CN113302250A

CN113302250A - Adhesive tape

Info

Publication number: CN113302250A
Application number: CN202080009722.7A
Authority: CN
Inventors: 安田妃那; 石堂泰志; 土居智; 西垣达哉; 福山诚; 堀尾明史
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2019-04-24
Filing date: 2020-04-23
Publication date: 2021-08-24
Anticipated expiration: 2040-04-23
Also published as: JP6966650B2; JP2021191877A; KR102559150B1; TW202104490A; JPWO2020218430A1; WO2020218430A1; CN113302250B; TWI833947B; KR102425598B1; MY190233A; KR20220103829A; KR20210079375A

Abstract

The purpose of the present invention is to provide an adhesive tape having excellent flexibility and impact resistance, while having excellent heat resistance. The adhesive tape of the present invention has an adhesive layer on both sides of a foam base, wherein the foam base contains a block copolymer having at least 1 or more hard blocks and 1 soft block, and the soft block is composed of a (meth) acrylic monomer.

Description

Adhesive tape

Technical Field

The present invention relates to an adhesive tape.

Background

In portable electronic devices such as mobile phones and Personal Digital Assistants (PDAs), adhesive tapes are used for assembly (for example, patent documents 1 and 2). In addition, an adhesive tape is also used for fixing a vehicle-mounted electronic device component such as a vehicle-mounted panel to a vehicle body.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2009 and No. 242541

Patent document 2: japanese laid-open patent publication No. 2009-258274

Disclosure of Invention

Problems to be solved by the invention

An adhesive tape used for fixing a portable electronic device part, a vehicle-mounted electronic device part, or the like is required to have high adhesion force and impact resistance such that the adhesive tape does not peel off even when an impact is applied. On the other hand, in recent years, portable electronic devices, in-vehicle electronic devices, and the like, have a tendency to be more complicated in shape with higher functionality, and therefore, they are sometimes used by being stuck to a surface such as a step, a corner, or a non-planar portion. In such a case, the pressure-sensitive adhesive tape is required to have excellent flexibility capable of following the shape of the adherend.

As the pressure-sensitive adhesive tape having excellent flexibility and impact resistance, a pressure-sensitive adhesive tape using a foam base material obtained by foaming a polyolefin resin is known. On the other hand, in recent years, with higher performance and higher integration, portable electronic devices, in-vehicle electronic devices, and the like, the temperature during operation becomes high. In the case where the pressure-sensitive adhesive tape using the foam base material obtained by foaming the polyolefin resin as described above is used in equipment having a high temperature for a long period of time, the pressure-sensitive adhesive tape may not be resistant to deformation due to heat and may be peeled off.

The purpose of the present invention is to provide an adhesive tape having excellent flexibility and impact resistance, while having excellent heat resistance.

Means for solving the problems

The adhesive tape of the present invention has an adhesive layer on both sides of a foam base, wherein the foam base contains a block copolymer having at least 1 or more hard blocks and 1 soft block, and the soft block is composed of a (meth) acrylic monomer.

The present invention is described in detail below.

The adhesive tape of the present invention has an adhesive layer on both sides of a foam base.

The adhesive tape of the present invention can exhibit excellent flexibility and impact resistance by using the foam base. The foam base material may have an open cell structure or an open cell structure, and preferably has an open cell structure. The foam base may have a single-layer structure or a multi-layer structure. The adhesive layer may be formed of the same adhesive on both sides, or different adhesives may be used.

The foam base material contains a block copolymer having at least 1 or more hard blocks and 1 soft block.

The hard block means a block having a high cohesive force and having a function of a pseudo crosslinking point, and the soft block means a soft block exhibiting rubber elasticity. In the case of a block copolymer having a hard block and a soft block, the hard block is hardly compatible with the soft block, and sometimes a heterogeneous phase separation structure in which islands formed by coagulation of the hard block are dispersed in the sea of the soft block is adopted. Further, it is considered that the islands of the hard block serve as pseudo crosslinking points to impart rubber properties to the copolymer, and the obtained adhesive tape has high flexibility and impact resistance. Further, it is considered that if the hard block has a crosslinkable functional group, the obtained adhesive tape can be further imparted with flexibility and impact resistance. The block copolymer may have a diblock structure in which both the hard block and the soft block are present in the main chain, or may have a triblock structure in which the hard block, the soft block and the hard block are present. In addition, the above block copolymer may be a graft copolymer in which a hard block and a soft block are separately present in the main chain and the side chain. Examples of the graft copolymer include a styrene macromonomer- (meth) acrylic acid monomer copolymer and the like.

The hard block is not particularly limited as long as it has a rigid structure, and may be a polymer of a single monomer having the rigid structure or a copolymer of a plurality of monomers including a monomer having the rigid structure. Examples of the monomer having a rigid structure include a vinyl aromatic compound, a compound having a cyclic structure, and a compound having a short side chain substituent. Among them, the hard block more preferably has a structure derived from a vinyl aromatic compound monomer, from the viewpoint of further improving the impact resistance. Examples of the vinyl aromatic compound monomer include styrene, α -methylstyrene, p-methylstyrene, and chlorostyrene. Among them, styrene is preferable in terms of further improving the impact resistance. In the present specification, the structures derived from the vinyl aromatic compound monomer refer to structures represented by the following general formulae (1) and (2).

[ chemical formula 1]

In the formulae (1) and (2), R¹Represents a substituent. As substituents R¹Examples thereof include phenyl, methylphenyl and chlorophenyl.

When the block copolymer has the structure derived from the vinyl aromatic compound monomer, the content of the structure derived from the vinyl aromatic compound monomer in the block copolymer is preferably 1 wt% or more and 30 wt% or less.

By setting the content of the vinyl aromatic compound-derived monomer structure in the above range, flexibility and impact resistance can be further improved. The content of the structure derived from the vinyl aromatic compound monomer has a more preferable lower limit of 1.5% by weight, a further preferable lower limit of 2% by weight, a particularly preferable lower limit of 2.5% by weight, a further preferable upper limit of 24% by weight, a further preferable upper limit of 19% by weight, a particularly preferable upper limit of 16% by weight, and a particularly preferable upper limit of 8% by weight.

The hard block preferably has a structure derived from a monomer having a crosslinkable functional group.

If the hard block has a crosslinkable functional group, the rubber properties of the block copolymer are improved by crosslinking, and therefore flexibility and impact resistance can be further improved. The crosslinkable functional groups may or may not be crosslinked, and even in the structure in which crosslinking is not performed, the interaction between the functional groups improves the cohesive force in the block and improves flexibility and impact resistance, but crosslinking is more preferably performed. In the present specification, the structure derived from the monomer having a crosslinkable functional group refers to structures represented by the following general formulae (3) and (4).

[ chemical formula 2]

Herein, R is²Represents a substituent. Substituent R²The resin composition may contain an alkyl group, an ether group, a carbonyl group, an ester group, a carbonate group, an amide group, a urethane group, or the like as its constituent element, but may contain at least one functional group selected from a carboxyl group, a hydroxyl group, an epoxy group, a double bond, a triple bond, an amino group, an amide group, a nitrile group, and the like.

