JPH1135608A - Production of aqueous pressure-sensitive type acrylic tacky agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject tacky agent excellent in tack and balance between permanent bond strength and cohesive force, bond strength on a curved surface and long-term retention, by subjecting a monomer mixture in a specific content ratio to emulsion polymerization in the presence of a prescribed emulsifying agent. SOLUTION: A monomer mixture comprising (A) 0.2-5 wt.% of a carboxyl group-containing unsaturated monomer, (B) 61-95 wt.% of an acrylic acid alkyl ester unsaturated monomer of the formula CH2 =CH-COOR (R is a 4-18C alkyl) and (C) 0-38.8 wt.% of another unsaturated monomer copolymerizable with the unsaturated monomers of the components A and B is subjected to emulsion polymerization by using an anionic surfactant (e.g. ammonium dioctyl sulfosuccinate) and a nonionic surfactant containing a copolymerizable double bond (e.g. a polyoxyethylene alkyl ether) as an emulsifying agent to give the objective tacky agent having <=-30 deg.C glass transition temperature (Tg) and 60-90% gel content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-based pressure-sensitive acrylic pressure-sensitive adhesive which exhibits excellent tack, permanent adhesion, high cohesion, etc., for films or molded products of non-polar polymers such as polyolefins. About.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesives have been used in various fields such as tapes, labels, seals, wallpapers, and the like, and the adherends are made of plastic, metal, glass, ceramics, paper,
It covers a wide area such as cloth, wood, and fresh food. As such a pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive has been conventionally known. However, water-based pressure-sensitive acrylic pressure-sensitive adhesives have insufficient adhesive strength, especially adhesiveness and cohesive strength to non-polar polymer films and molded products such as polyolefins, as compared with solvent-based acrylic pressure-sensitive adhesives. There is a problem.

In solving such a problem, for example,
There is a method of softening or reducing the molecular weight of a conventional acrylic emulsion to improve the adhesive strength, or a method of blending a plasticizer or the like. In addition, a method of blending a water-dispersible acrylic pressure-sensitive adhesive having a high Tg (glass transition temperature) with a water-dispersible acrylic pressure-sensitive adhesive having a low Tg, attempts to copolymerize divinyldiallyl monomer as an essential component, etc. Has been made.

[0004]

However, any of the above-mentioned methods has a drawback in that it is not possible to obtain a pressure-sensitive adhesive having a balance between high adhesion and high cohesion. For this reason, for example, there is a problem that the curved surface adhesive strength is not sufficient for a small rod-shaped molded product having a diameter of about 10 to 20 mm or a molded product having an edge portion made of nonpolar polymer or glass.

The present invention is intended to solve the above-mentioned problems of the prior art, and is excellent in the balance between tack, permanent adhesive force and cohesive force, and also excellent in curved surface adhesive force and long-term retention.
An object of the present invention is to provide an aqueous pressure-sensitive acrylic pressure-sensitive adhesive.

[0006]

The invention of claim 1 comprises (a) 0.2 to 5% by weight of a carboxyl group-containing unsaturated monomer and (b) a formula CH ₂ ＝ CH—COOR (where R is Carbon number 4-1
An alkyl group unsaturated monomer represented by the formula:
(C) A monomer mixture comprising 0 to 38.8% by weight of another unsaturated monomer copolymerizable with the unsaturated monomer of (a) or (b) in the presence of an emulsifier. Emulsion polymerization, glass transition temperature (Tg) of -30 ° C or less and gel content of 6
A method for producing an aqueous pressure-sensitive acrylic pressure-sensitive adhesive comprising an acrylic copolymer having 0% to 90% by weight, wherein the emulsifier comprises a nonionic surfactant having an anionic surfactant and a copolymerizable double bond. A method for producing an aqueous pressure-sensitive acrylic pressure-sensitive adhesive, characterized by comprising using a surfactant.

