group 15 or group 16 element as a catalyst (radical weight mediated by an organic hetero compound). (Combined method) (TERP method, etc.), living radical polymerization method (NMP method) via nitroxide, reversible addition-fragmentation chain transfer polymerization method (RAFT method), and the like.

  The atom transfer radical polymerization method (ATRP method) is a method of polymerizing the above acrylic monomer in the presence of, for example, a transition metal complex and an organic halide.

  As the transition metal constituting the transition metal complex, for example, Cu, Ru, Fe, Rh, V, Ni, and halides thereof can be used. Examples of the ligand that coordinates to the transition metal include bipyridyl derivatives, mercaptan derivatives, trifluorate derivatives, tertiary alkylamine derivatives, and the like.

  The organic halide is a polymerization initiator, for example, methyl 2-bromo (or chloro) propionate, ethyl 2-bromo (or chloro) propionate, methyl 2-bromo (or chloro) -2-methylpropionate 2-ethyl ethyl bromo (or chloro) -2-methylpropionate, 1-phenylethyl chloride (or bromide), 2-hydroxyethyl 2-bromo (or chloro) propionate, 2-bromo (or chloro) propionic acid 4-hydroxybutyl, 2-hydroxyethyl 2-bromo (or chloro) -2-methylpropionate, 4-hydroxybutyl 2-bromo (or chloro) -2-methylpropionate, and the like can be used.

  The radical polymerization method mediated by an organic hetero compound is a method of polymerizing the above-mentioned acrylic monomer in the presence of an organic hetero compound and a radical initiator. The radical polymerization method mediated by the organic hetero compound is preferable because the molecular weight of the acrylic copolymer is easily increased and the adhesive force is easily improved.

  As the organic hetero compound used in the radical polymerization method mediated by the organic hetero compound, an organic tellurium compound, an organic bismuth compound, and an organic antimony compound can be preferably used. Specific examples of these organic hetero compounds include JP-A No. 2004-323893, WO 2004/14818, JP-A 2006-225524, JP-A 2006-299278, JP-A 2008-291216, JP-A 2009. Organic tellurium compounds disclosed in JP-A-1149877, etc., organic bismuth compounds disclosed in JP2009-149877, WO2006 / 62255, etc., disclosed in JP2009-149877, WO2006 / 1496, etc. Well-known compounds such as certain organic antimony compounds can be used as appropriate. Specifically, for example, methyl 2-methylterranyl-2-methylpropionate, ethyl 2-methylterranyl-2-methylpropionate, ethyl 2-n-butyl-2-phenylterranylpropionate, 2-methyl-2- Ethyl phenylterranylpropionate, 2-methylterranylpropionitrile, 2-methyl-2-methylterranylpropionitrile, (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl- Propyl) benzene, 1-phenylterranyl-ethyl) benzene, 2-methyl-2-n-butylterranyl-propionic acid ethyl, 2-methyl-2-dimethylbismutanylpropionic acid methyl ester, 2-methyl-2-diphenyl Bismutanylpropionitrile, 2-methyl-2-dimethyl Compounds such as ruphenylbismutanylpropionitrile, methyl 2-methyl-2-dimethylstivanylpropionate, 2-methyl-2-dimethylstibanylpropionitrile, 1-dimethylstivanyl-1-phenylethane are preferred. It can be illustrated.

  The acrylic block copolymer is prepared by, for example, polymerizing a poly (meth) acrylate block (A) by the radical polymerization method described above, and then producing a polymer block (B) by the same method as described above. The (meth) acrylate block (A) and the polymer block (B) are combined by a click reaction such as a cycloaddition reaction of an acetylene group and an azide group introduced into the (A) and (B), respectively. Can also be manufactured.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention can achieve excellent adhesion and holding power at room temperature and high temperature without using a crosslinking agent by using the above acrylic copolymer as a main component. In the pressure-sensitive adhesive composition of the present invention, it may be a pressure-sensitive adhesive composition containing an acrylic polymer other than the above acrylic copolymer, but the proportion of the acrylic polymer in the pressure-sensitive adhesive composition is preferably Is preferably 80% by mass or more, and more preferably 90% by mass or more, and it is particularly preferable that substantially only the acrylic copolymer is used as a main agent. Moreover, you may contain tackifying resin, a crosslinking agent, another additive, etc. as needed.

