JPH11209725A - Production of tacky agent composition and its tacky sheets - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce tacky sheets according to facilitated production by efficiently converting an acrylic polymer emulsion excellent in environmental hygiene or safety into a hot-melt type tacky agent without accompanying complicatedness in processes, problems, or the like, about treatment of waste liquors and melt coating the top surface of a support with the resultant hot-melt type tacky agent. SOLUTION: An acrylic polymer emulsion prepared by carrying out the emulsion polymerization of a monomer consisting essentially of an alkyl (meth) acrylate with an emulsifying agent is charged into a single screw or a twin- screw extruder, dehydrated and dried by a venting treatment in the screw extruder and taken out as a solid tacky agent composition containing the acrylic polymer and the emulsifying agent. The top surface of a support is then melt coated with the resultant solid tacky agent composition and the curing treatment of the tacky agent composition, as necessary, is subsequently carried out to form a tacky agent layer. Thereby, tacky sheets such as of a sheetlike or a tapelike form are produced.

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 hot melt pressure-sensitive adhesive and a method for producing a sheet-like or tape-like pressure-sensitive adhesive sheet using the same.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental hygiene and safety,
As a method for producing adhesive sheets, a shift to using no organic solvent has been progressing. As one of the methods, there is a method using an acrylic polymer emulsion obtained by emulsion polymerization in an aqueous medium. In this method, the acrylic polymer emulsion is directly applied to a support and dried,
Alternatively, the above acrylic polymer emulsion is subjected to salting-out filtration, dried to obtain a hot-melt adhesive from which an aqueous medium has been removed, and melt-coated on a support to obtain a sheet-like or tape-like adhesive. Adhesive sheets.

[0003]

However, the method of directly applying and drying an acrylic polymer emulsion on a support has a problem that drying takes a long time. On the other hand, the method in which the acrylic polymer emulsion is hot-melt adhesive and then melt-coated on the support does not have the above-mentioned problem, but the salting-out filtration and the subsequent drying for making the hot-melt adhesive are as follows. The process is complicated, and there is a problem of waste liquid treatment.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention efficiently converts an acrylic polymer emulsion excellent in environmental hygiene and safety into a hot-melt pressure-sensitive adhesive without complicated processes and problems of waste liquid treatment. An object of the present invention is to obtain an adhesive sheet easily by melt-coating it on a support.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, put an acrylic polymer emulsion obtained by emulsion polymerization in an aqueous medium into a screw extruder. By dewatering and drying by venting in this extruder, it can be efficiently converted to a hot-melt type pressure-sensitive adhesive without the conventional process complexity and problems of waste liquid treatment, and this is melted on a support. It was found that by coating, adhesive sheets could be easily produced, and the present invention was completed.

That is, the present invention relates to an acrylic polymer emulsion obtained by emulsion-polymerizing a monomer containing an alkyl (meth) acrylate as a main component in an aqueous medium using an emulsifier, to obtain a uniaxial or biaxial acrylic polymer emulsion. A method for producing a pressure-sensitive adhesive composition, comprising: introducing the mixture into a screw extruder having a shaft, dehydrating and drying by venting in the screw extruder, and taking out as a solid pressure-sensitive adhesive composition containing an acrylic polymer and an emulsifier. (Claims 1 to 3) and further, the solid pressure-sensitive adhesive composition obtained by this method is melt-coated on a support, and then, if necessary, cured to form a pressure-sensitive adhesive layer. The present invention relates to a method for producing an adhesive sheet (claim 4).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an acrylic polymer emulsion is obtained by subjecting a monomer mainly composed of an alkyl (meth) acrylate to emulsion polymerization in an aqueous medium using an emulsifier as a stabilizer. Is what you get. The emulsion polymerization may be carried out according to a known method, and may be generally carried out by a general batch polymerization method, a continuous drop polymerization method, a split drop polymerization method or the like in a temperature range of usually 30 to 80 ° C. The polymerization conditions such as the polymerization method and the polymerization temperature are not particularly limited. In order to adjust the molecular weight of the acrylic polymer, a chain transfer agent such as mercaptan may be used.

Examples of the alkyl (meth) acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate. ,
Examples thereof include alkyl acrylates having an alkyl group having 14 or less carbon atoms, such as isononyl acrylate, and alkyl methacrylates having the same alkyl group as described above. In addition, these esters as a main component,
An appropriate modifying monomer may be used in combination. These monomer compositions should be such that the glass transition point of the acrylic polymer is 250 K or lower, and if the glass transition point is higher than this, good adhesive properties cannot be obtained.