In the present invention, (a) the carboxyl group-containing unsaturated monomer includes, for example, acrylic acid,
In addition to methacrylic acid, maleic acid, itaconic acid, etc., monoalkyl esters of unsaturated polycarboxylic acids such as monomethyl itaconate, monobutyl maleate and the like can be mentioned.

The carboxyl group-containing unsaturated monomer is contained in an amount of 0.2 to 5% by weight in the monomer mixture (total 100% by weight).
To be included. If it is less than 0.2% by weight, the effect of improving the adhesive strength is small, and if it exceeds 5% by weight, the water resistance of the pressure-sensitive adhesive tends to decrease.

The acrylic acid alkyl ester unsaturated monomer in the monomer (b) is an alkyl ester of acrylic acid having 4 to 18 carbon atoms. Such compounds include, for example, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, isononyl acrylate and the like. is there. These are Tg of acrylic polymer obtained by emulsion polymerization.
Is an essential component in order to make -30 ° C or less. Also,
These may be a single component or a combination of two or more.

The content of the unsaturated monomer of the alkyl ester is 61 to 95% by weight in the monomer mixture.
If it is less than 61% by weight, there is a problem in the balance of adhesion, tack and cohesion, while if it exceeds 95% by weight, there is a problem in mechanical stability and polymerization stability.

Next, "other unsaturated monomers" (c) copolymerizable with the unsaturated monomers (a) and (b) include:
Carboxylic acid vinyl esters such as vinyl acetate and methyl methacrylate; 2-hydroxyethyl acrylate
3,3-hydroxybutyl (meth) acrylate, hydroxypropyl methacrylate, glycerin mono (meth) acrylate, glycerin di (meth) acrylate
, Trimethylolethane mono (meth) acrylate-unsaturated monomer having an alcohol hydroxyl group such as trimethylolpropane mono (meth) acrylate; acrylamide, N-methylol (meth) acrylamide, N, N
Amide group-containing unsaturated monomers such as dimethylol (meth) acrylamide; nitrile group-containing unsaturated monomers such as (meth) acrylonitrile and 2-cyanoethyl (meth) acrylate; 2-dimethylaminoethyl (meth) ) Acrylate, 2-diethylaminoethyl (meth) acrylate
Aminoalkyl group-containing unsaturated monomers such as 1,2-dimethylaminopropyl (meth) acrylate, and carbonyl group-containing unsaturated monomers such as acrolein, diacetone acrylamide and diacetone (meth) acrylate; No.

The content of the "other unsaturated monomer" is 0 to 38.8% by weight in the monomer mixture. 38.
If it exceeds 8% by weight, it becomes difficult to maintain the balance of adhesive strength, tack and cohesive strength. Note that the above “other unsaturated monomer” may not be added.

Next, as an emulsifier used for emulsion polymerization of the monomer mixture comprising the above (a), (b) and (c), a nonionic having a copolymerizable double bond with an anionic surfactant is used. A surfactant is used. Examples of the anionic surfactant include alkyl sulfosuccinates such as dioctyl ammonium sulfosuccinate; higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecyl benzene sulfonate; Alkyl sulphate salts such as sodium lauryl sulphate; polyoxyethylene alkyl ether sulphate hydrochloride such as polyoxyethylene lauryl ether sulphate; polyoxyethylene salts such as polyoxyethylene nonyl phenol ether sulphate Ethylene alkyl aryl ether sulfates; and the like.

The amount of the anionic surfactant used is 40
A general nonionic surfactant (having no copolymerizable double bond) may be used in combination up to the range of weight%. If it exceeds 40% by weight, the mechanical stability of the obtained water-based pressure-sensitive acrylic pressure-sensitive adhesive becomes insufficient.

Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; for example, polyoxyethylene octyl phenol ether and polyoxyethylene nonyl phenol ether. Polyoxyethylene alkyl phenol ethers such as sorbitan monolaurate; sorbitan higher fatty acid esters such as sorbitan monostearate and sorbitan trioleate; polyoxyethylene sorbitan higher such as polyoxyethylene sorbitan monolaurate; Fatty acid esters; for example, polyoxyethylene such as polyoxyethylene monolaurate and polyoxyethylene monostearate Grade fatty acid esters; e.g., glycerol monooleate, glycerol monostearate, such as polyglycerol oleate, etc., glycerin higher fatty acid esters; e.g., polyoxyethylene
Polyoxypropylene block copolymer; and the like.

The "nonionic surfactant having a copolymerizable double bond" according to the present invention includes a methacryloyl group, a propenyl group, an allyl group, etc. Oxyethylene alkyl phenyl ether, polyoxyethylene nonyl phenyl ether and the like can be exemplified.

In the present invention, the monomer mixture comprising (a), (b) and (c) is emulsion-polymerized using the above-mentioned emulsifier, so that the glass transition temperature Tg is -30.
An aqueous pressure-sensitive acrylic pressure-sensitive adhesive comprising an acrylic copolymer having a gel content of 60 to 90% by weight at a temperature of not more than ° C is obtained.
This water-based pressure-sensitive acrylic pressure-sensitive adhesive is in a state of a copolymerized water-based dispersion.

When the water-based pressure-sensitive acrylic pressure-sensitive adhesive has a glass transition temperature exceeding -30 ° C., the tack of the pressure-sensitive adhesive layer tends to be insufficient, and sufficient curved surface adhesive strength cannot be obtained. The gel content is measured, for example, as the insoluble fraction (gel content) of THF (tetrahydrofuran) at 20 ° C. of the aqueous pressure-sensitive acrylic pressure-sensitive adhesive.

In measuring the gel content, an aqueous pressure-sensitive acrylic pressure-sensitive adhesive was first coated with a film having a thickness of 20 to 20 μm.
Dry at 120 ° C. for 2 minutes to 30 μm.
Next, 1-2 g of the obtained dried film was precisely weighed (W
1) Put in a 200ml beaker and add 100ml
Of THF and leave overnight.

After that, the mixture was filtered through a 200-mesh wire gauze whose weight was measured in advance, and the remaining THF insoluble material was removed.
Dry at 40 ° C. for 1 hour. After cooling at room temperature, the weight of the residue is measured (W2), and the value calculated by the following equation is defined as the gel content. Gel content = [W2 / W1] × 100 (% by weight)

The gel content of the water-based pressure-sensitive acrylic pressure-sensitive adhesive is 60% by weight to 90% by weight. Gel content is 6
If the content is less than 0% by weight, secondary workability such as sufficient cutting and punching cannot be obtained. On the other hand, if it exceeds 90% by weight, sufficient curved surface adhesive strength cannot be obtained.

According to the present invention, it is possible to provide a water-based pressure-sensitive acrylic pressure-sensitive adhesive composition having an excellent balance of tack, permanent adhesive strength and cohesive strength, and also having excellent curved surface adhesive strength and long-term retention. .

Next, as in the second aspect of the present invention, the emulsifier is added to 100% by weight of the monomer mixture.
0.3 to 1.5% by weight of an anionic surfactant, and 0.3 to 1.5% by weight of a nonionic surfactant having a copolymerizable double bond.
Preferably, 1.5% by weight is used, and the total of both surfactants is 0.6 to 2.5% by weight.
In this case, it is possible to stabilize the adhesive performance for a long period of time.

When the content of the anionic surfactant is 0.1.
If it is less than 3% by weight, the mechanical stability of the water-based pressure-sensitive acrylic pressure-sensitive adhesive tends to be insufficient, and emulsion polymerization becomes difficult. On the other hand, when the content exceeds 1.5% by weight, the cohesive force of the pressure-sensitive adhesive decreases and the water resistance tends to decrease.

