JP2000313865A - Emulsion type adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emulsion type adhesive which exerts an excellent adhesion property and water blush resistance. SOLUTION: This emulsion type adhesive is obtained by dissolving from 0.5 to 5 pts.wt. adhesion-imparting resin and an oil-soluble polymerization initiator in 100 pts.wt. monomer mixture containing (a) from 50 to 99.5 wt.% alkyl (meth)acrylate wherein the carbon number of the alkyl group is from 9 to 14 and (b) from 0.5 to 2.5 wt.% monomer having carboxyl group, hydroxyl group or amide group, which are then emulsion dispersed in an aqueous solution of an emulsifier to form monomer oil droplets having an average particle size of 1 μm or smaller, and then polymerizing these. An adhesive product is prepared by applying the emulsion type adhesive onto a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion-type pressure-sensitive adhesive excellent in water whitening resistance.

[0002]

2. Description of the Related Art Adhesive products such as adhesive tapes, labels, and double-sided adhesive tapes obtained by processing an adhesive are widely used for applications such as home appliances, daily necessities, and building materials. . As pressure-sensitive adhesives used in these pressure-sensitive adhesive products, acrylic pressure-sensitive adhesives excellent in durability such as heat resistance and weather resistance in addition to balance of physical properties are widely used. Above all, acrylic emulsion type pressure-sensitive adhesives are widely used from the viewpoint of air pollution prevention and work environment improvement, and it is common to add a hydrocarbon-based, terpene-based, rosin-based tackifier resin to improve the adhesive strength. It is. However, conventional acrylic emulsion-type pressure-sensitive adhesives become cloudy in a high-humidity environment or when immersed in water, have poor water-whitening resistance, and are hardly used in fields such as transparent labels where design is required. For example, JP-A-63-256672 discloses a pressure-sensitive adhesive obtained by blending a tackifier resin emulsion obtained by emulsifying a tackifier resin with an emulsifier and an acrylic polymer emulsion. With the agent, the tackifying resin and the acrylic resin are not uniformly mixed, so that the film forming property is poor and the water whitening resistance is reduced. In addition, mechanical stability is deteriorated, which causes streaks and unevenness on the coated surface during line coating.

Further, Japanese Patent Application Laid-Open Nos. 58-185668 and 8-2319
No. 37 and JP-A-9-111218 disclose a method of dissolving a tackifier resin in a monomer and performing drop polymerization. In this method, the monomer in which the tackifier resin is dissolved is converted into micelle or emulsified polymer. Because the polymer is diffused and polymerized, the final polymer particles and the tackifying resin particles are separately present after polymerization due to the difference in the diffusion rate between the monomer and the tackifying resin. cause. Therefore, it has been difficult to achieve both tackiness and water whitening resistance by these methods.

An object of the present invention is to provide an emulsion-type pressure-sensitive adhesive which is excellent in tackiness and water-whitening resistance.

[0005]

According to the present invention, there are provided (a) 50 to 99.5% by weight of an alkyl (meth) acrylate having 9 to 14 carbon atoms in an alkyl group, and (b) a carboxyl group, a hydroxyl group or an amide group. In 100 parts by weight of a mixed monomer containing 0.5 to 2.5% by weight of a monomer, 0.5 to 5 parts by weight of a tackifier resin and an oil-soluble polymerization initiator are dissolved, and this is emulsified and dispersed in an aqueous solution of an emulsifier to give an average particle size of 1 μm or less. After forming monomer oil droplets, emulsion-type adhesive obtained by polymerization,
Provided is an adhesive product obtained by applying the production method and the emulsion type adhesive to a substrate. Further, the present invention provides a method for improving the water whitening resistance of a pressure-sensitive adhesive product by using the emulsion-type pressure-sensitive adhesive.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the component (a) used in the present invention, for example, an alkyl ester of acrylic acid or methacrylic acid such as nonyl, isononyl, decyl, isodecyl, dodecyl, isododecyl, lauryl, tridecyl, isotridecyl, tetradecyl, etc. And lauryl methacrylate is most preferred. The content of the component (a) in the total amount of the monomers is 50% by weight or more, preferably 70% by weight or more, from the viewpoint of improving the adhesive strength to the olefin adherend, in order to secure the dispersion stability of the emulsion. , 9
It is at most 9.5% by weight, preferably at most 99% by weight.

