JP2015092003A - Method for producing acrylic pressure-sensitive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic pressure-sensitive adhesive combining high shear retention power under a high temperature condition with high adhesive power with respect to a curved surface.SOLUTION: A method for producing an acrylic pressure-sensitive adhesive containing an acrylic polymer is provided which comprises: a first step of photopolymerizing a monofunctional monomer composed of alkyl acrylate with an alkyl group having 1 to 18 carbon atoms of 70 to 99 mass% and unsaturated monomer having a vinyl carbonyl group and a polar group of 1 to 30 mass% to obtain a partial polymer of the monofunctional monomer; and a second step of photopolymerizing a mixture of the partial polymer and a polyfunctional methacrylate of 0.01 to 1.0 pts.mass with respect to the partial polymer of 100 pts.mass to obtain an acrylic polymer. The photopolymerization in the second step is conducted by ultraviolet irradiation with a condition of irradiation intensity of 0.05 to 10 mW/cm.

Description

  The present invention relates to an acrylic pressure-sensitive adhesive.

  Acrylic adhesives are widely used as adhesive substrates for single-sided or double-sided adhesive tapes, and are also used as acrylic foam adhesives by foaming the adhesive substrate. In general, such an acrylic foam pressure-sensitive adhesive is obtained by foaming a foaming agent in an acrylic monomer before curing and then curing, or by introducing an inert gas such as nitrogen gas into the acrylic monomer before curing. Then, it is manufactured by a mechanical foaming method for curing (Patent Documents 1 to 3).

JP-T-2004-518793 Japanese Patent Laid-Open No. 2002-80802 JP 2006-22189 A

  Acrylic foam pressure-sensitive adhesive has excellent adhesion to various adherends, so it can be applied to various applications such as electric / electronic, construction / housing, and transportation equipment. It is not easy to improve curved surface adhesion.

  Accordingly, an object of the present invention is to provide an acrylic pressure-sensitive adhesive that achieves both a high shear holding force under a high temperature condition and a high adhesion force to a curved surface.

  The present invention relates to a monofunctional monomer comprising 70 to 99% by mass of an alkyl acrylate having 1 to 18 carbon atoms in an alkyl group, and 1 to 30% by mass of an unsaturated monomer having a vinylcarbonyl group and a polar group, and the monofunctional An acrylic pressure-sensitive adhesive containing an acrylic polymer having a monomer unit of 0.01 to 1.0 part by weight of a polyfunctional methacrylate with respect to 100 parts by weight of a monomer is provided.

  Such an acrylic pressure-sensitive adhesive contains an acrylic polymer obtained by combining a specific monofunctional monomer in a predetermined ratio and reacting a predetermined amount of a polyfunctional monomer having a specific chemical structure (that is, a methacrylate structure). The flexibility and curved surface followability are improved, and both a high shear holding force under a high temperature condition and a high adhesion force to the curved surface are achieved.

  The present invention also provides a partial polymer of a monofunctional monomer comprising 70 to 99% by mass of an alkyl acrylate having 1 to 18 carbon atoms in the alkyl group and 1 to 30% by mass of an unsaturated monomer having a vinylcarbonyl group and a polar group. And an acrylic pressure-sensitive adhesive containing an acrylic polymer obtained by photopolymerizing a mixture of 0.01 to 1.0 part by mass of a polyfunctional methacrylate with respect to 100 parts by mass of the partial polymer. Such an acrylic pressure-sensitive adhesive is further excellent in the shear holding force and the adhesive force to a curved surface under high temperature conditions.

  The mixture in the acrylic pressure-sensitive adhesive preferably contains a photopolymerization initiator, and the photopolymerization is preferably ultraviolet polymerization.

  The monofunctional monomer and polyfunctional methacrylate can be polymerized without a polymerization initiator by high energy rays such as an electron beam (EB), but by ultraviolet polymerization of a mixture containing a photopolymerization initiator, An acrylic polymer can be stably produced by preventing modification or decomposition of the polymer during or after the polymerization that may occur when EB or the like is used. Further, the energy for polymerization can be within a practically appropriate range, which is suitable for mass production. Furthermore, there are a wide variety of monomers that can be polymerized with ultraviolet rays, and a variety of compositions are possible, so acrylic pressure-sensitive adhesives that excel in shear holding power and curved surface adhesion under high temperature conditions depending on the adherend and application. Makes it easy to design.

  The acrylic pressure-sensitive adhesive can contain surface-modified nanoparticles. By including surface-modified nanoparticles in the acrylic pressure-sensitive adhesive, not only can the filler fill, increase, and reinforce the effect, but it also contributes to the stabilization of bubbles when the acrylic pressure-sensitive adhesive is foamed. .

  The acrylic pressure-sensitive adhesive is preferably a foam. By adopting a foam, when shearing force or peeling force is applied to the joined body, it is possible to effectively absorb them as the energy of deformation of the foam, so that the adhesive strength can be improved. Become. Moreover, since it is a foam and it is further excellent in a softness | flexibility and curved surface followability, it comes to have a higher adhesive force with respect to a curved surface.

