WO2013147085A1

WO2013147085A1 - Emulsion-type adhesive composition and adhesive sheet

Info

Publication number: WO2013147085A1
Application number: PCT/JP2013/059383
Authority: WO
Inventors: 直一村瀬; 光則上田
Original assignee: 日本合成化学工業株式会社
Priority date: 2012-03-29
Filing date: 2013-03-28
Publication date: 2013-10-03
Also published as: TW201348396A; JP2013227551A

Abstract

Provided is an emulsion-type adhesive composition that is ideal for screen printing and the like and in which the surface is smooth during printing, foaming or cissing is unlikely to occur, the clearness of the printed edges is good, and drying performance and water resistance are excellent. The emulsion-type adhesive composition is characterized by comprising an emulsion [II] obtained by emulsion polymerization of a monomer mixture [I] containing a (meth)acrylic acid ester monomer, and in that BH20 is 20,000 mPa·s or greater, and a thixotropy index (Ti) is less than 1.5. (Ti = BH2/BH20 where BH20 is the viscosity as measured at a liquid temperature of 25ºC and a rotation speed of 20 rpm using a Brookfield viscometer, and BH2 is the viscosity as measured at a liquid temperature of 25ºC and a rotation speed of 2 rpm using a Brookfield viscometer.)

Description

Emulsion-type pressure-sensitive adhesive composition and pressure-sensitive adhesive sheets

The present invention relates to an emulsion-type pressure-sensitive adhesive composition suitably used for screen printing, particularly high-speed screen printing, and pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer containing this pressure-sensitive adhesive composition.

Conventionally, when assembling an operation panel such as a switch of an electric product or fixing a key button of a personal computer or a mobile phone, it has been pasted with a double-sided tape. In this case, the movable part that operates the switch, etc. has a hole and is a part that is difficult to bond, so according to its shape, punch the double-sided tape in advance and process it into the same shape as the product to be attached is doing. However, a punching process is required, and release paper is required on the front and back of the double-sided tape. Further, when the double-sided tape is stuck on the operation panel, the product may be displaced and wasteful. Moreover, since the punched double-sided tape portion is not used, a waste portion is generated.

The key buttons of PCs and mobile phones are complicated in shape and are even smaller than the operation panel, making it difficult for double-sided tape to be processed into a normal shape by punching, and sticking to key buttons becomes difficult ing. Similarly, regarding the adhesion of wiring on the flexible base of precision equipment, the circuit becomes denser as the equipment is miniaturized, and it is necessary to process the double-sided tape very thinly to about 0.5 mm, for example, but it is so thin The operation of applying the double-sided tape to the flexible substrate is difficult, and the possibility of the double-sided tape being cut or displaced increases. In recent years, the circuit has become denser, and there has been a demand to process the circuit so that it cannot be handled by double-sided tape.

From the viewpoints of omitting processing steps, reducing waste, reducing errors, and applying finer adhesive than double-sided tape, apply adhesive only to necessary parts directly on the operation panel, key buttons, and flexible circuits. “Screen printing” is being carried out.

The following processes are performed in screen printing. First, an 80-150 mesh “screen” knitted with polyester, nylon, stainless steel wire, etc. is pre-matched with the shape of the operation panel, key buttons, etc., and the parts where you do not want to apply adhesive are masked with epoxy resin etc. Keep it. If you place the screen on the substrate to which you want to apply the adhesive and print the adhesive with a plate called `` squeegee '' printed from the top of the screen, the masked part will not be coated with the adhesive. The adhesive is applied to the substrate as it was designed on the screen with the adhesive slipping through the part of the screen that is not. This eliminates the need for punching double-sided tape, eliminates the need for release paper for double-sided tape, applies adhesive only to the necessary areas, eliminates waste, and does not cause mistakes when attaching. This makes it possible to apply a pressure-sensitive adhesive to a substrate even with complicated and fine lines.

As the pressure-sensitive adhesive for screen printing, solvent-based pressure-sensitive adhesives and water-based pressure-sensitive adhesives are generally used, but water-based emulsion dispersion pressure-sensitive adhesives are mainly used from the viewpoint of environmental problems and fire prevention. An aqueous emulsion dispersion is a dispersion obtained by adsorbing a surfactant or the like on the surface of fine polymer particles (several tens to several hundreds of nanometers, hereinafter also simply referred to as “particles”) and stabilizing the dispersion in water. . When the solvent is water, since the drying speed is slower than when the solvent is a solvent, there is a disadvantage that the drying becomes insufficient and the water resistance of the adhesive is inferior. In order to compensate for this disadvantage, it is common to increase the drying speed by increasing the concentration of the aqueous emulsion dispersion.

However, the higher the emulsion concentration, the greater the number of particles, so the collision and friction between the particles also increases, and the Newtonian viscosity is lost, resulting in a thixotropic viscosity. In particular, when the concentration of the aqueous emulsion dispersion exceeds 55% by weight, the viscosity becomes high and a markedly thixotropic behavior is exhibited. When the viscosity is increased, immediately after the screen is separated from the substrate, the adhesive is pulled by the screen and the printing surface becomes rough.

Therefore, it can be said that the viscosity of the pressure-sensitive adhesive is desirably as low as possible so that the pressure-sensitive adhesive quickly leaves the screen when the screen moves away from the substrate after printing. If the viscosity of the pressure-sensitive adhesive is low, even if the pressure-sensitive adhesive is pulled and raised immediately after the screen is separated, the surface is leveled immediately and the surface becomes smooth, and the surface becomes smooth even after drying in the next drying step.
However, the lower the viscosity of the pressure-sensitive adhesive, the more easily the pressure-sensitive adhesive swells so as to surround the screen mesh (fine checkered pattern). In recent years, printing patterns have become complicated and precise, and screens with fine meshes are often used. Therefore, foaming and repelling of the printing surface are likely to occur.