The nonionic surfactant having a copolymerizable double bond is added in an amount of 0.3 to 1.5% by weight based on 100% by weight of the monomer mixture. If the content is less than 0.3% by weight, the obtained water-based pressure-sensitive acrylic pressure-sensitive adhesive does not have sufficient holding power, and the long-term holding property tends to deteriorate. On the other hand, if it exceeds 1.5% by weight, the tackiness of the water-based pressure-sensitive acrylic pressure-sensitive adhesive tends to decrease, which is not preferable.

Further, the total amount of the nonionic surfactant having an anionic surfactant and a copolymerizable double bond is in the range of 0.6 to 2.5% by weight based on 100% by weight of the monomer mixture. Preferably, it is used. If it is less than 0.6% by weight, there is a problem in polymerization stability and mechanical stability, while if it is more than 2.5% by weight, there is a problem particularly in wet heat resistance among adhesive properties.

The above-mentioned anionic surfactant and the nonionic surfactant having a copolymerizable double bond may be used in a lump and added to a monomer mixture or water. May be used in addition to a monomer mixture or water.

When the pressure-sensitive adhesive of the present invention is produced, a polymerization initiator or a chain transfer agent for controlling the molecular weight may be used. As the polymerization initiator, for example, inorganic peroxides such as potassium persulfate, sodium persulfate, ammonium persulfate and aqueous hydrogen peroxide are preferable. Also, azo initiators such as azobisisobutyronitrile and azobisvaleronitrile; and organic peroxide initiators such as benzoyl peroxide, lauroyl peroxide and t-butyl peroxide can be used.

Further, a reducing agent such as tartaric acid, citric acid, L-ascorbic acid, sodium thiosulfate, sodium sulfite, sodium metabisulfite, or a metal salt may be used in combination with these initiators as a redox initiator. good.
As the molecular weight regulator, a chain transfer agent such as an organic halide or an alkyl mercaptan can be used.

The solid content concentration in the water-based pressure-sensitive acrylic pressure-sensitive adhesive obtained as described above is not particularly limited, but is usually 55 to 65% by weight.

The water-based pressure-sensitive acrylic pressure-sensitive adhesive of the present invention may be, for example, a rosin resin, a terpene resin, a coumarone-indene resin, a terpene, a phenol resin, a phenol-formaldehyde, as long as the desired performance is not impaired. A tackifier resin such as a resin, a petroleum hydrocarbon resin, a turpentine resin, or a hydrogenated hydrocarbon resin can be added for use.

Further, a usual crosslinking agent can be added to the above-mentioned water-based pressure-sensitive acrylic pressure-sensitive adhesive to further improve cohesion. Examples of the crosslinking agent include isocyanate-based crosslinking agents such as tolylene diisocyanate (TDI), 4.4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI). Epoxy cross-linking agents such as emulsions of bisphenol A type and bisphenol F type epoxy resins and the like, emulsions of epoxidized diene polymers such as epoxidized polybutanediene and epoxidized polyisoprene, oxalic acid dihydrazide, malon Acid dihydrazide, adipic acid dihydrazide,
Ethylene-1,2-dihydrazine, propylene-1,3
And hydrazine derivatives containing at least two hydrazino groups in a molecule such as dihydrazine.

The water-based pressure-sensitive acrylic pressure-sensitive adhesive includes
If necessary, various conventionally known additives such as a plasticizer viscosity modifier, a thickener, a filler, a pigment, an antifoaming agent and the like can be contained. These additives may be used in a usual amount applied to this type of pressure-sensitive adhesive composition.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a water-based pressure-sensitive acrylic pressure-sensitive adhesive and the properties of the water-based pressure-sensitive acrylic pressure-sensitive adhesive obtained therefrom are specifically described below with reference to Examples and Comparative Examples according to the present invention. Will be described. First, preparation of the test piece,
Tests for tack, normal adhesion, cohesion, curved surface adhesion, and resistance to moist heat degradation were performed according to the following methods.