The monomer having a crosslinkable functional group is not particularly limited, and examples thereof include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an epoxy group-containing monomer, a double bond-containing monomer, a triple bond-containing monomer, an amino group-containing monomer, an amide group-containing monomer, and a nitrile group-containing monomer. Among them, from the viewpoint of further improving flexibility and impact resistance, at least 1 kind selected from the group consisting of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an epoxy group-containing monomer, an amide group-containing monomer, a double bond-containing monomer and a triple bond-containing monomer is preferable. Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate. The carboxyl group-containing monomer may be (meth) acrylic acid or the like. Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate. Examples of the amide group-containing monomer include (meth) acrylamide and the like. Examples of the double bond-containing monomer include allyl (meth) acrylate and hexanediol di (meth) acrylate. Examples of the triple bond-containing monomer include propargyl (meth) acrylate and the like. Among these, from the viewpoint of imparting excellent flexibility and impact resistance to the pressure-sensitive adhesive tape, a carboxyl group-containing monomer is preferable, a (meth) acrylic monomer is more preferable, and acrylic acid is further preferable.

In the case where the hard block is a copolymer of the monomer having a rigid structure and the monomer having a crosslinkable functional group, the hard block preferably contains a structure derived from the monomer having a crosslinkable functional group in an amount of 0.1 to 30 wt%.

By setting the content of the structure derived from the monomer having a crosslinkable functional group in the hard block to the above range, flexibility and impact resistance can be further improved. A more preferable lower limit of the content of the structure derived from the monomer having the crosslinkable functional group is 0.5 wt%, a further preferable lower limit is 1 wt%, a more preferable upper limit is 25 wt%, and a further preferable upper limit is 20 wt%.

The soft block is composed of a (meth) acrylic monomer.

The soft block is composed of a (meth) acrylic monomer, and therefore, the obtained adhesive tape can be provided with heat resistance, and deformation and peeling of the adhesive tape can be suppressed even when exposed to high temperatures for a long period of time. The (meth) acrylic monomer may be a single monomer or a plurality of monomers may be used. In addition, monomers other than the (meth) acrylic monomer may be used within a range in which the effects of the present invention are not lost.

The (meth) acrylic monomer that is a raw material of the soft block is not particularly limited as long as it has flexibility to exhibit rubber elasticity, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, and isostearyl (meth) acrylate. Among these, methyl acrylate, ethyl acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferable, and methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are more preferable, from the viewpoint of facilitating compatibility between heat resistance and flexibility.

As the (meth) acrylic monomer to be a raw material of the soft block, a (meth) acrylic monomer having a side chain carbon number of 2 or less is preferably used. When a (meth) acrylic monomer having a side chain of 2 or less carbon atoms is used, the resulting polymer chains are entangled with each other to increase the cohesive force, and therefore, the heat resistance and impact resistance can be further improved. Examples of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain include methyl (meth) acrylate and ethyl (meth) acrylate, and methyl acrylate and ethyl acrylate are particularly preferable.

The preferable lower limit of the content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain in the soft block is 5% by weight. When the lower limit amount is contained, the above-described cohesive force-improving effect is easily exhibited. The lower limit is more preferably 10% by weight, still more preferably 20% by weight, particularly preferably 25% by weight, and particularly preferably 30% by weight. The preferable upper limit of the content of the (meth) acrylic monomer having 2 or less carbon atoms in the side chain in the soft block is 90% by weight. If the amount exceeds the upper limit, the cohesive force becomes too high and the flexibility becomes low, and the flexibility as an adhesive tape is lost. The upper limit is more preferably 85% by weight, still more preferably 80% by weight, particularly preferably 75% by weight, and particularly preferably 70% by weight.

The block copolymer preferably contains the hard block in an amount of 1 to 40 wt%. By setting the hard block content to the above range, a foam base material excellent in flexibility, impact resistance and heat resistance can be formed. From the viewpoint of further improving flexibility, impact resistance and heat resistance, a more preferable lower limit of the content of the hard block is 2% by weight, a further preferable lower limit is 2.5% by weight, a particularly preferable lower limit is 3% by weight, a further preferable upper limit is 35% by weight, a further preferable upper limit is 30% by weight, a further preferable upper limit is 26% by weight, a further preferable upper limit is 20% by weight, a particularly preferable upper limit is 17% by weight, and a particularly preferable upper limit is 8% by weight.

The block copolymer preferably has a polymerization average molecular weight of 50000 to 800000.

By setting the weight average molecular weight of the block copolymer to the above range, flexibility, impact resistance and heat resistance can be further improved. A more preferable lower limit of the polymerization average molecular weight of the block copolymer is 75000, and a more preferable upper limit is 600000. The weight average molecular weight can be measured by, for example, GPC, using 2690Separations Module manufactured by Water corporation as a measuring device, GPC KF-806L manufactured by Showa Denko K.K. as a column, and ethyl acetate as a solvent, at a sample flow rate of 1mL/min and a column temperature of 40 ℃.

In order to obtain the block copolymer, the raw material monomers of the hard block and the soft block may be subjected to a radical reaction in the presence of a polymerization initiator to obtain the hard block and the soft block, and then the hard block and the soft block may be reacted or copolymerized, or the hard block may be obtained by the above method, and then the raw material monomers of the soft block may be charged and copolymerized. As a method for carrying out the radical reaction, that is, a polymerization method, conventionally known methods can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.

The foam base material may contain additives such as antistatic agents, mold release agents, antioxidants, weather-proofing agents, and crystal nucleating agents, and resin modifiers such as polyolefins, polyesters, polyamides, and elastomers.

The foam substrate has an apparent density of preferably 0.3g/cm³Above and 0.75g/cm³The following.

By making the apparent density of the foam base material to be higherThe pressure-sensitive adhesive tape having more excellent flexibility and impact resistance can be produced while maintaining the strength. From the viewpoint of further improving the strength, flexibility and impact resistance of the pressure-sensitive adhesive tape, a more preferable lower limit of the foam base is 0.33g/cm³More preferably, the upper limit is 0.73g/cm³Further, a more preferable lower limit is 0.35g/cm³Further, a more preferable upper limit is 0.71g/cm³。

Here, the apparent density means that the density of the adhesive tape is regarded as 1.0g/cm³The density of the foam base material in the case of the pressure-sensitive adhesive tape is determined from the weight of the pressure-sensitive adhesive tape.

The apparent density can be measured by using an electronic densitometer (for example, "ED 120T" manufactured by MIRAGE corporation) in accordance with JIS K6767.

The gel fraction of the foam base is preferably 90% or less.

By setting the gel fraction of the foam base material to the above range, the impact resistance of the obtained pressure-sensitive adhesive tape can be further improved. From the viewpoint of further improving the impact resistance of the pressure-sensitive adhesive tape, a more preferable upper limit of the gel fraction is 85%, and a more preferable upper limit is 80%. The lower limit of the gel fraction is not particularly limited, and is, for example, 10% or more, particularly 20% or more, and particularly 35% or more. The gel fraction can be adjusted by crosslinking at least one of the hard block and the soft block. The gel fraction can be measured by the following method.

From the resulting adhesive tape, only 0.1g of the foam base material was taken out, immersed in 50ml of ethyl acetate, and shaken by a shaker at a temperature of 23 ℃ and a speed of 120rpm for 24 hours. After shaking, ethyl acetate and the foam base material swollen by absorbing ethyl acetate were separated using a metal mesh (mesh # 200). The separated foam base material was dried at 110 ℃ for 1 hour. The weight of the foam base material including the metal mesh after drying was measured, and the gel fraction of the foam base material was calculated by using the following formula.

