JP4839707B2 - Double-sided adhesive tape and method for producing double-sided adhesive tape - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape in which a water-dispersed acrylic pressure-sensitive adhesive composition is laminated on both surfaces of a nonwoven fabric substrate. Moreover, this invention relates to the manufacturing method of the double-sided adhesive tape which laminated | stacked the water-dispersed acrylic adhesive composition on both surfaces of the nonwoven fabric base material.

  In industrial fields such as automobiles, building materials, OA, and home appliance industries, a large amount of double-sided pressure-sensitive adhesive tapes has been used for fixing parts and members such as metals, various plastics, and foam bodies. In these industrial applications, adhesion to adherends that are very difficult to adhere, such as urethane foam with irregularities on the surface, peeling resistance to withstand the repulsive force of the adherend, retention to withstand loads in the shear direction More demanding performance is required, such as adhesion reliability under severe environmental conditions and adhesion in a small area. In order to meet such strict demanded performance, as a pressure-sensitive adhesive composition used for a double-sided pressure-sensitive adhesive tape, a pressure-sensitive adhesive composition mainly composed mainly of a solution polymerization type acrylic resin has been conventionally used. However, since these pressure-sensitive adhesive compositions using a solution polymerization type acrylic resin are synthesized in an organic solvent, the organic solvent for producing a pressure-sensitive adhesive product such as stirring or coating is used for synthesis. Volatilization of the human body and the impact on the human body and the environmental impact of volatilization of the organic solvent remaining in the adhesive when the adhesive product is used in the market are regarded as problems. In addition, there is a problem with irritating odors such as organic solvents themselves and low molecular weight monomers in additives that volatilize with organic solvents, additives, etc., and solvent-free adhesive compositions that do not use such organic solvents Is desired. Among them, there is a demand for a pressure-sensitive adhesive composition that uses an existing production facility and uses a highly safe water-dispersed acrylic resin.

  A water-dispersed acrylic resin adhesive is produced by forming monomer fine particles in an aqueous medium by using an emulsifier and a surfactant, and allowing polymerization to proceed in the fine particles. In general, it is difficult to control the molecular weight and the resin structure by the method. In a state where the monomer is highly concentrated compared to solution polymerization, even if only a monofunctional monomer is used, radicals are easily generated at sites other than radically polymerizable unsaturated double bonds by the polymerization initiator, A branched or cross-linked resin is likely to be formed. Therefore, the pressure-sensitive adhesive containing a resin having a branched or cross-linked structure has a molecular chain that is not flexible and has an excessive cohesive force. For example, for a material that has unevenness on the surface, such as urethane foam, that is difficult to adhere. The deformation according to the irregularities on the surface hardly occurred, and the adhesiveness, particularly the initial adhesiveness, was poor.

  In addition, double-sided adhesive tape requires workability that does not stretch or tear when the tape is bonded to various materials, and when performing processing such as punching or cutting the bonded product with various materials Workability such as stable dimensional accuracy is required, and in order to satisfy such workability and workability, the double-sided pressure-sensitive adhesive tape requires a certain degree of waist and strength. On the other hand, double-sided pressure-sensitive adhesive tapes require flexibility to relieve the adherend having an uneven surface and stress caused by the repulsion of the adherend, and conflicting requirements such as strength and flexibility. In order to satisfy the above, for example, a nonwoven fabric has been suitably used as the core substrate of the double-sided pressure-sensitive adhesive tape. The pressure-sensitive adhesive layer is impregnated into the fiber when bonded to the nonwoven fabric, and is further in close contact with the pressure-sensitive adhesive layer on the opposite side, thereby improving anchoring to the nonwoven fabric substrate and attaching the double-sided pressure-sensitive adhesive tape to the adherend. The holding force when bonded together is applied. However, in the case of water-dispersed acrylic pressure-sensitive adhesive resin, a branched or cross-linked resin is generally easily generated, so the molecular chain is not flexible and the cohesive force is excessive. For these materials, the pressure-sensitive adhesive was hardly deformed and impregnated, resulting in poor adhesion of the pressure-sensitive adhesive. The pressure-sensitive adhesive dropped from the nonwoven fabric, and the holding property of the double-sided pressure-sensitive adhesive tape deteriorated. In addition, when the cohesive strength of water-dispersed acrylic pressure-sensitive adhesive resin is lowered to improve the impregnation of the nonwoven fabric substrate, the flowability of the pressure-sensitive adhesive increases and stress is applied to the double-sided pressure-sensitive adhesive tape. In particular, there was a concern that the adhesive would fall off the nonwoven fabric substrate and the tape would peel off, particularly in a high temperature atmosphere.

