JPS5956471A - Preparation of double-faced adhesive tape - Google Patents

Abstract

PURPOSE:To provide a baseless double-faced adhesive tape having different bonding characteristics on each side, by preparing an adhesive sheet having a polymn. product of an acrylic monomer as a principal material, applying a liq. contg. a photo-crosslinkable sensitizer homogeneously onto one side, and irradiating with light. CONSTITUTION:An acrylic monomer such as ethyl acrylate or 2-ethylhexyl acrylate is polymerized by such a method as soln. polymn. or emulsion polymn. to yield an acrylic polymer, which is applied onto a release paper, etc. and dried, preparing an adhesive tape. A liq. contg. about 0.01-5pts.wt., based on 100pts.wt. said polymer, photo-crosslinkable sensitizer (e.g., benzophenone or benzoin) is applied homogeneously onto one side of said tape and irradiated with a xenon lamp, mercury lamp, sunlight, etc. as an active light source, thereby yielding the intended double-faced adhesive tape having different bonding characteristics on each side with low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a double-sided adhesive tape in which the front and back surfaces have different adhesive properties and do not contain a base material.

A double-sided adhesive tape that has different adhesion properties on both sides is required in cases where the surface conditions of the adherends on both the front and back sides are significantly different, or where one side of the adherend is to be easily peeled off. For example, with double-sided adhesive tape for napkins, the napkin is attached to one side and the cotton cloth is attached to the other side, so it is desirable that the napkin side has relatively soft characteristics so that it has good adhesion to rough surfaces. The cotton fabric side is desired to be relatively hard so that it can be easily peeled off and no adhesive residue is left.

Similarly, double-sided adhesive tapes used to bond rough and flat materials, such as foam cushioning materials, felt, or carpets, require different adhesion properties on the front and back surfaces.

Double-sided adhesive tapes that have different adhesion properties on the front and back sides can generally be manufactured by using different adhesive compositions on both sides that sandwich the base material, or by varying the thickness of the adhesive on both sides of the base material. be. However, in the case of base material-less tapes, which are very ideal from the viewpoint of resource or energy conservation, that is, double-sided adhesive tapes that are composed of only an adhesive without using a base material such as non-woven fabric or rayon paper, the known means can However, it is not possible to obtain a tape that has different adhesive properties and still satisfies the requirements for a tape. For example, the method of laminating two adhesive sheets with different properties or the method of applying adhesives with different properties on a pre-fabricated adhesive sheet requires a lot of man-hours and is difficult to obtain a thin adhesive. The manufactured double-sided adhesive tape is susceptible to interlayer failure.

As a result of intensive studies in view of the above-mentioned situation, the inventors have discovered that by giving a difference in the degree of polymer crosslinking on the front and back sides of a single adhesive sheet, the adhesive properties of the front and back sides of a base material-less double-sided adhesive tape can be made different. The present inventors have discovered that this becomes possible, and that the difference in characteristics between the front and back sides can be adjusted arbitrarily, leading to the creation of this invention. That is, this invention involves producing an adhesive sheet mainly made of a polymer of acrylic monomers, uniformly coating one side of this adhesive sheet with a liquid agent containing a photocrosslinking sensitizer, and subjecting it to light irradiation treatment. The present invention relates to a method for producing a double-sided adhesive tape, characterized in that:

According to the method of this invention, a double-sided adhesive tape having different adhesion properties on the front and back sides can be easily manufactured using simple manufacturing equipment and a small space, with a small number of man-hours and no labor, and is extremely economical. .

In addition, the obtained double-sided adhesive tape is a so-called base material-less tape that does not use a base material, so it is very inexpensive, and it is possible to reduce the amount of adhesive used by reducing the thickness of the adhesive. Moreover, it has an extremely innovative feature in that the difference in characteristics between the front and back surfaces is set to an appropriate value depending on the purpose of use.

In the present invention, the acrylic polymer used for producing the above-mentioned pressure-sensitive adhesive sheet is obtained by polymerizing one or more acrylic monomers capable of producing a pressure-sensitive adhesive polymer by solution polymerization, emulsion polymerization, bulk polymerization, etc. It can be obtained by polymerization using various polymerization methods. Main monomers used for this include acrylic esters such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and inoctyl acrylate, and methacrylic esters such as ethyl methacrylate and butyl methacrylate. . Functional monomers that can be used in combination with the main monomer include acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, dimethylaminoethyl acrylate, and acrylamide. Furthermore, the polymerization initiators used in the polymerization include peroxynoid compounds such as benzoyl peroxide and cumene hydroperoxide, azo compounds such as azobisisobutyronitrile, ammonium versalphide, and potassium persulfide. There are various compounds such as versalphide.