Among the components (b) used in the present invention, examples of the monomer having a carboxyl group include methacrylic acid, acrylic acid, maleic acid and itaconic acid, and acrylic acid is most preferred. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate, and 2-hydroxyethyl methacrylate is most preferable. Examples of the monomer having an amide group include acrylamide, N, N-dimethylacrylamide,
N-methylol acrylamide and the like can be mentioned. These may be used alone or in combination of two or more. The content of the component (b) in the total amount of the monomers is 0.5% by weight or more, preferably 1.0% by weight, from the viewpoint of improving mechanical stability.
From the viewpoint of improving the water whitening resistance, it is at most 2.5% by weight, preferably at most 2.0% by weight.

In the present invention, a monomer copolymerizable with the above components (a) and (b) (hereinafter referred to as component (c)) can also be used. For example, methyl of acrylic acid or methacrylic acid,
Ethyl, propyl, butyl, isobutyl, t-butyl,
Pentyl, cyclohexyl, heptyl, octyl, 2-
Esters such as ethylhexyl and benzyl; acrylonitrile; styrene; vinyl acetate; The content of the component (c) in the total amount of the monomers is preferably 49.5% by weight or less.

As the tackifying resin used in the present invention,
For example, rosin-based resins, terpene-based resins, phenol-based resins, aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, xylene resins and the like can be mentioned. These may be used alone or in combination of two or more kinds by blending or modification. The amount of the tackifying resin used is 0.5 parts by weight or more, preferably 2 parts by weight or more, from the viewpoint of improving water whitening resistance, based on 100 parts by weight of all monomers, and 5 parts by weight or less to obtain high holding power. , Preferably 4 parts by weight or less.

In the present invention, the emulsifier can be an anionic emulsifier alone or a combination thereof with a nonionic emulsifier.
As the anionic emulsifier, a reactive emulsifier having a radical polymerizable double bond is particularly preferred. As a nonionic emulsifier,
For example, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ether, polyoxyethylene higher fatty acid ester, ethylene oxide / propylene oxide block copolymer and the like can be used. The amount of emulsifier used is from the viewpoint of polymerization stability and water whitening resistance, based on the monomer mixture in which the tackifier resin is dissolved.
0.5-2.5% by weight is preferred.

The oil-soluble polymerization initiator used in the present invention includes, for example, organic peroxides such as benzoyl peroxide and lauroyl peroxide, and azobisisobutyronitrile and azobis (2-methylbutyronitrile). Compounds. The amount of the oil-soluble polymerization initiator used is preferably 0.05 to 1.0% by weight, more preferably 0.1 to 0.5% by weight, based on all monomers. These initiators may be used alone or in combination of two or more.

In the present invention, a water-soluble initiator and / or a redox initiator may be used in combination as a polymerization initiator. Examples of the water-soluble initiator include persulfates such as potassium persulfate and ammonium persulfate, and azobis (4
-Cyanovaleric acid) and dimethyl azobisisobutyrate. The amount of the water-soluble initiator to be used is preferably 0.01 to 0.2% by weight based on all monomers. Redox initiators include, for example, organic hydroperoxide / ascorbic acid, organic hydroperoxide / iron ion, organic hydroperoxide / reducing sugar, persulfate /
Combinations of sulfites, hydrogen peroxide / iron ions and the like can be mentioned, but from the viewpoint of emulsion stability and water resistance, water-soluble organic peroxides such as t-butyl hydroperoxide / ascorbic acid / water-soluble organic Combinations of reducing agents are preferred. The amount of the redox initiator used is preferably from 0.01 to 0.2% by weight based on the total monomers.

In the present invention, the ratio of the monomer mixture in which the tackifier resin is dissolved to the total charge is preferably 20% by weight or more from the viewpoint of drying efficiency, and is preferably 70% by weight or less from the viewpoint of stirring efficiency during production.

