JP2008081564A - Aqueous adhesive composition - Google Patents

Abstract

To provide an aqueous pressure-sensitive adhesive composition having excellent water resistance while overcoming the drawbacks of conventional water-based emulsion-type pressure-sensitive adhesives and maintaining various adhesive properties equivalent to those of solvent-type pressure-sensitive adhesives.
(Meth) acrylic acid alkyl ester having 1 to 14 carbon atoms (a) 7 to 99.7% by weight, polymerizable unsaturated carboxylic acid (b) 0.1 to 10% by weight, alcohol 100 parts by weight of a monomer comprising 0.1 to 10% by weight of a copolymerizable vinyl monomer (c) having a functional hydroxyl group and 0.1 to 1.0% by weight of acetoacetoxyethyl methacrylate, and 30 terpene-based tackifying resin A co-polymer obtained by emulsion polymerization in a water medium in the presence of 0.1 to 10 parts by weight of a surfactant (e), a mixture comprising 1 to 10 parts by weight of a tackifier resin (d) containing at least% by weight. An aqueous pressure-sensitive adhesive composition comprising a polymer emulsion.
[Selection figure] None

Description

The present invention is an aqueous emulsion of a composition containing a polymer formed from a radical polymerizable monomer and a tackifying resin, and more specifically, a composition in which the polymer and the tackifying resin are combined is dispersed in water. And an acrylic polymer-containing composition emulsion.
Furthermore, this invention relates to the adhesive coating material which uses as a support body the film which consists of various plastics, such as a polyethylene terephthalate (henceforth "PET"), polyolefin, and vinyl chloride.

Conventionally, solvent-based acrylic pressure-sensitive adhesives have been mainly used as pressure-sensitive adhesives in pressure-sensitive adhesive coated products using various plastic films as a support. However, although a shift from solvent type to water-based acrylic pressure-sensitive adhesive has been attempted due to demands for environmental problems, it is not always sufficient water resistance, adhesive strength to adherends, cutting ability and retention of pressure-sensitive adhesive coatings. There was nothing that fulfilled the necessary physical properties such as power.
In general, water resistance can be obtained by using a reactive emulsifier as an emulsifier used for emulsion polymerization, but sufficient adhesion and retention to various adherends that can be compared with a solvent type. There is no power or cutting ability. This is because a solvent-type acrylic pressure-sensitive adhesive is a pressure-sensitive adhesive system in which a reactive functional group in an acrylic copolymer having a weight average molecular weight (2 million to 3 million or less) that can be measured by liquid chromatography is crosslinked with a crosslinking agent. However, in the case of the water-based pressure-sensitive adhesive, there is no curing system in which an emulsion having a relatively low molecular weight is sufficiently crosslinked between particles at a low temperature at which water as a dispersion medium is volatilized.

Therefore, a pressure-sensitive adhesive using a water-soluble titanium compound as a crosslinking agent (curing agent) has been proposed (see Patent Document 1: Japanese Patent Application Laid-Open No. 2006-249284).
Certainly, the pressure-sensitive adhesive disclosed in Patent Document 1 is excellent in terms of water resistance. However, the water resistance is insufficient under more severe conditions, and the improvement has been desired.
JP 2006-249284 A

  An object of the present invention is to provide a water-based pressure-sensitive adhesive composition having excellent water resistance while overcoming the drawbacks of conventional water-based emulsion pressure-sensitive adhesives and maintaining various physical properties equivalent to those of solvent-based pressure-sensitive adhesives. .

That is, the present invention relates to (meth) acrylic acid alkyl ester (a) having an alkyl group having 1 to 14 carbon atoms (a) 79 to 99.7% by weight, polymerizable unsaturated carboxylic acid (b) 0.1 to 10% by weight. 100 parts by weight of a monomer comprising 0.1 to 10% by weight of a copolymerizable vinyl monomer (c) having an alcoholic hydroxyl group and 0.1 to 1.0% by weight of acetoacetoxyethyl methacrylate, and a terpene-based tackifying resin Obtained by emulsion polymerization in an aqueous medium in the presence of 0.1 to 10 parts by weight of the surfactant (e). The present invention relates to an aqueous pressure-sensitive adhesive composition comprising a copolymer emulsion.
Moreover, this invention relates to the adhesive coating material formed using the aqueous adhesive composition of the said invention.

  According to the present invention, it is possible to provide an aqueous pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive coated product having good water resistance.