To create adhesive sheets from acrylic polymers obtained through polymerization, reverse coaters, dam coaters,
20 to 200 μ
m1 Preferably, a film is formed and coated with the required glue thickness in the thickness range of 30 to 100 μm. When the adhesive thickness is less than 20 μm, it is difficult to differentiate the characteristics between the front and back surfaces, and when it is thicker than 200 μm, light transmission becomes insufficient in the light irradiation treatment described below, making it impossible to obtain satisfactory tape characteristics.

In this invention, a liquid agent containing a photocrosslinking sensitizer is applied to one side of the above-mentioned pressure-sensitive adhesive sheet. These photocrosslinking sensitizers have the ability to extract active hydrogen from polymers by irradiation with actinic rays, such as benzophenone, 4-hydroxybenzophenone, 2-chloroanthraquinone, 2-methylanthraquinone, benzoin, acetophenone, Aromatic ketones such as anthrone, 1,4-naphthoquinone, 9,10-anthraquinone, and 1,2-benzaanthraquinone, aromatic aldehydes, aromatic carboxylic acids, and organic compounds containing photosensitizing halogen atoms. be. Such a photocrosslinking sensitizer is used as polymer 1 of the adhesive sheet.
0.01 to 5 parts by weight, preferably 0.00 parts by weight
．． It is used in a proportion of 2 to 2 parts by weight, and is applied to one side of an adhesive sheet in the form of a liquid containing it. If the amount used is too small, the effect will be insufficient, and if it is too large, the crosslinking density will become higher than necessary, and the flexibility of the adhesive sheet will be impaired due to the highly three-dimensional structure.

The solvent for blending the photocrosslinking sensitizer to form a liquid is preferably an organic solvent that can dissolve the photocrosslinking sensitizer, such as toluene, tetrahydrofuran, methyl ethyl ketone, acetone, methanol, or ethanol. If a certain degree of viscosity is required when adhering to the liquid, an appropriate amount of an acrylic polymer may be added to the liquid. In some cases, it can also be used in the form of an emulsion.

In addition, in this invention, a photoactive crosslinking agent may be used together with a photodistributive crosslinking sensitizer. This photoactive crosslinking agent is activated by receiving excitation energy from actinic light or a photocrosslinking sensitizer and leads to crosslinking of the acrylic polymer, and its use can shorten the photoirradiation time. Examples of photoactive crosslinkers include N,N-methylenebisacrylamide, ethylene glycol dimeth/acrylate, polyethylene glycol dimeth/acrylate, 5-
Acrylamino-N-acrylic caproamide and the like can be mentioned. The amount used is 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the acrylic polymer of the adhesive sheet. This type of photoactive crosslinking agent is used by being blended into a solution containing the photocrosslinking sensitizer described above. If the amount used is too small, the effect will not be sufficiently expressed, whereas if it is used too much, the crosslinking density will become unnecessarily high and the flexibility of the pressure-sensitive adhesive sheet will be impaired.

In addition to coating the above-mentioned photocrosslinking sensitizer and photoactive crosslinking agent on one side of the adhesive sheet in order to differentiate the properties of the front and back sides of the adhesive sheet, the photo-crosslinking sensitizer and the photoactive crosslinking agent are also applied to the tape properties of the entire adhesive sheet. It can be blended into acrylic polymers for the purpose of adjusting.

In order to apply a photo-crosslinking sensitizer or a liquid agent containing this and a photoactive cross-linking agent to one side of an adhesive sheet, this liquid agent is generally applied by coating or spraying onto the surface of the sheet by known means. However, it is also possible to prepare a pressure-sensitive adhesive sheet by applying a liquid agent on the separator in advance and applying the pressure-sensitive adhesive onto the applied surface. The pressure-sensitive adhesive sheet after the liquid agent has been applied by the above-mentioned method is desirably subjected to light irradiation treatment within a short time of 30 minutes, preferably within 5 minutes after the application. The reason for this is that the photocrosslinking sensitizer diffuses into the adhesive layer over time after the liquid is deposited, and over a long period of time, the concentration of the photocrosslinking sensitizer becomes uniform or nearly uniform from the adhered side to the opposite side. Therefore, the desired difference in characteristics does not occur between the front and back sides of the sheet after light irradiation.