(1) Preparation of Test Piece A sample of an aqueous pressure-sensitive acrylic pressure-sensitive adhesive was applied on release paper so that the pressure-sensitive adhesive layer after drying was 25 ± 1 g / m ² , and heated at 100 ° C. for 2 minutes. After drying in a circulating dryer, it is transferred to cast-coat paper to form a pressure-sensitive adhesive sheet.

(2) Normal adhesive strength test The test piece prepared in the above (1) was attached to a SUS304 stainless steel plate and a polyethylene (PE) plate polished with water-resistant abrasive paper of # 280 specified in JISR-6253, and 2 kg Roller is pressed back and forth once, and after 2 hours,
Leave at 0 ° C.-65% RH. Then, the peel strength (g / 25m) under the condition of a peel speed of 300mm / min.
m) is measured.

(3) Tack (initial adhesive strength) test In accordance with the Dow method, a length of 100
A steel ball having a diameter of x / 32 inches is rolled from a position 100 mm above the slope, and is indicated by the size x of the largest diameter ball that stops on the test.

(4) Cohesion test A test piece was stuck on a SUS304 stainless steel plate polished with # 280 water-resistant abrasive paper so that the stuck area of the test piece was 25 × 25 mm, and a 2 kg roller was reciprocated once. And crimped.
A 1 kg load is applied to the sample in an atmosphere of 40 ° C. and 65% by weight RH, and the time (min) until the load drops is measured.

(5) Moisture and heat resistance test The coated test piece is left for 7 days in an atmosphere of 50 ° C. and 95% by weight RH, and the adhesive strength is measured in the same manner as in (2) above.

(6) Curved Surface Adhesion Test A 10 mm × 20 mm test piece was coated on a 12 mm diameter glass rod with a Suntech film sprinkled on a 12 mm diameter glass rod.
Polyethylene (PE) rods, one for a 27 mm diameter rod
Each of the sticks was attached to a stick having a 00 mesh nylon net. Then, after standing for 24 hours under the condition of 20 ° C., the appearance of the test piece floating (peeling) from the rod is observed, and the following three-step evaluation is performed. ：: no lifting △: slightly floating ×: completely floating

Next, the aqueous pressure-sensitive acrylic pressure-sensitive adhesive of the present invention will be described in detail with reference to production examples, examples and comparative examples. Parts and% in each example are parts by weight and% by weight unless otherwise specified.

Production Example 1 25 parts of water and 0.06 part of sodium persulfate were charged into a reactor equipped with a temperature controller, a stirrer, a reflux condenser, a supply vessel, and a nitrogen inlet tube. Separately, the following were prepared as the feed (1).

Feed (1) 2-ethylhexyl acrylate ... 87.0 parts Methyl methacrylate ... 10.0 parts Vinyl acetate ... 2.0 parts Acrylic acid ... 1.0 parts HN-2200 (Chain transfer agent, product of Hitachi Chemical Co., Ltd.)
0.2 parts water 52 parts 25% by weight aqueous solution of propenyl group-added polyoxyethylene nonylphenyl ether (ethylene oxide added 10 moles) 0.6 parts sodium dioctyl sulfosuccinate (commercially available) Name Perex OT-P (Kao Corporation)) 0.3 parts Polyoxyethylene nonylphenyl ether sulfate ammonium salt EO addition number 30 mol (trade name Latemul E-93)
1A, Kao Corporation) 0.8 parts

Separately, as a feed (2), an initiator solution was prepared by dissolving 0.7 part of sodium persulfate in 10 parts of water.

After the inside of the reactor previously charged with the initiator solution was replaced with nitrogen gas, the feed (1) was introduced into the reactor.
Was added and the mixture was heated to 90 ° C.
Next, 10% by weight of the feed (2) is charged into the reactor, and the remaining of the feed (1) and the feed (2) is 3 to
The mixture was uniformly supplied into the reactor over 3.5 hours. After completion of the supply, the emulsion polymerization was carried out while maintaining the temperature at 90 ° C. for 1.5 hours to obtain an aqueous resin dispersion, that is, an aqueous pressure-sensitive acrylic pressure-sensitive adhesive.

