JP2000119616A - Adhesive composition and adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsion-type pressure-sensitive adhesive which is excellent in corrugated cardboard sealability and holding power characteristics at room temperature and low temperature, has no pot life problem, and has good adhesion to polyolefin-based adherends. Get the agent. A pressure-sensitive adhesive composition, (A) the general formula _{(1) CH 2 = C (} R 1) COOR 2 (1) ( In the formula, R ¹ is such as a hydrogen atom, R ² is 1 to 14 carbon atoms Which represents an alkyl group).
98% by weight, (B) general formula (2) CH ₂ ＣC (R ³ ) CONR ⁴ R ⁵ (2) (wherein, R ³ is a hydrogen atom, R ⁴ and R ⁵ are hydrogen atoms, carbon atoms Acrylamide-based monomer represented by the formula (C):
It comprises an emulsion of an acrylic polymer containing 1 to 6% by weight of an ethylenically unsaturated carboxylic acid or an acid anhydride thereof and (D) 0 to 20% by weight of another copolymerizable monomer as monomer units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an emulsion pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape for sealing cardboard using the composition.

[0002]

2. Description of the Related Art Emulsion-type pressure-sensitive adhesives are widely used from the viewpoints of environmental health and safety. However, when a conventional emulsion-type pressure-sensitive adhesive is used for a pressure-sensitive adhesive tape for corrugating cardboard, the chemical and physical interaction between the emulsion particles is weak and does not exhibit sufficient corrugating properties and holding power characteristics.

[0003] In order to improve the cardboard sealing property and the holding power property, there is known a method in which a crosslinking agent is added to a pressure-sensitive adhesive to crosslink particles to enhance the interaction. However,
When using a cross-linking agent, the pot life of the adhesive occurs,
The application work and process management of the adhesive are complicated. Also,
As another means for solving the above problem, there is a method of increasing the content of a polar group such as acrylic acid in the polymer composition. However, when the amount of the polar group is increased, there arises a problem that the sealing property of the pressure-sensitive adhesive tape at low temperatures and the adhesiveness to a polyolefin-based adherend are significantly reduced.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an emulsion type which can be applied without using an organic solvent, and which has excellent cardboard sealing properties and holding power properties,
Another object of the present invention is to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape for sealing cardboard, which have no pot life problem and are excellent in cardboard sealing properties at low temperatures and adhesion to polyolefin-based adherends.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, when an emulsion of an acrylic polymer obtained from a monomer having a specific composition is used as a pressure-sensitive adhesive, cardboard sealing is performed. The present invention has been found to be able to satisfy all of the properties, the cardboard sealing property at low temperature, the holding power property, the pot life, and the adhesiveness to an olefin-based adherend.

That is, the present invention relates to (A) a compound represented by the following general formula (1): CH ₂ ＣC (R ¹ ) COOR ² (1) wherein R ¹ is a hydrogen atom or a methyl group, and R ² is
(Showing an alkyl group of 14) 75 to 98% by weight of an acrylic monomer represented by the following general formula (2): CH ₂ ＣC (R ³ ) CONR ⁴ R ⁵ (2) (where R ³ is It represents a hydrogen atom or a methyl group, R ⁴ and R
⁵ is the same or different and is a hydrogen atom or carbon number 1 to
(C) ethylenically unsaturated carboxylic acid, which represents an alkyl group of 4 or may be bonded to each other to form a ring together with an adjacent nitrogen atom) Or 1 to 6% by weight of an acid anhydride thereof,
And (D) a pressure-sensitive adhesive composition comprising an acrylic polymer emulsion containing 0 to 20% by weight of another copolymerizable monomer as a monomer unit. Also, the present invention
Provided is a pressure-sensitive adhesive tape for sealing cardboard having a pressure-sensitive adhesive layer formed by applying and drying the pressure-sensitive adhesive composition on a support surface.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the general formula (1), examples of the alkyl group having 1 to 14 carbon atoms for R ¹ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, isoamyl, hexyl and 2-ethylhexyl. , Isooctyl, isononyl, isodecyl, dodecyl groups and the like.

As typical examples of the acrylic monomer (A) represented by the general formula (1), methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acryl Examples thereof include butyl acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.
Among these, acrylic acid C such as butyl acrylate
Preferred are _2-10 alkyl esters and the like. The acrylic monomers (A) may be used alone or in combination of two or more.