(Tackifying resin)
In the pressure-sensitive adhesive composition of the present invention, a tackifying resin may be used in order to adjust the strong adhesion of the pressure-sensitive adhesive layer obtained. Examples of the tackifying resin used in the present invention include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, terpene, terpene phenol, petroleum A resin system etc. can be illustrated.

(Crosslinking agent)
In the pressure-sensitive adhesive composition of the present invention, excellent pressure-sensitive adhesive properties can be realized without substantially containing a cross-linking agent, but a cross-linking agent may be added to adjust the adhesive properties. Examples of the crosslinking agent include known isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, polyvalent metal salt crosslinking agents, metal chelate crosslinking agents, keto-hydrazide crosslinking agents, oxazoline crosslinking agents, and carbodiimide crosslinking agents. A crosslinking agent, a silane crosslinking agent, a glycidyl (alkoxy) epoxysilane crosslinking agent, or the like can be used.

(Additive)
In the pressure-sensitive adhesive composition of the present invention, as an additive, a base (such as aqueous ammonia), an acid, a foaming agent, and a plasticizer for adjusting pH within a range that does not impair the desired effect of the present invention as necessary. , Softeners, antioxidants, fillers such as glass and plastic fibers, balloons, beads, metal powders, colorants such as pigments and dyes, pH adjusters, film formation aids, leveling agents, thickeners, Known materials such as water repellents and antifoaming agents can be optionally added to the pressure-sensitive adhesive composition.
The foaming agent can be used for proceeding with the disassembly of the pressure-sensitive adhesive. For example, an inorganic foaming agent, an organic foaming agent, a thermally expandable hollow sphere, and the like that expand by volume when heated can be used.

[Adhesive tape]
The adhesive tape of this invention is an adhesive tape which has an adhesive layer which consists of said adhesive composition. The pressure-sensitive adhesive layer may be a single-layer pressure-sensitive adhesive layer or a multilayer composed of a plurality of pressure-sensitive adhesive layers and sheets such as a double-sided pressure-sensitive adhesive tape. A double-sided pressure-sensitive adhesive tape can be suitably used in two or more member fixing applications.

  When using a base material for the pressure-sensitive adhesive tape of the present invention, examples of the base material include polyolefin (for example, polypropylene, polyethylene), polyester (for example, polyethylene terephthalate, polyethylene naphthalate), polystyrene, ABS, polycarbonate, polyimide film, poly Examples thereof include plastic films made of vinyl chloride, nylon, polyvinyl alcohol, etc., non-woven fabrics made of pulp, rayon, Manila hemp, acrylonitrile, nylon, polyester, paper, cloth, or metal foil. When forming a double-sided pressure-sensitive adhesive tape, a polyester film or a non-woven fabric can be suitably used as the core because it is easy to achieve both removability and adhesiveness. Further, for the purpose of improving the adhesion between the base material, the core and the pressure-sensitive adhesive layer, one or both surfaces of the base material or the core may be subjected to corona treatment, plasma treatment, anchor coating treatment, or the like.

  When the pressure-sensitive adhesive tape of the present invention has a substrate or a core, the pressure-sensitive adhesive solution is applied directly onto the substrate or the core using a roll coater or a die coater, and then a separator is attached through a drying process. It can be produced by a direct coating method or a transfer method in which a pressure-sensitive adhesive solution is once coated on a separator and dried, and then transferred to a substrate or a core. When it does not have a base material or a core, it can be produced by a method in which a pressure-sensitive adhesive solution is coated on a separator and another separator is bonded.

  In the pressure-sensitive adhesive tape of the present invention, the gel fraction of the pressure-sensitive adhesive layer made of the above pressure-sensitive adhesive composition is preferably less than 10% by mass, and particularly preferably 5% by mass or less. Even if the adhesive tape of this invention is the said low gel fraction, it can implement | achieve the outstanding adhesiveness and holding power. Moreover, suitable recyclability is realizable by using the adhesive layer of the said low gel fraction.