The (meth) acrylic acid alkyl ester (a) having 1 to 14 carbon atoms in the alkyl group capable of forming the copolymer emulsion constituting the aqueous pressure-sensitive adhesive composition of the present invention is specifically the following compound: Can be illustrated.
For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, iso-propyl (meth) acrylate, butyl (meth) acrylate, iso-butyl (meth) acrylate, (meth ) Acrylic esters of linear or branched aliphatic alcohols such as hexyl acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate and the like A methacrylic acid ester etc. can be mentioned. A preferred (meth) acrylic acid alkyl ester is an alkyl ester having 4 to 12 carbon atoms in the alkyl group.

  Examples of the polymerizable unsaturated carboxylic acid (b) include acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid, and crotonic acid.

  Examples of the copolymerizable vinyl monomer (c) having an alcoholic hydroxyl group include 2-hydroxylethyl (meth) acrylate, 2-hydroxylpropyl (meth) acrylate, 2-hydroxylbutyl (meth) acrylate, polyethylene glycol acrylate , Mono- (2-hydroxylethyl-α-chloroacrylate) acid phosphate, N-methylolacrylamide, N-methylolmethacrylamide and the like.

  (A)-(c) may use only 1 type, respectively, and may use 2 or more types together.

Next, acetoacetoxyethyl methacrylate used in the present invention will be described.
Acetoacetoxyethyl methacrylate is a compound represented by the following structural formula (I).

_{CH 2 = C (CH 3)} CO 2 CH 2 CH 2 OCOCH 2 COCH 3 (I)
Acetoacetoxyethyl methacrylate functions as a self-crosslinking agent.
When the reaction between ethyleneimine and oxazoline is used as a crosslinking system, there is a concern about toxicity, but there is no such concern when using the self-crosslinking reaction of acetoacetoxyethyl methacrylate. In addition, by utilizing the self-crosslinking reaction of acetoacetoxyethyl methacrylate, in terms of the balance between adhesive properties and cutting properties, transparency as an adhesive for film substrates, yellowing after heat aging, stability over time of the adhesive, etc. Excellent.

When obtaining the copolymer emulsion constituting the aqueous pressure-sensitive adhesive composition of the present invention, in addition to the above (a) to (c) and acetoacetoxyethyl methacrylate, a vinyl monomer copolymerizable therewith should be used. Can do.
For example, glycidyl acrylate, glycidyl methacrylate, vinyl blocked isocyanates, N-methylaminoethyl acrylate, N-tributylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N -Diethylaminoethyl methacrylate, acrylamide, methacrylamide, vinyl pyrrolidone, vinyl ester, vinyl pyridine, vinyl acetate, vinyl propionate, styrene, acrylonitrile, methacrylonitrile, butadiene, chloroprene and the like.
These may use only 1 type and may use 2 or more types together.

In a total of 100% by weight of monomers capable of forming a copolymer in the copolymer emulsion, (meth) acrylic acid alkyl ester (a) is 79 to 99.7% by weight, polymerizable unsaturated carboxylic acid (b ) Is 0.1 to 10% by weight, the copolymerizable vinyl monomer (c) having an alcoholic hydroxyl group is 0.1 to 10% by weight, and acetoacetoxyethyl methacrylate is 0.1 to 1.0% by weight. Contained.
Furthermore, it is preferable that the other copolymerizable vinyl monomer used as needed is contained in an amount of 0.01 to 5% by weight in a total of 100% by weight of the monomers.

Examples of the tackifier resin (d) used in the present invention include rosin resins, terpene resins, aromatic petroleum resins, aliphatic petroleum resins and the like. It is important to contain the above.
Examples of the rosin resin include natural rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, disproportionated rosin, and disproportionated rosin ester.
Examples of the terpene resin include α-pinene resin, β-pinene resin, terpene phenol resin, hydrogenated terpene phenol resin and the like.
Examples of aromatic petroleum resins include styrene oligomers and α-methylstyrene / styrene copolymers.