Gel fraction (wt%) < 100 × (W1-W2)/W0

(W0: initial foam substrate weight, W1: foam substrate weight after drying comprising metal mesh, W2: initial weight of metal mesh)

The foam base is preferably formed with a crosslinked structure between main chains of the resin constituting the foam base by adding a crosslinking agent. By forming a crosslinked structure between the main chains of the resin constituting the foam base, it is possible to disperse the intermittently applied peeling stress, and it is possible to further improve the heat resistance and impact resistance of the pressure-sensitive adhesive tape. The crosslinking agent is not particularly limited, and may be appropriately selected according to the functional group of the resin constituting the foam base material. Specific examples thereof include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents. Among them, epoxy-based crosslinking agents and isocyanate-based crosslinking agents are preferable because resins having alcoholic hydroxyl groups and carboxyl groups, which can further improve flexibility and impact resistance, can be crosslinked. The isocyanate-based crosslinking agent crosslinks alcoholic hydroxyl groups and carboxyl groups in the resin constituting the foam base and isocyanate groups of the crosslinking agent. The epoxy-based crosslinking agent crosslinks carboxyl groups in the resin constituting the foam base and epoxy groups in the crosslinking agent.

The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the resin which is the main component of the foam base.

The foam base material preferably has an average cell diameter of cells of 80 μm or less.

By making the average cell diameter of the foam base material in the above range, the balance of the strength, flexibility and impact resistance of the obtained adhesive tape can be further improved.

The average cell diameter of the foam base material is more preferably 60 μm or less, and still more preferably 55 μm or less. The lower limit of the average cell diameter of the foam base is not particularly limited, but is preferably 20 μm or more, and more preferably 30 μm or more, from the viewpoint of ensuring the flexibility of the tape.

The average cell diameter can be measured by the following method.

First, the foam base material was cut into a 50mm square, immersed in liquid nitrogen for 1 minute, and then cut with a razor blade on a plane perpendicular to the thickness direction of the foam base material. Next, the longest cell diameter (diameter of cells) was measured for all cells existing in the range of thickness X2 mm by taking a magnified photograph of the cut surface at a magnification of 200 times using a digital microscope (for example, "VHX-900" manufactured by KEYENCE Co., Ltd.). The operation was repeated 5 times, and the obtained total cell diameters were averaged, whereby the average cell diameter was calculated.

The thickness of the foam base is not particularly limited, but the lower limit is preferably 40 μm and the upper limit is preferably 2900. mu.m. When the thickness of the foam base is in the above range, the adhesive tape of the present invention can be suitably used for fixing portable electronic device parts, in-vehicle electronic device parts, and the like. From the viewpoint of being suitably used for fixing the member and the like, a more preferable lower limit of the thickness of the foam base is 60 μm, a more preferable upper limit is 1900 μm, a further preferable lower limit is 80 μm, a further preferable upper limit is 1400 μm, a particularly preferable lower limit is 100 μm, and a particularly preferable upper limit is 1000 μm.

The foam base material is not particularly limited as long as it has a cell structure. Examples of the production method include a method in which the foam base is produced by the action of a foaming gas, and a method in which hollow spheres are mixed into a base material. Among them, the foam produced by the latter method is called a syntactic foam (syntactic foam), and the foam base is preferably a syntactic foam in terms of more excellent impact resistance and heat resistance. By making the foam base material a composite foam, a closed cell foam having a uniform size distribution of foam cells is obtained, and therefore the density of the entire foam base material becomes more constant, and the impact resistance can be further improved. In addition, the composite foam is less likely to undergo irreversible disintegration at high temperature and high pressure, and thus exhibits higher heat resistance, as compared to other foams. The composite foam includes a composite foam having a foam structure formed of hollow inorganic particles and a composite foam having a foam structure formed of hollow organic particles, and is preferably a composite foam having a foam structure formed of hollow organic particles from the viewpoint of flexibility.

Examples of the hollow organic fine particles include Expancel DU series (manufactured by Japan Fillite corporation) and ADVANCELL EM series (manufactured by water chemical industry corporation). Among them, Expancel 461-20 (average cell diameter after foaming under optimum conditions is 20 μm), Expancel461-40 (average cell diameter after foaming under optimum conditions is 40 μm), Expancel 043-80 (average cell diameter after foaming under optimum conditions is 80 μm), ADVANCELL EML101 (average cell diameter after foaming under optimum conditions is 50 μm) are preferable because the cell diameter after foaming can be easily designed to a region of higher effect.

The foaming agent used when the foam base material is composed of a foam other than the above-mentioned syntactic foam is not particularly limited, and a conventionally known foaming agent such as a thermal decomposition type foaming agent can be used.

The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include an acrylic pressure-sensitive adhesive layer, a rubber pressure-sensitive adhesive layer, a urethane pressure-sensitive adhesive layer, and a silicone pressure-sensitive adhesive layer. Among them, an acrylic pressure-sensitive adhesive layer containing an acrylic copolymer is preferable in terms of excellent heat resistance and adhesion to a wide variety of adherends.

The acrylic copolymer constituting the acrylic pressure-sensitive adhesive layer is preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and/or 2-ethylhexyl acrylate, from the viewpoint that the initial tackiness thereof is improved and the ease of adhesion at low temperatures is improved. Among them, more preferably, the copolymer is obtained by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate.

The preferable lower limit of the content of the butyl acrylate in the whole monomer mixture is 40% by weight, and the preferable upper limit is 80% by weight. By setting the content of butyl acrylate to the above range, both high adhesion and viscosity can be achieved.

The content of the above-mentioned 2-ethylhexyl acrylate in the whole monomer mixture preferably has a lower limit of 10% by weight, a preferable upper limit of 100% by weight, a more preferable lower limit of 30% by weight, a more preferable upper limit of 80% by weight, a further preferable lower limit of 50% by weight, and a further preferable upper limit of 60% by weight. When the content of 2-ethylhexyl acrylate is in the above range, high adhesive force can be exhibited.

The monomer mixture may contain other polymerizable monomers copolymerizable with butyl acrylate and 2-ethylhexyl acrylate, as necessary. Examples of the other polymerizable monomer copolymerizable with the above-mentioned monomer include alkyl (meth) acrylates having an alkyl group of 1 to 3 carbon atoms, alkyl (meth) acrylates having an alkyl group of 13 to 18 carbon atoms, and functional monomers.

Examples of the alkyl (meth) acrylate in which the alkyl group has 1 to 3 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and the like. Examples of the alkyl (meth) acrylate in which the alkyl group has 13 to 18 carbon atoms include tridecyl methacrylate and stearyl (meth) acrylate. Examples of the functional monomer include hydroxyalkyl (meth) acrylate, glycerol dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, and fumaric acid.

In order to obtain the acrylic copolymer by copolymerizing the monomer mixture, the monomer mixture may be subjected to a radical reaction in the presence of a polymerization initiator. As a method for radically reacting the monomer mixture, that is, a polymerization method, conventionally known methods can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization.

The lower limit of the weight average molecular weight (Mw) of the acrylic copolymer is preferably 40 ten thousand, and the upper limit is preferably 150 ten thousand. By setting the weight average molecular weight of the acrylic copolymer to the above range, high adhesion force can be exhibited. From the viewpoint of further improving the adhesive force, a more preferable lower limit of the weight average molecular weight is 50 ten thousand, and a more preferable upper limit is 140 ten thousand.

The weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene based on GPC (Gel Permeation Chromatography).

The upper limit of the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer is preferably 10.0. When Mw/Mn is 10.0 or less, the proportion of low-molecular components is suppressed, and softening of the pressure-sensitive adhesive layer at high temperature, lowering of the overall strength, and lowering of the adhesive strength are suppressed. From the same viewpoint, a more preferable upper limit of Mw/Mn is 5.0, and a further preferable upper limit is 3.0.

The pressure-sensitive adhesive layer may contain a tackifier resin.

