JPH0730295B2 - Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention has an excellent balance of adhesive strength, cohesive strength and tack.
The present invention relates to a pressure-sensitive adhesive composition useful for pressure-sensitive adhesive sheets such as pressure-sensitive adhesive tapes and pressure-sensitive adhesive labels.

[Conventional technology and its problems]

Currently, there are natural rubber-based, synthetic rubber-based, and acrylic ester-based adhesives, and these adhesives are applied to base materials and used in a wide variety of applications in the form of adhesive sheets such as adhesive tapes and labels. ing. Among them, acrylic acid ester-based pressure-sensitive adhesives have been widely spread in recent years because of their excellent adhesiveness and weather resistance. However, when used as an adhesive tape, the acrylic ester adhesive has a problem that it is inferior in corrugated board sealing property to a rubber adhesive.
In order to solve such a problem, the cohesive force, which has been considered to have the greatest influence in the past, has been improved. As the method, the glass transition point of the copolymer constituting the pressure-sensitive adhesive is increased, the crosslink density is increased, and the molecular weight is increased. However, even if such a cohesive force improving means is implemented, the corrugated board sealing property is not improved as much as expected.
The tack was greatly reduced, and the adhesive strength, cohesive strength, and tack were out of balance, making it difficult to use.

(B) Configuration of the Invention [Means for Solving the Problems] The present inventors have completed the present invention as a result of extensive studies on the above conventional problems.

That is, the present invention is mainly composed of an additive which is a mixture of a copolymer containing an acrylic acid ester and / or a methacrylic acid ester as main components and a compound having the following structural formula, and the addition amount of the compound is All monomers that make up the polymer
A pressure-sensitive adhesive composition, which is 0.001 to 2.0 parts by weight with respect to 100 parts by weight.

R-O- in _{(CH 2 CH 2 O) n} -H ( wherein, n is a positive number, and R is a hydrogen atom, an alkyl group having seven or less carbon atoms, a phenyl group, a tolyl group, or a carbon atoms, Is 4 or less acyl groups) and a layer of the above-mentioned pressure-sensitive adhesive composition is formed on the surface of a base material.

[Action]

The pressure-sensitive adhesive composition of the present invention is excellent in adhesive strength, cohesive force, and tack balance, and for example, when the pressure-sensitive adhesive composition is applied to a substrate and used as a pressure-sensitive adhesive tape, the pressure-sensitive adhesive tape has excellent corrugated board sealing property. Become. The corrugated board sealing property of such a pressure-sensitive adhesive tape is greatly influenced by the cohesive force of the pressure-sensitive adhesive composition used, but at the same time, it is considered that the pressure-sensitive adhesive force and tack must be at a high level to be satisfactory. The pressure-sensitive adhesive composition of the present invention, by using an additive which is a compound having the above structural formula in the acrylic ester-based pressure-sensitive adhesive, the reason is not clear, but the adhesive strength, the decrease in tack is not seen,
It has been found that the cohesive force is improved, and, for example, when the pressure-sensitive adhesive composition is applied to a base material to form a pressure-sensitive adhesive tape, the corrugated board sealing property is improved.

However, when the carbon number of R (alkyl group etc.) in the above additive is 8 or more, or the amount of the above additive added is more than 2.0 parts by weight based on 100 parts by weight of the above copolymer. Results in insufficient holding power, sealing ability of corrugated board, etc.

<< Adhesive Composition >> The adhesive composition of the present invention is mainly composed of a mixture of an alkyl acrylate ester adhesive and a specific additive as described above. The acrylic ester-based pressure-sensitive adhesive is composed of a copolymer containing acrylic acid ester and / or methacrylic acid ester (hereinafter abbreviated as (meth) acrylic acid ester) as main components.

<Acrylic ester-based adhesive> In the above-mentioned copolymer which is the acrylic ester-based adhesive of the present invention, the preferable content of the (meth) acrylic acid alkyl ester is the total of all the monomers constituting the copolymer. 50% by weight or more based on the amount, more preferably 60% by weight
That is all. If the content of the (meth) acrylic acid alkyl ester is less than 50% by weight, the tackiness of the obtained pressure-sensitive adhesive composition is reduced.

As the (meth) acrylic acid alkyl ester,
Methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, isobutyl (meth) acrylate,
N-Butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth)
Examples thereof include 2-ethylhexyl acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and decyl (meth) acrylate.