The gel fraction of the pressure-sensitive adhesive layer was measured after measuring the weight a of the pressure-sensitive adhesive layer before toluene extraction, and after immersing the same test piece in toluene for 24 hours, taking out the gel product and drying at 100 ° C. for 2 hours. The weight b after toluene extraction is measured and calculated by the following formula.
Gel fraction (%) = (b / a) × 100
The test piece of the pressure-sensitive adhesive layer may be the same test piece before and after immersion in toluene. For example, the pressure-sensitive adhesive composition is formed on a polyester film (exfoliated) so that the thickness after drying is 25 μm. Is applied and dried to form an adhesive layer, then cut into a size of 20 mm × 100 mm, and the polyester film is peeled off, which can be used as a test piece.

  The pressure-sensitive adhesive tape of the present invention is formed by applying and drying the above pressure-sensitive adhesive on a PET film having a thickness of 50 μm using an applicator with a gap of 8 milli-inch, and forming a pressure-sensitive adhesive tape at 23 ° C. and 50% RH. Then, the hand roller with a weight of 2 kg was reciprocated on the SUS plate, pressed and allowed to stand for 1 hour, and then peeled off in the 180 ° direction at a speed of 30 mm / min using a tensile tester. The force is preferably 1 N / 20 mm or more, more preferably 2 to 30 N / 20 mm, and particularly preferably 3 to 20 N / 20 mm. The pressure-sensitive adhesive tape of the present invention can achieve suitable disassembly even if it has a high adhesive force suitable for fixing between parts.

  The pressure-sensitive adhesive tape of the present invention can be used for fixing parts in various industrial fields such as office automation equipment, IT / home appliances, automobiles, temporarily fixing parts, and labeling for displaying product information. The pressure-sensitive adhesive tape of the present invention using a non-crosslinking pressure-sensitive adhesive does not require an aging process necessary for a crosslinking reaction, and can thus greatly increase production efficiency. Further, it can be suitably used as a pressure-sensitive adhesive tape excellent in heat resistance and peeling resistance and having high adhesion reliability.

(Production Example 1)
Synthesis of poly t-butyl acrylate (1): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 0.86 mg, t-butyl acrylate (tBA) 1.46 g and ethyl acetate 1 .46 g of the mixed solution was put in a test tube and degassed by bubbling with argon gas for 30 minutes.The organic hetero compound was added to the test tube using a microsyringe and reacted in an oil bath at 50 ° C. for 2 hours. A reaction solution of poly t-butyl acrylate (4) was obtained, and the polymerization rate was 79% from ¹ H-NMR (300 MHz) analysis, and Mn = 73,800, PD = 1.28 from GPC analysis. Met.
Synthesis of Acrylic Block Copolymer (1): 4.48 g of 2-ethylhexyl acrylate (2EA) obtained by bubbling argon gas for 30 minutes in advance to the reaction solution of poly t-butyl acrylate (1) obtained above. A mixed solution of 0.82 g of 2-hydroxyethyl acrylate (HEA) and 5.30 g of ethyl acetate was added and reacted at 50 ° C. for 7 hours. ^{From 1} H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 82%, the polymerization rate of 2-ethylhexyl acrylate was 49%, and the polymerization rate of 2-hydroxyethyl acrylate was 58%.
After completion of the reaction, the polymerization solution was poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant liquid by decantation, it was vacuum-dried at 40 ° C. under reduced pressure for 10 hours to obtain an acrylic block copolymer (1). From the GPC analysis, it was Mn = 265,000, Mw = 462,000, PD = 1.74. The mass ratio of the structural components in the copolymer was tBA / 2EHA / HEA = 29.0 / 56.9 / 14.1.