Active light sources used for light irradiation treatment include xenon lamps, low-pressure and high-pressure mercury lamps, ultra-high-pressure mercury lamps, sunlight, carbon arcs, etc., and those with a wavelength of 1.50
0-6,000 holes, preferably 2,000-5,000
A is good. A wavelength shorter than 1.50 OA leads to decomposition of the polymer, and a wavelength longer than 6.0 OA cannot impart sufficient energy to excite the photocrosslinking sensitizer.

In addition, the light irradiation time is generally 10
A standard range is from seconds to two minutes, and the longer the light irradiation time and the greater the output of the light source, the greater the crosslinking density of the acrylic polymer and the greater the cohesive force of the adhesive. In addition to carrying out light irradiation from one side of the pressure-sensitive adhesive sheet, it is also possible to form a pressure-sensitive adhesive sheet by coating on a transparent film separator and irradiate it simultaneously from both sides thereof.

Through such light irradiation treatment, a difference in the degree of crosslinking occurs between the front and back sides of the adhesive sheet based on the difference in the concentration of the photocrosslinking sensitizer, and as a result, the base material can be cut into a predetermined width as desired. There is a difference in adhesive properties between the front and back sides of double-sided adhesive tape. This difference in properties can be arbitrarily adjusted by appropriately selecting the type of acrylic polymer, the type and amount of the photocrosslinking sensitizer and the photocrosslinking agent used in combination if desired, and the light irradiation time. Also, the thickness of the tape is 20 ~
It can be selected from a wide range of 200 μm. Furthermore, by mixing short fiber substances or adding a plasticizer into the adhesive polymer in advance, it is possible to adjust the tape properties such as strength and flexibility according to the use and purpose.

Next, examples of this invention will be shown. In addition, in the following, all parts are parts by weight, and the adhesive strength and holding power were measured by the following method.

<Adhesive strength> A sample of base material-less double-sided adhesive tape lined with a 25 μm thick polyester film was cut into 20 strips, and a 2 kg rubber roller was pressed against the surface of the stainless steel plate by making one reciprocation.
After 30 minutes had elapsed, the peel adhesive strength was measured at a peel angle of 180a at a temperature of 20° C. at a speed of 300 m/min using a Schopper type peel tester.

Holding power〉 A 10 x 20 m sample tape made of a base material-less double-sided adhesive tape lined with a 25 μm thick polyester film on one side was pasted on the surface of a Bakelite plate, and a load of 300 g was applied at a temperature of 40°C. The displacement distance after a certain period of time was measured.

Example 1 80 parts of butyl acrylate, 15 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, and 150 parts of toluene were charged into a polymerization pot purged with inert gas, and 0 parts of azobisisobutyronitrile was added as a polymerization initiator. Solution polymerization was performed using .5 parts, and the resulting polymer was coated on release paper using a reverse coater.

An adhesive sheet having a thickness of 30 μm was prepared by drying and lined with release paper. A 1% by weight acetone solution of 2-methylanthraquinone was applied to the surface of the adhesive sheet at a ratio of 0.5 part of 2-methylanthraquinone to 100 parts of the acrylic polymer of the adhesive sheet, and the mixture was coated for 20 seconds. Thereafter, the sheet was exposed to light for 30 seconds using a 400W mercury lamp at an irradiation distance of 20 m from the sheet surface. The obtained base material-less double-sided adhesive tape exhibited the following properties.

<Surface> Adhesive force 200 g/20 mm, holding force 0.2 mm/hour <Back side> Adhesive force 400 g/20 mm, holding force 0.5 m/hour Example 2 2-methyl was added to the solution polymer obtained in Example 1. Copolymer 100 of 1% by weight toluene solution of alatraquinone
This was applied onto a release paper using a reverse coater and dried to produce an adhesive sheet with an adhesive thickness of 30 μm and lined with release paper. A 1% by weight acetone solution of 2-methylanthraquinone was applied to the surface of the adhesive sheet, and the acrylic polymer 100% of the adhesive sheet was
2-methylanthraquinone was applied at a ratio of 0.3 parts per part of the sheet, and after 20 seconds, the sheet was exposed to light using a 400 W mercury lamp at an irradiation distance of 20 m from the sheet surface side for 30 seconds. The obtained base material-less double-sided adhesive tape exhibited the following properties.