The component (a) of the present invention has an extremely low solubility in water as compared with monomers generally polymerizable by emulsion polymerization or drop polymerization, such as 2-ethylhexyl (meth) acrylate and butyl (meth) acrylate. Emulsion polymerization or drop polymerization cannot stably carry out polymerization. However, as in the present invention, prior to polymerization, component (a) and
(b) The oil containing the monomer containing the component, the tackifying resin and the oil-soluble polymerization initiator is finely divided into particles having an average particle diameter of 1 μm or less by mechanical force, and a stable polymer emulsion is obtained by performing polymerization in the oil droplet particles. Obtainable. In this case, unlike the general emulsion polymerization or drop polymerization, the monomer proceeds without dispersing the monomer from the particles into micelles, and the polymerization proceeds in a state where the tackifier resin is uniformly dispersed in the same particles. Compatible polymer particles are obtained. For this reason, there is no decrease in water whitening resistance due to the addition of a tackifier resin as seen in the prior art.

In the present invention, examples of the emulsifier used for emulsifying and dispersing the monomer mixture include an ultrasonic emulsifier and a high-pressure homogenizer. When the average particle size of the monomer oil droplets in the emulsification is 1 μm or less, the water-whitening resistance becomes good, but it is more preferably 0.5 μm or less, and particularly preferably 0.35 to 0.40 μm.

In the polymerization reaction step of the present invention, the monomer emulsion is charged into a polymerization vessel equipped with a stirrer, and a polymerization initiator such as a water-soluble initiator or a redox initiator is added thereto. The heating initiates the polymerization reaction. At this time, it is preferable to replace the polymerization system with an inert gas such as nitrogen or argon so that the polymerization reaction is not suppressed. The polymerization temperature is suitably in the range of 40 to 90 ° C, and the polymerization time is suitably 1 to 10 hours.

In the present invention, various additives may be added in any of the above-mentioned production steps. Such additives include chain transfer agents, preservatives, antibacterial agents, antioxidants, antioxidants,
Examples include a viscosity adjuster, a pH adjuster, an antifoaming agent, and a plasticizer.

The pressure-sensitive adhesive product of the present invention can be obtained by applying the emulsion-type pressure-sensitive adhesive of the present invention to a substrate and drying. For coating, a wire coater, an applicator, a die coater, a roll coater, a comma coater, a lip coater, or the like is used. The substrate is preferably a transparent substrate, particularly a transparent film tape, such as an OPP (biaxially oriented polypropylene) film or PET (polyethylene terephthalate).
A film, further, a PE (polyethylene) film, a vinyl chloride film, or the like is used. In the case of directly applying the emulsion, those having a corona treatment applied to the film surface or those having a surface coating can be used. Alternatively, transfer coating can be performed by coating a release paper or a release film, drying and applying a transparent substrate. The coating thickness of the pressure-sensitive adhesive can be measured with a micrometer, and is generally applied to a coating thickness of about 20 μm. For drying the pressure-sensitive adhesive after coating, a hot air dryer is used, and the conditions for making the coated surface transparent and smooth (for example,
Drying is performed at 90 to 110 ° C for about 1 minute).

The emulsion-type pressure-sensitive adhesive of the present invention has little white turbidity even when immersed in water, has an excellent balance between strong tackiness and holding power, and shows good tackiness to polyolefin adherends. Therefore, it can be used not only as a general pressure-sensitive adhesive but also as a pressure-sensitive adhesive in a field requiring design such as a transparent label.

[0020]

EXAMPLES The percentages in the examples are percentages by weight unless otherwise specified. The physical properties of the emulsions and films thereof in Examples and Comparative Examples were measured by the following methods. (1) Average particle size The average particle size was measured using a particle size distribution analyzer (LA-910) manufactured by Horiba, Ltd. (2) The measurement was performed using an infrared moisture meter (FD-230) manufactured by Solid Packing Inc. (3) Viscosity Using a No. 4 rotor at 25 ° C. using a B-type viscometer manufactured by Tokyo Keiki, the viscosity was measured after 60 revolutions per minute for one minute.

(4) Holding force An adhesive film was attached to a stainless steel plate specified in JIS R6253 so as to have an attachment area of 25 × 25 mm, and was allowed to stand at 70 ° C. for 20 minutes. Subsequently, a load of 1 kg was applied and the shift width after 3 hours was measured. Those that could not be held for 3 hours recorded the fall time.