Examples of the surfactant (e) used in the present invention include the following compounds.
As anionic surfactants, long chain alkyl such as “Adekaria Soap SE-10N” manufactured by Asahi Denka Kogyo Co., Ltd., “Aqualon HS-10, HS-20” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Phosphoric esters such as “AQUALON KH-05, KH-10” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Asahi Denka Kogyo Co., Ltd. “Adekaria Soap SR-10N”, “Latemul PD-104” manufactured by Kao Corporation Examples thereof include “KAYARAD” manufactured by Nippon Kayaku Co., Ltd., and “RA9607, RA9608, RA9612, RA9614” manufactured by Nippon Emulsifier Co., Ltd.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, sorbitan higher fatty acid esters, glycerin higher fatty acid esters, and the like. Examples thereof include those having a heavy bond and copolymerized with a monomer.
For example, “Adekaria soap NE-10” manufactured by Asahi Denka Kogyo Co., Ltd., “Aqualon RN-10, RN-20, RN-50” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Antox manufactured by Nippon Emulsifier Co., Ltd.” NA-16 ”,“ Latemul PD-450, Latemuru PD-420, Latemuru PD-430 ”manufactured by Kao Corporation.

  It is important that these surfactants are 0.1 to 10 parts by weight, preferably 0.1 to 5.0 parts by weight, and 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the total amount of monomers. Part is more preferred. Moreover, it is preferable that anionic surfactant is 50 to 100 weight% in total 100 weight% of surfactant.

  The copolymer emulsion used in the present invention is obtained by emulsion polymerization of the above monomer in an aqueous medium in the presence of the above surfactant.

In starting the polymerization reaction, a water-soluble pyrolytic polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate or an azobis cation salt or a hydroxyl adduct can be used.
A redox initiator can also be used.
As redox initiators, combinations of organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and reducing agents such as Rongalite, sodium metabisulfite, or potassium persulfate, ammonium persulfate and A combination with Rongalite, sodium thiosulfate, or the like, or a combination of hydrogen peroxide and ascorbic acid is used.

  As a chain transfer agent for controlling the molecular weight and molecular weight distribution of the (meth) acrylic copolymer constituting the dispersoid in the copolymer emulsion used in the present invention, mercaptan, thioglycol, and β-mercaptopropionic acid Alkyl esters of the system can be used. The amount added is preferably 0.01 to 0.2 parts by weight, more preferably 0.05 to 0.1 parts by weight, based on 100 parts by weight of the total amount of monomers.

The average particle size of the emulsion particles of the copolymer emulsion used in the present invention is preferably 60 to 400 nm. When the average particle size is less than 60 nm, the mechanical stability is deteriorated. On the other hand, when the average particle size exceeds 400 nm, the water whitening resistance is deteriorated, which is not preferable.
For example, by adding a part of the surfactant to the reaction kettle before the reaction, the average particle size of the emulsion particles to be produced can be in the range of 60 to 400 nm. The average particle diameter can be determined by “Microtrac particle size distribution analyzer UPA” (manufactured by Nikkiso Co., Ltd.).

The aqueous pressure-sensitive adhesive composition of the present invention may contain a tackifier by post-addition into the copolymer emulsion.
For example, rosin resin, phenol resin, polyterpene, acetylene resin, petroleum hydrocarbon resin, ethylene vinyl acetate copolymer, synthetic rubber, natural rubber or the like may be added as a tackifier.

  Furthermore, the aqueous pressure-sensitive adhesive composition of the present invention can contain various additives as required. For example, wetting agents (surfacting prevention surfactants, etc.), antifoaming agents, neutralizing agents, plasticizers, thickeners, fillers, colorants, preservatives, antifungal agents, solvents and the like can be mentioned.

  The viscosity of the aqueous pressure-sensitive adhesive composition of the present invention is preferably 500 to 10,000 mPa · s, preferably 1000 to 5000 mPa · s under the conditions of measurement for 1 minute using a # 4 rotor at a BL type viscometer 60 rpm. It is more preferable. The pH is preferably 4 to 9, and more preferably 7.0 to 8.5, from the viewpoint of storage stability over time and work environment.

The pressure-sensitive adhesive coated product of the present invention is obtained by coating a water-based pressure-sensitive adhesive composition on a release material with a comma coater, reverse coater, slot die coater, lip coater, gravure coater, etc. For example, it can be obtained by transfer coating in which a film support such as PET, polyolefin such as polypropylene, or vinyl chloride is laminated and laminated. Preferably such coating amount of the adhesive in the adhesive coating material is 5 to 50 g / ^{m 2} by dry weight, and more preferably 15 to 30 g / ^{m 2.}
The obtained adhesive sheet agent coated product is used as an adhesive sheet for films and laminates, labels, tapes, building materials and packaging materials, and is used in places where water resistance is required such as places where water drops are applied. In addition, it retains effective adhesiveness and is useful as a general-purpose adhesive sheet.

  The present invention will be described based on examples. In the examples, “part” is “part by weight”, and “%” is “% by weight”.