  An acrylic adhesive can be made into a sheet form. The sheet-like acrylic pressure-sensitive adhesive is not only easy to manufacture, but also when a bonded body is manufactured using this, the thickness of the pressure-sensitive adhesive layer is easily maintained, so that uniform adhesive strength can be obtained. It becomes possible to obtain a bonded assembly. Moreover, if it is a sheet form, it can be easily applied to various curved surface shapes.

  The acrylic pressure-sensitive adhesive preferably has a loss on drying at 120 ° C. for 2 hours of 1.0% by mass or less. Such an acrylic pressure-sensitive adhesive has a low residual ratio of unreacted monomers and a small amount of other volatile components. Therefore, the pressure-sensitive adhesive property does not change with time and can be used stably for a long time.

  The acrylic pressure-sensitive adhesive has a floating height of 10 mm or less after 24 hours in a curved surface adhesion test (40 ° C./80% RH condition), and a heat-resistant shear retention time at 90 ° C. of 5000 minutes or more. preferable. Such acrylic pressure-sensitive adhesives are very useful in practice as super strong double-sided pressure-sensitive adhesive tapes. For example, in applications that require curved surface adhesion in applications such as electrical / electronic, architectural / residential, and transportation equipment. It can be used suitably.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic adhesive which made compatible the high shear holding power on high temperature conditions, and the high adhesive force with respect to a curved surface is provided.

It is a schematic cross section which shows the test sample of a curved surface adhesiveness test. It is a schematic cross section which shows the outline | summary of a curved surface adhesiveness test.

  Hereinafter, preferred embodiments of the acrylic pressure-sensitive adhesive according to the present invention will be described.

  The acrylic pressure-sensitive adhesive according to this embodiment contains an acrylic polymer having a monofunctional monomer and a polyfunctional monomer as monomer units.

  Examples of the acrylic polymer include 70 to 99% by mass of alkyl acrylate having 1 to 18 carbon atoms in the alkyl group, and 1 to 30% by mass of an unsaturated monomer having a vinylcarbonyl group and a polar group, An acrylic polymer having a monomer unit of 0.01 to 1.0 part by mass of polyfunctional methacrylate with respect to 100 parts by mass of the monofunctional monomer is used.

  Since the acrylic pressure-sensitive adhesive containing such an acrylic polymer contains the acrylic polymer, the flexibility and curved surface followability are good, the shear holding force under high temperature conditions, and the adhesion to curved surfaces Excellent in both strength and power. In the present specification, “high temperature condition” refers to a condition of 40 to 200 ° C.

  The acrylic pressure-sensitive adhesive according to the present embodiment is excellent in both shear holding force under high temperature conditions and adhesive force with respect to a curved surface, and thus is excellent in use under conditions of, for example, 40 to 200 ° C. Moreover, it can use more suitably on the conditions of 60-180 degreeC.

  The monofunctional monomer includes an alkyl acrylate having an alkyl group having 1 to 18 carbon atoms (hereinafter sometimes referred to as “C1-18 alkyl acrylate”), and an unsaturated monomer having a vinylcarbonyl group and a polar group (hereinafter referred to as “C1-18 alkyl acrylate”). Sometimes referred to as "polar unsaturated monomer").

  The proportion of the C1-18 alkyl acrylate and the polar unsaturated monomer in the monofunctional monomer is 70 to 99% by mass and 1 to 30% by mass, respectively, where the total amount of the monofunctional monomer is 100% by mass. It is preferable that the said ratio is 85-99 mass% and 1-15 mass%, and it is more preferable that they are 88-94 mass% and 6-12 mass%. When the proportion of the C1-18 alkyl acrylate and the polar unsaturated monomer in the monofunctional monomer is within the above range, the effect of exhibiting good adhesive force immediately after pressure bonding is achieved.

The alkyl acrylate having 1 to 18 carbon atoms in the alkyl group means that the alkyl alcohol has 1 to 18 carbon atoms when the alkyl acrylate is viewed as an ester of acrylic acid and alkyl alcohol. Namely, when an alkyl acrylate ^{_{CH 2 = CH-COO-R}} 1 and, ^{R 1} is meant an alkyl group having 1 to 18 carbon atoms.

  The number of carbon atoms in the alkyl group of the alkyl acrylate is preferably 4 or more, and more preferably 8 or more. Moreover, it is preferable that it is 12 or less. When such an alkyl acrylate is included as a monofunctional monomer, not only the adhesiveness of the acrylic pressure-sensitive adhesive is improved, but also the shear holding power is improved.

  As alkyl acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl Acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, n-undecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, n-tetra Decyl acrylate, n-pentadecyl acrylate, n-hexadecyl acrylate, n-heptadecyl acrylate, n Octadecyl acrylate, and the like.

  Among these, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, and n-decyl acrylate are preferable, and 2-ethylhexyl acrylate, Octyl acrylate is more preferred.

  The polar unsaturated monomer has a vinylcarbonyl group and a polar group.

  Examples of the polar group include a hydroxyl group, a carboxyl group, a carbamoyl group, an amino group, an epoxy group, and a nitrile group, and among these, a hydroxyl group, a carboxyl group, and a carbamoyl group are preferable.