(Production Example 2)
Synthesis of poly t-butyl acrylate (2): 1.21 mg of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN), 1.33 g of t-butyl acrylate and 2.66 g of ethyl acetate The mixed solution was put into a test tube and degassed by argon gas bubbling for 30 minutes.The organic hetero compound was added to the test tube using a microsyringe and reacted in an oil bath at 50 ° C. for 2 hours. A reaction solution of butyl acrylate (2) was obtained, and the polymerization rate was 79% from ¹ H-NMR (300 MHz) analysis, and Mn = 73,800 and PD = 1.26 from GPC analysis. .
Synthesis of acrylic block copolymer (2): 5.90 g of n-butyl acrylate (nBA) obtained by bubbling argon gas for 30 minutes in advance to the reaction solution of poly t-butyl acrylate (2) obtained above. And a mixed solution of 1.16 g of 2-hydroxyethyl acrylate was added and reacted at 50 ° C. for 3 hours. ^{From 1} H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 90%, the polymerization rate of 2-ethylhexyl acrylate was 42%, and the polymerization rate of n-butyl acrylate was 49%.
After completion of the reaction, the polymerization solution was poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant liquid by decantation, it was vacuum dried at 40 ° C. under reduced pressure for 10 hours to obtain an acrylic block copolymer (2). From the GPC analysis, it was Mn = 266,300, Mw = 570,000, PD = 2.14. The mass ratio of the constituent components in the copolymer was tBA / nBA / HEA = 33.2 / 53.1 / 13.7.

(Production Example 3)
Synthesis of acrylic random copolymer (1): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 0.49 mg, t-butyl acrylate (tBA) 1.00 g, 2- A mixed solution of 1.63 g of ethylhexyl acrylate (2EHA), 0.40 g of 2-hydroxyethyl acrylate (HEA) and 3.01 g of ethyl acetate was put in a test tube and degassed by bubbling with argon gas for 30 minutes. , Added to a test tube using a microsyringe, and allowed to react for 2 hours in an oil bath at 50 ° C. From ¹ H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 77%, and 2-ethylhexyl acrylate The polymerization rate was 73%, and the polymerization rate of 2-hydroxyethyl acrylate was 81%.

  After completion of the reaction, the polymerization solution was diluted with 20 mL of chloroform, poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant liquid by decantation, it was vacuum dried at 40 ° C. under reduced pressure for 10 hours to obtain an acrylic random copolymer (1). From the GPC analysis, it was Mn = 285,700, Mw = 580,300, PD = 2.03. The mass ratio of the constituent components in the copolymer was tBA / 2EHA / HEA = 33.2 / 51.9 / 14.9.

(Production Example 4)
Synthesis of acrylic random copolymer (2): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 0.96 mg, t-butyl acrylate 1.89 g, n-butyl acrylate 3 A mixed solution of .11 g, 0.65 g of 2-hydroxyethyl acrylate and 5.65 g of ethyl acetate was placed in a test tube and degassed by argon gas bubbling for 30 minutes.The organic hetero compound was put into the test tube using a microsyringe. The resulting mixture was reacted for 4 hours in an oil bath at 50 ° C. From ¹ H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 77%, the polymerization rate of n-butyl acrylate was 76%, and 2-hydroxy The degree of polymerization of ethyl acrylate was 79% After completion of the reaction, the polymerization solution was treated with methanol: water (80:20 volume fraction). The polymer was precipitated by decantation and the supernatant was removed by decantation, and the resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. The supernatant liquid was removed by decantation, followed by vacuum drying under reduced pressure at 40 ° C. for 10 hours to obtain an acrylic random copolymer (2), which was determined by GPC analysis to have Mn = 253,400, Mw = 475,000. PD = 1.87 The mass ratio of the constituent components in the copolymer was tBA / nBA / HEA = 33.5 / 53.7 / 12.8.