The amount of the acrylic monomer (A) is from 75 to 98% by weight of the total monomers constituting the acrylic polymer.
, Preferably 80 to 96% by weight, more preferably 90 to 96% by weight. Acrylic monomer (A)
If the amount is less than 75% by weight, the performance as an acrylic pressure-sensitive adhesive cannot be exhibited. If the amount exceeds 98% by weight, the absolute amount of a monomer having a functional group such as an amide group described later will be insufficient, and The good corrugated cardboard sealability and holding power characteristics of the invention cannot be obtained.

In the general formula (2), examples of the alkyl group having 1 to 4 carbon atoms for R ⁴ and R ⁵ include a methyl, ethyl, isopropyl, butyl, isobutyl and t-butyl group. In addition, the ring formed by R ⁴ and R ⁵ together with an adjacent nitrogen atom by bonding to each other may have a hetero atom in addition to the nitrogen atom, for example,
Examples thereof include 3- to 8-membered rings (particularly, 5- to 6-membered rings) such as pyrrolidine, piperidine, morpholine, and piperazine rings. R
Preferably, at least one of ⁴ and R ⁵ is an alkyl group having 1 to 4 carbon atoms, or R ⁴ and R ⁵ are bonded to each other to form a ring together with an adjacent nitrogen atom. The acrylamide monomer (B) may be used alone,
Two or more kinds may be used in combination.

As typical examples of the acrylamide monomer (B) represented by the general formula (2), N, N-dimethylacrylamide, N, N-diethylacrylamide, N
-Isopropylacrylamide, N-acryloylmorpholine and the like.

The amount of the acrylamide monomer (B) is
0.5 to 1 of all monomers constituting the acrylic polymer
0% by weight, preferably about 0.8 to 8% by weight, and more preferably about 0.8 to 6% by weight. If the amount of the acrylamide-based monomer (B) is less than 0.5% by weight, the good corrugated cardboard sealing property and the holding power property of the present invention cannot be obtained. On the other hand, if it exceeds 10% by weight, the sealing properties of the cardboard at low temperatures are significantly reduced.

Specific examples of the ethylenically unsaturated carboxylic acid or its acid anhydride (C) include acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid and maleic anhydride. These monomers can be used alone or in combination of two or more.

The amount of the ethylenically unsaturated carboxylic acid or its acid anhydride (C) is 1 to 6% by weight, preferably about 1.5 to 5% by weight, based on the total amount of the monomers constituting the acrylic polymer. Range. If the amount of the ethylenically unsaturated carboxylic acid or its acid anhydride (C) is less than 1% by weight, the good corrugated cardboard sealability and the holding power characteristics of the present invention cannot be obtained. If it exceeds 6% by weight, good corrugated cardboard sealing properties cannot be obtained at low temperatures.

Other copolymerizable monomers (D) include, for example, vinyl esters such as vinyl acetate; styrene monomers such as styrene and vinyl toluene; monomers containing an epoxy group such as glycidyl acrylate and glycidyl methacrylate; Examples include hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate. One or more of the other copolymerizable monomers (D) may be used.
These monomers are used to adjust adhesive properties and the like.

The amount of the other copolymerizable monomer (D) is
0 to 20% by weight, preferably 0 to 10% by weight, more preferably 0 to 20% by weight of the whole monomers constituting the acrylic polymer
About 5% by weight.

The acrylic polymer emulsion of the present invention can be obtained by subjecting a mixture of the above monomers to a conventional emulsion polymerization. As the polymerization method, general batch polymerization, continuous drop polymerization, divided drop polymerization, and the like can be adopted, and the polymerization is performed at a temperature of about 30 to 80 ° C.

Examples of the polymerization initiator include, for example, 2,2'-
Azobisisobutyronitrile, 2,2'-azobis (2
-Amidinopropane) dihydrochloride, 2,2'-
Azobis (N, N'-dimethyleneisobutylamidine)
Azo initiators such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-
Peroxide initiators such as butyl hydroperoxide; and redox initiators such as persulfate and sodium bisulfite.

Examples of the emulsifier include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate and sodium polyoxyethylene alkyl phenyl ether sulfate; polyoxyethylene alkyl ether, polyoxyethylene Nonionic emulsifiers such as ethylene alkyl phenyl ether are exemplified. In both the anionic and nonionic types, a radical polymerizable emulsifier into which a propenyl group or the like is introduced may be used. One or more of these emulsifiers are used.