  As means for improving the adhesion and rebound resistance of the double-sided pressure-sensitive adhesive tape to the adherend, an acrylic polymer containing an alkyl (meth) acrylate or an alicyclic ester as a main monomer component, and in the total solid content An aqueous pressure-sensitive adhesive composition having a solvent-soluble content of 20 to 90% by weight, wherein (A) the glass transition temperature is −20 ° C. or lower and the weight average molecular weight is 100,000 or higher. A water-based pressure-sensitive adhesive composition containing an acrylic polymer and (B) an acrylic polymer having a glass transition temperature of 40 ° C. or higher and a weight average molecular weight of 300 to 50,000 has been proposed (for example, Patent Document 1). However, when the solvent-soluble content of the pressure-sensitive adhesive is too high, or when the polymer is three-dimensional even though the solvent-soluble content is low, the initial adhesion to an adherend having an uneven surface such as urethane foam is poor. In addition, when the pressure-sensitive adhesive layer penetrates into the nonwoven fabric base material and the double-sided pressure-sensitive adhesive tape is stressed, the pressure-sensitive adhesive may fall off the nonwoven fabric base material and the tape may be peeled off. In fact, the pressure-sensitive adhesive resins described in the examples all have a solvent-soluble content of 60% (and therefore a solvent-insoluble content of 40%). It is. In this case, the molecular chain is not flexible, the cohesive force is excessive, and the initial adhesion to an adherend having an uneven surface such as urethane foam is poor. For example, when a nonwoven fabric is used as the substrate, the adhesive is highly likely to fall off the nonwoven fabric substrate. The adhesive composition disclosed in Patent Document 1 cannot be said to have satisfactory characteristics as a pressure-sensitive adhesive tape using a water-dispersed acrylic pressure-sensitive adhesive composition.

  In addition, an adhesive tape has been proposed in which a nonwoven fabric containing rayon of 30% by weight or more is used as a substrate and the permeability of the water-dispersed adhesive is controlled (for example, Patent Document 2). However, if the rayon content is too high, the adhesive tape will come off the nonwoven fabric substrate when left in a high-temperature atmosphere or when stress such as repulsion is applied to the adhesive tape, causing the adhesive tape to peel off. Easy and poor adhesion reliability. In particular, when the cohesive force of the pressure-sensitive adhesive is small, there is a problem that the tendency becomes remarkable. Further, there is no description about the water-dispersed pressure-sensitive adhesive resin, and only the technique described in Patent Document 2 is a water-dispersed acrylic having initial adhesiveness, peel resistance, holding power, etc., to an adherend having an uneven surface. It was difficult to produce an adhesive tape using the adhesive composition.

JP 2003-105298 A Japanese Patent Laid-Open No. 8-12954

Therefore, the object of the present invention is to easily deform in accordance with the unevenness of the surface, such as urethane foam, which has unevenness on the surface, and has good initial adhesiveness, and from the outside. To provide a double-sided pressure-sensitive adhesive tape using a pressure-sensitive adhesive composition mainly composed of a water-dispersible acrylic pressure-sensitive adhesive resin, which is difficult to peel off from an adherend even when stress such as slippage or deformation is applied for a long time. It is.
Furthermore, the other object of this invention is to provide the manufacturing method of the double-sided adhesive tape using the adhesive composition which has the water dispersion type acrylic adhesive resin as a main component which solves the said subject.

  As a result of intensive studies to solve the above problems, a water-dispersed acrylic pressure-sensitive adhesive resin having a gel fraction after polymerization of 15% by mass or less is produced, and then a pressure-sensitive adhesive layer containing a resin obtained by crosslinking the resin It was found that a double-sided pressure-sensitive adhesive tape that solves the above-mentioned problems can be obtained by laminating on both sides of a nonwoven fabric base material in which rayon and pulp are mixed at a specific ratio, thereby completing the present invention.

That is, the present invention is a double-sided pressure-sensitive adhesive tape comprising a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material,
The double-sided adhesive tape is
A water dispersion in which a monomer containing a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is emulsion-polymerized in an aqueous medium, and the gel fraction is 15% by mass or less Type acrylic adhesive resin (A1),
Next, a water-dispersible acrylic pressure-sensitive adhesive resin (A2) having a gel fraction increased by adding a crosslinking agent capable of reacting with the polar group to the water-dispersible acrylic copolymer resin (A1) and performing a crosslinking reaction. )
Thereafter, a pressure-sensitive adhesive layer containing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is produced,
Furthermore, the pressure-sensitive adhesive layer is a tape manufactured by laminating both sides of a base material composed of a nonwoven fabric containing rayon and pulp in a mass ratio of 2/8 to 7/3 (rayon / pulp). A double-sided pressure-sensitive adhesive tape is provided.

Further, the present invention is a method for producing a double-sided pressure-sensitive adhesive tape comprising a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material,
A water dispersion in which a monomer containing a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is emulsion-polymerized in an aqueous medium, and the gel fraction is 15% by mass or less Type acrylic adhesive resin (A1),
Next, a water-dispersible acrylic pressure-sensitive adhesive resin (A2) having a gel fraction increased by adding a crosslinking agent capable of reacting with the polar group to the water-dispersible acrylic copolymer resin (A1) and performing a crosslinking reaction. )
Thereafter, a pressure-sensitive adhesive layer containing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is produced,
Furthermore, the pressure-sensitive adhesive layer is laminated on both surfaces of a substrate composed of a nonwoven fabric containing rayon and pulp in a mass ratio of 2/8 to 7/3 (rayon / pulp). A method for producing a tape is provided.

