JPH09169959A - Tacky tape or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tacky tape or sheet which is an acrylic tacky tape having sufficient low-temperature applicability without causing the deterioration with time even when applied to a flexible vinyl chloride resin product. SOLUTION: This tacky tape or sheet comprises 50-98wt.% alkyl (meth) acrylate having a 4-12C alkyl group and 2-50wt.% polar group-containing vinyl monomer. A part or all of the polar group-containing vinyl monomer is N- vinylacetamide contained in an amount of 1-15wt.% therein.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive tape or sheet. In particular, it relates to an adhesive tape or sheet that can be favorably attached to the surface of a soft vinyl chloride resin product.

[0002]

BACKGROUND OF THE INVENTION Acrylic pressure-sensitive adhesive tapes or sheets have excellent adhesiveness, heat resistance, and weather resistance, and are therefore preferably used for various adherends. On the other hand, since vinyl chloride resin products have a large mechanical strength and are inexpensive, they are used after being molded into various products. The vinyl chloride resin includes a hard vinyl chloride resin product containing almost no plasticizer and a soft vinyl chloride resin product containing many plasticizers such as dioctyl phthalate and dibutyl adipate. Then, when an acrylic pressure-sensitive adhesive tape is attached to the surface of this soft vinyl chloride resin product, the plasticizer in the soft vinyl chloride resin product migrates into the acrylic pressure-sensitive adhesive over time, and the pressure-sensitive adhesive softens,
There is a problem that the adhesive strength is extremely deteriorated. As a pressure-sensitive adhesive tape for solving this, as described in JP-A-5-302070, an acrylic pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer sufficiently crosslinked by adding a crosslinking agent to an acrylic polymer is laminated is known. There is.

[0003]

However, it is preferable to add this crosslinking agent because the migration of the plasticizer in the soft vinyl chloride resin is suppressed, but since the elastic modulus of the pressure-sensitive adhesive at room temperature increases, However, there is a problem that the adhesive strength of is reduced. In particular, when the temperature becomes low in winter, there is a problem that the tackiness of the adhesive becomes hard and almost no tack occurs. Therefore,
An object of the present invention is to provide an acrylic pressure-sensitive adhesive tape, which does not deteriorate with time even when applied to a soft vinyl chloride resin product, and has sufficient low-temperature adhesiveness.

[0004]

The present invention has been made in order to achieve the above-mentioned object and comprises 50 to 98% by weight of an alkyl (meth) acrylate having 4 to 12 carbon atoms and a polar group. A pressure-sensitive adhesive tape or sheet comprising a copolymer obtained by copolymerizing 2 to 50% by weight of a vinyl monomer containing, wherein a part or all of the polar group-containing vinyl monomer is N-vinylacetamide, and This N-vinylacetamide is 1 to 15% by weight.

The alkyl (meth) acrylate used in the present invention means an ester of an alcohol having 4 to 12 carbon atoms and (meth) acrylic acid. Such compounds include
n-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl ( Examples thereof include alkyl (meth) acrylates such as (meth) acrylate. And these alkyl (meth) acrylates may be used individually or may be used in mixture of 2 or more types. In particular, due to the balance between adhesiveness and cohesiveness, etc., alkyl (meth) having a glass transition temperature (Tg) of -50 ° C or lower
Acrylate is used, but its glass transition temperature (Tg)
Is preferably -50 ° C. or less as the main component, and other alkyl (meth) acrylate is preferably used in combination. When used in combination as described above, an alkyl (meth) acrylate having 1 to 3 carbon atoms can also be used.

The polar group-containing vinyl monomer used in the present invention includes a carboxylic acid monomer having a double bond such as (meth) acrylic acid, maleic acid, fumaric acid and itaconic acid, or an anhydride thereof, or (meth) acrylonitrile. , N
-Vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and other nitrogen-containing monomers;
Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyoxyethylene (meth)
Examples thereof include hydroxyl group-containing monomers such as acrylate, polyoxypropylene (meth) acrylate, and caprolactone-modified (meth) acrylate.

When the content of the above alkyl (meth) acrylate is low, the glass transition temperature of the resulting copolymer becomes high and it becomes difficult to obtain sufficient tackiness, and when it is high, the cohesive force becomes low and sufficient adhesion is obtained. Since it becomes difficult to obtain strength, it is 50 to 98% by weight, preferably 70 to 85% by weight, based on the total amount of the monomers.