Examples of the tackifier resin include rosin ester resins, hydrogenated rosin resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, and the like. These tackifying resins may be used alone or in combination of 2 or more.

The content of the tackifier resin is not particularly limited, and a preferable lower limit is 10 parts by weight and a preferable upper limit is 60 parts by weight with respect to 100 parts by weight of a resin (for example, an acrylic copolymer) which is a main component of the pressure-sensitive adhesive layer. If the content of the tackifier resin is 10 parts by weight or more, the decrease in the adhesive strength of the pressure-sensitive adhesive layer can be suppressed. If the content of the tackifier resin is 60 parts by weight or less, it is possible to suppress a decrease in adhesive force or tackiness due to hardening of the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer preferably has a crosslinked structure formed between main chains of resins (for example, the acrylic copolymer, the tackifier resin, and the like) constituting the pressure-sensitive adhesive layer by adding a crosslinking agent. The crosslinking agent is not particularly limited, and examples thereof include an isocyanate-based crosslinking agent, an aziridine-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate-based crosslinking agent. Among them, isocyanate-based crosslinking agents are preferable. When an isocyanate-based crosslinking agent is added to the pressure-sensitive adhesive layer, the isocyanate group of the isocyanate-based crosslinking agent reacts with an alcoholic hydroxyl group in a resin (for example, the acrylic copolymer, the tackifier resin, or the like) constituting the pressure-sensitive adhesive layer, thereby crosslinking the pressure-sensitive adhesive layer. If a crosslinked structure is formed between the main chains of the resin constituting the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer can disperse the intermittently applied peeling stress, and the adhesive strength of the pressure-sensitive adhesive tape can be further improved.

The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the resin (for example, the acrylic copolymer) which is the main component of the pressure-sensitive adhesive layer.

The above adhesive layer may contain a silane coupling agent for the purpose of improving the adhesive force. The silane coupling agent is not particularly limited, and examples thereof include epoxysilanes, acrylic silanes, methacrylic silanes, amino silanes, and isocyanate silanes.

The above adhesive layer may contain a coloring material for the purpose of imparting light-shielding properties. The coloring material is not particularly limited, and examples thereof include carbon black, aniline black, and titanium oxide. Among these, carbon black is preferred in terms of being relatively inexpensive and chemically stable.

The pressure-sensitive adhesive layer may contain conventionally known fine particles such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, inorganic fillers, and the like, and additives, as required.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and the lower limit is preferably 0.01mm and the upper limit is preferably 0.1 mm. By setting the thickness of the pressure-sensitive adhesive layer to the above range, the pressure-sensitive adhesive tape of the present invention can be suitably used for fixing portable electronic device parts, in-vehicle electronic device parts, and the like. From the viewpoint of being more suitable for fixing the member and the like, a more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 0.015mm, and a more preferable upper limit is 0.09 mm.

The adhesive tape of the present invention preferably has a resin layer on at least one surface of the foam base.

By having the resin layer, the strength of the obtained pressure-sensitive adhesive tape is improved, and therefore, the impact resistance, particularly the durability (roll-ability) when the impact is repeatedly applied can be further improved. The resin layer may be formed on one side or both sides of the foam base, and is preferably formed on one side of the foam base.

The resin constituting the resin layer preferably has heat resistance. Examples of the resin constituting the resin layer having heat resistance include polyester resins such as polyethylene terephthalate, acrylic resins, silicone resins, phenol resins, polyimides, and polycarbonates. Among them, acrylic resins and polyester resins are preferable, and polyethylene terephthalate is more preferable, from the viewpoint of obtaining an adhesive tape having excellent flexibility.

The above resin layer may be colored. By coloring the resin layer, the adhesive tape can be provided with light-shielding properties.

The method of coloring the resin layer is not particularly limited, and examples thereof include a method of mixing particles such as carbon black and titanium oxide or fine bubbles into the resin constituting the resin layer, and a method of applying ink to the surface of the resin layer.

The resin layer may contain conventionally known fine particles such as inorganic fine particles, conductive fine particles, plasticizers, tackifiers, ultraviolet absorbers, antioxidants, foaming agents, organic fillers, and inorganic fillers, and additives, as required.

The thickness of the resin layer is not particularly limited, but the lower limit is preferably 5 μm and the upper limit is preferably 100 μm. By setting the thickness of the resin layer to the above range, both the workability and the impact resistance of the pressure-sensitive adhesive tape can be satisfied. From the viewpoint of further achieving both workability and impact resistance, a more preferable lower limit of the thickness of the resin layer is 10 μm, and a more preferable upper limit is 70 μm.

The adhesive tape of the present invention may have other layers than the foam base, the adhesive layer, and the resin layer as necessary.

The pressure-sensitive adhesive tape of the present invention preferably has a ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the foam base (pressure-sensitive adhesive layer thickness/foam base thickness) of 0.1 to 2. When the ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the foam base material is in the above range, the strength of the entire pressure-sensitive adhesive tape to be obtained is improved, and therefore, the impact resistance can be further improved. The ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the foam base material is more preferably 0.15 or more, and still more preferably 1.2 or less. The thickness of the pressure-sensitive adhesive layer is the sum of the thicknesses of the pressure-sensitive adhesive layers on both sides.

The thickness of the adhesive tape of the present invention is not particularly limited, and the lower limit is preferably 0.04mm, the lower limit is more preferably 0.05mm, the upper limit is preferably 2mm, and the upper limit is more preferably 1.5 mm. By setting the thickness of the adhesive tape of the present invention to the above range, an adhesive tape having excellent workability can be obtained.

The method for producing the adhesive tape of the present invention is not particularly limited, and examples thereof include the following methods. First, a pressure-sensitive adhesive solution was applied to a release film and dried to form a pressure-sensitive adhesive layer, and the 2 nd pressure-sensitive adhesive layer was formed by the same method. Next, an unfoamed base material was produced by the above method, and the resin layer was laminated on the unfoamed base material to form a laminate. Then, the obtained pressure-sensitive adhesive layers are bonded to both surfaces of the obtained laminate, and heated to foam the unfoamed substrate, thereby producing the pressure-sensitive adhesive tape.

The shape of the pressure-sensitive adhesive tape of the present invention is not particularly limited, and examples thereof include a rectangular shape, a frame shape, a circular shape, an oval shape, a doughnut shape, and the like.

The adhesive tape of the present invention can exhibit excellent flexibility, impact resistance and heat resistance by using the block copolymer as a foam base. On the other hand, the present inventors have conducted studies and as a result, have found that excellent flexibility, impact resistance and heat resistance can be exhibited even when the foam base is a random copolymer containing a structure derived from the vinyl aromatic compound monomer, a structure derived from the monomer having a crosslinkable functional group and a structure derived from the (meth) acrylic monomer. This is considered to be because the same interaction as the above phase separation structure acts on an extremely small scale such as a nanometer level or a molecular level. In the present specification, the structures derived from (meth) acrylic monomers refer to structures represented by the following general formulae (5) and (6).

[ chemical formula 3]

Herein, R is³Represents a side chain. As side chain R³Examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, lauryl, and isostearyl groups.

Therefore, an adhesive tape having an adhesive layer on both sides of a foam base containing a copolymer having a structure derived from a vinyl aromatic compound monomer, a structure derived from a monomer having a crosslinkable functional group, and a structure derived from a (meth) acrylic monomer is also one aspect of the present invention.

The copolymer is not particularly limited, and examples thereof include a block copolymer and a random copolymer.