(Production Example 5)
Synthesis of poly t-butyl acrylate (3): 2,3′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 0.93 mg, t-butyl acrylate 1.71 g and ethyl acetate 3.42 g The mixed solution was put into a test tube and degassed by argon gas bubbling for 30 minutes.The organic hetero compound was added to the test tube using a microsyringe and reacted in an oil bath at 50 ° C. for 2 hours. A reaction solution of butyl acrylate (3) was obtained, and the polymerization rate was 76% from ¹ H-NMR (300 MHz) analysis, and Mn = 93,200 and PD = 1.30 from GPC analysis. .
Synthesis of acrylic block copolymer (3): 5.66 g of 2-ethylhexyl acrylate (2EHA) obtained by bubbling argon gas for 30 minutes in advance to the reaction solution of poly-t-butyl acrylate (3) obtained above. 0.23 g of 2-hydroxyethyl acrylate was added and reacted at 50 ° C. for 4 hours. ^{From 1} H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 87%, the polymerization rate of 2-ethylhexyl acrylate was 46%, and the polymerization rate of 2-hydroxyethyl acrylate was 52%.
After completion of the reaction, the polymerization solution was poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant liquid by decantation, it was vacuum dried at 40 ° C. under reduced pressure for 10 hours to obtain an acrylic block copolymer (3). From the GPC analysis, it was Mn = 257,800, Mw = 383,000, PD = 1.49. The mass ratio of the constituent components in the copolymer was tBA / 2EHA / HEA = 35.3 / 61.5 / 3.2.

(Production Example 6)
Synthesis of poly t-butyl acrylate (4): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 1.15 mg, t-butyl acrylate (tBA) 1.48 g and ethyl acetate 2 .95 g of the mixed solution was put into a test tube and degassed by bubbling with argon gas for 30 minutes.The organic hetero compound was added to the test tube using a microsyringe and reacted in an oil bath at 50 ° C. for 2 hours. A reaction solution of poly t-butyl acrylate (4) was obtained, and the polymerization rate was 74% from ¹ H-NMR (300 MHz) analysis, and Mn = 68,600, PD = 1.32 from GPC analysis. Met.
Synthesis of acrylic block copolymer (4): 5.76 g of n-butyl acrylate (nBA) obtained by bubbling argon gas for 30 minutes in advance to the reaction solution of poly-t-butyl acrylate (1) obtained above. Then, a mixed solution of 0.23 g of 2-hydroxyethyl acrylate (HEA) was added and reacted at 50 ° C. for 12 hours. ^{From 1} H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 90%, the polymerization rate of n-butyl acrylate was 60%, and the polymerization rate of 2-hydroxyethyl acrylate was 62%.
After completion of the reaction, the polymerization solution was poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant by decantation, it is vacuum-dried at 40 ° C. for 10 hours under reduced pressure, and an acrylic block copolymer (4) comprising a poly t-butyl acrylate chain and a polyacrylate chain composed of other copolymer components. Got. From the GPC analysis, it was Mn = 239,200, Mw = 354,000, PD = 1.48. The mass ratio of the structural components in the copolymer was tBA / nBA / HEA = 29.2 / 67.2 / 3.6.

(Production Example 7)
Synthesis of acrylic random copolymer (3): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 0.50 mg, t-butyl acrylate (tBA) 1.28 g, 2-ethylhexyl A mixed solution of 1.80 g of acrylate (2EHA), 0.095 g of 2-hydroxyethyl acrylate (HEA) and 3.07 g of ethyl acetate was put into a test tube and degassed by argon gas bubbling for 30 minutes. The sample was added to a test tube using a microsyringe and reacted for 2 hours in an oil bath at 50 ° C. From ¹ H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 78%, and polymerization of 2-ethylhexyl acrylate. The rate was 75%, and the polymerization rate of 2-hydroxyethyl acrylate was 73%.
After completion of the reaction, the polymerization solution was diluted with 20 mL of chloroform, poured into methanol: water (80:20 volume fraction) to precipitate the polymer, and the supernatant was removed by decantation. The resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. After removing the supernatant liquid by decantation, it was vacuum dried at 40 ° C. under reduced pressure for 10 hours to obtain an acrylic random copolymer (3). From the GPC analysis, it was Mn = 234,600 and PD = 1.37. The mass ratio of the constituent components in the copolymer was tBA / 2EHA / HEA = 39.6 / 57.6 / 2.8.