The vinylcarbonyl group refers to a group represented by CH ₂ ═C—C (═O) —. By containing such a group, the polar unsaturated monomer has a higher reactivity than the polyfunctional methacrylate.

Examples of polar unsaturated monomers include:
Hydroxyl group-containing unsaturated monomers such as 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate;
Carboxyl group-containing unsaturated monomers such as acrylic acid;
Carbamoyl group-containing unsaturated monomers such as acrylamide;
Amino group-containing monomers such as N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminopropyl acrylate;
And epoxy group-containing unsaturated monomers such as glycidyl acrylate.

  Among these, a hydroxyl group-containing unsaturated monomer, a carboxyl group-containing unsaturated monomer, and a carbamoyl group-containing unsaturated monomer are preferable, a carboxyl group-containing unsaturated monomer and a carbamoyl group-containing unsaturated monomer are more preferable, and a carboxyl group-containing unsaturated monomer is Further preferred. Specifically, 2-hydroxyethyl acrylate, acrylic acid, and acrylamide are preferable, acrylic acid and acrylamide are more preferable, and acrylic acid is more preferable.

  The acrylic polymer has 0.01 to 1.0 part by mass of a polyfunctional methacrylate as a monomer unit with respect to 100 parts by mass of the monofunctional monomer. When the content of the polyfunctional methacrylate is 0.01 parts by mass or less, the shear holding force of the acrylic pressure-sensitive adhesive under high temperature conditions decreases. Moreover, the adhesive force with respect to the curved surface of an acrylic adhesive falls that content of a polyfunctional methacrylate is 1.0 mass part or more. That is, by setting the content of the polyfunctional methacrylate within the above range, it is possible to realize both a high shear holding force under a high temperature condition and a high adhesion force to a curved surface.

  The content of the polyfunctional methacrylate is preferably 0.04 parts by mass or more and more preferably 0.06 parts by mass or more with respect to 100 parts by mass of the monofunctional monomer. Moreover, it is preferable that it is 0.8 mass part or less, and it is more preferable that it is 0.40 mass part or less. Thereby, the acrylic adhesive which is excellent in the shear holding power under high temperature conditions and the adhesive force with respect to a curved surface is obtained.

  As the polyfunctional methacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, Examples include pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, and the like.

  Of these, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, ethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate are preferred.

  The acrylic polymer is a monofunctional monomer part composed of 70 to 99% by mass of an alkyl acrylate having 1 to 18 carbon atoms in the alkyl group and 1 to 30% by mass of an unsaturated monomer having a vinylcarbonyl group and a polar group. It is preferable that it is an acrylic polymer formed by photopolymerizing a mixture of a polymer and 0.01 to 1.0 part by mass of a polyfunctional methacrylate with respect to 100 parts by mass of the partial polymer. An acrylic pressure-sensitive adhesive containing such an acrylic polymer is further excellent in shear holding power and adhesion to a curved surface under high temperature conditions.

  Here, the definitions and preferred examples of the alkyl acrylate having 1 to 18 carbon atoms of the alkyl group, the ethylenically unsaturated monomer having a polar group, the monofunctional monomer, and the polyfunctional methacrylate are the same as described above.

  A “monofunctional monomer partial polymer” is a composition obtained by polymerizing at least a part of a monofunctional monomer and contains an unreacted monomer monomer. That is, “partial polymer 100 parts by mass” means that the total amount of the monomer monomer polymer and the unreacted monomer monomer is 100 parts by mass.

  As the partial polymer, for example, a polymer obtained by irradiating a composition containing a monofunctional monomer and a photopolymerization initiator with light to photopolymerize the monofunctional monomer is preferable.

As a photopolymerization initiator,
Azo compounds such as azobisinbutyronitrile;
Benzoins such as benzoin, benzoin methyl ether, benzoisoethyl ether, benzoin propyl ether, benzoin isobutyl ether, α-methylbenzoin, α-phenylbenzoin;
Anthraquinones such as anthraquinone, methylanthraquinone and chloroanthraquinone;
and onium salts such as p-methoxybenzenediazonium, hexafluorophosphate, diphenyliodonium, triphenylsulfonium, and the like.

In addition, as a photopolymerization initiator,
Benzyl dialkyl ketals such as 2,2-dimethoxy-1,2-diphenylethane-1-one;
1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl Α such as -1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, etc. -Hydroxyalkylphenones;
2-Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2- (dimethyl Α-aminoalkylphenones such as amino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone;
Acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide;
Titanocenes such as bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium;
1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3 And oxime esters such as 1- (0-acetyloxime);

The light irradiation is preferably ultraviolet irradiation. For example, the irradiation intensity is 0.05 to 10 mW / cm ² (preferably 0.1 mW / cm ² or more, preferably 5 mW / cm ² or less), and the irradiation time is 5 to 300 seconds (preferably 10 to the composition). A partial polymer can be obtained by irradiating with ultraviolet rays under conditions of at least 2 seconds, and preferably at most 240 seconds.

  The viscosity of the partial polymer is preferably 2000 mPa · s or more, and more preferably 3000 mPa · s or more. Moreover, it is preferable that it is 40000 mPa * s or less, and it is more preferable that it is 20000 mPa * s or less.