The N-vinylacetamide used in the present invention is

[0009]

Embedded image

It is a compound having the following structure and is a kind of polar group-containing vinyl monomer which is polymerizable with alkyl (meth) acrylate. In the present invention, a part or all of the polar group-containing vinyl monomer is added to the N-
Replace with vinylacetamide. The content of this N-vinylacetamide is 1 to 15% by weight, preferably 2
10 to 10% by weight. The reason for this is that when N-vinylacetamide exceeds 15% by weight, the glass transition temperature becomes high and it is difficult to obtain the necessary adhesive force, and when it is less than 1% by weight, the adhesive strength to the soft polyvinyl chloride resin product decreases with time. Because.

In the present invention, other monomers can be contained in addition to the above-mentioned monomers. Other monomers include vinyl acetate, vinyl propionate, styrene,
Isobornyl (meth) acrylate etc. can be mentioned. When the amount of this monomer exceeds 30 parts by weight with respect to 100 parts by weight of an acrylic monomer such as alkyl (meth) acrylate, the cohesive force becomes too high and the tackiness decreases, so 30 parts by weight or less is preferable.

In addition to the above monomers, if excellent cohesive strength is desired, a crosslinking agent may be added to the extent that the glass transition temperature does not rise more than necessary. Examples of such cross-linking agents include isocyanate cross-linking agents, epoxy cross-linking agents, aziridine cross-linking agents, and metal chelate cross-linking agents. Specifically, an adduct of tolylene diisocyanate of trimethylol propane (Nippon Polyurethane Co .: Coronate L), polyfunctional aliphatic isocyanate (Sumitomo Bayer: Sumidule N), isophorone diisocyanate,
N-hexamethylene-1,6-bis (1-aziridinecarboxamide), polyfunctional aziridine crosslinking agent (manufactured by Nippon Shokubai Co., Ltd .: Keitite series), 1,3bis (N, N-diglycidylaminomethyl) cyclohexane, N, N,
Polyfunctional epoxy crosslinking agent such as N ', N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company: TE
TRAD series), and metal chelate compounds such as acetylacetonate chelate compounds such as aluminum, titanium and zinc.

When a monomer such as an alkyl (meth) acrylate is polymerized with light such as ultraviolet rays, a polyfunctional vinyl monomer having two or more unsaturated condensations in the molecule can be used as a crosslinking agent. Examples of these include:
1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate
Examples thereof include acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, and other epoxy acrylate, polyester acrylate, urethane acrylate and the like. The addition amount of these cross-linking agents varies depending on the system used, but generally, it is preferably in the range of 0.05 to 5 parts by weight with respect to 100 parts by weight of the solid content of the pressure-sensitive adhesive. The reason for setting the addition amount of the crosslinking agent in this range is that the gel fraction of the crosslinked adhesive obtained here is 20% to 98%, and the gel fraction in this range is the adhesive force and the cohesive force (holding performance). This is because the range of (1) is a range in which the adhesive physical properties can be balanced.

Further, a tackifying resin may be added to improve the tackiness of the pressure-sensitive adhesive. In particular, the addition of this tackifying resin improves the adhesion to polyolefin resin products. As the tackifying resin, a rosin resin,
Modified rosin resin, terpene resin, terpene phenol resin, C5 / C9 petroleum resin, coumarone resin, etc.,
These hydrogenated substances and the like can be mentioned. These tackifying resins can be used alone or in combination. Further, in the present invention, in order to impart an adhesive force, hollow bodies and fine particles of an inorganic compound such as glass balloons and glass beads,
Fine particles of an organic compound such as polymethylmethacrylate or polyethylene may be added.

A composition in which the alkyl (meth) acrylate is mixed with a polar group-containing vinyl monomer copolymerizable with the alkyl (meth) acrylate, N-vinylacetamide and, if necessary, other monomers and a crosslinking agent. Various methods can be used to obtain a copolymer by copolymerizing the products. For example, it may be dissolved in a solvent and copolymerized with a catalyst, or may be formed into a film and irradiated with radiation or light to be copolymerized.

An example of a method of dissolving in a solvent and copolymerizing with a catalyst will be described. N-vinylacetamide, an alkyl (meth) acrylate and a polar group-containing vinyl monomer copolymerizable with the alkyl (meth) acrylate. If necessary, other monomers and a crosslinking agent are put in a solvent and mixed, and the temperature of the system is a temperature at which polymerization is possible, for example,
After the temperature is raised to 50 to 80 ° C. and the atmospheric oxygen concentration is sufficiently removed by an inert gas such as nitrogen gas, copolymerization is started by adding a polymerization catalyst such as benzoyl peroxide or azobisisobutyronitrile. It The polymerization time usually requires 6 to 20 hours. If necessary, a cross-linking agent, a filler, a tackifying resin, etc. are added to the copolymer produced in this way, and then applied to a base material such as a polyester (PET) film or a polyvinyl chloride film in a predetermined thickness. Then, the solvent is dried to obtain an adhesive tape or sheet.