Patent Document 1 discloses a water-dispersed pressure-sensitive adhesive for rotary screen printing for continuous printing at a high speed without such repellency or dripping. The water-dispersed pressure-sensitive adhesive of Patent Document 1 is a water-dispersed pressure-sensitive adhesive obtained by polymerizing a monomer mixture mainly composed of acrylic ester and / or methacrylic ester in an aqueous solvent. Viscosity measured by a BH viscometer is 10,000 to 40,000 cps, and (viscosity measured at a rotational speed of the rotor of 2 rpm) / (viscosity measured at a rotational speed of the same rotor as the rotor of 20 rpm) The thixotropic index is 1.5 to 4.5.

However, with the water-dispersed pressure-sensitive adhesive of Patent Document 1, in high-speed screen printing suitable for recent mass production, quick self-leveling cannot be expected immediately after the screen is separated from the substrate, and the surface is smooth. However, there is a drawback that the surface becomes rough due to drying in the next drying step. Further, when the viscosity is in the vicinity of 10,000 cps, there is a drawback that bubbles are easily involved when the screen is separated from the substrate at a high speed, and repelling is likely to occur. That is, the water-dispersed pressure-sensitive adhesive of Patent Document 1 is still not satisfactory in terms of entrainment of bubbles and sharpness on the printed surface (edge pattern irregularities, jaggedness in detailed patterns). .

Therefore, when applying a water-based emulsion-type pressure-sensitive adhesive to a substrate by screen printing, solve the problems that are likely to occur when the screen leaves the substrate after printing, that is, suppress the occurrence of foaming and repellency on the coated surface. Therefore, it is required to form a pressure-sensitive adhesive layer having a smooth printing surface by quick self-leveling.

Japanese Unexamined Patent Publication No. Sho 62-48780

The object of the present invention is that the surface is flat at the time of printing, hardly causes foaming or repellency, the sharpness of the edge of printing is good, and it is excellent in drying and water resistance, and is suitably used for screen printing and the like. An emulsion-type pressure-sensitive adhesive composition is provided.

As a result of diligent efforts, the present inventors have succeeded in lowering the thixotropy index even when the viscosity is increased in the emulsion-type pressure-sensitive adhesive composition. In other words, the above-mentioned problems have been solved by creating an emulsion-type pressure-sensitive adhesive composition that achieves both conflicting phenomena.

That is, the gist of the present invention is an emulsion-type pressure-sensitive adhesive composition comprising an emulsion [II] obtained by emulsion polymerization of a monomer mixture [I] containing a (meth) acrylic acid ester monomer, and BH20 is 20 The emulsion-type pressure-sensitive adhesive composition is characterized by having a thixotropic index (Ti) of less than 1.5.
However, Ti = BH2 / BH20, BH20 is a viscosity value measured using a Brookfield viscometer at a liquid temperature of 25 ° C. and a rotation speed of 20 rpm, and BH2 is measured using a Brookfield viscometer. The viscosity is measured at a liquid temperature of 25 ° C. and a rotational speed of 2 rpm.

The gist of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the emulsion-type pressure-sensitive adhesive composition. The “adhesive sheets” in the present invention conceptually includes an adhesive sheet, an adhesive film, and an adhesive tape.

Examples of the method for preparing the emulsion-type pressure-sensitive adhesive composition so that the viscosity and the thixotropy index satisfy the above conditions include any of the following methods, or any combination thereof.
(I) The usage-amount of an emulsifier (surfactant) shall be 1 weight part or less with respect to 100 weight part of monomer mixtures [I].
(Ii) An emulsion having a particle size distribution having two or more peak distributions.
(Iii) A urethane thickener (X) is used.

(I): The emulsifier (surfactant) used for emulsion polymerization is 1 part by weight or less with respect to 100 parts by weight of the monomer mixture [I], so that it exists in the aqueous phase without being adsorbed on the particles. Foaming can be made difficult to occur by reducing the amount of emulsifier to be reduced as much as possible. Further, since the total amount of the emulsifier is small, it is surmised that the interaction between the particles is reduced, contributing to the realization of a low thixotropic index. Furthermore, the drying property is improved and the water resistance of the dried coating film is also improved.

(Ii); the higher the concentration of the emulsion, the more likely the collision and friction between the particles and the more likely to become a thixotropic viscosity. However, when the particle size distribution has two or more peak distributions (so-called bimodal) If the particle size distribution is small), small particles enter the gaps between adjacent large particles, which reduces collisions and friction between particles even at high concentrations, making it difficult to achieve thixotropic viscosity. Conceivable.