  In the mixture of the partial polymer and the polyfunctional methacrylate, the content of the polyfunctional methacrylate is 0.01 parts by mass or more with respect to 100 parts by mass of the partial polymer, preferably 0.04 parts by mass or more. Preferably it is 0.06 mass part or more. Moreover, content of polyfunctional methacrylate is 1.0 mass part or less with respect to 100 mass parts of partial polymers, Preferably it is 0.80 mass part or less, More preferably, it is 0.40 mass part or less. . When the content of the polyfunctional methacrylate in the mixture is less than 0.01 parts by mass, the shear holding force of the obtained acrylic pressure-sensitive adhesive under high temperature conditions is significantly reduced. Moreover, when content of the polyfunctional methacrylate in a mixture exceeds 1.0 mass part, the adhesive force with respect to the curved surface of the acrylic adhesive obtained will fall remarkably. That is, by setting the content of the polyfunctional methacrylate in the above mixture within the above range, an acrylic pressure-sensitive adhesive that achieves both high shear holding power under high temperature conditions and high adhesion to curved surfaces can be obtained. .

  The mixture preferably contains a photopolymerization initiator, and the light irradiation of the mixture is preferably ultraviolet irradiation. An acrylic polymer obtained by subjecting a mixture containing a photopolymerization initiator to ultraviolet polymerization proceeds more reliably, and becomes more excellent in shear retention and adhesion to curved surfaces under high temperature conditions.

  Examples of the photopolymerization initiator include the same ones as described above.

Ultraviolet polymerization, for example, with respect to the mixture, the irradiation intensity 0.05~10mW / cm ² (preferably 0.1 mW / cm ² or more, and preferably 5 mW / cm ² or less), the irradiation time 5 to 300 seconds ( Preferably, the irradiation is performed with ultraviolet irradiation under conditions of 10 seconds or more, and preferably 240 seconds or less.

  The content of the acrylic polymer in the acrylic pressure-sensitive adhesive is preferably 40 to 100% by mass, and preferably 60 to 100% by mass, based on the total amount of the acrylic pressure-sensitive adhesive.

  The acrylic pressure-sensitive adhesive preferably contains surface-modified nanoparticles. The surface-modified nanoparticle is a nanometer-sized particle whose surface is modified (surface treatment) with a compound that chemically reacts with the particle or a compound that physically adheres to the particle. By containing the surface-modified nano fine particles, it becomes possible to stably hold air bubbles in the acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive can be suitably used as a foam. In addition, the combination of the above-mentioned acrylic polymer and surface-modified nanoparticles makes it possible to form a foam that has superior flexibility and curved surface followability and higher adhesion to curved surfaces than conventional foaming adhesives. Will be able to.

  Examples of the surface-modified nanoparticles include silica, titania, alumina, zirconia, vanadia, ceria, iron oxide, antimony oxide, tin oxide, aluminum / silica, and inorganic nanoparticles selected from the group consisting of combinations thereof. Are modified with a modifying agent such as silane, alcohol, organic acid, organic base, or organic titanate.

  As the nanoparticle, a nanoparticle made of silica is preferable. And as the surface-modified nanoparticles, the surface of the nanoparticles made of silica is chlorosilane, alkylalkoxysilane, arylalkoxysilane, vinylalkoxysilane, mercaptoalkoxysilane, polyetheralkoxysilane, ((meth) acryloyloxy) alkylalkoxy. Those modified (surface treatment) with a silane modifier such as silane are preferred. That is, as the surface-modified nano fine particles, silica fine particles having an organosilyl group on the surface are preferable.

  The particle diameter of the surface-modified nanoparticles is preferably 0.1 to 10 nm, and more preferably 0.1 to 8 nm. When the particle diameter of the surface-modified nanoparticle is within the above range, since the effect as a foaming aid is excellent, it is possible to obtain a foam that sufficiently contains bubbles and has excellent flexibility.

  The content of the surface-modified nanoparticles in the acrylic pressure-sensitive adhesive is preferably 0.1 to 10% by mass and more preferably 0.1 to 5% by mass based on the total amount of the acrylic pressure-sensitive adhesive. When the content of the surface-modified nanoparticle is within the above range, bubbles can be held more stably, and a foam having a higher adhesive force with respect to a curved surface can be formed.

  The acrylic pressure-sensitive adhesive may contain other additives for adjusting the pressure-sensitive adhesive properties. Examples of other additives include foaming aids, plasticizers, tackifiers, pigments, reinforcing agents, reinforcing agents, flame retardants, antioxidants, stabilizers, fillers, and the like.

  As fillers, glass fillers such as glass beads and glass balloons (including glass bubbles); polymer bubbles or beads (which may be foamed or unfoamed); fibers; hydrophobic Or hydrophilic silica; polymer particles such as polyester, nylon and polypropylene; and the like.

  The acrylic pressure-sensitive adhesive can be a foam. Since the acrylic pressure-sensitive adhesive that is a foam is more excellent in flexibility and curved surface followability, the acrylic pressure-sensitive adhesive has higher adhesion to curved surfaces. In addition, it can also be said that an acrylic adhesive is porous that an acrylic adhesive is a foam.