(Example 1)
2-ethylhexyl acrylate 73.8 parts, methyl acrylate 20 parts, methyl methacrylate 2 parts, acrylic acid 2 parts, 2-hydroxyethyl acrylate 2 parts, acetoacetoxyethyl methacrylate 0.2 parts, a total of 100 of these monomers "Superester A-125" (made by Arakawa Chemical Co., Ltd.), which is a rosin resin as a tackifying resin, 2 parts, "YS Resin PX1250" (made by Yasuhara Chemical Co., Ltd.) which is a terpene resin: 3 parts were mixed and the tackifying resin was dissolved in the radical polymerizable monomer to obtain a mixture of both. To this mixture, 1.0 part of “RA9612” manufactured by Nippon Emulsifier Co., Ltd. as a sodium-neutralizing anionic surfactant and 28.5 parts of ion-exchanged water as solids are added, and the emulsion viscosity is 1000 mPa · s. The mixture was emulsified to obtain an emulsion and charged into a dropping funnel.
A polymerization tank equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 80 parts of ion exchange water and 0.12 part of RA9612 as a solid content, saturated with nitrogen gas, stirred, and heated to 80 ° C. Later, 0.075 part of a 5% aqueous solution of ammonium persulfate was added as a solid content.
After 5 minutes, dropping of the emulsion of the dropping funnel previously emulsified was started, and in parallel with this, 0.225 part of 5% ammonium persulfate aqueous solution was added dropwise over 3 hours in solid content.
30 minutes after the completion of dropping while maintaining the reaction temperature at 80 ° C., a 10% aqueous solution of ammonium persulfate was added in 0.04 parts as a solid content every 30 minutes in two portions. Further, the mixture was aged at 80 ° C. for 2 hours with stirring, then cooled and neutralized with ammonia, and a copolymer emulsion was taken out.

The emulsion had a nonvolatile content of 45%, an average particle size of 142 nm, and a gel fraction of 60%.
The measurement of the non-volatile content was performed by measuring the weight ratio after drying at 150 ° C. for 20 minutes in an electric oven, and the average particle size was measured with “Microtrac particle size distribution analyzer UPA” manufactured by Nikkiso Co., Ltd.
The gel fraction was determined by coating the emulsion on a PET film having a thickness of 50 μm so that the dry film thickness was 15 to 25 μm, cutting it into a size of 10 cm × 3 cm, and measuring 12 cm × 5 cm. The sample was affixed to a 200 mesh stainless steel net and immersed in reflux of ethyl acetate for 6 hours, and calculated from the weight of the pressure-sensitive adhesive layer before immersion and the weight of the residue (insoluble content) after immersion.

Wetting agents and preservatives were added to the obtained copolymer emulsion, and the pH was adjusted to 8.5 with aqueous ammonia.
Further, a thickener was added to obtain an adhesive having a viscosity of 1500 mPa · s (measured with a BL type viscometer, # 4 rotor, 60 rpm).

The obtained pressure-sensitive adhesive was coated on a commercially available release paper with a comma coater so as to have a dry film thickness of 24 g / m ² , passed through a body oven at 90 ° C. for 35 seconds, and after removing the dispersion medium, the thickness was 50 μm. After laminating and winding the PET film, it was cut into a sheet.
Further, a predetermined press was applied in a thermostatic chamber at 23 ° C.-50% RH and left for 24 hours to obtain a coated adhesive.
The following tests were performed on the obtained adhesive coated product, and the results are shown in Table 1.

Water resistance test L value: Peel off the release paper of the coated adhesive, laminate the adhesive layer on the aluminum surface of the aluminum-deposited PET film, immerse in warm water at 60 ° C. for 72 hours, take out the adhesive immediately The L value of the layer was measured with a spectrocolorimeter (manufactured by Suga Test Instruments Co., Ltd.).
It shows that whitening of an adhesive layer is so remarkable that L value is high.

HAZE: The release paper of the adhesive coating is peeled off, the adhesive layer is attached to a PET film, immersed in warm water at 60 ° C. for 72 hours, taken out, and then immediately a spectrocolorimeter (Suga Test Instruments Co., Ltd.) HAZE was measured.
It shows that whitening of an adhesive layer is so remarkable that HAZE is high.

  Adhesive strength test: The release paper of the pressure-sensitive adhesive coated material was peeled off, and the pressure-sensitive adhesive layer was attached to a polished stainless steel (SUS) plate or polyethylene (PE) plate, followed by one round trip with a 2 kg roll, and then 180 hours later. It was measured by the degree peel test.

