JPH0551570A - Acrylic polymer emulsion for pressure sensitive adhesive - Google Patents

Abstract

(57) [Summary] [Structure] 100 parts by weight of a monomer as an emulsifier in emulsion polymerization of a monomer consisting of 50 to 100% by weight of (meth) acrylic acid ester and 0 to 50% by weight of another monomer. On the other hand, it is obtained by polymerizing with 0.2 to 15 parts by weight of polyoxyalkylene aryl ether sulfonate and / or polyoxyalkylene alkyl phenyl ether sulfonate, preferably the glass transition temperature of the polymer is 0 ° C.
The following are acrylic polymer emulsions for pressure sensitive adhesives. [Effect] The pressure-sensitive adhesive using the acrylic polymer emulsion of the present invention is particularly excellent in roll stain resistance and has excellent adhesive strength, tackiness, and cohesive strength in a well-balanced manner. It is possible to obtain a pressure-sensitive adhesive tape having excellent properties and stable quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic polymer emulsion for pressure-sensitive adhesives which is particularly excellent in roll stain resistance and has excellent adhesive strength, tackiness and cohesive strength.

[0002]

2. Description of the Related Art As one of pressure-sensitive adhesives constituting a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive composed of an acrylic polymer emulsion and a filler is used.

Usually, a pressure-sensitive adhesive sheet is produced by applying a pressure-sensitive adhesive to a release paper using a roll coater and drying the paper,
It is manufactured by transferring to a substrate such as cloth or plastic film.

However, the pressure-sensitive adhesive using the conventional acrylic polymer emulsion tends to adhere to the roll coater when it is applied using the above roll coater, and thus the gap between the roll coaters is large. Is not constant, and as a result, the pressure-sensitive adhesive layer has a non-uniform thickness, and there is a problem in that a pressure-sensitive adhesive sheet with stable quality cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is a pressure-sensitive adhesive having excellent resistance to roll contamination and having excellent adhesive strength, tackiness, and cohesive strength. It is an object to provide an acrylic polymer emulsion for use.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to the emulsification of a monomer comprising 50 to 100% by weight of a (meth) acrylic acid ester and 0 to 50% by weight of another monomer copolymerizable therewith. Polymerization: Obtained by polymerizing 100 parts by weight of a monomer with 0.2 to 15 parts by weight of a polyoxyalkylene aryl ether sulfonate and / or a polyoxyalkylene alkylphenyl ether sulfonate as an emulsifier. And an acrylic polymer emulsion for pressure-sensitive adhesives.

According to the present invention, by using the above-mentioned specific compound as an emulsifier during polymerization, its action is not always clear, but it is excellent in basic properties such as adhesive strength, tackiness, cohesive strength, etc. and is resistant to roll contamination. It is possible to provide an acrylic polymer emulsion for pressure-sensitive adhesives having markedly improved properties.

Here, the adhesive force, tackiness and cohesive force mainly refer to the following properties. 1. Adhesive force: When the surfaces of two objects are adhered to each other via an adhesive, it refers to the magnitude of the resistance exhibited when separating the two. 2. Tack (adhesive force): It is often referred to as a property of instantaneously adhering when one surface is brought into contact with another surface, particularly a stickiness of an adhesive. 3. Cohesive force: The main valence force or sub valence force that acts between molecules, atoms, or ions that make up a single substance, and refers to the strength of the adhesive itself.

[0009]

The present invention will be described in detail below.

Examples of the (meth) acrylic acid ester used in the present invention include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate,
Cyclohexyl acrylate, dodecyl acrylate,
Acrylic esters such as octadecyl acrylate, phenyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, phenyl Methacrylic acid esters such as methacrylic acid and benzyl methacrylate can be mentioned. Preferably, octyl (meth) acrylate, 2
-A (meth) acrylic acid ester having 8 to 12 carbon atoms in the alkyl group such as ethylhexyl (meth) acrylate and dodecyl (meth) acrylate.

The other monomer copolymerizable with the above-mentioned (meth) acrylic acid ester is not particularly limited as long as it is a monomer which can be copolymerized, but preferably a conjugated diene compound or an aromatic compound is used. Examples thereof include group vinyl compounds, vinyl cyanide compounds, α, β-unsaturated carboxylic acid compounds, and polyfunctional monomers.