A water-dispersed acrylic resin adhesive is produced by forming monomer fine particles in an aqueous medium by using an emulsifier and a surfactant, and allowing polymerization to proceed in the fine particles. In general, it is difficult to control the molecular weight and the resin structure by the method. In a state where the monomer is highly concentrated compared to solution polymerization, even if only a monofunctional monomer is used, radicals are easily generated at sites other than radically polymerizable unsaturated double bonds by the polymerization initiator, A branched or cross-linked resin is likely to be formed.
However, the water-dispersed acrylic pressure-sensitive adhesive resin (A2) used for the double-sided pressure-sensitive adhesive tape of the present invention has a gel fraction of 15% by mass or less, and the water-dispersed resin structure has an unlimited linear resin structure. Type acrylic pressure-sensitive adhesive resin (A1) is crosslinked. Therefore, immediately after polymerization, a general water-dispersed acrylic pressure-sensitive adhesive resin containing a considerable proportion of gel component is already used, and the pressure-sensitive adhesive resin obtained by crosslinking the resin with a crosslinking agent is the final resin structure. Is different. For example, even if the final gel fraction is the same, the flexibility and cohesion of molecular chains are different. This is because the distance between the crosslinking points is different between the resin obtained by crosslinking the linear resin to a specific gel fraction and the case where the already crosslinked resin is further crosslinked, and the molecular weight between the crosslinking points is the former. It is presumed that this is because it is longer.
As described above, the double-sided pressure-sensitive adhesive tape of the present invention is easy to be deformed in accordance with the unevenness of the surface, for example, urethane foam, which is difficult to adhere to the surface. Is considered to be good and has excellent peeling resistance and holding power.

  The double-sided pressure-sensitive adhesive tape of the present invention shows a good initial adhesion to an adherend having an uneven surface such as a urethane foam, and when stress such as displacement or deformation is applied for a long time from the outside. Also, it is difficult to peel off from the adherend and has excellent peeling resistance and holding power. In addition, since organic solvents are not used as polymerization solvents or dilution solvents, the effects on the human body and the environment due to volatilization of organic solvents, and the stimulation of low molecular weight monomers and additives in adhesives that volatilize with organic solvents themselves or organic solvents. It is possible to provide a double-sided pressure-sensitive adhesive tape having a low odor and high safety.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention is composed of a base material composed of a nonwoven fabric and a pressure-sensitive adhesive layer laminated on both surfaces of the base material.

(Nonwoven fabric substrate)
The nonwoven fabric used in the double-sided pressure-sensitive adhesive tape of the present invention is a nonwoven fabric containing rayon and pulp in a mass ratio of 2/8 to 7/3 (rayon / pulp). When rayon / pulp is contained at a mass ratio of 2/8 to 7/3, the water-dispersed acrylic pressure-sensitive adhesive resin has good impregnation and adhesion to the nonwoven fabric substrate, and stress is applied to the double-sided pressure-sensitive adhesive tape. In this case, the peeling resistance and the retention are good. Even within the above range, the mass ratio of rayon / pulp is more preferably 3/7 to 7/3, and more preferably 3/7 to 6/4.

  Examples of fibers other than rayon and pulp include manila hemp, acrylonitrile, nylon, polyester, polypropylene, and polyvinyl alcohol. If necessary, the substrate properties such as adhesive impregnation, adhesion, and tensile strength are deteriorated. These may be contained within a range that does not allow them. Further, in order to satisfy the tensile strength, a viscose impregnation treatment, an impregnation treatment using a thermoplastic resin as a binder, or a surface treatment may be performed as necessary.

The basis weight of the nonwoven fabric is not particularly limited, 5 to 25 g / ^{m 2,} preferably from 8 to 20 g / ^{m 2.} Within the above range, the water-dispersed pressure-sensitive adhesive resin has good impregnation and adhesion properties, and has good peeling resistance and retention when stress is applied to the double-sided pressure-sensitive adhesive tape, as well as the tensile strength of the double-sided pressure-sensitive adhesive tape. And the balance of flexibility is excellent. Moreover, the thickness of a nonwoven fabric is although it does not specifically limit, It is 15-100 micrometers, Preferably it is 20-80 micrometers. Within the above range, the water-dispersed pressure-sensitive adhesive resin has good impregnation and adhesion properties, and has good peeling resistance and retention when stress is applied to the double-sided pressure-sensitive adhesive tape, as well as the tensile strength of the double-sided pressure-sensitive adhesive tape. And the balance of flexibility is excellent.

(Adhesive layer)
The pressure-sensitive adhesive layer used in the present invention is a resin obtained by emulsion polymerization of a monomer containing a radically polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule in an aqueous medium, and has a gel content. A water-dispersed acrylic pressure-sensitive adhesive resin (A1) having a rate of 15% by mass or less is produced, and then a cross-linking agent capable of reacting with the polar group is added to the water-dispersed acrylic copolymer resin (A1). A water-dispersed acrylic pressure-sensitive adhesive resin (A2) whose gel fraction is increased by carrying out the reaction is used.

  As an index of the degree of crosslinking of the water-dispersed acrylic pressure-sensitive adhesive resin, the value of the gel fraction for measuring the insoluble content after the resin layer is immersed in toluene for 24 hours is used. The gel fraction of the pressure-sensitive adhesive layer used in the present invention is less than 15% by mass after emulsion polymerization and before crosslinking, and preferably 20 to 50% by mass after crosslinking with a crosslinking agent. Furthermore, after emulsion polymerization, it is less than mass% before crosslinking, and more preferably 25 to 40 mass% after crosslinking with a crosslinking agent. The gel fraction before crosslinking is particularly preferably 5% or less. If the gel fraction of the pressure-sensitive adhesive layer is in the above range, it becomes a water-dispersed acrylic pressure-sensitive adhesive resin having a small branched or cross-linked structure, a flexible molecular chain, and an appropriate cohesive force, such as urethane foam. In addition to good initial adhesion to the adherend having irregularities on the surface, the non-woven fabric base material has good impregnation and adhesion, and has good peeling resistance and retention when stress is applied.