  Holding power test: The release paper was peeled off from the 10 cm × 25 mm adhesive coated product, and the adhesive layer was affixed to a polished stainless steel plate with an area of 25 mm × 25 mm, followed by one round trip with a 2 kg roll, and then in an atmosphere at 40 ° C. A 1 kg load was applied to the pressure-sensitive adhesive coated material and left for a maximum of 70,000 seconds, and the time until dropping or the distance of displacement of the applied position was measured.

  Ball tack: Tested according to “JIS Z 0237 tilt ball tack”.

Cutting property: The pressure-sensitive adhesive coated material was cut into a size of 10 cm square, 20 sheets were piled up, the edges were cut off with a cutter, and the state where the pressure-sensitive adhesive adhered to the blade was observed.
○: Adhesive adhesion is small.
X: Adhesive amount is large.

Heat yellowing: Peel off the release paper of the adhesive coating, stick the adhesive layer to the glass plate, measure each Y value before and after exposure at 125 ° C for 1 week with a colorimeter, and the difference (ΔY value) Asked.
It shows that yellowing of an adhesive layer is so remarkable that (DELTA) Y value is high.

(Example 2)
An emulsion is obtained using 1.5 parts by weight of “RA9612” manufactured by Nippon Emulsifier Co., Ltd. as a surfactant and 0.5 parts by weight of “RA9607” manufactured by Nippon Emulsifier Co., Ltd. as a solid content. A copolymer emulsion, a pressure-sensitive adhesive, and a pressure-sensitive adhesive coated product were obtained in the same manner as Example 1 except that.

(Comparative Example 1)
The experiment was performed in the same manner as in Example 1 except that acetoacetoxyethyl methacrylate was not used.

(Comparative Example 2)
The experiment was conducted in the same manner as in Example 1 except that the amount of acetoacetoxyethyl methacrylate was changed to 2 parts.

(Comparative Example 3)
A copolymer emulsion is obtained by using 0.2 part of diacetone acrylamide (hereinafter abbreviated as “DAAM”) instead of 0.2 part of acetoacetoxyethyl methacrylate, and further to 100 parts of solid content of the copolymer emulsion. The experiment was conducted in the same manner as in Example 1 except that 0.06 part of 6% adipic acid dihydrazide (hereinafter abbreviated as “ADH”) aqueous solution as a crosslinking agent was added in terms of solid content.

(Comparative Example 4)
A copolymer emulsion was obtained without using acetoacetoxyethyl methacrylate, and “Orgatics TC-310” manufactured by Matsumoto Pharmaceutical Co., Ltd., which is an organic titanium compound as a crosslinking agent, with respect to 100 parts of the solid content of the copolymer emulsion. The experiment was conducted in the same manner as in Example 1 except that 1.0 part in terms of solid content was added.

(Comparative Example 5)
An experiment was conducted in the same manner as in Example 1 except that a coated adhesive product was obtained using “BPS-5160” manufactured by Toyo Ink Manufacturing Co., Ltd., which is a solvent-type pressure-sensitive adhesive.

Abbreviations in Table 1 represent the following.
AAEM: acetoacetoxyethyl methacrylate DAAM: diacetone acrylamide ADH: adipic acid dihydrazide Ti: “Orgatechs TC-310” manufactured by Matsumoto Pharmaceutical Co., Ltd.
In Examples 1 and 2 using acetoacetoxyethyl methacrylate as a cross-linking agent, water whitening resistance was improved as compared with Comparative Example 4 in which DAAM and ADH used as cross-linking agents were combined.

Claims (2)

  (Meth) acrylic acid alkyl ester having 1 to 14 carbon atoms (a) 79 to 99.7% by weight, polymerizable unsaturated carboxylic acid (b) 0.1 to 10% by weight, and having an alcoholic hydroxyl group 100 parts by weight of monomer comprising 0.1 to 10% by weight of copolymerizable vinyl monomer (c) and 0.1 to 1.0% by weight of acetoacetoxyethyl methacrylate, and 30% by weight or more of terpene-based tackifier resin A copolymer emulsion obtained by emulsion polymerization of a mixture comprising 1 to 10 parts by weight of a tackifying resin (d) in an aqueous medium in the presence of 0.1 to 10 parts by weight of a surfactant (e) An aqueous pressure-sensitive adhesive composition comprising.   A pressure-sensitive adhesive coated product comprising the aqueous pressure-sensitive adhesive composition according to claim 1.