Among them, a soft block (a block containing a structure derived from the above-mentioned (meth) acrylic monomer) and a hard block (a block containing a structure derived from the above-mentioned vinyl aromatic compound monomer) adopt an uneven phase separation structure, and the hard block becomes a pseudo crosslinking point, thereby imparting rubbery properties to the copolymer, and a block copolymer is preferable from the viewpoint of being able to impart high flexibility and impact resistance to the obtained adhesive tape. Examples of the block copolymer include a diblock copolymer, a triblock copolymer, and a graft copolymer, and from the viewpoint of the formation of the above-mentioned layer separation, the diblock copolymer and the triblock copolymer are preferable, and the triblock copolymer is more preferable.

When the copolymer is a block copolymer, the block copolymer preferably contains 1 to 40 wt% of the hard block. By setting the hard block content to the above range, a foam base material excellent in flexibility, impact resistance and heat resistance can be formed. From the viewpoint of further improving flexibility, impact resistance and heat resistance, a more preferable lower limit of the content of the hard block is 2% by weight, a further preferable lower limit is 2.5% by weight, a particularly preferable lower limit is 3% by weight, a further preferable upper limit is 35% by weight, a further preferable upper limit is 30% by weight, a further preferable upper limit is 26% by weight, a further preferable upper limit is 20% by weight, a particularly preferable upper limit is 17% by weight, and a particularly preferable upper limit is 8% by weight.

When the copolymer is a block copolymer, the polymerization average molecular weight of the block copolymer is preferably 50000 to 800000.

By setting the weight average molecular weight of the block copolymer to the above range, flexibility, impact resistance and heat resistance can be further improved. A more preferable lower limit of the polymerization average molecular weight of the block copolymer is 75000, and a more preferable upper limit is 600000.

In order to obtain the block copolymer, the raw material monomers of the hard block and the soft block are subjected to a radical reaction in the presence of a polymerization initiator to obtain the hard block and the soft block, and then the hard block and the soft block are reacted or copolymerized, or the hard block is obtained by the above method, and then the raw material monomers of the soft block are charged and copolymerized. As the method for carrying out the radical reaction, i.e., the polymerization method, conventionally known methods can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.

The vinyl aromatic compound monomer is not particularly limited, and examples thereof include styrene, α -methylstyrene, p-methylstyrene, chlorostyrene, and the like. Among them, styrene is preferable in terms of further improving the impact resistance.

The content of the structure derived from the vinyl aromatic compound monomer in the copolymer is preferably 1% by weight or more and 30% by weight or less. A more preferable lower limit is 1.5% by weight, a further preferable lower limit is 2% by weight, a particularly preferable lower limit is 2.5% by weight, a more preferable upper limit is 24% by weight, a further preferable upper limit is 19% by weight, a particularly preferable upper limit is 16% by weight, and a particularly preferable upper limit is 8% by weight.

The monomer having the crosslinkable functional group is not particularly limited, and examples thereof include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an epoxy group-containing monomer, a double bond-containing monomer, a triple bond-containing monomer, an amino group-containing monomer, an amide group-containing monomer, and a nitrile group-containing monomer. Among them, from the viewpoint of further improving flexibility and impact resistance, at least 1 kind selected from the group consisting of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an epoxy group-containing monomer, an amide group-containing monomer, a double bond-containing monomer and a triple bond-containing monomer is preferable. Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate. Examples of the carboxyl group-containing monomer include (meth) acrylic acid and the like. Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate. Examples of the amide group-containing monomer include (meth) acrylamide and the like. Examples of the double bond-containing monomer include allyl (meth) acrylate and hexanediol di (meth) acrylate. Examples of the triple bond-containing monomer include propargyl (meth) acrylate and the like. Among these, from the viewpoint of imparting more excellent flexibility and impact resistance to the pressure-sensitive adhesive tape, a carboxyl group-containing monomer is preferable, a (meth) acrylic monomer is more preferable, and acrylic acid is further preferable.

The content of the structure derived from the monomer having a crosslinkable functional group in the copolymer is preferably 0.1% by weight or more and 30% by weight or less. The lower limit is more preferably 0.5% by weight, the lower limit is still more preferably 1% by weight, the upper limit is still more preferably 25% by weight, and the upper limit is still more preferably 20% by weight.

The (meth) acrylic monomer is not particularly limited, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, and isostearyl (meth) acrylate 2-ethylhexyl acrylate. The (meth) acrylic monomer may be a single monomer or a plurality of monomers may be used. In addition, monomers other than the (meth) acrylic monomer may be used within a range in which the effects of the present invention are not lost.

The content of the structure derived from the (meth) acrylic monomer in the copolymer is not particularly limited as long as the effects of the present invention can be exerted, and is preferably 30% by weight or more and 99% by weight or less, more preferably 40% by weight or more and 98% by weight or less, and further preferably 50% by weight or more and 97% by weight or less.

The foam base is preferably a composite foam having a foam structure formed of hollow organic fine particles.

Examples of the hollow organic fine particles constituting the composite foam include Expancel DU series (manufactured by Japan Fillite corporation) and ADVANCELL EM series (manufactured by water chemical industry corporation). Among them, Expancel 461-20 (average cell diameter after foaming under optimum conditions is 20 μm), Expancel461-40 (average cell diameter after foaming under optimum conditions is 40 μm), Expancel 043-80 (average cell diameter after foaming under optimum conditions is 80 μm), ADVANCELL EML101 (average cell diameter after foaming under optimum conditions is 50 μm) are preferable because the cell diameter after foaming can be easily designed to a region of higher effect.

The same additive as that used for the foam layer of the pressure-sensitive adhesive tape using the block copolymer can be used for the foam base material.

The foam substrate has an apparent density of preferably 0.3g/cm³Above and 0.75g/cm³Hereinafter, more preferably 0.33g/cm³Above and 0.73g/cm³Hereinafter, more preferably 0.35g/cm³Above and 0.71g/cm³The following.

The gel fraction of the foam base is preferably 90% or less, more preferably 85% or less, and still more preferably 80% or less. The lower limit of the gel fraction is not particularly limited, and is, for example, 10% or more, particularly 20% or more, and particularly 35% or more.

The average cell diameter of the cells of the foam base is preferably 80 μm or less, more preferably 60 μm or less, and still more preferably 55 μm or less. The average cell diameter of the cells is preferably 20 μm or more.

The thickness of the foam base is not particularly limited, but is preferably 40 μm at the lower limit, more preferably 60 μm at the lower limit, still more preferably 80 μm at the lower limit, particularly preferably 100 μm at the lower limit, more preferably 2900 μm at the upper limit, more preferably 1900 μm at the upper limit, even more preferably 1400 μm at the upper limit, and particularly preferably 1000 μm at the upper limit.

As a method for producing the copolymer, for example, a solution obtained by mixing a vinyl aromatic compound monomer, a monomer having a crosslinkable functional group, a (meth) acrylic monomer, and if necessary, another monomer may be subjected to a radical reaction in the presence of a polymerization initiator. As a method for carrying out the radical reaction, conventionally known methods can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.

The method for producing the foam base is not particularly limited, and examples thereof include the following methods: first, a foaming agent is added to a solution of the copolymer, the mixture is coated in a desired shape, and the resultant is dried to form an unfoamed base material. In addition, when the foam base material is a composite foam, there may be mentioned a method in which the hollow organic fine particles are added to a solution of the copolymer, mixed, coated in a desired shape, and dried.

The adhesive tape preferably has a resin layer on at least one surface of the foam base.