(5) Water Whitening Resistance A piece of the adhesive film was cut into a size of 45 × 45 mm, the release film was peeled off to expose the adhesive layer, and a glass cell (50 × 50 mm, width: 23 ° C.) filled with water at 23 ° C. 4 mm), and quickly set the glass cell on a haze meter (Haze Meter HR-100 manufactured by Murakami Color Research Laboratory), and measured the haze value of the immersion for 0 hour. This was used as a blank, which was subsequently immersed, and the haze value was measured after 24 hours. Water whitening resistance is 24
It is represented by the difference between the haze value of the blank and the haze value after immersion in water for a period of time. The smaller the difference, the less the whitening, and the better the water whitening resistance.

Example 1 In a container, 972 g of lauryl methacrylate, 51.7 g of methyl methacrylate, 10.3 g of acrylic acid, and superester S-
100 [Rosin ester resin manufactured by Arakawa Chemical Industry Co., Ltd.] 26
g, 3.10 g of benzoyl peroxide and stirred at room temperature until the mixture became homogeneous. The effective concentration is 1.7
% Latemul S-180 [Kao Co., Ltd. anionic emulsifier] 929 g of an aqueous solution was charged and treated with an ultrasonic emulsifier [Nihon Seiki Seisakusho] for 15 minutes while stirring to give an average particle size of 0.39.
A μm emulsion was obtained. After transferring 1500 g of this emulsion to a separable flask and purging with nitrogen, 3.88 g of a 10% aqueous solution of t-butyl hydroperoxide was added, and 11.7 g of a 1% aqueous solution of ascorbic acid were added. I made it. After aging at that temperature for 6 hours, cooling to room temperature, adjusting the pH to 7.5 with 25% aqueous ammonia,
The mixture was filtered through a mesh wire net to obtain a polymer emulsion. The average particle size was 0.28 μm, and the solid content was 52.7%. On the other hand, Primer ASE60 (a thickener manufactured by Rohm and Haas Co.) was added to adjust the viscosity to 4500 to 5500 mPa · s to obtain an emulsion-type adhesive.

The obtained emulsion-type pressure sensitive adhesive was applied to a 38 μm polyethylene terephthalate release film (ID-8) manufactured by San-A Kaken Co., Ltd. using an applicator to have a dry thickness of 20 to 25.
μm, 110 ℃ / 30 in hot air circulation dryer
After drying under the condition for 2 seconds, a 50 μm polyethylene terephthalate film (Lumirror 50S105) manufactured by Toray Industries, Inc. was laminated on the non-treated surface, and then aged for 3 days to produce an adhesive film.

Example 2 An adhesive film was prepared in the same manner as in Example 1 except that 10.3 g of acrylic acid was changed to 10.3 g of 2-hydroxyethyl methacrylate.

Example 3 An adhesive film was prepared in the same manner as in Example 1 except that the addition ratio of the tackifying resin was changed to 1% of all monomers.

Example 4 An adhesive film was produced in the same manner as in Example 1 except that the addition ratio of the tackifying resin was changed to 5% of all monomers.

Example 5 An adhesive film was prepared in the same manner as in Example 1 except that the monomer composition was changed to 559 g of lauryl methacrylate, 465 g of 2-ethylhexyl acrylate, and 10.3 g of acrylic acid.

Example 6 An adhesive film was prepared in the same manner as in Example 1 except that a redox-based initiator composed of a combination of t-butyl hydroperoxide and ascorbic acid was not added.

Comparative Example 1 The average particle size of the monomer emulsion in Example 1 was 1.1 μm.
A pressure-sensitive adhesive film was produced in the same manner as in Example 1 except that

Comparative Example 2 In Example 1, the ratio of the tackifier resin added to the total monomers was
An adhesive film was prepared in the same manner as in Example 1 except that the content was 10%.

Comparative Example 3 An adhesive film was prepared in the same manner as in Example 1 except that no tackifier resin was added.

Comparative Example 4 After adjusting the pH to 7.5 in Comparative Example 3, QME-120
[Toho Chemical Industry Co., Ltd. hydrocarbon resin emulsion]
An adhesive film was produced in the same manner as in Example 1 except that 103 g was added.