The amount of the emulsifier used is, for example, about 0.2 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, based on 100 parts by weight of the total amount of the monomers constituting the acrylic polymer.

As the pressure-sensitive adhesive composition of the present invention, the above-mentioned acrylic polymer emulsion may be used as it is,
If necessary, a base (such as aqueous ammonia) or an acid may be added to the emulsion to adjust the pH, or an additive usually used for an adhesive, for example, a tackifying resin, a surfactant, an antiaging agent. It may be prepared by adding agents, fillers, pigments, colorants, and the like. Further, a curing agent may be added for curing by radiation.

In the pressure-sensitive adhesive tape for sealing cardboard of the present invention, the support may be, for example, a plastic film such as a polypropylene film, an ethylene-propylene copolymer film, or a polyester film; A support or the like can be used. The plastic film may be any of a non-stretched film and a stretched (uniaxially stretched or biaxially stretched) film. The surface of the support to which the pressure-sensitive adhesive is applied may be subjected to a surface treatment such as a commonly used primer or a corona discharge method. The thickness of the support can be appropriately selected depending on the purpose,
Generally, it is about 10 to 500 μm.

The pressure-sensitive adhesive tape for sealing cardboard can be produced, for example, by applying the pressure-sensitive adhesive composition on the surface of the support and drying to form a pressure-sensitive adhesive layer having a desired thickness. The pressure-sensitive adhesive composition can be applied using a conventional coater, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, or the like. The thickness of the pressure-sensitive adhesive layer can be appropriately selected within a range that does not impair the adhesiveness, for example, 10 to 100.
It is about μm.

The back surface of the pressure-sensitive adhesive tape may be subjected to a back surface treatment with a release agent such as a silicone release agent or a long-chain alkyl release agent.

The pressure-sensitive adhesive composition and the pressure-sensitive adhesive tape having the above-mentioned constitutions have good corrugated cardboard sealing properties and holding power properties, have no pot life problem, and are suitable for corrugated cardboard sealing properties at low temperatures and polyolefin-based adherends. Excellent adhesion. Although the reason why such adhesive properties are obtained is not necessarily clear, it is because acid-base interaction between the monomer unit of the component (B) and the monomer unit of the component (C) acts between the acrylic copolymer particles. Guessed.

[0026]

According to the present invention, since an acrylic polymer obtained by polymerizing a monomer having a specific composition is used, it is a solventless type which can be applied without a solvent, and has a cardboard sealing property and a holding power. It has excellent properties, has no pot life problem, and has excellent cardboard sealing properties at low temperatures and excellent adhesion to polyolefin-based adherends.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Note that, in the following example, simply
"" Means "parts by weight".

Production Example 1 50 parts of water and 0.2 parts of potassium persulfate were charged into a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer, and the atmosphere was replaced with nitrogen for 1 hour with stirring. A solution obtained by emulsifying 95 parts of butyl acrylate, 3 parts of N, N-dimethylacrylamide, 2 parts of acrylic acid, 2 parts of sodium lauryl sulfate, and 1 part of polyoxyethylene lauryl ether with 150 parts of water at 70 ° C. for 3 hours. The mixture was dropped and aged at 70 ° C. for 2 hours. Thereafter, the mixture was cooled to room temperature and neutralized with 10% aqueous ammonia to prepare an adhesive A.

Preparation Example 2 An adhesive B was prepared in the same manner as in Preparation Example 1, except that the monomer composition was changed to 95 parts of butyl acrylate, 1 part of N-isopropylacrylamide and 4 parts of acrylic acid.

Production Example 3 An adhesive C was prepared in the same manner as in Production Example 1 except that the monomer composition was changed to 97 parts of butyl acrylate and 3 parts of acrylic acid.
Was prepared.

Production Example 4 An adhesive D was prepared in the same manner as in Production Example 1 except that the monomer composition was changed to 92 parts of butyl acrylate and 8 parts of acrylic acid.
Was prepared.

Production Example 5 An adhesive E was prepared in the same manner as in Production Example 1, except that the monomer composition was changed to 97 parts of butyl acrylate and 3 parts of N-isopropylacrylamide.

Example 1 The pressure-sensitive adhesive A was applied to the surface of a biaxially oriented polypropylene film (thickness: 40 μm) which had been subjected to surface oxidation treatment by a corona discharge method so that the tape thickness after drying was 70 μm.
After drying, an adhesive tape was obtained.