The monomer for producing the water-dispersed acrylic pressure-sensitive adhesive resin (A1) is preferably a monomer mainly composed of a (meth) acrylic acid alkyl ester monomer. A known compound can be used as the (meth) acrylic acid alkyl ester monomer. Examples of such compounds include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) ) Acrylate, isoamyl (meth) acrylate, isodecyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, methoxyethyl ( (Meth) acrylate, butoxyethyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, nonylphenoxyethyl tet Tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl (meth) acrylate. In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid, and the same applies to derivatives of acrylic acid or methacrylic acid.
Among the (meth) acrylic acid alkyl ester monomers, it is preferable to use a compound represented by the following formula (1).

（式中、R₁は分岐鎖を有していても良い炭素数４〜１８のアルキル基を表し、Ｘは水素原子又はメチル基を表す。）

(In the formula, R ₁ represents an alkyl group having 4 to 18 carbon atoms which may have a branched chain, and X represents a hydrogen atom or a methyl group.)

  When the water-dispersed acrylic pressure-sensitive adhesive resin (A1) is produced, the copolymerization ratio of the monomer represented by the formula (1) is preferably 60 to 98% by mass, more preferably based on the total monomers. It is 80-97 mass%. If it is the said range, both adhesive force and cohesion force are favorable.

In order to use a water-dispersed acrylic resin as a pressure-sensitive adhesive resin, among the monomers represented by the formula (1), R ¹ in the formula (1) may have a branched chain having 4 to 4 carbon atoms. It is preferable that it is an 18 alkyl group, and it is preferable that it is a compound whose glass transition point at the time of a homopolymerization is -10 degrees C or less. Such monomers include butyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, dodecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, isodecyl acrylate, isostearyl acrylate, cyclohexyl acrylate, and the like. The use ratio of such a monomer is preferably 10 to 70% by mass with respect to the total monomers. More preferably, it is 20-50 mass%. If it is the said range, both adhesive force and cohesion force are favorable.

  Further, when the water-dispersed acrylic pressure-sensitive adhesive resin (A1) is produced, a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is used. Examples of the monomer having a carboxyl group include (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, (meth) acrylic acid dimer, crotonic acid and the like, and monomers having a hydroxyl group include 2-hydroxyethyl ( Examples of the monomer having an amino group such as (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypropyl (meth) acrylate, polyethylene glycol monoacrylate, and polypropylene glycol monoacrylate include N-vinylpyrrolidone, N-vinylcaprolactam, Examples of the monomer having glycidyl group such as acryloylmorpholine, dimethylaminoethyl acrylate, acrylamide, N, N-dimethylacrylamide, and the like include glycidyl (meth) acrylate.

  Other monomers include sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified succinic acid acrylate, 2-acrylamido-2-methylpropane sulfonic acid, and isocyanate group-containing monomers.

  The copolymerization ratio of the radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule used for the production of the water-dispersed acrylic pressure-sensitive adhesive resin (A1) is preferably 0.5 to 15% by mass. More preferably, it is 1.5-10 mass%, More preferably, it is 2-8 mass%. If it is the said range, the adhesive force and cohesive force of an adhesive will be favorable, and also the mechanical stability of water-dispersed acrylic resin and the stability of the emulsion during emulsion polymerization (polymerization stability) will be good.

  In emulsion polymerization, an azo-based, peroxide-based, redox-based or other heat-induced polymerization initiator is used for publicly known purposes. In emulsion polymerization of acrylic resins, in order to keep the gel fraction after emulsion polymerization low, it is necessary to control the branching reaction, and it is easy to decompose even at low temperatures. It is required to have a small hydrogen abstraction effect. Among the above initiators, an azo polymerization initiator is preferably used.

  When an azo initiator is used, there is no generation of aggregates when a nonionic or anionic water-soluble azo initiator is used rather than a cationic water-soluble azo initiator among azo initiators. Branching reaction can be suppressed. When a cationic water-soluble azo initiator is used, for example, when an anionic surfactant is used, an ion pair is likely to be generated, and the stability of the emulsion is reduced, resulting in the formation of aggregates. It becomes difficult. On the other hand, the nonionic or anionic water-soluble azo initiator does not generate an ion pair with the anionic surfactant, so that the stability of the emulsion is maintained and the production without the generation of aggregates becomes possible. .

  The 10-hour half-life temperature of the nonionic or anionic water-soluble azo initiator is preferably 80 ° C. or less. More preferably, the 10-hour half-life temperature is 70 ° C. or lower.

  The polymerization temperature is preferably set to a temperature lower than the 10-hour half-life temperature of the initiator (however, limited to the range in which the initiation reaction is performed). By carrying out the polymerization at a temperature lower than the 10-hour half-life temperature of the initiator, the radical concentration can be kept low and the branching reaction can be restrained, so that a highly flexible adhesive resin can be produced. High initial adhesion to an adherend having irregularities on the surface such as foam, and excellent peeling resistance can be exhibited. Preferably, the temperature is set to a temperature lower by 5 to 30 ° C, more preferably 10 to 30 ° C lower than the 10-hour half-life temperature. However, it is not preferable at a temperature lower than 30 ° C. because polymerization hardly proceeds.