<Surface> Adhesive force 180g/20mm, Holding power 0.2■/hour <Back> Adhesive force 300g/2On+m, Holding force 0.3W
rrn/hour Example 3 50 parts of butyl acrylate, 40 parts of 2-ethylhexyl acrylate, 10 parts of acrylic acid, and 100 parts of toluene were charged into a polymerization pot purged with inert gas, and benzoyl peroxide 2 was added as a polymerization initiator. Solution polymerization was carried out using On the other hand, a 2% by weight solution of benzophenone in toluene was sprayed onto a 25 μm thick polyester film separator, and the polymer obtained by the solution polymerization was applied onto this coated surface using a reverse coater. After drying, an adhesive sheet with a glue thickness of 60 μm and benzophenone adhered to the back side at a ratio of 0.5 parts to 100 parts of the copolymer was prepared, and immediately
The sheet was exposed to light for 30 seconds using a W mercury lamp at an irradiation distance of 206 nm from the sheet surface side.

The obtained base material-less double-sided adhesive tape exhibited the following properties.

<Surface> Adhesive force 480g/20 tone, Holding force 0.5 74 Terama <Back> Adhesive force 400g/20m+n, Holding force 0.4m
+n/R Example 4 45 parts of ethyl acrylate, 45 parts of butyl acrylate, 10 parts of acrylic acid, and 100 parts of toluene were charged into a polymerization pot purged with inert gas, and azobisisobutyronitrile was added as a polymerization initiator. Solution polymerization was carried out using 2 parts, and the obtained polymer was coated on a 25 μm thick polyester film separator using a reverse coater, and dried to produce a separator-backed adhesive sheet with an adhesive thickness of 120 μm. A 1% by weight acetone solution of 2-methylanthraquinone was sprayed onto the surface of this adhesive sheet, so that 2-methylanthraquinone was added to 0% per 100 parts of the copolymer.
．． Spray at a ratio of 6 parts and apply 400W after 1 minute.
The sheet was simultaneously exposed to light from the front and back sides of the sheet for 1 minute at an irradiation distance of 20 crn using a mercury lamp. The obtained base material-less double-sided adhesive tape exhibited the following properties.

Surface> Adhesive strength 320g/20mm, retention jE O,4
-mm/It Teramaku back side〉 Adhesive strength 580g/20mm, Holding strength 0.7mm
/ time Comparative Example 1 Copolymerization of 1% by weight toluene solution of 2-methylanthraquinone to the solution polymer obtained in Example 1 Polymer 100
0.5 part to 100 parts was added and mixed, and this was coated on a release paper using a reverse coater and dried to produce a pressure-sensitive adhesive sheet with an adhesive thickness of 3 μm and lined with release paper. This adhesive sheet was exposed to light from a 400W mercury lamp for 30 seconds at an irradiation distance of 20α from the sheet surface side. The obtained base material-less double-sided adhesive tape exhibited the following properties.

<Surface> Adhesive strength 250g/20m, holding power 0.3 am
/ll@ Listening back side〉 Adhesive strength 280g/20ynm, Holding strength 0.3m
Comparative example 2 between m/#f A solution prepared by dissolving 0.6 parts of benzophenone in 150 parts of toluene was added to and mixed with the solution copolymer obtained in Example 4, and this was coated with a 25 μm thick polyester using a reverse coater. The adhesive sheet was coated on a film separator and dried to produce a 120 μm adhesive sheet backed with a separator. This adhesive sheet was simultaneously exposed to light for 1 minute using a 400 W mercury lamp at an irradiation distance of 20 cm from both sides of the sheet.

The obtained base material-less double-sided adhesive tape exhibited the following properties.

<Surface> Adhesive strength 450g/20mm, holding power 0.5m
+n/fJ'4a"J (back side) Adhesive force 490g/20mn+, Holding force 0.5m
m/Shima Patent Applicant: Nitto Electric Industry Co., Ltd. 543

Claims (1)

[Claims] (1) A pressure-sensitive adhesive sheet mainly made of a polymer of acrylic monomer is prepared, a liquid agent containing a photocrosslinking sensitizer is uniformly applied to one side of the pressure-sensitive adhesive sheet, and a photo-irradiation treatment is performed. Features: A manufacturing method for double-sided adhesive tape.