Table 1 shows the composition of the monomer mixture, the glass transition temperature (calculated value), gel content, and solid content of the resulting aqueous dispersion (aqueous pressure-sensitive acrylic pressure-sensitive adhesive).

Production Examples 2 to 11 The same equipment as in Production Example 1 was used, and the composition of the monomer mixture and the composition of the emulsifier were changed as shown in the respective tables, except that the aqueous composition was prepared according to Production Example 1. A pressure-type acrylic pressure-sensitive adhesive was obtained. The results are shown in Tables 1 to 3.

The emulsifiers used other than the emulsifier used in Production Example 1 are shown below. Anionic surfactant: sodium alkyl diphenyl ether terdisulfonate (trade name: Perex SS)
-H, Kao Corporation)

Nonionic surfactant: polyoxyethylene nonylphenyl ether; Neugen EA70, or Neugen EM-230D (Daiichi Kogyo Seiyaku Co., Ltd.)

Nonionic surfactant having a copolymerizable double bond: Aqualon RN10, Aqualon RN20, Aqualon RN50 (Daiichi Kogyo Seiyaku Co., Ltd.)

Examples 1 to 6 and Comparative Examples 1 to 4 Next, a thickener, an alkali solution and a pigment were added to the aqueous pressure-sensitive acrylic pressure-sensitive adhesives shown in the above Production Examples 1 to 11. ,
Additives such as an antifoaming agent were added and stirred to prepare a pressure-sensitive adhesive composition. Tables 4 and 5 for each composition
Were measured.

As can be seen from the above Tables 1 to 5, the pressure-sensitive adhesives of Examples 1 to 6 using Production Examples 1 to 4, 8 and 11 according to the present invention have excellent adhesive performance. I understand.

On the other hand, Production Example 5 in which the nonionic surfactant having a copolymerizable double bond is 0.1% by weight, and Production Example in which the general nonionic surfactant different from the above is 40% by weight or more. 6, Production Example 7 in which the total surfactant exceeds 2.6% by weight, Production Example 9 in which the glass transition temperature Tg is -28 ° C., and Production Example 10 in which the gel content is 58% by weight, Is inferior.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

According to the present invention, it is possible to provide a water-based pressure-sensitive acrylic pressure-sensitive adhesive excellent in the balance of tack, permanent adhesive strength and cohesive strength, and also excellent in curved surface adhesive strength and long-term retention. .

Claims (2)

[Claims] (1) 0.2 to 5% by weight of a carboxyl group-containing unsaturated monomer and (b) a compound represented by the formula CH ₂ ＣＨCH—COOR
(Where R represents an alkyl group having 4 to 18 carbon atoms) and 61 to 95% by weight of an alkyl acrylate unsaturated monomer represented by the following formula (c): )) Other unsaturated monomers 0 to 3 copolymerizable with the unsaturated monomer of
The monomer mixture consisting of 8.8% by weight was emulsion-polymerized in the presence of an emulsifier and had a glass transition temperature (Tg) of -30.
A method for preparing an aqueous pressure-sensitive acrylic pressure-sensitive adhesive comprising an acrylic copolymer having a gel content of 60% by weight or less and a gel content of 60% to 90% by weight, wherein the emulsifier is copolymerizable with an anionic surfactant. A method for producing an aqueous pressure-sensitive acrylic pressure-sensitive adhesive, characterized by using a nonionic surfactant having a double bond. 2. The composition according to claim 1, wherein the emulsifier has an anionic surfactant in an amount of 0.3 to 1.5% by weight and a copolymerizable double bond based on 100% by weight of the monomer mixture. 0.3 to 1.5% by weight of nonionic surfactant is used, and the total of both surfactants is 0.6 to 2.5%.
A method for producing a water-based pressure-sensitive acrylic pressure-sensitive adhesive, characterized in that the content is% by weight.