(Iii); In a high-viscosity emulsion-type pressure-sensitive adhesive composition having a BH20 of 20,000 mPa · s or more, it is difficult for foaming and repelling of the printed surface to occur. On the other hand, if the viscosity is high, when the screen moves away from the base material, the conventional technique will remain raised. In the present invention, it is particularly preferable to use the urethane thickener (X) among the above preparation methods. That is, by using the urethane-based thickener (X), the thixotropic index can satisfy a predetermined condition. This is considered that the urethane-based thickener (X) also acts as a shock absorber that reduces the collision and friction between the particles due to the presence of the urethane-based thickener (X), thereby reducing the thixotropic behavior. This is because the urethane thickener (X) increases the viscosity while adsorbing the hydrophobic group portion on the surface of the particles and linking the particles together with a network structure, but it is as strong as an alkali thickener. This is because it is presumed that it is easy to desorb because it is adsorbed on the surface to the end, not a simple bond, and therefore can also play the role of a shock absorber that relieves collision and friction between particles.
Therefore, for example, the thixotropic property of the pressure-sensitive adhesive composition is maintained while maintaining a high viscosity by setting the content of the non-volatile content in the emulsion [II] to 60% by weight or more with respect to the total weight of the emulsion [II]. The index can be lowered, and even if the pressure-sensitive adhesive composition is pulled and raised immediately after the screen is released, the leveling is immediately performed, the surface becomes smooth, and bubbles are less likely to be entrained.

The emulsion-type pressure-sensitive adhesive composition of the present invention has a flat surface at the time of printing, hardly causes foaming and repellency, has good sharpness at the edge of printing, and has excellent effects on drying and water resistance. And can be suitably used for screen printing and the like.

Hereinafter, the present invention will be described in detail, but these show examples of desirable embodiments. In this specification, (meth) acryl is acrylic or methacrylic, (meth) acryloyl is acryloyl or methacryloyl, (meth) acrylate is acrylate or methacrylate, and (meth) acryloxy is acryloxy or methacryloxy, respectively. That means.

The emulsion-type pressure-sensitive adhesive composition of the present invention is an emulsion-type pressure-sensitive adhesive composition containing an emulsion [II] obtained by emulsion polymerization of a monomer mixture [I] containing a (meth) acrylate monomer.

BH20 of the emulsion-type pressure-sensitive adhesive composition of the present invention is 20,000 mPa · s or more, preferably 25,000 mPa · s or more, particularly preferably 30,000 mPa · s or more. BH20 is preferably 60,000 mPa · s or less, particularly preferably 50,000 mPa · s or less, and further preferably 40,000 mPa · s or less.
The BH20 is a viscosity value measured using a Brookfield viscometer (rotor no. 5 or no. 6) at a liquid temperature of 25 ° C. and a rotation speed of 20 rpm.
If the value of BH20 is too low, when the screen moves away from the base material, the liquid swells up to surround the screen mesh (lattice stripes) and tends to close up and become bubbles, and if it is extremely low, it is easy to repel. Tend to be.
On the other hand, if the value of BH20 is too high, it will be difficult to keep the Ti value described below below 1.5, and the actual handling will tend to be poor.

The thixotropy index (Ti) of the emulsion-type pressure-sensitive adhesive composition of the present invention is less than 1.5, preferably 1.4 or less, particularly preferably 1.3 or less.
The Ti value is preferably 1 or more.
Ti is BH2 / BH20, and BH2 is a viscosity value measured at a liquid temperature of 25 ° C. and a rotation speed of 2 rpm using a Brookfield viscometer (rotor no. 5 or no. 6).
If the Ti value is too large, self-leveling will decrease, and the adhesive will be pulled up and raised immediately after leaving the screen, the adhesive application surface after printing tends to be rough, and the Ti value is too small In addition, the leveling property is too good, and there is a tendency that the coated surface after printing is inferior in sharpness.

The nonvolatile content contained in the emulsion-type pressure-sensitive adhesive composition of the present invention is preferably 60% by weight or more, particularly preferably 60 to 70% by weight, based on the total weight of the emulsion-type pressure-sensitive adhesive composition. More preferably, it is 62 to 68% by weight. The nonvolatile content can be measured, for example, from a change in weight before and after drying when the emulsion is dried and solidified. If the non-volatile content is too small, the drying rate tends to be slow, and if it is too large, it tends to be difficult to make the Ti value less than 1.5.

The monomer mixture [I] contains a (meth) acrylic acid ester monomer (a1) as an essential component, and further contains a carboxyl group-containing unsaturated monomer (a2) and other unsaturated monomers as necessary. (A3) may be included.

Examples of the (meth) acrylic acid ester monomer (a1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (Meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl ( A) acrylate, tridecyl (meth) acrylate, isotridecyl (meth) acrylate, aliphatic (meth) acrylate such as tetradecyl (meth) acrylate, aromatic (meth) acrylate such as benzyl (meth) acrylate, phenyl (meth) acrylate, etc. Among them, (meth) acrylic acid alkyl ester containing an alkyl group having 4 to 12, particularly 4 to 10, more preferably 4 to 8 carbon atoms is preferable, and specifically, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like are preferably used, and 2-ethylhexyl (meth) acrylate is particularly preferably used. Moreover, these can use 1 type (s) or 2 or more types.

Examples of the carboxyl group-containing unsaturated monomer (a2) include acrylic acid, acrylic acid dimer, methacrylic acid, crotonic acid, itaconic acid, maleic acid and the like, among which acrylic acid, methacrylic acid and the like are preferably used. It is done. Moreover, these can use 1 type (s) or 2 or more types.

Further, as other unsaturated monomer (a3), for example, dimethylaminoethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, Examples thereof include acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl chloride, and alkyl vinyl ether. Among them, vinyl acetate is preferably used because it can provide sufficient cohesion.