The resin constituting the resin layer preferably has heat resistance, and examples thereof include polyester resins such as polyethylene terephthalate, acrylic resins, silicone resins, phenol resins, polyimides, and polycarbonates. Among them, acrylic resins and polyester resins are preferable, and polyethylene terephthalate is more preferable, from the viewpoint of obtaining an adhesive tape having excellent flexibility.

The thickness of the resin layer is not particularly limited, but is preferably 5 μm at the lower limit, more preferably 10 μm at the lower limit, preferably 100 μm at the upper limit, and more preferably 70 μm at the upper limit.

The pressure-sensitive adhesive layer may be the same as that of the pressure-sensitive adhesive tape using the block copolymer.

The use of the pressure-sensitive adhesive tape of the present invention is not particularly limited, and the pressure-sensitive adhesive tape is excellent in flexibility, impact resistance and heat resistance, and therefore can be suitably used as an impact-resistant pressure-sensitive adhesive tape for fixing electronic parts such as portable electronic device parts and in-vehicle electronic device parts. The adhesive tape of the present invention used for fixing such electronic components is also one aspect of the present invention.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an adhesive tape having excellent flexibility and impact resistance and also excellent heat resistance can be provided.

Drawings

Fig. 1 is a schematic diagram illustrating a holding force test of an adhesive tape.

Detailed Description

The mode of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(example 1)

(1) Production of unfoamed substrates

0.902g of 1, 6-hexanedithiol, 1.83g of carbon disulfide and 11mL of dimethylformamide were put into a 2-neck flask and stirred at 25 ℃. 2.49g of triethylamine was added dropwise thereto over 15 minutes, and the mixture was stirred at 25 ℃ for 3 hours. Next, 2.75g of methyl-. alpha. -bromobenzoic acid was added dropwise over 15 minutes, followed by stirring at 25 ℃ for 4 hours. Then, 100mL of an extraction solvent (n-hexane: ethyl acetate 50: 50) and 50mL of water were added to the reaction mixture, and liquid separation and extraction were performed. The organic layers obtained in the first and second liquid-separation extractions were mixed, and washed with 50mL of 1M hydrochloric acid, 50mL of water, and 50mL of saturated saline in this order. After sodium sulfate was added to the washed organic layer and dried, the sodium sulfate was filtered, and the filtrate was concentrated by an evaporator to remove the organic solvent. The obtained concentrate was purified by silica gel column chromatography, whereby a RAFT agent was obtained.

91.3g of styrene (St), 8.7g of Acrylic Acid (AA), 1.9g of RAFT agent and 0.2g of 2, 2' -azobis (2-methylbutyronitrile) (ABN-E) were put into a 2-neck flask, and the flask was heated to 85 ℃ while the inside of the flask was replaced with nitrogen gas. Then, the mixture was stirred at 85 ℃ for 6 hours to carry out polymerization (first-stage reaction).

After the reaction was completed, 4000g of n-hexane was charged into the flask, and after stirring to precipitate the reaction product, the unreacted monomers (St, AA) and RAFT agent were filtered, and the reaction product was dried under reduced pressure at 70 ℃.

A mixture containing 100g of Butyl Acrylate (BA), 0.058g of ABN-E and 50g of ethyl acetate, and the copolymer (hard block) obtained above were put into a 2-neck flask, and the temperature was raised to 85 ℃ while the inside of the flask was replaced with nitrogen gas. Then, the mixture was stirred at 85 ℃ for 6 hours to carry out a polymerization reaction (second-stage reaction) to obtain a reaction solution containing a block copolymer composed of a hard block and a soft block. The blending amount of the mixture (soft block) and the hard block is set to an amount such that the content of the hard block in the obtained block copolymer becomes 17% by weight.

A part of the reaction solution was collected, 4000g of n-hexane was added thereto, and after precipitating the reaction product by stirring, the unreacted monomer (BA) and the solvent were filtered, and the reaction product was dried under reduced pressure at 70 ℃ to take out the block copolymer from the reaction solution. The weight average molecular weight of the obtained block copolymer was measured by GPC and found to be 25 ten thousand. As a measuring apparatus, a "2690 Separations Module" manufactured by Water corporation was used, and a "GPC KF-806L" manufactured by Showa Denko K.K. was used as a column, and ethyl acetate was used to perform measurement under conditions of a sample flow rate of 1mL/min and a column temperature of 40 ℃.

The obtained block copolymer was dissolved in ethyl acetate so that the solid content was 35%, 0.5 part by weight of Expancel461-40 (DU 40 in the table) as a foaming agent and 0.2 part by weight of tetra d C (MITSUBISHI GAS CHEMICAL) as a crosslinking agent were added to 100 parts by weight of the block copolymer a, and the mixture was sufficiently stirred to obtain a base material solution. The obtained substrate solution was applied to a release-treated surface of a 50 μm polyethylene terephthalate (PET) film, which was subjected to release treatment on one surface, and dried at 90 ℃ for 7 minutes, thereby obtaining an unfoamed substrate. The thickness of the unfoamed substrate was adjusted so that the unfoamed substrate became 100 μm when heated at 130 ℃ for 1 minute.

(2) Preparation of the Binder solution

52 parts by weight of ethyl acetate was charged into a reactor equipped with a thermometer, a stirrer and a condenser, and after nitrogen substitution, the reactor was heated to start reflux. After the ethyl acetate was boiled, 0.08 part by weight of azobisisobutyronitrile as a polymerization initiator was added 30 minutes later. A monomer mixture comprising 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid and 0.2 part by weight of 2-hydroxyethyl acrylate was uniformly and slowly added dropwise thereto over 1 hour and 30 minutes to effect reaction. After 30 minutes from the completion of the dropwise addition, 0.1 part by weight of azobisisobutyronitrile was added, and polymerization was further carried out for 5 hours, and while adding ethyl acetate to the reactor and diluting, the reactor was cooled to obtain a solution of an acrylic random copolymer having a solid content of 40% by weight.

The weight average molecular weight of the resulting acrylic random copolymer was measured by GPC using a "2690 Separations Model" manufactured by Water as a column, and the result was 71 ten thousand. The ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) was 5.5.

To 100 parts by weight of the solid content of the obtained acrylic random copolymer, 15 parts by weight of a polymerized rosin ester having a softening point of 150 ℃, 10 parts by weight of a terpene phenol having a softening point of 145 ℃, and 10 parts by weight of a rosin ester having a softening point of 70 ℃ were added. Further, 30 parts by weight of ethyl acetate (manufactured by Doku chemical Co., Ltd.) and 3.0 parts by weight of an isocyanate-based crosslinking agent (Coronate L45 manufactured by Tosoh Co., Ltd.) were added thereto and stirred to obtain a binder solution.

(3) Production of adhesive tapes

The obtained adhesive solution was coated on a release-treated surface of a 50 μm polyethylene terephthalate (PET) film, which was subjected to release treatment on one surface thereof, with a doctor blade so that the thickness of the dried coating film became 50 μm, and the coating solution was dried by heating at 110 ℃ for 5 minutes to obtain an adhesive layer. Next, 1 adhesive layer was remanufactured by the same operation to obtain 2 adhesive layers. Then, the release film was peeled off from the unfoamed substrate obtained above, and the obtained 2 pressure-sensitive adhesive layers were attached to both surfaces of the unfoamed substrate, respectively, and allowed to stand at 40 ℃ for 48 hours. After 48 hours, the substrate was taken out from the 40 ℃ atmosphere and heated at 130 ℃ for 1 minute, whereby the substrate was foamed to obtain an adhesive tape.

(4) Determination of tape Density

The density of the obtained adhesive tape was measured using an electron densitometer (ED 120T, manufactured by MIRAGE corporation).