Examples of the conjugated diene compound include butadiene and isoprene. Examples of the aromatic vinyl compound include styrene, α-methylstyrene,
p-methylstyrene etc. are mentioned. Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile. Examples of the α, β-unsaturated carboxylic acid compound include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and the like. Examples of the polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate (or acrylate), diethylene glycol dimethacrylate (or acrylate), triethylene glycol methacrylate (or acrylate), polyethylene glycol dimethacrylate (or acrylate), polypropylene Examples thereof include glycol dimethacrylate (or acrylate), trimethylolpropane trimethacrylate (or acrylate), and tetramethylolmethane tetramethacrylate (or acrylate).
Further, in addition to the above monomers, vinyl acetate, hydroxyalkyl acrylate, hydroxyalkyl methacrylate, methoxyethyl acrylate, ethoxymethyl acrylate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-
Methylol acrylamide, N-methoxymethyl acrylamide, N-methoxybutyl acrylamide, etc. can also be used.

The above-mentioned other monomers can be used alone or in combination of two or more. Examples of preferable monomers in the above include styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, itaconic acid, vinyl acetate, N-methylol acrylamide and the like.

The ratio of the (meth) acrylic acid ester to the other monomer used is 50 to 50 for the (meth) acrylic acid ester.
It is 100% by weight, preferably 60 to 99% by weight, more preferably 70 to 98% by weight.

The amount of the other monomer is 0 to 50% by weight, preferably 1 to 40% by weight, more preferably 2 to 30% by weight.

The amount of (meth) acrylic acid ester used is 5
If it is less than 0% by weight, the adhesive strength and tack are poor.

In the polyoxyalkylene aryl ether sulfonate which is the emulsifier used in the present invention,
The aryl group generally means an aryl group obtained by removing one hydrogen atom from the benzene ring of an aromatic compound, but here, in a broader sense, it also includes those having other substituents on the benzene ring, such as a chlorophenyl group, A nitrophenyl group and the like are also included. Examples of the polyoxyalkylene aryl ether sulfonate include ammonium polyoxyethylene styryl phenoxy ether sulfonate, sodium polyoxyethylene styryl phenoxy ether sulfonate, ammonium polyoxypropylene styryl phenoxy ether sulfonate, and polyoxypropylene styryl phenoxy ether. Examples thereof include sodium sulfonate. Preferred is ammonium polyoxyethylene styryl phenoxy ether sulfonate.

Examples of the polyoxyalkylene alkyl phenyl ether sulfonate include ammonium polyoxyethylene nonylphenyl ether sulfonate, sodium polyoxyethylene nonyl phenyl ether sulfonate, ammonium polyoxypropylene nonyl phenyl ether sulfonate, and polyoxypropylene nonyl. Examples thereof include sodium phenyl ether sulfonate. Preferred is sodium polyoxyethylene nonylphenyl ether sulfonate.

A feature of the present invention is that the polymer obtained by using the above-mentioned emulsifier in the emulsion polymerization of an acrylic polymer emulsion is used as a pressure-sensitive adhesive polymer emulsion for a pressure-sensitive adhesive sheet. Roll contamination resistance is significantly improved.

The amount of the emulsifier used is 0.2 to 15 parts by weight, preferably 0.2 to 1 part by weight, based on 100 parts by weight of the monomer.
0 parts by weight. If the amount of the emulsifier used is less than 0.2 parts by weight, the roll stain resistance will be insufficient, while if it exceeds 15 parts by weight, the adhesive strength, tackiness and cohesive strength will be poor.

As the emulsifier, the above emulsifier can be used in combination with other emulsifiers if necessary. Examples of such emulsifiers that can be used include sodium dodecylbenzene sulfonate, ammonium lauryl sulfate, and polyoxyethylene nonylphenyl ether. The addition amount of these emulsifiers is preferably 0 to 10 parts by weight based on 100 parts by weight of all the monomers.

However, the above-mentioned essential emulsifier is preferably used in an amount of 30% by weight or more, and more preferably 50 to 100% by weight, based on the total weight of the emulsifier. If the amount of the emulsifier essential in the present invention is less than 30% by weight, there arises a problem that the roll stain resistance becomes insufficient.

The emulsion polymerization method of the acrylic polymer emulsion of the present invention will be described below.

The emulsion polymerization method of the present invention is not special, and a generally used polymerization method can be adopted.

There are no particular restrictions on the polymerization initiator used in the emulsion polymerization in the present invention. For example, hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide and paramenthane hydroperoxide, benzoyl peroxide and lauroyl. Organic polymerization initiators such as peroxides such as peroxides and azo compounds such as azobisisobutyronitrile, and inorganic polymerization initiators such as persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate Can be used.

The above polymerization initiator can also be used as a so-called redox type polymerization initiator in combination with a reducing agent such as sodium bisulfite. Of these polymerization initiators, potassium persulfate, persulfates such as ammonium persulfate, or a combination thereof with azobisisobutyronitrile or benzoyl peroxide,
Further, a combination of these and a reducing agent is preferably used.