  In the case of an azo initiator having a 10-hour half-life temperature of 69 ° C, the polymerization temperature is preferably 64 ° C to 39 ° C. More preferably, it is 59 degreeC-39 degreeC.

  The initiator addition amount is preferably in the range of 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the total monomer amount. When the amount is 0.5 parts by mass or less, the polymerization reaction hardly proceeds and the production becomes difficult. If it is 5.0 parts by mass or more, the branching reaction is likely to proceed, the gel fraction after emulsion polymerization is large, and the flexibility of the pressure-sensitive adhesive is lowered.

  As an emulsifier used in emulsion polymerization, an anionic surfactant is widely used. In general, nonionic surfactants have a low critical micelle concentration and tend to form micelles with a small amount of emulsifier, but anionic surfactants are more suitable for emulsion polymerization because of higher polymerization stability. The reason why the anionic surfactant is more stably polymerized is that the surface charge of the formed particles is increased.

As the anionic surfactant, known and publicly used ones are used. Examples include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl sulfosuccinate, etc. It is done.
One or more of these are used.

  In an anionic surfactant, particles tend to exist independently due to electrical repulsion, so that even when the radical concentration is low, the polymerization stability is kept high and production without occurrence of aggregates becomes possible. The anionic surfactant is preferably used in the range of 0.5 part to 2.0 parts by weight with respect to 100 parts by weight of the acrylic monomer. If it is the said range, emulsification stability, adhesive force, and water resistance will be favorable.

  Among the anionic surfactants, an anionic surfactant having a copolymerizable double bond is preferable. Since an anionic surfactant having a copolymerizable double bond is copolymerized with a reactive monomer, it has little influence on adhesive performance such as adhesive strength and cohesive strength and water resistance, and has an uneven surface. High initial adhesive strength and excellent cohesive strength can be expressed.

  Next, examples of the polymerization method of the acrylic pressure-sensitive adhesive composition of the present invention include a batch polymerization method, a pre-emulsion method, a monomer dropping method, and the like. Among these, the pre-emulsion method in which water, a monomer, and an emulsifier previously mixed are added dropwise is preferable because of high polymerization stability.

  Moreover, you may use a chain transfer agent for superposition | polymerization. By using a chain transfer agent, the molecular weight of the acrylic polymer can be adjusted. Examples of the chain transfer agent include known chain transfer agents such as lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. Can be used.

  Further, in the present invention, for the purpose of improving the cohesive force of the pressure-sensitive adhesive, a crosslinking agent capable of reacting with the polar group is added to the water-dispersed acrylic copolymer resin (A1), and a crosslinking reaction is performed. A water-dispersed acrylic pressure-sensitive adhesive resin (A2) with an increased amount of is produced. As the crosslinking agent, known isocyanates, epoxy compounds, aziridine compounds, polyvalent metal salts, metal chelates, organic peroxides, and the like can be used. However, a type in which a crosslinking agent is added after the polymerization is completed to advance the crosslinking reaction is preferable. . For example, an epoxy compound, an isocyanate compound, etc. are mentioned. When producing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) used in the present invention, radical polymerizability having a carboxyl group as a polar group during the production of the water-dispersed acrylic copolymer resin (A1) before crosslinking. It is preferable to use an epoxy compound as a compound that uses a monomer and undergoes a crosslinking reaction.

  As described above, the gel fraction of the pressure-sensitive adhesive layer used in the present invention is 15% by mass or less after emulsion polymerization and before crosslinking, and preferably 20 to 50% by mass after crosslinking with a crosslinking agent. Furthermore, after emulsion polymerization, it is 10 mass% or less before crosslinking, and more preferably 25 to 40 mass% after crosslinking with a crosslinking agent. The gel fraction before crosslinking is particularly preferably 5% or less. If the gel fraction of the pressure-sensitive adhesive layer is in the above range, it becomes a water-dispersed acrylic pressure-sensitive adhesive resin having a small branched or cross-linked structure, a flexible molecular chain, and an appropriate cohesive force, such as urethane foam. In addition to good initial adhesion to the adherend having irregularities on the surface, the non-woven fabric base material has good impregnation and adhesion, and has good peeling resistance and holding power when stress is applied.

  Moreover, tackifying resin can be added for the purpose of improving the initial adhesiveness and peeling resistance to the adherend having an uneven surface such as urethane foam.

  As tackifying resins, known aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins and other petroleum resins, rosin resins, rosin ester resins, disproportionated rosin resins, polymerized rosin resins, polymerization One or more types of tackifying resins selected from rosin resins such as rosin ester resins and rosin phenol resins, terpene resins, terpene phenol resins, coumarone indene resins and the like can be used. Among them, a polymerized rosin ester resin, a rosin phenol resin, a terpene resin, a terpene phenol resin in order to be appropriately compatible with the water-dispersed acrylic pressure-sensitive adhesive resin (A2) and to improve adhesion and peel resistance. A resin having a relatively bulky molecular structure is preferred. Further, in order to improve the peel resistance, a tackifying resin having a relatively high molecular weight with a softening point of 140 ° C. or higher and lower than 200 ° C. and a high glass transition temperature, in particular, a polymerized rosin ester resin, rosin Phenol resins and terpene phenol resins are preferred.