Monomers that can be used in addition to the (meth) acrylic acid alkyl ester include vinyl aromatic monomers such as styrene, α-methylstyrene and vinyltoluene, (meth) acrylic acid, crotonic acid, cinnamic acid, Unsaturated carboxylic acids such as itaconic acid, fumaric acid and maleic acid; monoalkyl esters of unsaturated dicarboxylic acids such as itaconic acid monoethyl ester, fumaric acid monobutyl ester and maleic acid monobutyl ester; acrylonitrile, α-chloroacrylonitrile and Vinyl cyanide monomers such as methacrylonitrile; ethylenically unsaturated carboxylic acid amides such as acrylamide, methacrylamide, N-methylolacrylamide and N-substituted compounds; unsaturated alcohols such as allyl alcohol; (meth) acrylic acid 2 -Hydroxyethyl, ( (2) Functional alkyl esters of (meth) acrylic acid such as 2-hydroxypropyl acrylate and glycidyl methacrylate; and vinyl acetate, vinyl chloride, vinylidene chloride and the like.

Among the above monomers, the amount of the unsaturated monomer having a functional group such as a carboxyl group, a hydroxyl group, an amide group or an epoxy group is based on the total amount of all the monomers constituting the copolymer.
It is preferably 10% by weight or less, more preferably 1
~ 5% by weight. When the amount of the functional unsaturated monomer used exceeds 10% by weight, the glass transition temperature of the obtained polymer becomes high, and as a result, the tackiness of the pressure-sensitive adhesive composition decreases.

In addition to the above monomers, a monomer having two or more polymerizable vinyl groups such as ethylene glycol dimethacrylate or diallyl phthalate in one molecule may be used as a crosslinkable monomer in an amount of 5% by weight or less. . When the amount of the crosslinkable monomer used exceeds 5% by weight, the crosslinking density of the copolymer becomes too high and the tackiness of the obtained pressure-sensitive adhesive composition disappears.

<Additive> The compound (referred to as an additive) used together with the copolymer in the present invention is a compound having the following structural formula.

R-O- in _{(CH 2 CH 2 O) n} -H ( wherein, n is a positive number, and R is a hydrogen atom, an alkyl group having seven or less carbon atoms, a phenyl group, a tolyl group, or a carbon atoms, Is 4 or less acyl groups).

Although n in the above general formula, that is, the number of moles of ethylene oxide units added has a distribution in the specific additives shown below, it is preferably 2 to 40 on average.
And more preferably 4 to 20. When the number of added moles of ethylene oxide exceeds 40, the holding power of the obtained pressure-sensitive adhesive composition is lowered, and, for example, a pressure-sensitive adhesive tape using such a pressure-sensitive adhesive composition is apt to lower the corrugated board sealing property.

Specific examples of R in the general formula include a hydrogen atom; an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and a heptyl group; a phenyl group, a p-methylphenyl group, and m-. Methylphenyl group, o
And a tolyl group such as a methylphenyl group; an acyl group such as a formyl group, an acetyl group, a propionyl group, and a butyryl group.

Examples of such compounds include polyethylene glycol (molecular weight 300) and PhG-40, which is a polyoxyethylene phenyl ether with an ethylene oxide addition mole number of 4.
(Nippon Emulsifier Co., Ltd., trade name) and the like.

The desirable amount of the above additive is 0.001 to 100 parts by weight of all monomers constituting the acrylic ester copolymer.
2.0 parts by weight. If it is less than 0.001 part by weight, the effect of improving the holding power and the sealing property of the corrugated board cannot be seen, and if it exceeds 2.0 parts by weight, on the contrary, the holding force and the sealing property of the corrugated board become insufficient.

There is no particular limitation on the mixing timing of these additives, and for example, they may be mixed and dissolved in a monomer when polymerizing a copolymer that is an acrylic ester-based adhesive, and used.
Moreover, you may add and mix to the said copolymer obtained by superposition | polymerization. Of course, it is possible to use one kind of additive, but it is also possible to use two or more kinds in combination.

<Production of Acrylic Ester-Based Adhesive> Polymerization for producing the copolymer which is the acrylic ester-based adhesive of the present invention may be carried out by a conventionally known emulsion polymerization method, solution polymerization method or suspension polymerization method. If necessary, a chain transfer agent or a plasticizer may be added during the polymerization, and after the polymerization, a thickener, a cross-linking agent, a preservative, a rust preventive agent, a pigment, a plasticizer, a filler, and a freezing agent. An inhibitor, a high boiling point solvent and an antifoaming agent can also be added appropriately.