(Production Example 8)
Synthesis of acrylic random copolymer (4): 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile (AMVN) 1.23 mg, t-butyl acrylate 1.89 g, n-butyl acrylate 3 A mixed solution of .29 g, 0.16 g of 2-hydroxyethyl acrylate and 2.05 g of ethyl acetate was put into a test tube and deaerated by argon gas bubbling for 30 minutes.The organic hetero compound was put into the test tube using a microsyringe. And the reaction was allowed to proceed for 5 hours in an oil bath at 50 ° C. From ¹ H-NMR (300 MHz) analysis, the polymerization rate of t-butyl acrylate was 91%, the polymerization rate of n-butyl acrylate was 90%, and 2-hydroxy The degree of polymerization of ethyl acrylate was 90% After completion of the reaction, the polymerization solution was treated with methanol: water (80:20 volume fraction). The polymer was precipitated by decantation and the supernatant was removed by decantation, and the resulting precipitate was dissolved in 50 mL of chloroform and poured into methanol: water (80:20 volume fraction) to reprecipitate the polymer. The supernatant liquid was removed by decantation, followed by vacuum drying under reduced pressure at 40 ° C. for 10 hours to obtain an acrylic random copolymer (4), which was determined by GPC analysis to have Mn = 277,100, Mw = 463,000. PD = 1.67 The mass ratio of the constituent components in the copolymer was tBA / nBA / HEA = 33.6 / 61.1 / 3.4.

Example 1
The acrylic block copolymer (1) obtained in Production Example 1 was diluted with acetone to obtain a pressure-sensitive adhesive composition comprising a 15 wt% acetone solution. The obtained pressure-sensitive adhesive composition was applied onto a PET film having a thickness of 50 μm using an applicator having a gap of 8 milli-inch and dried under reduced pressure for 12 hours to prepare a pressure-sensitive adhesive sheet.

(Example 2)
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the acrylic block copolymer (2) obtained in Production Example 2 was used in place of the acrylic block copolymer (1).

(Example 3)
An adhesive tape was obtained in the same manner as in Example 1 except that the acrylic random copolymer (1) obtained in Production Example 3 was used instead of the acrylic block copolymer (1).

Example 4
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the acrylic random copolymer (2) obtained in Production Example 4 was used instead of the acrylic block copolymer (1).

(Comparative Example 1)
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the acrylic block copolymer (3) obtained in Production Example 5 was used in place of the acrylic block copolymer (1).

(Comparative Example 2)
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the acrylic block copolymer (4) obtained in Production Example 6 was used instead of the acrylic block copolymer (1).

(Comparative Example 3)
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the acrylic random copolymer (3) obtained in Production Example 7 was used in place of the acrylic block copolymer (1).

(Comparative Example 4)
An adhesive tape was obtained in the same manner as in Example 1 except that the acrylic random copolymer (4) obtained in Production Example 8 was used instead of the acrylic block copolymer (1).

  The following evaluation was performed about the adhesive tape obtained in the said Example and comparative example. The results obtained are shown in the table below.

<Glass transition temperature of copolymer>
A DSC curve was measured for 5 mg of the acrylic copolymer obtained in the above production example using a differential scanning calorimeter EXTRA 6200 manufactured by SII Nanotechnology, Inc. under a nitrogen stream of 30 mL / min. The block copolymer was rapidly cooled from room temperature to −120 ° C./min, then heated to 20 ° C./min to 80 ° C., then cooled to 10 ° C./min to −120 ° C., and again 80 ° C. at 20 ° C./min. The temperature was raised to ° C. The random copolymer was rapidly cooled from room temperature to −90 ° C./min, heated to 20 ° C. at 20 ° C./min, then cooled to −90 ° C. at 10 ° C./min, and again 20 ° C. at 20 ° C./min. The temperature was raised to ° C. In either case, the glass transition temperature observed in the second temperature raising process was measured.

<High temperature adhesive strength>
After the test piece was prepared by cutting the adhesive sheet into a strip with a width of 20 mm and a length of 120 mm, it was weighed on a SUS plate with a width of 50 mm, a length of 150 mm and a thickness of 2 mm in an environment of 23 ° C. and 50% RH. A 2 kg hand roller was reciprocated once and pressed.
The pressure-bonded test piece is allowed to stand at 23 ° C. and 50% RH for 1 hour, and then left to stand at 70 ° C. for 10 minutes, and then at a speed of 300 mm / min using a tensile tester in the 70 ° C. environment. Was peeled off and 180 ° peel strength was measured.