In addition to the above, as the unsaturated monomer (a3), a monomer that reacts with the carboxyl group-containing unsaturated monomer (a2), a monomer that can react with each other, and a self-crosslinkable functional group. Unsaturated monomer containing a hydroxyl group-containing unsaturated monomer, an epoxy group-containing unsaturated monomer, an alkoxysilyl group-containing unsaturated monomer, an amide group, a methylol group, or a carbonyl group A body or the like may be used.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.
Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

Examples of the alkoxysilyl group-containing monomer include (meth) acryloxyethyltrimethoxysilane, (meth) acryloxyethyltriethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acrylic. Roxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxy Propyldimethylethoxysilane, γ- (meth) acryloxypropyltrichlorosilane, γ- (meth) acryloxypropylmethyldichlorosilane, γ- (meth) acryloxypropyldimethylchlorosilane, γ- (meth) acryloxypropyltripropioxy Silane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxypropyltributoxysilane, (meth) acryloxybutyltrimethoxysilane, (meth) acryloxypentyltrimethoxysilane, (meth ) Acryloxyhexyltrimethoxysilane, (meth) acryloxyhexyltriethoxysilane, (meth) acryloxyoctyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) acryloxydecyltrimethoxysilane, (meth) ) Acryloxyoctadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldipropoxy Silane and the like.

Examples of monomers containing an amide group, a methylol group, or a carbonyl group include acrylamide, methacrylamide, N-methylol acrylamide, butoxy N-methylol acrylamide, diacetone acrylamide, and 2- (acetoacetoxy) ethyl (meth) acrylate. And allyl acetoacetate.

As a content ratio of the (meth) acrylic acid ester monomer (a1), the carboxyl group-containing unsaturated monomer (a2) and the other unsaturated monomer (a3) with respect to the total amount of the monomer mixture [I]. Preferably, (meth) acrylic acid ester monomer (a1) is 80 to 98.5% by weight, carboxyl group-containing unsaturated monomer (a2) is 0.5 to 10% by weight, and other unsaturated monomers (A3) is 0 to 15% by weight, particularly preferably (meth) acrylic acid ester monomer (a1) is 85 to 97% by weight, and carboxyl group-containing unsaturated monomer (a2) is 1 to 8% by weight. The other unsaturated monomer (a3) is 0.5 to 10% by weight, more preferably 90 to 95% by weight of the (meth) acrylic acid ester monomer (a1), and the carboxyl group-containing unsaturated monomer. Body (a2) 2-5 wt%, and other unsaturated monomer (a3) is from 1 to 8 wt%.

In the present invention, an emulsifier is preferably present when the above monomer mixture [I] is subjected to emulsion polymerization. In such emulsion polymerization, only an anionic reactive emulsifier is used, or only an anionic non-reactive emulsifier is used, or an anionic reactive emulsifier and an anionic non-reactive emulsifier are used in combination. You can also.

Such an anionic reactive emulsifier is not particularly limited as long as it is an anionic emulsifier and has reactivity, and examples thereof include those having the structures of the following general formulas (1) to (11). It is done.

[Wherein, in general formulas (1) to (11), R ₁ is an alkyl group, R ₂ is hydrogen or a methyl group, R ₃ is an alkylene group, n is an integer of 1 or more, and m and l are integers of 1 or more. (M + 1 = 3), X is either SO ₃ NH ₄ or SO ₃ Na. ]

Specific examples of the anionic reactive emulsifier include “ADEKA rear soap SE-20N”, “ADEKA rear soap SE-10N”, “ADEKA rear soap PP-70”, “ADEKA rear soap PP-710”, “ADEKA “Rear Soap SR-10”, “Adeka Rea Soap SR-20” (above, manufactured by Asahi Denka Kogyo Co., Ltd.), “Eleminol JS-2”, “Eleminol RS-30” (above, manufactured by Sanyo Kasei Kogyo Co., Ltd.), “Latemuru "S-180A", "Latemul S-180", "Latemul PD-104" (manufactured by Kao Corporation), "Aqualon BC-05", "Aqualon BC-10", "Aqualon BC-20", "Aquaron HS -05, Aquaron HS-10, Aqualon HS-20, New Frontier S-510, Aqualon KH-05, Aqua Emissions KH-10 "[manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.]," phosphino - Le TX "[manufactured by Toho Chemical Industry Co., Ltd.]) commercially available products, and the like. Among these, “AQUALON KH-10” is preferably used.

Examples of the anionic non-reactive emulsifier include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates, and the like. Preferably, alkylbenzene sulfonate, alkyl diphenyl ether disulfonate, polyoxyalkylene polycyclic phenyl ether / sulfate ammonium salt and the like can be mentioned. Specific examples include commercially available products such as “Perex SS-L” (manufactured by Kao Chemical Co., Ltd.) and “New Coal 707SF” (manufactured by Nippon Emulsifier Co., Ltd.).

The use amount of the anionic reactive emulsifier and the anionic nonreactive emulsifier is preferably 1.5 parts by weight or less, particularly preferably 100 parts by weight or less of the monomer mixture [I]. Is 1 part by weight or less.
Further, the total amount is preferably 0.3 parts by weight or more, particularly preferably 0.4 parts by weight or more, and further preferably 0.5 parts by weight with respect to 100 parts by weight of the monomer mixture [I]. More than a part.
If the amount of the emulsifier used is too small, the emulsion polymerization tends to be unstable, while if too large, the drying property and water resistance tend to be low, and Ti tends to be difficult to adjust to less than 1.5.

Furthermore, if necessary, a nonionic non-reactive emulsifier or a nonionic reactive emulsifier can be used in combination.

Examples of nonionic non-reactive emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, oxyethylene-oxypropylene block polymer, sorbitan fatty acid ester, polyoxyethylene fatty acid and the like.