(5) Measurement of apparent Density of foam base Material

The density of the resulting foam base material was measured by using an electron densitometer (ED 120T, manufactured by MIRAGE corporation) according to JISK-6767. According to the results, the density of the adhesive was regarded as 1.0g/cm³The apparent density of the foam substrate was calculated.

(6) Measurement of gel fraction of foam base Material

Gel fraction (wt%) < 100 × (W1-W2)/W0

(examples 2 to 24, 27 to 29)

Adhesive tapes were obtained in the same manner as in example 1, except that the composition and thickness of the foam base and the thickness of the adhesive layer were changed as shown in tables 1 and 2. In example 20, the base material was foamed by heating at 150 ℃ for 1 minute. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1. The raw materials in the table are as follows.

MA: acrylic acid methyl ester

AA: acrylic acid

HEA: 2-Hydroxyethyl acrylate

EML 101: ADVANCELL EML101 (manufactured by hydrops chemical industries, Ltd.)

(example 25)

Adhesive tapes were obtained in the same manner as in example 1, except that the composition and thickness of the foam base and the thickness of the adhesive layer were changed as shown in table 2, and the base solution was applied to a polyethylene terephthalate (PET) sheet (manufactured by toyobo co., ltd., E5007) having a thickness of 25 μm as a resin layer. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(examples 26, 30 to 34)

Adhesive tapes were obtained in the same manner as in example 25, except that the composition and thickness of the foam base and the thickness of the adhesive layer were changed as shown in table 2. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 35)

(1) Production of unfoamed substrates

52 parts by weight of ethyl acetate was charged into a reactor equipped with a thermometer, a stirrer and a condenser, and after nitrogen substitution, the reactor was heated to start reflux. After the ethyl acetate was boiled, 0.08 part by weight of azobisisobutyronitrile as a polymerization initiator was added 30 minutes later. A monomer mixture comprising 93.888 parts by weight of butyl acrylate, 4 parts by weight of a styrene macromonomer (AS-6S, manufactured by Toyo Synthesis Co., Ltd.) 1.92 parts by weight of acrylic acid, and 0.192 part by weight of 2-hydroxyethyl acrylate was uniformly and slowly added dropwise over 1 hour and 30 minutes to the mixture to effect a reaction. After 30 minutes from the completion of the dropwise addition, 0.1 part by weight of azobisisobutyronitrile was added to the reaction mixture, and polymerization was further carried out for 5 hours, and ethyl acetate was added to the reaction vessel and the reaction mixture was cooled while being diluted, whereby a solution of an acrylic graft copolymer having a solid content of 40 wt% was obtained.

The weight average molecular weight of the acrylic graft copolymer obtained was measured by GPC and found to be 60 ten thousand. As a measuring apparatus, a "2690 Separations Module" manufactured by Water corporation was used, a "GPC KF-806L" manufactured by Showa Denko K.K. was used as a column, and ethyl acetate was used as a solvent, and measurement was performed under conditions of a sample flow rate of 1mL/min and a column temperature of 40 ℃.

The obtained graft copolymer was dissolved in ethyl acetate so that the solid content rate became 35%, and 2.12 parts by weight of Expancel461-40 as a blowing agent and 0.3 part by weight of TETRAD C as a crosslinking agent were added to 100 parts by weight of the graft copolymer, followed by sufficient stirring to obtain a base material solution. The obtained substrate solution was coated on a release-treated surface of a 50 μm polyethylene terephthalate (PET) film, which was release-treated on one surface, and dried at 90 ℃ for 7 minutes, thereby obtaining an unfoamed substrate containing a graft copolymer. The thickness of the unfoamed substrate was adjusted so that the unfoamed substrate became 100 μm when heated at 130 ℃ for 1 minute.

(2) Production of adhesive tapes

An adhesive tape was obtained in the same manner as in example 1, except that the obtained unfoamed substrate containing the graft copolymer was used. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 36)

Adhesive tapes were obtained in the same manner as in example 35, except that the contents of the hard block component and the soft block component were changed as shown in table 2. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 37)

An unfoamed substrate comprising a graft copolymer was obtained in the same manner as in example 35, except that the composition and thickness of the foamed substrate were changed to those shown in table 2. Adhesive tapes were obtained in the same manner as in example 25, except that the thickness of the adhesive layer was changed to the thickness shown in table 2. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 38)

(1) Production of unfoamed substrates

52 parts by weight of ethyl acetate was charged into a reactor equipped with a thermometer, a stirrer and a condenser, and after nitrogen substitution, the reactor was heated to start reflux. After the ethyl acetate was boiled, 0.08 part by weight of azobisisobutyronitrile as a polymerization initiator was added after 30 minutes. A monomer mixture comprising 94.8 parts by weight of butyl acrylate, 3 parts by weight of styrene, 2 parts by weight of acrylic acid and 0.2 part by weight of 2-hydroxyethyl acrylate was uniformly and slowly added dropwise over 1 hour and 30 minutes to effect a reaction. After 30 minutes from the completion of the dropwise addition, 0.1 part by weight of azobisisobutyronitrile was added to the reaction mixture, and polymerization was further carried out for 5 hours, and ethyl acetate was added to the reaction vessel and the reaction mixture was cooled while being diluted, whereby a solution of a random copolymer having a solid content of 40% by weight was obtained. The weight average molecular weight of the obtained random copolymer was measured by GPC and found to be 37 ten thousand. As a measuring apparatus, the flow rate of a sample was 1mL/min and the column temperature was 40 ℃ using "2690 Separations Module" manufactured by Water, as a column, "GPC KF-806L" manufactured by Showa Denko K.K., as a solvent, and ethyl acetate.

The obtained random copolymer was dissolved in ethyl acetate so that the solid content rate became 35%, 2.12 parts by weight of Expancel461-40 as a blowing agent and 0.25 part by weight of TETRAD C as a crosslinking agent were added to 100 parts by weight of the random copolymer, and the mixture was sufficiently stirred to obtain a base material solution. The obtained substrate solution was applied to a release-treated surface of a 50 μm polyethylene terephthalate (PET) film, which was subjected to release treatment on one surface, and dried at 90 ℃ for 7 minutes, thereby obtaining an unfoamed substrate containing a random copolymer. The thickness of the unfoamed substrate was adjusted so that the unfoamed substrate became 100 μm when heated at 130 ℃ for 1 minute.

(2) Production of adhesive tapes

An adhesive tape was obtained in the same manner as in example 1, except that the obtained unfoamed substrate containing the random copolymer was used. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 39)

Adhesive tapes were obtained in the same manner as in example 38, except that the composition of the foam base was changed as shown in table 2. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

(example 40)

An unfoamed substrate comprising a random copolymer was obtained in the same manner as in example 38, except that the composition and thickness of the foamed substrate were changed to those shown in table 2. Adhesive tapes were obtained in the same manner as in example 25, except that the thickness of the adhesive layer was changed to the thickness shown in table 2. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

Comparative example 1

An adhesive tape was obtained in the same manner as in example 1, except that no foaming agent was added to the adhesive tape, heating at 130 ℃ for 1 minute was not performed, and a foam base was not formed. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

Comparative example 2

(1) Preparation of foam base Material

Volara H03001 (polyethylene resin, 100 μm thick, manufactured by WASTE CHEMICAL Co., Ltd.) was used as the foam base material.

(2) Production of adhesive tapes

A pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that the obtained substrate was used. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

Comparative example 3

(1) Preparation of foam base Material

Volara H0250012 (polyethylene resin, produced by accumulated Water chemical industries, Ltd., thickness: 120 μm) was used as the foam base material.