Specific examples of the molecular weight modifier include octyl mercaptan, n-dodecyl mercaptan,
Mercaptans such as t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan; xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, diisopropylxanthogen disulfide; tetramethylthiuram disulfide, tetraethyl Thiuram disulfides such as thiuram disulfide and tetrabutyl thiuram disulfide; halogenated hydrocarbons such as ethylene bromide; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, terpinolene , Α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer (2,4-diphenylene 4- methyl-1-pentene is preferably not less than 50 wt%), 2,5
Dihydrofuran, 3,6-dihydro-2H-pyran, phthalane, 1,2-butadiene, 1,4-hexadiene,
Examples thereof include 9,10-dihydroanthracene and 1,4-dihydronaphthalene. These alone,
Alternatively, two or more kinds can be used in combination.

The preferred amount of the molecular weight modifier used is 0.001 to 5 parts by weight per 100 parts by weight of the monomer. The polymerization water is preferably 5 per 100 parts by weight of all the monomers.
0 to 300 parts by weight.

The method of adding the monomers in the emulsion polymerization is not particularly limited, but a method of charging all the monomers into the reactor for polymerization, or charging a part of the monomers into the reactor to start the polymerization, A method in which the remaining monomers are polymerized palindromically or continuously, or a combination thereof, and all the monomers are batchwise, continuously, one-stage, or multi-stage, or a combination thereof. And the like.

The polymerization temperature is preferably 50 to 120 ° C.

The final polymerization conversion rate is preferably 80% by weight.
More preferably, it is 95% by weight or more.

When the acrylic polymer emulsion of the present invention is used in a releasable pressure-sensitive adhesive, it is crosslinked with 100 parts by weight of the polymer of the acrylic polymer emulsion in order to impart excellent removability. Agents, preferably 0.1-
Use 20 parts by weight.

Examples of the cross-linking agent include polyglycidyl compounds and the like. Specific examples include ethylene glycol or polyethylene glycol diglycidyl ether, propylene glycol or polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, dibromoneopentyl glycol diglycidyl ether, o- Examples thereof include phthalic acid diglycidyl ester, glycerin polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether. Others, N, N, N ', N'
-Tetraglycidyl-m-xylylenediamine, N,
Two or more epoxy groups such as N, N ′, N′-pentaglycidyldiethylenetriamine, N, N, N ′, N′-tetraglycidylethylenediamine and one or more third group
Examples thereof include polyglycidyl compounds having a primary amino group.

The glass transition temperature of the polymer component in the acrylic polymer emulsion of the present invention is usually 0 ° C or lower, preferably -20 ° C or lower, more preferably -30 ° C or lower. If the glass transition temperature is higher than 0 ° C, the adhesive strength and tack will be poor. The glass transition temperature here is determined by the following mathematical formula 1.

[0035]

[Equation 1] In Equation 1, each item has the following contents.

Tg: glass transition point of copolymer (indicated by absolute temperature) Tgi: glass transition point of homopolymer of monomer component (i) (indicated by absolute temperature) Wi: component (i) in copolymer Weight Fraction (J. Brandrup et al., "Polymer Handbook", J. Willie, ed.
“Polymer Hand Book”, J. Wiley, 2nd e
See d.)).

In the preparation of pressure-sensitive adhesives using the acrylic polymer emulsion of the present invention, various additives such as white pigments, thickeners, wetting agents, alkalis, stabilizers and emulsifiers can be added. ..

[0038]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, "part" and "%" are based on weight. (1) Emulsifier EM-1; polyoxyethylene styryl phenoxy ether ammonium sulfonate represented by the following general formula (Formula 1), which is an emulsifier belonging to the scope of the present invention (New
col740SF, manufactured by Nippon Emulsifier Co., Ltd.). This is because in Chemical formula 1, n is relatively large (n; 30 to 50).

EM-2: an emulsifier (Newcol 707) represented by the following general formula (Formula 1) and belonging to the scope of the present invention.
SF, manufactured by Nippon Emulsifier Co., Ltd.). This is
Is relatively small (n; 1 to 10).

[0040]

[Chemical 1] EM-3: sodium polyoxyethylene nonylphenyl ether sulfonate represented by the following general formula (Formula 2), which is an emulsifier included in the scope of the present invention (Emar N
C: manufactured by Kao Corporation.