Comparative Example 5 A separable flask was charged with 139 g of ion-exchanged water in which 0.26 g of ammonium persulfate was dissolved.
Warmed to ° C. 5.2 g of acrylic acid and methacrylic acid in a container
5.2 g, n-butyl acrylate 145.6 g, 2-ethylhexyl acrylate 104 g, Superester S-100
[Rosin ester resin manufactured by Arakawa Chemical Industry Co., Ltd.] 6.5 g,
0.13 g of n-dodecyl mercaptan was charged, 101 g of a 3.87% aqueous solution of Latemul S-180 was charged with an effective component, and the mixture was stirred and emulsified. After completion of the dropwise addition, polymerization was carried out at 80 ° C. for 2 hours to complete the polymerization. After cooling to room temperature, adjust the pH to 7.5 with 25% aqueous ammonia,
The mixture was filtered through a 00 mesh wire net to obtain a polymer emulsion.
The average particle size was 0.27 μm, and the solid content was 52.0%. Thereafter, an adhesive film was produced in the same manner as in Example 1.

Table 1 shows the results of measurement and evaluation of the physical properties and the like of the emulsions and pressure-sensitive adhesive films obtained in Examples 1 to 6 and Comparative Examples 1 to 5 by the above methods.

[0036]

[Table 1]

Note) * 1: Weight% based on all monomers * 2: Abbreviations in the table mean the following. Initiator BPO: benzoyl peroxide Redox: t-butyl hydroperoxide / ascorbic acid APS: ammonium persulfate monomer LMA: lauryl methacrylate MMA: methyl methacrylate AA: acrylic acid HEMA: 2-hydroxyethyl methacrylate 2EHA: 2-ethylhexyl acrylate BA: Butyl acrylate MAA: Methacrylic acid

[0038]

The emulsion-type pressure-sensitive adhesive of the present invention is not only required as a general pressure-sensitive adhesive but also has a design property such as a transparent label because of little white turbidity when immersed in water. It can be used as a pressure-sensitive adhesive in fields that have not been used.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08F 220/62 C08F 220/62 (72) Inventor Yasuhiro Doi 1334 Minato 1334 Minato, Wakayama-shi, Wakayama Ken Kao Co., Ltd. F-term in the laboratory (reference) JB09 KA11 KA21 KA26 KA38 LA03 LA07 QA01 4J100 AB02R AG04R AJ02Q AJ09Q AL03R AL04P AL05P AL08R AL09Q AM02R AM15Q AM19Q AM21Q BA03Q BC04R BC43R CA04 CA05 DA44 EA07 FA03 FA20 FA27 JA05

Claims (5)

[Claims] 1. A monomer having (a) 50 to 99.5% by weight of an alkyl (meth) acrylate having 9 to 14 carbon atoms in an alkyl group, and (b) a monomer having a carboxyl group, a hydroxyl group or an amide group.
0.5 to 5 parts by weight of a tackifier resin and an oil-soluble polymerization initiator are dissolved in 100 parts by weight of a mixed monomer containing 0.5 to 2.5% by weight, and this is emulsified and dispersed in an aqueous emulsifier solution to obtain a monomer having an average particle size of 1 μm or less. An emulsion-type adhesive obtained by forming oil droplets and then polymerizing. 2. The emulsion-type pressure-sensitive adhesive according to claim 1, wherein a water-soluble initiator and / or a redox-based initiator are further used as a polymerization initiator. 3. A monomer having (a) 50 to 99.5% by weight of an alkyl (meth) acrylate having 9 to 14 carbon atoms in an alkyl group, and (b) a monomer having a carboxyl group, a hydroxyl group or an amide group.
0.5 to 5 parts by weight of a tackifier resin and an oil-soluble polymerization initiator are dissolved in 100 parts by weight of a mixed monomer containing 0.5 to 2.5% by weight, and this is emulsified and dispersed in an aqueous emulsifier solution to obtain a monomer having an average particle size of 1 μm or less. 3. The method for producing an emulsion-type pressure-sensitive adhesive according to claim 1, wherein polymerization is performed after oil droplets are formed. 4. An adhesive product obtained by applying the emulsion type adhesive according to claim 1 to a substrate. 5. A method for improving the water-whitening resistance of a pressure-sensitive adhesive product by using the emulsion-type pressure-sensitive adhesive according to claim 1 or 2.