  The bubbles contained in the foamed acrylic pressure-sensitive adhesive (hereinafter referred to as “acrylic foam pressure-sensitive adhesive” in some cases) preferably have an average diameter of 5 to 300 μm, more preferably 5 to 200 μm. . The acrylic foam pressure-sensitive adhesive containing such bubbles is further excellent in flexibility and curved surface followability.

  The bubble content of the acrylic foam pressure-sensitive adhesive is preferably 5 to 40% by volume, more preferably 5 to 30% by volume based on the total volume of the acrylic foam pressure-sensitive adhesive. When the bubble content is less than the above lower limit value, the flexibility of the acrylic foam pressure-sensitive adhesive may be reduced. When the bubble content is more than the above upper limit value, the strength of the acrylic foam pressure-sensitive adhesive may be reduced. . That is, by setting the bubble content within the above range, both the flexibility and strength of the acrylic foam pressure-sensitive adhesive can be achieved.

The density of the acrylic foam pressure-sensitive adhesive is preferably 0.3 g / cm ³ or more, and more preferably 0.5 g / cm ³ or more. Further, it is preferably 2.0 g / cm ³ or less, more preferably 1.5 g / cm ³ or less. When the density of the acrylic foam pressure-sensitive adhesive is within the above range, both flexibility and strength are excellent.

  The acrylic pressure-sensitive adhesive preferably has a loss on drying at 120 ° C. for 2 hours of 1.0% by mass or less. Since such an acrylic pressure-sensitive adhesive has few volatile components, there is little change in the pressure-sensitive adhesive property over time, and it can be used stably for a long time.

  The loss on drying is the ratio ((A−B) / A) of the difference (A−B) between the initial mass A and the mass B after standing at 120 ° C. for 2 hours with respect to the initial mass A. Say.

  In the present embodiment, in the curved surface adhesion test of the acrylic pressure-sensitive adhesive, the floating height H after being left for 24 hours under conditions of a temperature of 40 ° C. and a humidity of 80% can be 10 mm or less. A small value of the height H indicates that the adhesive force to the curved surface of the acrylic pressure-sensitive adhesive is strong.

  The acrylic adhesive preferably has a height H of 5 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. Such an acrylic pressure-sensitive adhesive is very useful in practical use as an ultra-strong pressure-sensitive adhesive tape. In the present embodiment, an acrylic pressure-sensitive adhesive having a smaller value of height H can be obtained by appropriately selecting the above-described preferred aspects.

  The curved surface adhesion test is a test performed by the following method. 1 is a schematic cross-sectional view showing a test sample of a curved surface adhesion test, and FIG. 2 is a schematic cross-sectional view showing an outline of the curved surface adhesion test.

  First, a sheet-like acrylic pressure-sensitive adhesive 1 (hereinafter referred to as “pressure-sensitive adhesive sheet 1”) is attached to an aluminum plate 2 (20 mm width × 180 mm × 0.4 mm thickness). The pressure-sensitive adhesive sheet 1 is molded so as to have the same size as the aluminum plate 2. Next, the ABS plate 3 (plate made of acrylonitrile-butadiene-styrene resin) (30 mm width, 200 mm, 2 mm thickness) and the adhesive sheet 1 are bonded together so that one end of the ABS plate and one end of the adhesive sheet overlap. The test sample 10 is obtained by reciprocating once with a 2 kg roller and press-bonding, and left at room temperature for 20 minutes.

  Next, the test sample 10 is bent and fixed to the jig 4 having an interval 5 of 190 mm, and is left under a condition of 40 ° C./80% RH for 24 hours.

  After being left for 24 hours, the floating height 6 of the end portion of the pressure-sensitive adhesive sheet 1 (the end portion on the side not overlapping with the end portion of the ABS plate) was measured.

  The same measurement is performed twice, and the average value is defined as the floating height H after 24 hours in the curved surface adhesion test.

  Moreover, in this embodiment, the heat resistant shear retention time at 90 ° C. of the acrylic pressure-sensitive adhesive can be 5000 minutes or more. Such an acrylic pressure-sensitive adhesive is very useful in practical use as an ultra-strong pressure-sensitive adhesive tape.

  The heat-resistant shear holding time at 90 ° C. is a time obtained by the following method.

  First, a sheet-like acrylic pressure-sensitive adhesive (hereinafter referred to as “pressure-sensitive adhesive sheet”) is cut into a size of 25 mm × 25 mm, and SUS plates (plates made of stainless steel) (30 mm width × 60 mm) are formed on both sides of the pressure-sensitive adhesive sheet. × 0.5 mm thickness, 6.82 g weight) is affixed and allowed to stand horizontally. A weight of 1 kg is placed on this, and it is allowed to stand for 15 minutes for pressure bonding to obtain a test sample.

  Next, one stainless steel plate SUS (304) plate is fixed so that the test sample is vertical, and after standing for 10 minutes at 90 ° C., a 1.5 kg weight is applied to the unfixed SUS plate. Multiply. And after applying a weight, time until an adhesive sheet peels and the SUS board which is not fixed falls is measured.

  The same measurement is performed three times, and the average time is defined as the heat-resistant shear retention time at 90 ° C.