<< Adhesive Sheet >> The adhesive composition of the present invention is applied to the surface of a substrate to provide an adhesive sheet. The base material is paper, polyethylene,
There is a sheet of plastic such as polyester, etc., and the pressure-sensitive adhesive composition is usually on the surface of the substrate in a thickness of about 20-
The pressure-sensitive adhesive composition layer is formed by coating so as to have a thickness of 50 μm. The adhesive sheet thus obtained includes an adhesive tape, an adhesive label, an adhesive poster and the like.

[Examples and Comparative Examples]

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In each example, "part" means "part by weight" and "%"
By means by weight. The adhesive force, the holding force, the tack, and the corrugated board sealing property were measured by the following methods.

<Adhesive strength> A pressure-sensitive adhesive is directly applied to a 50μ-thick polyester film so that the thickness after drying becomes 25μ, and dried at 100 ° C for 2 minutes to prepare a pressure-sensitive adhesive film. For this, a stainless steel plate was used as the adherend and the measurement was performed according to the 180-degree peeling method specified in JIS Z-0237.

<Holding power> Make an adhesive film similar to the adhesive strength test and make it on a stainless steel plate.
The pieces were stuck together at 25 × 25 mm, and a time for peeling off was measured by applying a load of 1 kg at 80 ° C. When held for 3 hours, the deviation width was measured.

<Tack> An adhesive film similar to the adhesive strength test was prepared and measured according to the ball rolling method of JIS Z-0237.

<Corrugated cardboard sealing property> An adhesive was applied to kraft paper so that the thickness after drying was 40 μm, and a kraft tape having a width of 5 cm and a length of 50 cm was prepared. 3
0cm × 30cm × 30cm K-liner-finished double cardboard box with double-sided door joints and kraft tape attached so that the length of the mimi is 5 cm, sealed, and left at 23 ° C × 65% RH for one week. The number of kraft tapes peeled off and the lid opened was measured. Since two boxes of cardboard were used, the total number of measurement points was eight.

Example 1 34 equipped with a stirrer, thermometer, condenser, and dropping funnel
The neck flask was charged with 50 parts of water and heated to 80 ° C. 80 parts of 2-ethylhexyl acrylate (hereinafter referred to as "HA"), 17 parts of n-butyl acrylate (hereinafter referred to as "BA") and ethylene oxide addition of polyethylene glycol phenyl ether to 4 parts of PhG-40 (Japan Emulsifier Co., Ltd.
(Trade name), 0.03 part was added and dissolved, and then 2.8 parts of acrylic acid (hereinafter referred to as "AA") and 0.2 part of N-methylol acrylamide (hereinafter referred to as "N-MAM") were mixed.
To this mixture, sodium lauryl sulfate as an emulsifier 1.
The monomer emulsion obtained by adding 0 part with 22 parts of water and emulsifying was mixed with 15 parts of a 5% ammonium persulfate aqueous solution to prepare 4 parts.
Polymerization was carried out by continuously dropping it over time. After dropping, aging at 80 ℃ for 2 hours, cooling to room temperature, and viscosity
A copolymer emulsion of 240 cps, solid content 53.1%, pH 2.0 was obtained. The obtained emulsion was stable with almost no aggregates. To 100 parts of this emulsion, 1.1 parts of a polycarboxylic acid type thickener (trade name: B-300, manufactured by Toagosei Co., Ltd.) adjusted to pH 7.0 by adding 10% aqueous ammonia, and a viscosity of 12,000 were added. An adhesive composition of cps was obtained. The adhesive properties of this adhesive composition are shown in Table 1.

Example 2 A pressure-sensitive adhesive composition having a viscosity of 11,500 cps was obtained in the same manner as in Example 1 except that the PhG-40 was replaced with polyethylene glycol having a molecular weight of 300. The adhesive physical properties of this adhesive composition are shown in Table-1.
It was shown to.

Example 3 34 equipped with a stirrer, thermometer, condenser, and dropping funnel
A neck flask was charged with 80 parts of toluene and heated to 75 ° C. BA
85 parts, ethyl acrylate 10 parts, polyoxyethylene phenyl ether ethylene oxide addition mole number 6
0.2 part of PhG-60 (trade name, manufactured by Nippon Emulsifier Co., Ltd.) was added and dissolved, and then 5 parts of AA were mixed. This mixture and 50 parts of a toluene solution in which 1.0 part of azobisisobutyronitrile (hereinafter referred to as "AIBN") were dissolved were continuously added dropwise over 4 hours to carry out polymerization. After the dropping, add 0.3 parts of AIBN and age it at 75 ℃ for 5 hours.
A copolymer having 00 cps and a solid content of 43.4% was obtained. This copolymer 1
Coronate L (Japan Polyurethane Industry Co., Ltd.)
Manufactured, trade name) was added to obtain an adhesive composition. The adhesive properties of this adhesive composition are shown in Table 1.