  As for the addition amount of tackifying resin, 10-40 mass parts is preferable. More preferably, it is 15-35 mass parts, More preferably, it is 20-35 mass parts. By setting the addition amount of the tackifying resin in the range of 10 to 40 parts by mass, the initial adhesive force and the peel resistance to an adherend having an uneven surface such as urethane foam are good.

  Furthermore, in addition to the tackifying resin as described above, it is preferable to use an acrylic resin (B) having a glass transition temperature of 20 ° C. or higher and a weight average molecular weight of 300 to 50,000. By using such an acrylic polymer in combination, the compatibility with the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is improved, and the peel resistance is improved.

Among acrylic resins (B) having a glass transition temperature of 20 ° C. or higher and a weight average molecular weight of 300 to 50,000, R ₁ in the formula I is an alkyl group having 2 to 8 carbon atoms, and X is a hydrogen atom or a methyl group. Polymers obtained by polymerizing monomers are preferred. Examples of such a monomer include isobutyl methacrylate and cyclohexyl methacrylate.

  In addition, the pressure-sensitive adhesive composition includes, as necessary, plasticizers, softeners, antioxidants, glass and plastic fibers, balloons, beads, metal powders and the like as long as the desired effects of the present invention are not impaired. Known materials such as fillers, colorants such as pigments and dyes, pH adjusters, film forming aids, leveling agents, thickeners, water repellents and antifoaming agents can be optionally added.

  The water-dispersed acrylic pressure-sensitive adhesive resin is laminated on both surfaces of the nonwoven fabric base material to form a double-sided pressure-sensitive adhesive sheet.

  To form a pressure-sensitive adhesive layer on a nonwoven fabric substrate, a water-dispersed acrylic pressure-sensitive adhesive resin solution can be applied directly onto a support using a roll coater or die coater, or once a pressure-sensitive adhesive layer is formed on a separator Thereafter, a method of transferring to a support is used. The preferable thickness of the pressure-sensitive adhesive layer after drying is 20 to 150 μm, preferably 30 to 100 μm.

  The form of the double-sided pressure-sensitive adhesive tape is not particularly limited, and may be a sheet-like or roll-like product form, or may be a tape form.

[Production method of double-sided adhesive tape]
Further, the present invention is a method for producing a double-sided pressure-sensitive adhesive tape comprising a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material,
A water dispersion in which a monomer containing a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is emulsion-polymerized in an aqueous medium, and the gel fraction is 5% by mass or less Type acrylic adhesive resin (A1),
Next, a water-dispersible acrylic pressure-sensitive adhesive resin (A2) having a gel fraction increased by adding a crosslinking agent capable of reacting with the polar group to the water-dispersible acrylic copolymer resin (A1) and performing a crosslinking reaction. )
Thereafter, a pressure-sensitive adhesive layer containing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is produced,
Furthermore, it is a manufacturing method of the double-sided adhesive tape characterized by providing this adhesive layer on both surfaces of a base material.

  The double-sided pressure-sensitive adhesive tape produced by the above production method adheres well to an adherend having an uneven surface such as urethane foam, and is excellent in peeling resistance and holding power. Since it is not used as a diluting solvent, the safety of the human body and the environment due to the volatilization of the organic solvent, and the irritating odor such as the low molecular weight monomer and additives in the adhesive that volatilizes with the organic solvent itself or the organic solvent are high.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
(1) Preparation of Emulsion A A container was charged with 10 parts of the anionic surfactant Latemul S-180 (manufactured by Kao Corporation; active ingredient 50%) and 100 parts of deionized water and dissolved uniformly. Thereto, 225 parts of 2-ethylhexyl acrylate, 230 parts of n-butyl acrylate, 30 parts of methyl methacrylate, 15 parts of acrylic acid and 0.5 part of lauryl mercaptan were added and emulsified to obtain Emulsion A (610.5 parts). It was.

(2) Production of water-dispersed acrylic polymer In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 0.1 part of S-180 and 350 parts of deionized water were placed. The temperature was raised to 55 ° C. while blowing nitrogen. Under stirring, an anionic water-soluble polymerization initiator V-501 (manufactured by Wako Pure Chemical Industries, Ltd .; active ingredient 100%), 5 parts of an aqueous solution (active ingredient 5%: neutralized and dissolved with aqueous ammonia) was added. Then, 6.1 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 55 ° C. Subsequently, a part (300 parts) of the remaining emulsion A and 20 parts of an aqueous V-501 solution (active ingredient 5%: neutralized and dissolved with aqueous ammonia) were added to a reaction vessel 55 using a separate dropping funnel. The polymerization was carried out dropwise over 4 hours while maintaining the temperature. During this time, 5 parts of Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd., active ingredient 100%] is added to emulsion A (304.4 parts) that was not added dropwise, and stirred until uniform. B (309.4 parts) was prepared.

  Immediately after the end of dropping of emulsion A, emulsion B (309.4 parts) and V-501 aqueous solution 20 parts (active ingredient 5%: neutralized and dissolved with aqueous ammonia) were used in a reaction vessel using separate dropping funnels. Was dropped over 4 hours while maintaining the temperature at 55 ° C. to produce a water-dispersed acrylic polymer.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with ammonia water so that the pH was 7.5. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 49.5%, a viscosity of 460 mPa · s, and an average particle size of 270 nm.