Nonionic reactive emulsifiers include, for example, those in the above general formulas (1) to (11) in which X is changed to hydrogen. Specifically, “Adekalia soap NE-10”, “Adekalia” “SOPE NE-20”, “ADEKA rear soap NE-30”, “ADEKA rear soap NE-40”, “ADEKA rear soap ER-10”, “ADEKA rear soap ER-20”, “ADEKA rear soap ER-30” "Adekaria soap ER-40" (manufactured by Asahi Denka Kogyo Co., Ltd.), "AQUALON RN-10", "AQUALON RN-20", "AQUALON RN-30", "AQUALON RN-50" [above, Commercial products such as “Daiichi Kogyo Seiyaku Co., Ltd.”.
In addition, an emulsifier may be added to the emulsion monomer liquid which consists of a monomer mixture, may be previously added to the superposition | polymerization can, and may use both together.

In carrying out the emulsion polymerization, it is preferable to use a polymerization initiator, and the polymerization initiator is not particularly limited, and any of water-soluble and oil-soluble can be used. Oxide, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butylcumyl peroxide, benzoyl Peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3,3,5- Trimethylcyclohexanone peroxide, methyl Organic peroxides such as cyclohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxyisobutyrate, 2,2′-azobisisobutyronitrile, dimethyl -2,2'-azobisisobutyrate, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate Ammonium persulfate, hydrogen peroxide, ammonium (amine) salt of 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (2-methylamidooxime) dihydrochloride, 2,2′-azobis (2-Methylbutanamide oxime) dihydrochloride tetrahydrate, 2,2'-a Bis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propion Amide], various redox catalysts (in this case, as the oxidizing agent, ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, etc. As the reducing agent, sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid, etc. are used.) Among these, potassium persulfate, ammonium persulfate, 2,2′-azobisisobutyronitrile, 2 , 2'-azobis (2-methylbutyronitrile), 2,2 '-Azobis (2,4-dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, various redox catalysts and the like are suitable.

The amount of the polymerization initiator used is preferably 0.03 to 5 parts by weight, particularly preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the monomer mixture [I]. When the amount of the polymerization initiator used is too small, the polymerization rate tends to be slow, and when it is too large, the water resistance tends to decrease.

The polymerization initiator may be added in advance to the polymerization can, may be added immediately before the start of polymerization, or may be additionally added during the polymerization as necessary. Further, it may be added in advance to the monomer mixture [I] or may be added to an emulsion comprising the monomer mixture [I]. In the addition, the polymerization initiator may be added separately by dissolving it in a solvent or monomer mixture [I], or the dissolved polymerization initiator may be further emulsified and added.

Further, if necessary, a pH buffering agent may be used at the time of polymerization to adjust the pH during the polymerization. The amount of the pH buffering agent used is 100 parts by weight of the monomer mixture [I]. The content is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 3 parts by weight.
The pH buffering agent is not particularly limited as long as it has a pH buffering action. Specifically, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, phosphorus Examples thereof include trisodium acid, sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

The amount of water used is preferably 25 to 100 parts by weight, particularly preferably 30 to 75 parts by weight, and more preferably 35 to 50 parts by weight with respect to 100 parts by weight of the monomer mixture [I]. .
If the amount of water used is too small, the resulting resin composition will have a high viscosity, and the polymerization stability will tend to decrease. If it is too much, the concentration of the resulting resin composition will be low, and drying will occur when forming a film. Tend to decrease.

The emulsion-type pressure-sensitive adhesive composition of the present invention is obtained by subjecting the monomer mixture [I] containing a (meth) acrylic acid ester monomer to emulsion polymerization, preferably in the presence of an emulsifier and further a polymerization initiator. Can be manufactured. As such a manufacturing method,
(A) After water is charged in a reaction can and heated, an emulsion prepared by mixing and emulsifying water, an emulsifier and a monomer mixture [I] in advance is dropped or dividedly added and polymerized.
(B) After adding water to the reaction can and raising the temperature, a part of the emulsion prepared by mixing and emulsifying water, the emulsifier and the monomer mixture [I] in advance is charged and polymerized, and the remaining emulsion is added dropwise or Continue polymerization by adding in portions,
(C) Water, an emulsifier, etc. are charged into a reaction can and heated up, and then the emulsion is prepared by dropping or dividing the whole amount of water, an emulsifier and a monomer mixture [I] mixed in advance and polymerizing.
Etc.

The polymerization conditions in the above polymerization method are not particularly limited. For example, in the methods (a) and (c), a temperature range of about 40 to 90 ° C. is usually appropriate, and dropping or divided addition is performed for 1 to 8 hours. The reaction is carried out at about the same temperature, and then ripened at the same temperature for about 1 to 5 hours.
In the method (b), 1 to 50% by weight of the monomer mixture is polymerized at 40 to 90 ° C. for 0.1 to 1 hour, and then the remaining monomer mixture [I] is taken for about 1 to 8 hours. Add dropwise or dividedly, and then age at the same temperature for about 1 to 5 hours.

In the above polymerization method, the monomer mixture may be used by dissolving an emulsifier (or a part of the emulsifier) in the monomer mixture [I]. The liquid state is preferable from the viewpoint of polymerization stability.
The method for preparing the emulsified liquid is not particularly limited. After the emulsifier is dissolved in water, the monomer mixture [I] is charged, and the mixed liquid is stirred and emulsified, or the emulsifier is dissolved in water and stirred. Examples of the method include charging the monomer mixture [I].

Agitation at the time of emulsification of the emulsion can be carried out using a stirring device in which the components are mixed and a stirring blade such as a homodisper or paddle blade is attached.
There is no problem as long as the temperature during emulsification is such that the mixture does not react during emulsification, and usually about 5 to 60 ° C. is appropriate.