  Furthermore, in this embodiment, the acrylic pressure-sensitive adhesive can be a super strong double-sided pressure-sensitive adhesive tape that conforms to Type 1 No. 1 in the evaluation method based on JIS Z 1541.

  The acrylic pressure-sensitive adhesive according to the present embodiment is excellent in heat resistance and curved surface adhesiveness, and thus can be suitably used for electrical equipment, electrical appliances, and the like. Further, it can be suitably used in applications requiring curved surface adhesion in applications such as construction / housing and transportation equipment.

  Next, the suitable manufacturing method of the acrylic adhesive which concerns on this embodiment is demonstrated.

  The acrylic polymer constituting the acrylic pressure-sensitive adhesive contains C1-18 alkyl acrylate, polar unsaturated polymer, and polyfunctional methacrylate as monomer units. Therefore, the acrylic pressure-sensitive adhesive can be polymerized by mixing them all. Alternatively, after polymerizing a part of these monomers, the remaining monomers may be added for polymerization. The polymerization may be performed in one stage, or may be performed in multiple stages by gradually adding a polymerization initiator or changing the polymerization temperature. During polymerization, the reaction product is covered with an inert gas, the reaction product is covered with a film, or a closed reaction vessel (for example, a polymerization machine for bulk polymerization or a reactive extrusion machine) is used. It is preferable not to touch oxygen. Moreover, what is necessary is just to add them in any step of reaction, when an acrylic adhesive contains monomers and additives other than the said monomer.

  The following method is mentioned as a manufacturing method of a preferable acrylic polymer. That is, first, the first composition containing the monofunctional monomer and the photopolymerization initiator is irradiated with light to obtain a monomer monomer partial polymer. Next, a partial polymer, a polyfunctional methacrylate, and a photopolymerization initiator are mixed to obtain a second composition, and an acrylic polymer is formed by irradiating the second composition with light.

  In this case, the polymerization of the partial polymer is allowed to proceed until a viscous fluid is obtained, and the second composition in which the polyfunctional methacrylate and the photopolymerization initiator are added thereto is formed to have a predetermined thickness on the film. It is also possible to produce an acrylic polymer by coating and covering the coated product with an ultraviolet ray transmissive film such as a PET film and then irradiating the second composition with light through the film to promote polymerization. Thereby, a sheet-like acrylic pressure-sensitive adhesive can be formed without the influence of oxygen.

  When the acrylic pressure-sensitive adhesive is used as a foam, the second composition preferably contains surface-modified nanoparticles.

  The acrylic pressure-sensitive adhesive that is a foam can be obtained by mixing bubbles in the second composition. As a method of mixing the bubbles, a known bubble mixing method can be used, but a bubble mixing method using a mechanical foaming mechanism is preferable.

  The bubble mixing method using the mechanical foaming mechanism is a method in which the second composition is shaken, vibrated, stirred or stirred at a high speed to mix the bubbles, and the second composition is used for bubble formation by nozzle injection or blowing. The method of mixing gas etc. is mentioned, You may combine these methods.

  In addition, as a method for mixing bubbles using a mechanical foaming mechanism, a method using a vibration type (vibration type) stirring and mixing device may be used (for example, the method described in JP-A-2002-080802 may be used). it can.). Generally, the vibration type stirring and mixing apparatus includes a casing provided with a passage through which a fluid flows, and a stirring blade disposed in the casing and capable of vibrating in the axial direction of the casing. When such an apparatus is used, since the shearing force applied to the second composition contributes to efficient bubble dispersion, fine and uniform bubbles can be dispersed in the second composition without increasing the temperature. it can.

  The surface-modified nanoparticles contribute to stably holding the bubbles in the second composition. Therefore, by including the surface-modified nanoparticles in the second composition, bubbles can be mixed efficiently and a foam can be easily formed.

  The mixing of the bubbles is preferably performed such that the bubble content of the second composition is 5 to 40% by volume based on the total volume of the second composition, and is 5 to 30% by volume. More preferably. Thereby, the acrylic foam adhesive whose density is in the above-mentioned suitable range by this can be obtained.

(Production Example 1: Production of surface-modified nanoparticles)
61.42 g of isooctyltrimethoxysilane (trade name “BS1316”, Wacker Silicones Corp., Adrian, Mich.), 1940 g of 1-methoxy-2-propanol, 1000 g of colloidal silica (trade name “NALCO 2326”, manufactured by Nalco Chemical) ) Was placed in a 1 gallon glass container, stirred and left at 80 ° C. overnight. The mixture in the glass container was dried at 180 ° C. in an exhaust oven (manufactured by Espec Corp.) to obtain surface-modified nanoparticles as white solid particles.

Example 1
A composition obtained by mixing 2550 g of 2-ethylhexyl acrylate, 450 g of acrylic acid and 2 g of a photopolymerization initiator Irgacure 651 (product name, manufactured by Ciba Japan) is irradiated with ultraviolet rays having an irradiation intensity of 3 mW / cm ² for 3 minutes in a nitrogen atmosphere. As a result, a partial polymer having a viscosity of 6000 mPa · s was obtained.