(3) Production of water-dispersed acrylic pressure-sensitive adhesive composition 1.2 parts of Surfinol 420 (produced by Air Products Japan; active ingredient 100%) as a leveling agent in the water-dispersed acrylic polymer described above, 0.25 parts by mass of an epoxy compound tetrad C (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added as a cross-linking agent, and a terpene resin Tamanol E-100 (manufactured by Arakawa Chemical Industries, Ltd .; softening point 150 ° C.) as a tackifier resin 100 parts by mass in solid content, rosin resin super ester E-788 [Arakawa Chemical Industries, Ltd .; softening point 160 ° C.] is added in 50 parts by mass in solid content, and the mixture is filtered through a 100 mesh wire mesh. A water-dispersed acrylic pressure-sensitive adhesive composition a was obtained. The gel fraction (before crosslinking) with no epoxy crosslinking agent added was 0.7%.

(4) Preparation of double-sided pressure-sensitive adhesive tape On a polyester film having a thickness of 75 μm obtained by subjecting the water-dispersed acrylic pressure-sensitive adhesive composition to a release treatment, the thickness after drying is applied to be 65 μm, and at 100 ° C. The pressure-sensitive adhesive layer obtained by drying for 3 minutes was transferred to both surfaces of a nonwoven fabric containing 14 g / m ^{2 of} mass (basis weight) and 50/50% by weight of rayon / pulp, and 4 kgf / min with a 80 ° C. hot roll. A double-sided pressure-sensitive adhesive tape was obtained by laminating at a pressure of cm. The obtained double-sided adhesive tape was used for the test after aging in an oven at 40 ° C. for 2 days. The gel fraction (after crosslinking) of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape was 28%.

(Example 2)
A water-dispersed acrylic polymer was produced in the same manner as in Example 1. Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition b was obtained by the same operation as in Example 1 except that 0.25 part by mass of the epoxy compound tetrad C was changed to 0.35 parts by mass as a crosslinking agent. . Subsequently, a double-sided adhesive tape was prepared by the same operation as in Example 1. The gel fraction (after crosslinking) of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet was 40%. In addition, the gel fraction (before bridge | crosslinking) at the time of superposing | polymerizing without adding tetrad C was 0.7%.

(Example 3)
A water-dispersed acrylic polymer was produced in the same manner as in Example 1. Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition c was obtained by the same operation as in Example 1 except that Aqualon KH-10 was removed. Subsequently, a double-sided adhesive tape was prepared by the same operation as in Example 1. The gel fraction (after crosslinking) of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet was 40%. In addition, the gel fraction (before bridge | crosslinking) at the time of superposing | polymerizing without adding tetrad C was 6%.

Example 4
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the nonwoven fabric was changed to a nonwoven fabric containing 10 g / m ² in mass (basis weight) and 25/75% by mass of rayon / pulp.

(Comparative Example 1)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the nonwoven fabric was changed to a nonwoven fabric having a mass (basis weight) of 12 g / m ² and a pulp of 100% by mass.

(Comparative Example 2)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the nonwoven fabric was changed to a nonwoven fabric having a mass (basis weight) of 10 g / m ² and rayon of 100 mass%.

(Comparative Example 3)
The polymerization initiator was changed to a redox initiator composed of 1.0 part ammonium persulfate and 0.5 part sodium bisulfite, and the monomer composition was 225 parts 2-ethylhexyl acrylate, 230 parts n-butyl acrylate, 30 parts methyl methacrylate. , 15 parts of acrylic acid was changed to 240 parts of 2-ethylhexyl acrylate, 245 parts of n-butyl acrylate, 15 parts of acrylic acid, and 0.25 part of triethoxysilane was added as a cross-linking agent. A water-dispersed acrylic polymer was produced by the above procedure. Subsequently, a water-dispersed acrylic pressure-sensitive adhesive composition d was obtained by the same operation as in Example 1 except that the epoxy compound tedrad C was removed. Subsequently, a double-sided adhesive tape was prepared by the same operation as in Example 1. The gel fraction (after crosslinking) of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet was 37%. The gel fraction (before crosslinking) when polymerized without addition of triethoxysilane was 32%.

  Table 1 shows the evaluation results of adhesive strength, urethane foam initial adhesiveness, holding power, and constant load peelability of each double-sided pressure-sensitive adhesive tape.

[Method for measuring gel fraction]
(Gel fraction after crosslinking)
A sample obtained by cutting a double-sided adhesive tape into a size of 40 mm × 50 mm was used as a sample. Next, the mass (G1) of the sample before being immersed in toluene and the mass (G0) of the nonwoven fabric serving as the core substrate are measured in advance and immersed in a toluene solution at room temperature (25 ± 2 ° C.) for 24 hours. I put it. And the toluene insoluble matter of the sample after immersion is separated by filtering with a 300 mesh wire mesh, and the mass (G2) of the residue after drying at 105 ° C. for 1 hour is measured. The fraction was determined.

  Gel fraction (mass%) = [(G2-G0) / (G1-G0)] × 100 (1)

(Gel fraction before cross-linking)
In the production of the water-dispersed acrylic pressure-sensitive adhesive composition, a water-dispersed acrylic pressure-sensitive adhesive composition was produced without adding a crosslinking agent. Subsequently, a double-sided pressure-sensitive adhesive tape was prepared using the water-dispersed acrylic pressure-sensitive adhesive composition, and the gel fraction was determined in the same manner as the post-crosslinking gel fraction.