<Constant load holding force>
After the test piece was prepared by cutting the pressure-sensitive adhesive sheet into a strip having a width of 10 mm and a length of 80 mm, it was applied on a PMMA plate having a width of 50 mm, a length of 150 mm and a thickness of 2 mm in a 23 ° C. and 50% RH environment. The hand roller having a weight of 2 kg was reciprocated once so as to have a width of 10 mm and a length of 50 mm. The pressure-bonded test piece was allowed to stand for 1 hour in an environment of 23 ° C. and 50% RH, then loaded with 100 g, and allowed to stand in an environment of 23 ° C. and 50% RH for 3 hours.
(Double-circle): The time stuck on the PMMA board is 3 hours.
○: The time applied to the PMMA plate is 20 minutes or more and less than 3 hours.
(Triangle | delta): The time stuck on the PMMA board is 10 minutes or more and less than 20 minutes.
X: The time stuck on the PMMA board is less than 10 minutes.

The numerical value of each component in the acrylic block polymer in the table represents the molar ratio. Abbreviations in the table are as follows.
tBA: t-butyl acrylate (glass transition temperature of homopolymer: 43 ° C.)
co-tBA: t-butyl acrylate contained in a poly (meth) acrylate block consisting of other copolymerization components copolymerized with a poly-t-butyl acrylate block 2EHA: 2-ethylhexyl acrylate (glass transition temperature of homopolymer: -50 ° C)
nBA: n-butyl acrylate (glass transition temperature of homopolymer: −54 ° C.)
HEA: 2-hydroxyethyl acrylate

  As is clear from the above table, each of the pressure-sensitive adhesive compositions of Examples 1 to 4 had excellent high-temperature adhesive force and constant load holding force. On the other hand, the pressure-sensitive adhesive compositions of Comparative Examples 1 to 4 were both low in high-temperature adhesive force and constant load holding force.

Claims (9)

An adhesive composition mainly comprising an acrylic copolymer,
The acrylic copolymer contains, as a monomer component, a (meth) acrylate monomer (a), a polar group-containing monomer (b), and a monomer (c) having a glass transition temperature of 20 ° C. or higher as a homopolymer. The pressure-sensitive adhesive composition, wherein the content of the group-containing monomer (b) is 5% by mass or more in the monomer component constituting the acrylic copolymer.   The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate monomer (a) is a (meth) acrylate monomer having a homopolymer having a glass transition temperature of 0 ° C. or less.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the polar group-containing monomer (b) is a hydroxyl group-containing monomer.   Monomer (c) having a glass transition temperature of 20 ° C. or higher of the homopolymer is tert-butyl (meth) acrylate, methyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, 1-adamantyl (meth) acrylate, 4. At least one selected from 3,5-dimethyl-1-adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and styrene. The pressure-sensitive adhesive composition described.   Monomer (c) wherein the content of the (meth) acrylate monomer (a) is 25% by mass or more in the monomer component constituting the acrylic copolymer, and the glass transition temperature of the homopolymer is 20 ° C. or higher. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the content of is 10% by mass or more.   The acrylic copolymer is a poly (meth) acrylate block (A) containing the (meth) acrylate monomer (a) and the polar group-containing monomer (b) as monomer components, and the glass transition temperature of the homopolymer. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, which is an acrylic block copolymer containing a polymer block (B) containing a monomer (c) of 20 ° C or higher as a monomer component.   The ratio of the poly (meth) acrylate block (A) to the polymer block (B) in the acrylic block copolymer is 25/75 to 80/20 in a molar ratio represented by (A) / (B). The pressure-sensitive adhesive composition according to claim 6.   The adhesive tape which has an adhesive layer which consists of an adhesive composition as described in any one of Claims 1-7.   The pressure-sensitive adhesive tape according to claim 8, wherein the pressure-sensitive adhesive layer has a gel fraction of less than 10%.