Examples of the modifying monomer include (meth) acrylic acid, maleic acid, crotonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxyethylacryloyl phosphate, and 2-hydroxypropylacryloyl. Phosphate, vinyl acetate, styrene, glycidyl (meth) acrylate, acrylic acid 2-
Hydroxyethyl, 2-hydroxypropyl acrylate, N-vinyl-2-piperidone, N-vinyl-3-monomorpholine, N-vinyl-2-caprolactam, N-
Vinyl-2-pyrrolidone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione and the like. These modifying monomers are generally used in a proportion of less than 50% by weight based on the total amount of the monomers.

In the emulsion polymerization, an appropriate polymerization initiator is used. The polymerization initiator is not particularly limited. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobisisobutyronitrile,
Azo compounds such as 2'-azobis (2-amidinopropane) dihydrochloride and 2,2'-azobis (N, N'-dimethyleneisobutylamidine); persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide Organic peroxides such as tert-butyl hydroperoxide, and redox initiators such as persulfate and sodium bisulfite.

The emulsifier used as a stabilizer is
Although not particularly limited, for example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkylphenyl ether sulfate,
Nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether are exemplified. In both cases of the anionic emulsifier and the nonionic emulsifier, a radical polymerizable emulsifier having a propenyl group introduced therein can be used.
According to this type of emulsifier, it participates in the polymer reaction at the time of kneading or heating in the emulsion polymerization or in the subsequent dehydration and drying step, and a good result is obtained in improving the water resistance.

The acrylic polymer emulsion thus obtained preferably has a solid content of 40% by weight or more, and more preferably 55% by weight or more. When the solid content is less than 40% by weight, the propulsive force in the extruder for dehydration and drying is low, and it is difficult to remove the solid content from the extruder. Therefore, when the solid content of the acrylic polymer emulsion after emulsion polymerization is less than 40% by weight,
It is desirable to increase the solid content by means such as salting-out filtration. Further, an appropriate thickener may be added to increase the viscosity of the emulsion.

In the present invention, this acrylic polymer emulsion is charged into a single-screw or twin-screw extruder and dehydrated and dried. With the above screw extruder, the contents continuously fed from one end side are transferred to the other end side while renewing the surface by rotating the screw, and uniformly kneaded while controlling the heating to a predetermined temperature throughout the entire transfer process. Then, it is structured to take out continuously from the other end side. In the present invention, one or two or more venting points are provided in the extruder, and the emulsion continuously charged from one end side is dehydrated and dried by venting treatment to obtain a solid pressure-sensitive adhesive composition, which is the other end side. Are taken out continuously.

In the screw structure of the extruder, it is preferable to increase the filling rate before and after the venting location and sufficiently reduce the pressure in the venting location. In order to increase the filling rate, there is a method of incorporating a screw component that generates a propulsive force in a direction opposite to the direction in which the contents are transferred. In addition, it is preferable to lower the filling rate and increase the surface area of the polymer at the vented portion to increase the evaporation efficiency. To increase the surface area,
A screw with a large propulsion or a screw with an increased surface area is used.

The charging rate of the acrylic polymer emulsion into the extruder depends on the outside diameter of the screw, the length of the barrel, the interval between the barrel and the screw mountain, the structure of the venting point, the number of rotations of the screw, etc. of the extruder. It may be appropriately determined in consideration of the properties of the emulsion and the like. The temperature conditions and the degree of decompression of the extruder are appropriately determined in consideration of the charging speed and the water content. Generally, the extruder temperature setting is 60
The temperature is preferably set to ~ 200 ° C. If the temperature is lower than 60 ° C., dehydration and drying may be incomplete, or the viscosity of the pressure-sensitive adhesive composition after dehydration and drying may be too high, which may make it difficult to remove the composition from the extruder. If the temperature exceeds 200 ° C., the acrylic polymer may be denatured.

When the antioxidant is added to the extruder together with the acrylic polymer emulsion, the above-mentioned problem of modification may be sometimes solved. In this case, the temperature may be set higher than the above. Further, when providing two or more venting points in the extruder, by changing the temperature setting and the degree of pressure reduction at each venting point as necessary, inconveniences such as pulsation and stop during transfer in the extruder can be avoided. If the dehydration and drying can be performed more efficiently, some effects may be obtained.