(2) Production of adhesive tapes

Comparative example 4

(1) Manufacture of substrates

An unfoamed substrate was obtained in the same manner as in example 1, except that a 30% toluene solution of Cepton 2063 (hydrocarbon resin, manufactured by kuraray) was prepared, 0.5 parts by weight of Expancel461-40 (manufactured by Japan Fillite) as a blowing agent was used per 100 parts by weight of the solid content, and no crosslinking agent was used.

(2) Production of adhesive tapes

A pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that the obtained unfoamed substrate was used. The obtained adhesive tape was subjected to the respective measurements in the same manner as in example 1.

Comparative example 5

(1) Production of unfoamed substrates

An unfoamed substrate was obtained in the same manner as in example 1, except that the acrylic random copolymer solution obtained in the preparation of the binder solution in example 1 was used instead of the acrylic copolymer a, and 1 part by weight of a crosslinking agent and 0.5 part by weight of a foaming agent were used based on 100 parts by weight of the solid content of the acrylic random copolymer solution. The following crosslinking agents and foaming agents were used.

A crosslinking agent: L-45E manufactured by Tosoh corporation

Foaming agent: expancel461-40, manufactured by Japan Fillite

(2) Production of adhesive tapes

< evaluation >

The adhesive tapes obtained in examples and comparative examples were evaluated as follows. The results are shown in tables 1 to 3.

(evaluation of impact resistance)

The obtained adhesive tape was punched out in an ロ -shaped form having an outer shape of 45mm × 60mm and a width of 1 mm. One side of the adhesive tape after punching was attached to the center of an ロ -shaped stainless steel plate having a hole of 40mm × 40mm in the center and a thickness of 2 mm. Then, a tempered glass plate 50mm × 70mm and 4mm in thickness was attached to the other surface of the pressure-sensitive adhesive tape, and the tape was pressure-bonded with a 5kg weight for 10 seconds and allowed to stand at 23 ℃ for 24 hours to obtain a laminate for testing. The resulting laminate was fixed to a stainless steel frame (inner diameter 60mm × 90mm) so that the tempered glass plate became the lower surface. Then, 150g of the iron balls were dropped toward the center of the tempered glass plate. The height of the iron ball was gradually increased to drop the iron ball, and the height of the iron ball was measured when the tempered glass plate was peeled from the stainless steel plate. The reinforced glass plate was evaluated for impact resistance by designating the height of the iron ball at the time of separation from the stainless steel plate as "excellent", the height of the iron ball at the time of separation from the stainless steel plate as "o", the height of the iron ball at the time of separation from the stainless steel plate as "Δ", the height of the iron ball at the time of separation from the stainless steel plate as "20 cm or more and less than 60cm as" Δ ", and the height of the iron ball at the time of separation from the stainless steel plate as" x ".

(evaluation of holding force)

Fig. 1 shows a schematic diagram illustrating a holding force test of an adhesive tape. First, one surface (front surface) of a test piece 1 having a size of 25mm × 25mm of an adhesive tape was bonded to the SUS plate 2, and a 2kg rubber roller was reciprocated once at a speed of 300 mm/min from the other surface (back surface) side of the test piece 1. Next, an aluminum plate 3 was bonded to the back surface of the test piece 1, and the test piece was pressed and bonded with a 0.5kg weight for 10 seconds from the aluminum plate 3 side, and then left for 24 hours in an environment of 23 ℃ and a relative humidity of 50%, to prepare a sample for a holding force test. For the retention test sample, a weight 4 of 0.5kg or 1.0kg was attached to one end of the aluminum plate 3 at 100 ℃ so as to apply a load in the horizontal direction to the test piece 1 and the aluminum plate 3, and the offset length of the weight after 1 hour was measured. Further, a 1.0kg weight 4 was attached, and the offset length after 2 hours was measured. The obtained measurement results were evaluated for retention force by assuming that the offset length was 0 (no offset), the offset length was more than 0 and less than 1mm, the offset length was "x", and the offset length was 1mm or more or the adhesive tape was peeled off and dropped.

(evaluation of Rolling Performance)

2 adhesive tapes cut to 1mm × 70mm were prepared. Then, adhesive tapes were attached to the short sides of a polycarbonate sheet having a length of 72mm, a width of 135mm and a thickness of 1 mm. Then, the surface of the polycarbonate plate to which the adhesive tape was attached was overlapped with a polycarbonate plate having a length of 77mm, a width of 150mm and a thickness of 4mm so that the short sides of the 2 polycarbonate plates were opposed to the long sides thereof, and the pressure was applied at 0.7MPa for 15 seconds, thereby bonding the 2 polycarbonate plates. Then, it was left standing at 23 ℃ for 24 hours, thereby obtaining a test sample. The obtained test sample was put into a TD-1000A roller rotation drop tester (manufactured by Xinrong electronic measuring instruments) and rotated at a speed of 12 rpm while maintaining a room temperature environment at 23 ℃ to repeatedly drop the test sample from a height of 1 m. The rolling property was evaluated by designating the number of drops more than 1500 times when the polycarbonate sheet was peeled as "excellent", designating the number of drops more than 1000 and 1500 times or less as "o", and designating the number of drops 1000 or less as "x".

[ Table 1]

[ Table 2]

[ Table 3]

Industrial applicability

Description of the reference numerals

1: test piece of adhesive tape with size of 25mm × 25mm

2: SUS plate

3: aluminium plate

4: weight (0.5kg or 1.0kg)

Claims

1. An adhesive tape having adhesive layers on both sides of a foam base,

the foam base material contains a block copolymer having at least 1 or more hard blocks and 1 soft block, the soft block being composed of a (meth) acrylic monomer.

2. The adhesive tape according to claim 1, wherein the hard block has a structure derived from a monomer having a crosslinkable functional group.

3. The adhesive tape according to claim 1 or 2, wherein the monomer having a crosslinkable functional group is at least 1 selected from the group consisting of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an epoxy group-containing monomer, an amide group-containing monomer, a double bond-containing monomer, and a triple bond-containing monomer.

4. The adhesive tape according to any one of claims 1 to 3, wherein the hard block has a structure derived from a vinyl aromatic compound monomer.

5. The adhesive tape according to any one of claims 1 to 4, wherein the hard block has a structure derived from a vinyl aromatic compound monomer and a structure derived from a monomer having a crosslinkable functional group.

6. The adhesive tape according to any one of claims 1 to 5, wherein the block copolymer contains 1% by weight or more and 40% by weight or less of the hard block.

7. An adhesive tape having adhesive layers on both sides of a foam base,

the foam base material contains a copolymer which is,

the copolymer has a structure derived from a vinyl aromatic compound monomer, a structure derived from a monomer having a crosslinkable functional group, and a structure derived from a (meth) acrylic monomer.

8. The adhesive tape according to claim 7, wherein a content of the structure derived from the (meth) acrylic monomer in the copolymer is 30% by weight or more and 99% by weight or less.

9. The adhesive tape according to any one of claims 1 to 8, wherein the foam base has a gel fraction of 90% or less.

10. The adhesive tape according to any one of claims 1 to 9, wherein the apparent density of the foam base is 0.3g/cm³Above and 0.75g/cm³The following.

11. The adhesive tape according to any one of claims 1 to 10, wherein a resin layer is provided on at least one surface of the foam base.

12. The adhesive tape according to any one of claims 1 to 11, wherein the average cell diameter of the cells of the foam base is 80 μm or less.

13. The adhesive tape according to any one of claims 1 to 12, which is used for fixing an electronic component.