The emulsion-type pressure-sensitive adhesive composition of the present invention preferably contains, for example, the emulsion [II] obtained by the above polymerization method and the urethane thickener (X). As such a urethane-based thickener (X), BH20 in a 30% by weight aqueous solution is preferably 10,000 mPa · s or more, particularly preferably 20,000 mPa · s or more, and 30,000 mPa · s or more. Is more preferable.
BH20 is preferably 100,000 mPa · s or less, particularly preferably 90,000 mPa · s or less, and more preferably 80,000 mPa · s or less.
If the BH20 is too small, it tends to be difficult to adjust the emulsion to a desired viscosity, and if it is too large, it tends to be difficult to adjust the Ti value of the resulting emulsion to less than 1.5.

The thixotropic index (Ti) of a 30% by weight aqueous solution of the urethane-based thickener (X) is preferably 0.9 to 1.2, particularly preferably 0.9 to 1.15, 0.95 to 1.1 is more preferable. If the Ti value is too small, it tends to be difficult to adjust the emulsion to a desired viscosity, and if it is too large, it tends to be difficult to adjust the Ti value of the resulting emulsion to less than 1.5.

Examples of the urethane thickener (X) include polyether polyol urethane polymers. Specifically, “Adecanol UH-420” (weight average molecular weight (Mw) = 29000; BH20 = 31,000 mPa.s; Ti = 1.0), “Adecanol UH-540” (weight average molecular weight (Mw) = 42000; BH20 = 26,000 mPa.s, Ti = 0.99) [manufactured by ADEKA, Inc.] “SN thickener 621N” (BH20 = 16,000 mPa.s, Ti = 1.0) [manufactured by San Nopco] A commercial item is mentioned. Urethane type thickener (X) can use 1 type (s) or 2 or more types.

The content of the urethane thickener (X) is preferably 0.1 parts by weight or more, particularly preferably 0.2 parts by weight with respect to 100 parts by weight of the nonvolatile content contained in the emulsion [II]. It is above, More preferably, it is 0.3 weight part or more.
Moreover, it is preferable that it is 3 weight part or less with respect to 100 weight part of non volatile matters contained in emulsion [II], More preferably, it is 2 weight part or less, More preferably, it is 1.5 weight part or less.
If the content of urethane-based thickener (X) is too small, the viscosity will not increase and the target viscosity will tend to be difficult to obtain. If it is too large, the target viscosity will be exceeded, and the water resistance will decrease. Tend to.

The emulsion-type pressure-sensitive adhesive composition of the present invention further contains a tackifier (for example, rosin-based, rosin-ester-based, polyterpene resin, chroman-indene resin, petroleum-based resin, terpene phenol-based resin, etc.) as necessary. can do. As a method of blending such a tackifier, for example, a method of blending an emulsion-type tackifier during or after emulsion polymerization, or dissolving a solid-type tackifier in an unsaturated monomer mixture, The method of mix | blending by emulsion polymerization is mentioned. Other plasticizers (eg liquid polybutene, mineral oil, lanolin, liquid polyisoprene and liquid polyacrylate), antiseptic / antifungal agents, rust preventives, freeze-thaw stabilizers, plasticizers, high boiling point solvents, pigments, colorants, Add fillers (zinc white, titanium white, calcium carbonate, clay, etc.), metal powder, antifoaming agent, thickener, adhesion control agent, etc. as appropriate, or before or during polymerization of the above emulsion polymerization It can also be added.

The emulsion-type pressure-sensitive adhesive composition of the present invention is suitably used for lithographic screen printing and rotary screen printing capable of continuous printing, and more preferably for high-speed screen printing with a squeegee speed of 10 m / min or more.

As a base material on which the pressure-sensitive adhesive composition is printed, for example, a plastic film base material is preferable.
Examples of such plastic film substrates include polyvinyl chloride, polybutene, polybutadiene, polyurethane, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polyethylene, polypyropylene, ethylene-propylene copolymer, polymethylpentene, polybutylene terephthalate, etc. The film base material is mentioned.

The thickness of the pressure-sensitive adhesive layer containing the emulsion-type pressure-sensitive adhesive composition formed by printing on the substrate is preferably 1 to 200 μm, particularly preferably 5 to 100 μm, and further preferably 10 to 80 μm. If the thickness of the adhesive layer is too thin, there is a tendency that sufficient adhesive force cannot be obtained.If the thickness is too thick, the screen mesh becomes too large to create a delicate pattern, and sufficient drying is obtained. There is a tendency to become difficult to get.

The emulsion-type pressure-sensitive adhesive composition of the present invention can also be used for pressure-sensitive adhesive sheets, for example. When used as such pressure-sensitive adhesive sheets, first, the emulsion-type pressure-sensitive adhesive composition is adjusted as it is or to an appropriate concentration, and is applied to the treated surface of a base material that has been subjected to silicon treatment or the like, or directly to the base material. For example, the pressure-sensitive adhesive layer can be formed by drying by, for example, heat treatment at 15 to 150 ° C. for 5 seconds to 24 hours. Moreover, after apply | coating an emulsion type adhesive composition to a release film and drying, it can also transcribe | transfer on a base material.

The base material of the pressure-sensitive adhesive sheet is not particularly limited, and examples thereof include paper, synthetic paper, plastic film, metal foil and the like. Examples of the paper and synthetic paper base material include high-quality paper, cast paper, and the like. Examples thereof include paper materials such as coated paper, coated paper, neutral paper, art paper, synthetic paper mainly made of polypropylene, and thermal paper. In addition, a porous material such as a nonwoven fabric can be used as the base material for the double-sided tape. The thickness of the substrate is usually 10 to 300 μm, particularly 20 to 100 μm.

The thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheets is preferably 1 to 200 μm, particularly preferably 5 to 100 μm, and further preferably 10 to 80 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, there is a tendency that sufficient adhesive force cannot be obtained. If the thickness is too thick, it becomes difficult to obtain sufficient drying, and the cohesive force tends to decrease.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the specification, “%” and “parts” mean weight basis.

[Example 1]
2-ethylhexyl acrylate (a1: 2EHA) 64 parts, butyl acrylate (a1: BA) 20 parts, methyl methacrylate (a1: MMA) 8 parts, vinyl acetate (a3: VAc) 5 parts, methacrylic acid (a2: MAA) 3 Parts, anionic non-reactive emulsifier (0.67 part of “New Coal 707SF” manufactured by Nippon Emulsifier Co., Ltd. (active ingredient 30% = 0.2 part equivalent of active ingredient)), “Perex SS-L” manufactured by Kao Chemical Co., Ltd. 0.8 parts (active ingredient 50% = active ingredient equivalent amount 0.4 part) and 25 parts of water were mixed and stirred to obtain an emulsion composed of the monomer mixture [I].

Next, 12 parts of water was added to a flask equipped with a condenser and a stirring blade, dissolved by stirring, heated to 75 ° C., 0.6 parts of 10% ammonium persulfate aqueous solution was added, and after 5 minutes. Then, dropwise addition of 1.9 parts of the above emulsion and 10% aqueous ammonium persulfate solution was started, and the entire amount was dropped over 4 hours to carry out emulsion polymerization. After completion of the dropwise addition, stirring was continued for 2 hours while maintaining the temperature at 75 ° C., followed by cooling to 60 ° C. and adding 2 parts of a 10% aqueous ammonia solution to neutralize the acid groups. Thereafter, the mixture was cooled to 55 ° C., and 0.5 parts of 10% aqueous solution of tertiary butyl hydroperoxide (manufactured by NOF Corporation, “Perbutyl H-69”) and 0.5 parts of 10% aqueous sodium hydrogen sulfite solution were added. After reacting for 15 minutes, 0.5 parts of a 10% aqueous solution of tertiary butyl hydroperoxide (manufactured by NOF Corporation, "Perbutyl H-69") and 0.5 parts of a 10% aqueous sodium hydrogen sulfite solution were again added. Added and allowed to react for 15 minutes. Thereafter, the mixture was cooled to 30 ° C., filtered through a 150 mesh nylon mesh, and adjusted to pH 7 with 10% aqueous ammonia to obtain an acrylic emulsion [II-1] (nonvolatile content: 66%).

In the acrylic emulsion [II-1] obtained above, the urethane thickener (X) (“Adecanol UH-420” (BH20 = 31, 000 mPa.s, Ti = 1.0) 1.4 parts (active ingredient 30% = active ingredient equivalent amount 0.42 parts), “Adecanol UH-540” (BH20 = 26,000 mPa.s, Ti = 0.99) ) 1.4 parts (active ingredient 30% = active ingredient equivalent amount 0.42 parts) (above, manufactured by ADEKA)) and water, 65% non-volatile content, viscosity (BH20) 34,000 mPa · s (BM Mold, 20 rpm, 25 ° C.) to obtain an emulsion-type pressure-sensitive adhesive composition of the present invention.

[Examples 2 to 4, Comparative Examples 1 to 4]
In the same manner as in Example 1, emulsions composed of the monomer mixture [I] and acrylic emulsions [II-1] to [II-4] were prepared at the composition ratio shown in Table 1. Furthermore, using the emulsions [II-1] to [II-4] at the composition ratios shown in Table 2, emulsion type pressure-sensitive adhesive compositions of Examples 2 to 4 and Comparative Examples 1 to 4 were obtained.
In Table 1, “Aqualon KH-10 (active ingredient 99% or more)” is an anionic reactive emulsifier manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In Table 2, “SN thickener 621N” (BH20 = 16,000 mPa .S, Ti = 1.0, active ingredient 30%) is a urethane thickener (X) manufactured by San Nopco, "Movinyl LDM7010" (BH20 = 100 mPa.s, Ti = 1.0, active ingredient 25) %) Is an acrylic alkali thickener manufactured by Nippon Synthetic Chemical Industry. The nonvolatile content, viscosity (BH20), and Ti value described in Tables 1 and 2 were measured by the following methods.

(Non-volatile content)
1 g of each of the acrylic emulsion [II] and the emulsion-type pressure-sensitive adhesive composition obtained by emulsion polymerization is precisely weighed into a commercially available aluminum cup, and the water is evaporated and dried and solidified in an oven at 105 ° C. for 60 minutes. The non-volatile content was measured from the weight change before and after drying.

(viscosity)
The emulsion pressure-sensitive adhesive composition was adjusted to 25 ° C., and the viscosity value was measured at a rotation speed of 20 rpm using a Brookfield viscometer. The rotor was changed as appropriate and No. 5 or No. 6 was used as appropriate.

(Ti value)
The emulsion pressure-sensitive adhesive composition was adjusted to 25 ° C., and the viscosity value (BH20) at a rotation speed of 20 rpm was measured using a Brookfield viscometer. Subsequently, the viscosity value (BH2) at a rotational speed of 2 rpm was measured, and the viscosity value of BH2 was divided by the viscosity value of BH20 and rounded off to the second decimal place.