The solid pressure-sensitive adhesive composition thus obtained is an acrylic polymer having a weight average molecular weight (in terms of polystyrene measured by gel permeation chromatography) of 300,000 to 1,000,000. And an emulsifier, and the melt viscosity at 170 ° C. or lower is adjusted to 5,000 by adjusting the molecular weight and the monomer composition of the polymer.
It is preferable that the value is set to 0 poise or less, particularly 1,000 poise or less. If the above-mentioned melt viscosity exceeds 5,000 poise, problems such as roughening of the coated surface during melt coating on the support occur, which is not preferable.

The solid pressure-sensitive adhesive composition may, if necessary,
Various known additives such as a tackifier resin, a filler, a pigment, and a colorant may be blended. Further, in order to increase cohesion by a curing treatment after melt coating, divinylbenzene, vinyl (meth) acrylate, N, N'-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, trimethylol A monomer having one or more radiation-reactive unsaturated bonds in a molecule such as lupropanetri (meth) acrylate may be added. These additives can be added before or after removal from the screw extruder. In the former, it may be added together with the acrylic polymer emulsion from the input port on one end side of the screw extruder, or an additive input port is provided at an arbitrary position in the transfer area of the extruder, and from this input port. It may be added.

In the present invention, the above solid pressure-sensitive adhesive composition is used as a hot-melt pressure-sensitive adhesive, which is melt-coated on one or both surfaces of a support, and a pressure-sensitive adhesive layer having a thickness of usually 5 to 120 μm is formed on one surface. Adhesive sheets such as sheet and tape. Here, plastic film, paper, nonwoven fabric, foam, metal foil, etc. are used as the support. For the hot-melt pressure-sensitive adhesive, either a roll coater or a die coater can be used, but a die coater is particularly preferably used for uniform coating. In that case, the manifold of the die coater may be plural, and a plurality of pressure-sensitive adhesive compositions having different compositions may be applied in a laminated manner.

After the above-mentioned melt coating, an appropriate curing treatment may be applied to increase the cohesive force of the pressure-sensitive adhesive composition.
The curing treatment is performed by irradiating ionizing radiation such as α-ray, β-ray, γ-ray, neutron beam and electron beam, or active light such as ultraviolet rays. In the case of ultraviolet rays, 180 to 46
A wavelength range of 0 nm is preferable, and as a source, a mercury lamp, a metahalide lamp, or the like is preferable.

When curing by irradiation with ultraviolet rays,
It is preferable to add a photoreaction initiator (photosensitizer) to the solid pressure-sensitive adhesive composition in advance. As a photoreaction initiator,
For example, radical initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, dibenzyl and benzyldimethyl ketal, bis (dodecylphenyl) iodonium hexafluoroantimonate,
(1-6-η-cumene) (η-cyclopentadienyl)
A cationic initiator such as iron (1+) hexafluorophosphoric acid (1-) is used.

[0022]

Next, an embodiment of the present invention will be described in more detail. Hereinafter, “parts” means “parts by weight”. The acrylic polymer emulsions A and B used in Examples 1 and 2 were prepared by emulsion polymerization in an aqueous medium according to Reference Examples 1 and 2 below, respectively.

REFERENCE EXAMPLE 1 60 parts of water and 0.2 part of potassium persulfate were charged into a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer, and 97 parts of butyl acrylate and 3 parts of acrylic acid were added thereto. Department,
0.03 part of lauryl mercaptan, 2 parts of sodium lauryl sulfate as an emulsifier and 1 part of polyoxyethylene lauryl ether were added and emulsified.
Purging with nitrogen for 1 hour. Emulsion polymerization was conducted for 3 hours at a polymerization temperature of 70 ° C., followed by aging at 70 ° C. for 2 hours to prepare an acrylic polymer emulsion A. The solid content of this emulsion A was 62.5% by weight.

Reference Example 2 As an emulsifier, 2 parts of sodium lauryl sulfate and 1 part of polyoxyethylene lauryl ether were replaced by 1 part of a polyoxyethylene / propenyl-substituted nonylphenyl ether represented by the following formula (1). An acrylic polymer emulsion B was prepared in the same manner as in Reference Example 1, except that 1 part of ammonium polyoxyethylene-propenyl group-substituted nonylphenyl ether sulfate represented by the following formula (2) was used. The solid content of this emulsion B is 6
It was 2.5% by weight.