[Measurement method of adhesive strength]
A 20-mm wide double-sided adhesive tape sample lined with a 25 μm polyethylene terephthalate film was applied to a mirror-finished stainless steel plate and polypropylene plate (manufactured by Nippon Test Panel Co., Ltd.), and a 2 kg roller was reciprocated once. After leaving still for 1 hour in an atmosphere of 23 ° C. and 50% RH, the film was pulled in the 180 ° direction at a pulling speed of 300 mm / min, and the adhesive strength was measured.

[Measurement method of initial adhesiveness]
A 20 mm wide double-sided adhesive tape sample lined with a 25 μm-thick polyethylene terephthalate film was bonded to an ECS urethane foam with a 2 kg roll in an atmosphere of 23 ° C. and 50% RH, and immediately afterwards slowly peeled off by hand. The destruction state of the urethane foam surface at this time was evaluated according to the following criteria.

◎: Urethane foam material breakage and adhesion particularly good ○: Urethane foam material breakage △: Transfer of urethane foam surface to adhesive layer ×: No transfer of urethane foam surface to adhesive layer

[Method of measuring holding force]
A 20 mm wide double-sided adhesive tape sample lined with a 25 μm polyethylene terephthalate film was affixed to a stainless steel plate with an area of 20 mm width × 20 mm length, and a 2 kg roller was pressed and adhered by reciprocating once on the double-sided adhesive sheet. . After standing at 23 ° C. and 50% RH for 1 hour, under a 70 ° C. atmospheric condition, a stainless steel plate to which the double-sided pressure-sensitive adhesive sheet was attached was vertically placed. The drop time was measured in a state where a load of 5 kg was applied and shear stress was applied vertically downward. In addition, when it was held after 3 hours, the holding time was recorded as a shift distance.

[Constant load peel test]
A 10 mm-wide double-sided adhesive tape sample lined with a 25 μm thick polyester film was affixed to a stainless steel plate and a polypropylene plate (manufactured by Nippon Test Panel Co., Ltd.) to a length of 50 mm, and a 2 kg roller was placed on the double-sided adhesive sheet. Pressurized by reciprocating and adhered. After being left for 1 hour in an atmosphere of 23 ° C. and 50% RH, a load of 300 g was applied so as to be in the direction of 90 ° with respect to the peeling direction, and the peeling distance or dropping time after 1 hour was measured (mm or Min). The constant load peel test is a substitute evaluation method that assumes a case in which a deformation stress is applied to the double-sided pressure-sensitive adhesive tape for a long time from the outside. The smaller the data, the better the peel resistance.

Claims (7)

A double-sided pressure-sensitive adhesive tape comprising a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material,
The double-sided adhesive tape is
A water dispersion in which a monomer containing a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is emulsion-polymerized in an aqueous medium, and the gel fraction is 15% by mass or less Type acrylic adhesive resin (A1),
Next, a water-dispersible acrylic pressure-sensitive adhesive resin (A2) having a gel fraction increased by adding a crosslinking agent capable of reacting with the polar group to the water-dispersible acrylic copolymer resin (A1) and performing a crosslinking reaction. )
Thereafter, a pressure-sensitive adhesive layer containing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is produced,
Furthermore, the pressure-sensitive adhesive layer is a tape manufactured by laminating both sides of a base material composed of a nonwoven fabric containing rayon and pulp in a mass ratio of 2/8 to 7/3 (rayon / pulp). A double-sided adhesive tape characterized by being. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the water-dispersed acrylic pressure-sensitive adhesive resin is a resin produced by emulsion polymerization in an aqueous medium using a nonionic or anionic water-soluble azo polymerization initiator. . The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the water-dispersed acrylic pressure-sensitive adhesive resin is a resin produced at a polymerization temperature lower than the 10-hour half-life temperature of the polymerization initiator. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the gel fraction after adding the crosslinking agent is 20 to 50% by mass. 5. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein a mass per unit area of the nonwoven fabric is 5 to 25 g / m ² . The pressure-sensitive adhesive layer further contains one or more types of tackifying resins selected from polymerized rosin ester resins having a softening point of 140 ° C to 200 ° C, rosinphenol resins, terpene resins, and terpenephenol resins. The double-sided pressure-sensitive adhesive tape according to any one of 2, 3, 4, and 5. A method for producing a double-sided pressure-sensitive adhesive tape comprising a substrate and a pressure-sensitive adhesive layer provided on both surfaces of the substrate,
A water dispersion in which a monomer containing a radical polymerizable monomer having a carboxyl group, a hydroxyl group, an amino group or a glycidyl group as a polar group in the molecule is emulsion-polymerized in an aqueous medium, and the gel fraction is 15% by mass or less Type acrylic adhesive resin (A1),
Next, a water-dispersible acrylic pressure-sensitive adhesive resin (A2) having a gel fraction increased by adding a crosslinking agent capable of reacting with the polar group to the water-dispersible acrylic copolymer resin (A1) and performing a crosslinking reaction. )
Thereafter, a pressure-sensitive adhesive layer containing the water-dispersed acrylic pressure-sensitive adhesive resin (A2) is produced,
Furthermore, the pressure-sensitive adhesive layer is laminated on both surfaces of a substrate composed of a nonwoven fabric containing rayon and pulp in a mass ratio of 2/8 to 7/3 (rayon / pulp). Tape manufacturing method.