Examples 4 to 7 HA 50 parts, BA 40 parts, vinyl acetate 6 parts and acrylic acid 4 parts were mixed and polymerized in the same manner as in Example 3 to obtain a copolymer having a viscosity of 4,100 cps and a solid content of 43.0%. PhG-20 (manufactured by Nippon Emulsifier Co., Ltd.) in which 100 parts of this copolymer has a molar number of ethylene oxide addition of polyoxyethylene phenyl ether of 2
0.005 parts, 0.05 parts, 0.2 parts or 0.7 parts and 1.2 parts of Coronate L were added and mixed. The adhesive properties of this adhesive composition are shown in Table 1.

Example 8 34 equipped with a stirrer, thermometer, condenser, and dropping funnel
The neck flask was charged with 50 parts of water and heated to 80 ° C. HA80 part,
Addition of ethylene oxide to polyethylene glycol phenyl ether to 15 parts of methyl acrylate
1.9 parts of G-40 (trade name, manufactured by Nippon Emulsifier Co., Ltd.) was added and dissolved, and then 4.7 parts of AA and 0.3 part of N-MAM were mixed. To this mixture, a monomer emulsion obtained by emulsifying 1.0 part of sodium lauryl sulfate together with 22 parts of water as an emulsifier,
Polymerization was carried out by continuously dropping it with 15 parts of a 5% aqueous solution of ammonium persulfate over 4 hours. After the dropping is completed,
Aged at 80 ℃ for 2 hours, cooled to room temperature, viscosity 300 cps,
A copolymer emulsion having a solid content of 53.4% and a pH of 1.5 was obtained.
To 100 parts of the obtained emulsion, 10% ammonia water and 1.1 parts of a polycarboxylic acid type thickener (manufactured by Toagosei Chemical Industry Co., Ltd., trade name B-300) were added to give an adhesive composition having a viscosity of 10,000 cps and pH 7. I got a thing. The adhesive physical properties of this adhesive composition are shown in Table-1.
It was shown to.

Comparative Example 1 After the emulsion polymerization was carried out in the same manner as in Example 1 except that the additive PhG-40 was not used, the obtained copolymer emulsion was similarly thickened to obtain a pressure-sensitive adhesive composition. The adhesive properties of this adhesive composition were as shown in Table 2.

Comparative Example 2 In the organic solvent solution of the copolymer obtained in Example 3,
Without adding the polyethylene glycol-based compound to be used in the present invention, 1.2 parts of Coronate L was added to obtain an adhesive composition. The adhesive properties of this adhesive composition are as shown in Table-2.

Comparative Examples 3 to 4 Instead of the additive PhG-40, polypropylene glycol having an average molecular weight of 400 (Comparative Example 3) or polyoxyethylene octylphenyl ether having an ethylene oxide addition mole number of 10 (Comparative Example 4) was used as the PhG-in Example 1. Emulsion polymerization was carried out in the same manner as in Example 1 except that the same amount as 40 was used, and the obtained copolymer emulsion was thickened to obtain a pressure-sensitive adhesive composition. The adhesive properties of this adhesive composition are also shown in Table 2.

Comparative Example 5 A pressure-sensitive adhesive composition was obtained in the same manner as in Example 8 except that the amount of the additive PhG-40 was changed to 2.6 parts. The adhesive physical properties of this adhesive composition are shown in Table 2.

(C) Effect of the invention The adhesive of the present invention, the adhesive strength, the cohesive strength, the tack, and the excellent sealing ability of the corrugated board are excellent, and therefore not only for adhesive tapes but also for adhesive sheets such as adhesive labels. Can also be used widely.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 58-127758 (JP, A) JP 57-67664 (JP, A) JP 52-22768 (JP, B2)

Claims (2)

[Claims] 1. A mixture containing a copolymer having an acrylic ester and / or a methacrylic ester as a main component and a compound represented by the following structural formula as a main component, and the addition amount of the compound constituting the copolymer. 100 parts by weight of all monomers
A pressure-sensitive adhesive composition, which is 0.001 to 2.0 parts by weight. R-O- in _{(CH 2 CH 2 O) n} -H ( wherein, n is a positive number, and R is a hydrogen atom, an alkyl group having seven or less carbon atoms, a phenyl group, a tolyl group, or a carbon atoms, Is 4 or less acyl groups.) 2. A pressure-sensitive adhesive sheet in which a layer of the pressure-sensitive adhesive composition according to claim 1 is formed on a substrate surface.