Example 2 An adhesive tape was obtained in the same manner as in Example 1 except that the above-mentioned adhesive B was used as the adhesive.

Comparative Example 1 An adhesive tape was obtained in the same manner as in Example 1 except that the above-mentioned adhesive C was used as the adhesive.

Comparative Example 2 An adhesive tape was obtained in the same manner as in Example 1 except that the above-mentioned adhesive D was used as the adhesive.

COMPARATIVE EXAMPLE 3 The above adhesive C was used as the adhesive, and 0.1 part of an epoxy-based crosslinking agent (100 parts of the solid content of the adhesive) was added. I got the tape.

Comparative Example 4 An adhesive tape was obtained in the same manner as in Example 1 except that the above-mentioned adhesive E was used as the adhesive.

Evaluation Test The following tests were performed on the pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples. (Holding force) Each adhesive tape was applied to a stainless steel plate sanded with # 280 sand paper as an adherend for 25 m.
After 20 minutes from bonding with an adhesion area of mx 25 mm, 40
At 20 ° C. for 20 minutes, then hang down the stainless steel plate and apply a uniform load of 2000 g to the free end of the adhesive tape.
The time until the adhesive tape dropped at 40 ° C. was measured.

(Cardboard sealing property) 0 ° C. or 23 ° C. × 6
Under a condition of 0% RH, the cardboard box was sealed with each adhesive tape, and the cardboard sealing property was measured. The sample with the adhesive tape peeled off and the cardboard box opened was evaluated as "x",
A sample in which the adhesive tape did not peel off and the cardboard box did not open was evaluated as "O".

(Pot life of pressure sensitive adhesive) The pot life of pressure sensitive adhesive was evaluated by a change in viscosity of the pressure sensitive adhesive solution applied to each pressure sensitive adhesive tape over time. A sample whose viscosity increased with time was evaluated as “x”, and a sample whose viscosity did not change with time was evaluated as “○”.

(Adhesive Strength to Polyolefin Peel) Each adhesive tape cut into a size of 25 mm × 100 mm was pressure-bonded to a polyethylene plate as an adherend by reciprocating a 2 kg roller once, and after 20 minutes at 23 ° C. The force required for the peeling was measured (180 ° peeling, pulling speed 3
00 mm / min, 23 ° C., 65% RH atmosphere).

Table 1 shows the results.

[Table 1] From the results in Table 1, the pressure-sensitive adhesive tapes of Examples 1 and 2 of the present invention use a solventless coating-type pressure-sensitive adhesive that can be coated without a solvent, and have good cardboard sealing properties and holding power properties. Not only that, there is no problem with the pot life, and it is clear that the cardboard sealing properties at low temperatures and the adhesion to polyolefin-based adherends are excellent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) C09J 135: 00) (72) Inventor Charlie Mathie 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Incorporated F term (reference) 4J004 AA10 AB01 CA02 CA04 CA06 CB02 CC02 CC03 FA06 4J040 DF041 DF051 GA07 GA12 GA22 JA03 JA09 JB09 LA11 MA11 NA07

Claims (2)

[Claims] (A) General formula (1) CH ₂ ＣC (R ¹ ) COOR ² (1) (wherein, R ¹ is a hydrogen atom or a methyl group, and R ² is a C ¹ -C ¹ )
(Showing an alkyl group of 14) 75 to 98% by weight of an acrylic monomer represented by the following general formula (2): CH ₂ ＣC (R ³ ) CONR ⁴ R ⁵ (2) (where R ³ is It represents a hydrogen atom or a methyl group, R ⁴ and R
⁵ is the same or different and is a hydrogen atom or carbon number 1 to
(C) ethylenically unsaturated carboxylic acid, which represents an alkyl group of 4 or may be bonded to each other to form a ring together with an adjacent nitrogen atom) Or 1 to 6% by weight of an acid anhydride thereof,
And (D) a pressure-sensitive adhesive composition comprising an emulsion of an acrylic polymer containing 0 to 20% by weight of another copolymerizable monomer as a monomer unit. 2. A pressure-sensitive adhesive tape for sealing cardboard having a pressure-sensitive adhesive layer formed by applying and drying the pressure-sensitive adhesive composition according to claim 1 on the surface of a support.