[0041]

[Chemical 2] EM-4; polyoxyethylene nonyl phenyl ether EM-5; sodium dodecylbenzene sulfonate EM-6; sodium polyoxyethylene alkyl ether sulfonate EM-7; sodium alkyldiphenyl ether disulfonate EM-8; sodium lauryl sulfate EM-9 Sodium alkylnaphthalene sulfonate (2) Method for producing acrylic polymer emulsion 50 parts of water and 0.5 part of sodium persulfate are charged into a reactor and the temperature is raised to 70 ° C. Separately, the monomers, emulsifiers, 0.02 parts of n-dodecyl mercaptan, and 40 parts of water shown in the polymerization formulations of Tables 1, 2 and 3 were mixed, and this mixture was continuously added to the reactor for 6 hours. And reacted. The polymerization conversion rate was 99%. 0.1 part of an antifoaming agent was added to the obtained emulsion, the pH was adjusted to 5 with ammonia, and the acrylic polymer emulsion A of Example was used.
E1-6, Acrylic polymer emulsion AE of Comparative Example
7 to 15 were obtained.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3] Examples 1-6 and Comparative Examples 1-9  (1) Preparation of pressure-sensitive adhesive Each emulsion obtained by the above method was individually
Adjust the pH to 8.5 with MONMONIA and use Natri polyacrylate.
Um (made by Rohm & Haas, brand name ASE-60)
In addition, the viscosity (Brookfield type viscometer, No. 4
Spindle, measured at 6 rpm) 2 x 10^Fouradjusted to cp
Then, the pressure sensitive adhesive was adjusted. (2) Preparation of pressure-sensitive adhesive sheet and property evaluation The pressure-sensitive adhesive obtained by the above adjustment was applied to release paper,
After drying, transfer to high-quality paper and cut into a predetermined size.
An adhesive sheet test piece was prepared.

The following evaluations were carried out using the above-mentioned pressure-sensitive adhesive sheet test pieces.

The evaluation results are shown in Table 1, Table 2 and Table 3.

Measurement of Adhesive Strength The above test piece was attached to a stainless steel plate (SUS304) as an adherend and left at 40 ° C. for 1 week. Then JI
A peeling test is performed by the method of S-Z0237, and the adhesive force is g /
It was determined in units of 25 mm.

Measurement of cohesive force A test piece was adhered to a stainless steel plate in an area of 2.5 cm × 2.5 cm, pressure-bonded with a 2 kg roller, the adhered surface was held vertically, and a load of 1 kg was applied to the sample. The time until sliding down was measured in units of hours. The larger the value, the higher the cohesive force.

Measurement of tack The tack was measured by the method of JIS-Z0237 by ball tack. Ball NO. The larger the value, the greater the adhesive strength.

(3) Evaluation of Roll Contamination Resistance Furthermore, the pressure sensitive adhesive was applied to the roll coater, and the roll coater was operated for 10 minutes. Then, the degree of stain on the roll coater was visually judged. The judgment was performed in the following three stages.

O: Almost no adhesion of the adhesive to the roll coater.

Δ: There is some adhesion of the adhesive to the roll coater.

X: Adhesive is considerably attached to the roll coater.

(4) Evaluation Results Examples 1 to 6 are examples of pressure-sensitive adhesives using an acrylic polymer emulsion within the scope of the present invention, which is the object of the present invention, that is, roll contamination resistance. Excellent balance is obtained in all of the properties of adhesiveness, adhesive strength, tackiness, and cohesive strength.

Comparative Examples 1 and 2 are examples in which the amount of emulsifier exceeds the range of the present invention, and the adhesive strength, tackiness and cohesive strength are poor.

Comparative Example 3 is an example in which the glass transition temperature exceeds the range of the present invention, and the adhesive strength and tack are poor.

In Comparative Example 4, the amount of the (meth) acrylic acid ester used was less than the range of the present invention, and the adhesive strength and tack were poor.

Comparative Examples 5 to 9 are examples in which the emulsifiers outside the scope of the present invention were used, and the roll contamination resistance was particularly poor.

[0059]

The pressure-sensitive adhesive using the acrylic polymer emulsion of the present invention is particularly excellent in roll stain resistance,
In addition, since it has excellent adhesive strength, tackiness, and cohesive strength, it is excellent in productivity of the adhesive tape and can be manufactured with stable quality, so that it has an extremely high industrial value.

Claims (1)

[Claims] 1. (Meth) acrylic acid ester 50 to 10
In the emulsion polymerization of a monomer consisting of 0% by weight and 0 to 50% by weight of another monomer copolymerizable therewith, the monomer 10
0 parts by weight of polyoxyalkylene aryl ether sulfonate and / or polyoxyalkylene alkyl phenyl ether sulfonate as an emulsifier.
An acrylic polymer emulsion for pressure-sensitive adhesives, which is obtained by polymerization using 2 to 15 parts by weight.