To this partial polymer, 45 g of 1,6-hexanediol dimethacrylate, 250 g of photopolymerization initiator Darocur TPO (trade name, manufactured by Ciba Japan), 8 g of Glass Bubbles K15 (trade name, manufactured by 3M) are added, After stirring well, the mixture was deaerated with a vacuum defoamer, and 42.5 g of the surface-modified nanoparticles obtained in Production Example 1 were added to obtain a pressure-sensitive adhesive composition. The viscosity of the obtained pressure-sensitive adhesive composition was 0.73 g / cm ³ .

Nitrogen gas was dispersed into the obtained pressure-sensitive adhesive composition using a vibration type stirring and mixing device to obtain a bubble-containing composition having a density of 0.62 g / cm ³ . The bubble content of the obtained bubble-containing composition was 15.1% by volume. In addition, bubble content is a value calculated | required by a following formula.
Bubble content (volume%) = ((density of pressure-sensitive adhesive composition before foaming) − (density of bubble-containing composition)) × 100 / (density of pressure-sensitive adhesive composition before foaming)

The obtained bubble-containing composition was sandwiched between two polyethylene terephthalate (PET) liners treated with a silicone release agent, and calendared into a sheet having a thickness of 0.42 mm. By irradiating both sides of the molded sheet with ultraviolet rays having an irradiation intensity of 0.6 mW / cm ² for 3 minutes, and subsequently for 3 minutes with ultraviolet rays having an irradiation intensity of 7.0 mW / cm ² , an acrylic having a thickness of 0.40 mm A system pressure-sensitive adhesive sheet was obtained.

  The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesive strength, heat-resistant shear retention strength, curved surface adhesiveness, super-strong double-sided tape compatibility, and heat loss by the following methods. The results were as shown in Table 2.

[90 ° peel adhesion (to stainless steel plate)]
The obtained acrylic pressure-sensitive adhesive sheet was cut into a size of 10 mm × 150 mm and backed with an anodized aluminum foil (thickness 130 μm). The lined sample was attached to a stainless steel plate (SUS304), and a 5 kg roller was reciprocated once for pressure bonding. After crimping, leave at room temperature for 72 hours, peel with a tensile tester (manufactured by Shimadzu Corporation, trade name “Autograph AG-X”) at a tensile rate of 300 mm / min in the 90 ° direction, and have an adhesive strength (N · cm ^{− 1} ) was measured. The same measurement was performed three times, and the average value was taken as the measured value.

[Heat resistant shear retention]
The obtained acrylic pressure-sensitive adhesive sheet was cut into a size of 25 mm × 25 mm, and SUS plates (plates made of stainless steel (304)) (30 mm width × 60 mm × 0.5 mm thickness, weight 0. 82g) was affixed and allowed to stand horizontally. A 1 kg weight was placed on this and allowed to stand for 15 minutes for pressure bonding to obtain a test sample.

  Next, one SUS plate was fixed so that the test sample was vertical, and the sample was left at 90 ° C. for 10 minutes. And after applying a weight, the time until an SUS board which the adhesive sheet peeled and was not fixed fell was measured. The same measurement was performed three times, and the average time was taken as the measurement time. In addition, “5000+” is displayed when it does not fall for more than 5000 minutes.

[Curved surface adhesion]
The obtained acrylic adhesive sheet was attached to an aluminum plate (20 mm width × 180 mm × 0.4 mm thickness), and the protruding portion was removed so that the acrylic adhesive sheet had the same size as the aluminum plate. Next, an ABS plate (plate made of acrylonitrile-butadiene-styrene resin) (30 mm width, 200 mm, 2 mm thickness) and an acrylic adhesive sheet are placed so that one end of the ABS plate and one end of the acrylic adhesive sheet overlap each other. Bonding was performed by reciprocating once with a 2 kg roller, and the sample was allowed to stand at room temperature for 20 minutes to obtain a test sample.

  The obtained test sample was bent and fixed on a jig having a spacing of 190 mm, and left under conditions of 40 ° C./80% RH for 24 hours. After leaving for 24 hours, the floating height of the end of the acrylic pressure-sensitive adhesive sheet (the end on the side not overlapping with the end of the ABS plate) was measured. The same measurement was performed twice, and the average value was taken as the measured value.

[Super strong double-sided tape compatibility]
In accordance with JIS Z 1541, the obtained acrylic pressure-sensitive adhesive sheet was evaluated to determine suitability. The results were displayed as A for those that conform to Type 1 No. 1 and B for those that did not conform to Type 1 No. 1.

[Weight loss on drying]
The polyester mesh was dried at 120 ° C. for 24 hours and cooled to room temperature in a desiccator. The cooled polyester mesh was weighed and its mass was designated W1. Next, the obtained acrylic pressure-sensitive adhesive sheet was cut into a size of 100 mm × 100 mm and placed on a weighed polyester mesh to obtain a test sample. The test sample was weighed and its mass was designated as W2. The test sample was then dried at 120 ° C. for 2 hours and cooled to room temperature in a desiccator. The cooled test sample was weighed and its mass was designated as W3. The loss on drying was calculated using the following formula.
Loss on drying (% by mass) = 100− (W3−W1) × 100 / (W2−W1)

(Example 2)
A composition in which 91 g of 2-ethylhexyl acrylate, 9 g of acrylic acid and 0.04 g of a photopolymerization initiator Irgacure 651 (trade name, manufactured by Ciba Japan) was mixed with ultraviolet rays having an irradiation intensity of 3 mW / cm ² for 3 minutes in a nitrogen atmosphere. By irradiation, a partial polymer having a viscosity of 4000 mPa · s was obtained.