〔Evaluation test〕
Screen printing suitability: Using the emulsion-type pressure-sensitive adhesive compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4, solid printing was performed on an 80 mesh polyester screen with a screen printer. The substrate to be printed was PET having a thickness of 100 μm, and printing was performed so that the thickness of the adhesive layer was 30 to 40 μm. The pressure-sensitive adhesive coated surface obtained by this printing was visually observed, and the following items were evaluated. The evaluation results are summarized in Table 2.

(Surface roughness)
A: The screen mesh was not marked at all and was applied uniformly.
B: The coating was almost uniform with almost no screen mesh.
C: Screen mesh marks remained partially (30% or less of the entire surface), but coated almost uniformly.
D: Screen mesh marks remained partially (80% or less of the entire surface), resulting in coating with a non-uniform surface.
E: Most of the screen eyes (over 80% of the entire surface) or the entire surface remained, resulting in a coating with a nonuniform surface.

(Sharpness of print edge (clearness))
A: The printing edge is in a straight line state.
B: The printing edge is in a substantially straight state.
C: There is a jagged portion at the printing edge (not more than 30% of the whole edge).
D: There is a jagged portion at the printing edge (not more than 80% of the whole edge).
E: Most (more than 80% of the entire edge) of the printing edge or a jagged portion exists entirely.

(With or without foaming / repelling)
A: The printing surface was uniformly coated.
B: Almost no foaming or repelling on the printed surface C; Foaming or repelling exists partially (30% or less of the whole) on the printed surface.
D: Foaming and repelling are present partially (80% or less of the whole) on the printed surface.
E: Foaming or repellency exists on most (over 80% of the entire edge) or the entire printed surface.

(water resistant)
The screen-printed adhesive sheet substrate is immediately put in a dryer at 40 ° C., taken out after 20 minutes, and the adhesive-coated surface obtained by screen printing is immersed in water at room temperature for 1 hour, and then it is placed on newspaper. And evaluated as follows.
A: The coating film is transparent and the letters on the newspaper can be read clearly.
B: The coating film was slightly whitened and it was difficult to read newspaper letters.
C: The film is whitened and the letters on the newspaper cannot be read at all.

(Drying)
The screen-printed pressure-sensitive adhesive sheet substrate was immediately put into a dryer at 40 ° C., taken out after 20 minutes, and the pressure-sensitive adhesive-coated surface was rubbed with a finger to confirm whether it was dry.
A: Dry.
B: Not dry.

As shown in Table 2, Examples 1 to 4 were uniformly applied during printing, the surface was flat, the sharpness of the printed edge was good, and no foaming or repellency was observed. Further, the emulsion type pressure-sensitive adhesive compositions of Examples 1 to 4 have excellent screen printing suitability.

On the other hand, Comparative Examples 1, 3, and 4 have a Ti value of 1.5 or more, and Comparative Example 2 has a BH20 of less than 20,000 mPa · s, so the surface roughness and the sharpness of the printing edge (sharpness) In addition, none showed excellent performance in all items of presence / absence of foaming / repelling, water resistance, and drying property.
Note that this application is based on a Japanese patent application filed on March 29, 2012 (Japanese Patent Application No. 2012-0706203), the contents of which are incorporated herein by reference.

The emulsion-type pressure-sensitive adhesive composition of the present invention can be suitably used for screen printing, particularly rotary screen printing capable of continuous printing and high-speed screen printing. Moreover, it can also use for the adhesive sheet which has an adhesion layer containing an emulsion type adhesive composition.

Claims

It is an emulsion-type pressure-sensitive adhesive composition containing an emulsion [II] obtained by emulsion polymerization of a monomer mixture [I] containing a (meth) acrylic acid ester monomer, and BH20 is 20,000 mPa · s or more, And the thixotropy index (Ti) is less than 1.5, The emulsion type adhesive composition characterized by the above-mentioned.
(However, Ti = BH2 / BH20, BH20 is a viscosity value measured using a Brookfield viscometer at a liquid temperature of 25 ° C. and a rotation speed of 20 rpm, and BH2 is a Brookfield viscometer. And the viscosity measured at a liquid temperature of 25 ° C. and a rotation speed of 2 rpm.)
The emulsion-type pressure-sensitive adhesive composition according to claim 1, wherein the monomer mixture [I] contains vinyl acetate.
The emulsion-type pressure-sensitive adhesive composition according to claim 1 or 2, wherein the monomer mixture [I] is emulsion-polymerized in the presence of an emulsifier.
The emulsion-type pressure-sensitive adhesive composition according to claim 3, wherein the amount of the emulsifier used is 1.5 parts by weight or less with respect to 100 parts by weight of the monomer mixture [I].
The emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the content of nonvolatile components contained in the emulsion [II] is 60% by weight or more.
The emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 5, comprising an emulsion [II] and a urethane thickener (X).
BH20 in a 30% by weight aqueous solution of urethane thickener (X) is 10,000 mPa · s or more, and the thixotropic index (Ti) of a 30% by weight aqueous solution of urethane thickener (X) is 0.00. The emulsion-type pressure-sensitive adhesive composition according to claim 6, which is 9 to 1.2.
The content of the urethane-based thickener (X) is 0.1 part by weight or more with respect to 100 parts by weight of the nonvolatile content contained in the emulsion [II]. Emulsion type pressure-sensitive adhesive composition.
9. The emulsion-type pressure-sensitive adhesive composition according to claim 1, wherein the emulsion-type pressure-sensitive adhesive composition is used for screen printing.
A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the emulsion-type pressure-sensitive adhesive composition according to any one of claims 1 to 8.