[0025]

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[0026]

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Example 1 Acrylic polymer emulsion A prepared in Reference Example 1
With a screw outside diameter of 37 mm, a barrel length of 1,800 mm,
In a biaxial screw extruder with a distance of 0.4 mm between the barrel and the screw mountain, a screw rotation speed of 300 rotations / min.
Under a condition where heating was controlled at a rate of 3 times and under a condition where each of the vents was treated at three places and each vent pressure was set at 10 to 35 cmHg, the mixture was charged at a charging rate of 200 g / min and continuously dehydrated and dried. The solid pressure-sensitive adhesive composition containing the acrylic polymer and the emulsifier discharged from the outlet at the other end had a water content of 1% by weight or less and a melt viscosity at 130 ° C. of 500 poise.

100 parts of the solid pressure-sensitive adhesive composition was mixed with 3 parts of trimethylolpropane trimethacrylate to obtain a hot melt type pressure-sensitive adhesive. This was coated on the polyester film using a die coater heated to 130 ° C., and cured by irradiating 5 Mrad of an electron beam to prepare an adhesive tape having an adhesive layer having a thickness of 50 μm.

Example 2 Except that the acrylic polymer emulsion B prepared in Reference Example 2 was used, dehydration and drying were carried out in the same manner as in Example 1, and the water content containing the acrylic polymer and the emulsifier was 1% by weight or less. ,
A solid pressure-sensitive adhesive composition having a melt viscosity at 130 ° C. of 500 poise was obtained. Also, using this solid pressure-sensitive adhesive composition,
In the same manner as in Example 1, an adhesive tape having an adhesive layer having a thickness of 50 μm was produced.

With respect to each of the pressure-sensitive adhesive tapes of Examples 1 and 2, adhesive strength, holding power and water resistance were examined in the following manner. The results were as shown in Table 1.

<Adhesive Strength> An adhesive tape of 20 mm × 100 mm was pressure-bonded to a stainless steel plate, which was sanded with an # 280 sandpaper, as an adherend by reciprocating a 2 kg roller once at 23 ° C. After 20 minutes at 23 ° C, 65%
Under an atmosphere of RH and a pulling speed of 300 mm / min, 18
The force required for 0 ° peeling was measured.

<Holding force> An adhesive tape is attached to the phenol resin plate.
The tape was adhered with an adhesion area of 10 mm x 20 mm, and after 20 minutes, left at 80 ° C for 20 minutes. Then, a phenol resin plate was hung down and 500 g of uniform adhesive was applied to the free end of the adhesive tape. A load was applied, and the time until the adhesive tape dropped at 80 ° C. was measured.

<Water Resistance> A 20 mm × 100 mm pressure-sensitive adhesive tape (adhesive layer thereof) was immersed in water, and the whitening of the pressure-sensitive adhesive tape after 1 hour was observed.

[0034]

As is clear from Table 1 above, as in Examples 1 and 2, the acrylic polymer emulsion was efficiently dehydrated and dried to obtain a solid pressure-sensitive adhesive composition, which was then melt-coated. Adhesive tape with excellent adhesion and holding power
In particular, the method of Example 2 using a radically polymerizable emulsifier as a stabilizer for the emulsion can provide good results in terms of water resistance.

[0036]

As described above, according to the present invention, an acrylic polymer emulsion having excellent environmental hygiene and safety can be efficiently produced by a hot-melt type emulsion without complicated processes and problems of waste liquid treatment. By converting the adhesive into a pressure-sensitive adhesive and melt-coating it on a support, pressure-sensitive adhesive sheets can be easily produced.

Claims (4)

[Claims] An acrylic polymer emulsion obtained by emulsion-polymerizing a monomer containing an alkyl (meth) acrylate as a main component in an aqueous medium using an emulsifier, is subjected to uniaxial or biaxial screw extrusion. A method for producing a pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition is charged into an apparatus, dehydrated and dried by venting in the screw extruder, and taken out as a solid pressure-sensitive adhesive composition containing an acrylic polymer and an emulsifier. 2. The method for producing a pressure-sensitive adhesive composition according to claim 1, wherein the solid pressure-sensitive adhesive composition has a melt viscosity at 170 ° C. or lower of 5,000 poise or less. 3. The method for producing a pressure-sensitive adhesive composition according to claim 1, wherein a required additive is added before or after taking out from the screw extruder. 4. The method of claim 1, wherein the solid pressure-sensitive adhesive composition obtained by the method according to any one of claims 1 to 3 is melt-coated on a support and, if necessary, cured to form a pressure-sensitive adhesive layer. Characteristic method for producing adhesive sheets.