  To this partial polymer, 0.09 g of 1,6-hexanediol dimethacrylate, photopolymerization initiator Darocur TPO (trade name, manufactured by Ciba Japan) 0.16 g, Glass Bubbles K15 (trade name, manufactured by 3M) 5 g Was added and stirred well, followed by degassing with a vacuum defoamer to obtain an adhesive composition.

The obtained pressure-sensitive adhesive composition was sandwiched between two polyethylene terephthalate (PET) liners treated with a silicone release agent, and calendered into a sheet having a thickness of 0.42 mm. By irradiating both sides of the molded sheet with ultraviolet rays having an irradiation intensity of 0.6 mW / cm ² for 3 minutes, and subsequently for 3 minutes with ultraviolet rays having an irradiation intensity of 7.0 mW / cm ² , an acrylic having a thickness of 0.40 mm A system pressure-sensitive adhesive sheet was obtained. The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 2.

(Example 3)
An acrylic pressure-sensitive adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.11 g of 1,9-nonanediol dimethacrylate was used instead of 1,6-hexanediol dimethacrylate. . The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 2.

Example 4
An acrylic pressure-sensitive adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.14 g of polyethylene glycol 400 dimethacrylate was used instead of 1,6-hexanediol dimethacrylate. The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 2.

(Comparative Example 1)
An acrylic adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.02 g of 1,6-hexanediol diacrylate was used instead of 1,6-hexanediol dimethacrylate. . The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 3.

(Comparative Example 2)
An acrylic adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.04 g of 1,6-hexanediol diacrylate was used instead of 1,6-hexanediol dimethacrylate. . The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 3.

(Comparative Example 3)
An acrylic adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.065 g of 1,6-hexanediol diacrylate was used instead of 1,6-hexanediol dimethacrylate. . The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 3.

(Comparative Example 4)
An acrylic pressure-sensitive adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.14 g of triallyl isocyanurate was used instead of 1,6-hexanediol dimethacrylate. The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 3.

(Comparative Example 5)
An acrylic pressure-sensitive adhesive sheet having a thickness of 0.40 mm was obtained in the same manner as in Example 2 except that 0.26 g of triallyl isocyanurate was used instead of 1,6-hexanediol dimethacrylate. The obtained acrylic pressure-sensitive adhesive sheet was evaluated for 90 ° peel adhesion, heat-resistant shear retention, curved surface adhesion, super-strong double-sided tape compatibility, and heat loss by the above methods. The results were as shown in Table 3.

  In Table 1, the compounding ratio (mass ratio) of each component mix | blended in Examples 1-4 and Comparative Examples 1-5 is shown. In the table, A1 represents 2-ethylhexyl acrylate, A2 represents acrylic acid, D1 represents Irgacure 651, B1 represents 1,6-hexanediol dimethacrylate, and B2 represents 1,9-nonanediol dimethacrylate. B3 represents polyethylene glycol 400 dimethacrylate, B4 represents 1,6-hexanediol diacrylate, B5 represents triallyl isocyanurate, D2 represents Darocur TPO, E1 represents glass bubbles K15, C1 represents the surface-modified nanoparticles obtained in Production Example 1.

  The acrylic pressure-sensitive adhesive of the present invention is compatible with both high shear holding power under high temperature conditions and high adhesion to curved surfaces. For example, in applications such as electric / electronic use, construction / housing use, transportation equipment, etc. It can be suitably used in applications requiring curved surface adhesion, and is very useful in practice.

  DESCRIPTION OF SYMBOLS 1 ... Sheet-like acrylic adhesive, 2 ... Aluminum plate, 3 ... ABS plate, 4 ... Jig, 5 ... Jig spacing, 6 ... Floating height, 10 ... Test sample.

Claims (2)

A method for producing an acrylic pressure-sensitive adhesive containing an acrylic polymer,
A monofunctional monomer comprising 70 to 99% by mass of an alkyl acrylate having 1 to 18 carbon atoms in the alkyl group and 1 to 30% by mass of an unsaturated monomer having a vinylcarbonyl group and a polar group, and photopolymerizing the monofunctional monomer. A first step of obtaining a partial polymer of
A second step of photopolymerizing a mixture of the partial polymer and 0.01 to 1.0 part by weight of a polyfunctional methacrylate with respect to 100 parts by weight of the partial polymer to obtain an acrylic polymer. ,
The manufacturing method with which the photopolymerization in said 2nd process is performed by irradiating with an ultraviolet-ray on the conditions of irradiation intensity 0.05-10 mW / cm < ² >. The manufacturing method in which the photopolymerization in said 1st process is performed by irradiating with ultraviolet-ray on the conditions of irradiation intensity 0.05-10 mW / cm < ² >.

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