As a coating method at this time, a conventional coating method can be used. For example, a roll coater, a die coater, etc. can be mentioned. The thickness of the adhesive layer varies depending on the type and application of the adhesive tape, but is usually 15
Mostly μm to 2 mm. By subjecting the surface of the PET film or polyvinyl chloride film to be coated to a release treatment, the copolymer can be removed from the polyester film or polyvinyl chloride film and used as a double-sided adhesive tape.

Next, an example of the photopolymerization method will be described.
A photopolymerization initiator is added to the composition, the composition is applied to a thin film of a predetermined thickness on a polyester film or a polyvinyl chloride film, and if it is irradiated with light from this, an adhesive tape or sheet is immediately produced. It is convenient because you can get As the photopolymerization initiator used here, 4- (2-
Hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone "Ciba Geigy product name: Darocur 2959", α-hydroxy-α, α'-dimethyl-
Acetophenone "Ciba-Geigy product name: Darocur-1173", methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone "Ciba-Geigy product name: Irgacure-651", 2-hydroxy-
2-Cyclohexyl acetophenone "Ciba Geigy Co., Ltd .: trade name: Irgacure 184", acetophenone type, ketal type such as benzyl dimethyl ketal, halogenated ketone, acyl phosphinoxide, acyl phosphonate and the like.

If the amount of this photopolymerization initiator is less than 0.01 parts by weight, the polymerization conversion rate will be lowered and only a copolymer having a strong monomer odor will be obtained. If it exceeds 5 parts by weight, the amount of radicals generated will increase. Since the molecular weight decreases and the necessary cohesive force cannot be obtained, 0.01 to 5 parts by weight is preferable,
More preferably, it is 0.05 to 3 parts by weight.

On the polyester film or polyvinyl chloride resin film, a desired thickness, for example, 50 μm
When coating a thin film having a thickness of 5 mm, if the viscosity is too low to form a thin film having a desired thickness, it is necessary to increase the viscosity. For example, if the thickness of the thin film is 100 μm or less, 1
The coating can be performed even at a TI value of about 1.5 at 000 cps, but it is necessary to increase the viscosity to a high viscosity when forming a thicker film. As a means for increasing the viscosity, acrylic rubber, nitrile rubber, elastomer such as styrene-isoprene-styrene (SIS), thermoplastic resin such as polymethylmethacrylate (PMMA) and polystyrene (PSt), synthetic rubber and the like are included in the composition. It is good to dissolve in. or,
It is also possible to preliminarily polymerize a part of the monomer to increase the viscosity.

As the lamps used for light irradiation in photopolymerization, the optimum wavelength varies depending on the type of photopolymerization initiator, but a lamp having an emission distribution of a light wavelength of 400 nm or less is usually used. Examples of the light source that emits a light emission distribution with a light wavelength of 400 nm or less include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp. Among these, the chemical lamp efficiently emits light in the active wavelength region of the photopolymerization initiator, and since light absorption by monomers other than the photopolymerization initiator is small, light is transmitted to the inside and a high-thickness film is formed. It is preferable because an adhesive tape can be produced. The light irradiation intensity of the film-shaped composition by the above-mentioned lamp is important because it is a factor that influences the degree of polymerization of the copolymer obtained, and is appropriately controlled for each performance of the target film-shaped composition. In the case of a composition in which a cleavage type photopolymerization initiator having a usual acetophenone group is mixed, the range is a wavelength region effective for photodecomposition of the photopolymerization initiator (it varies depending on the photopolymerization initiator, but usually 365 nm to 420 nm). Light is used) is preferably 0.1 to 100 mW / cm ² .

The photopolymerization in the present invention is inhibited by oxygen in the air and oxygen dissolved in the thin film monomer. For this reason, it is necessary to remove oxygen before light irradiation. As the oxygen removing method, a thin film composition from which oxygen has been removed in advance is sandwiched from both sides by a release-treated film such as a polyester film having a surface release-treated and a release film for a cover, and irradiation through this film, or There is a method of reacting in an inert zone having a light transmissive window in which oxygen is replaced with an inert gas such as nitrogen gas or carbon dioxide gas. In order to sufficiently polymerize the monomer by the latter method to such an extent that the polymerization conversion rate of the monomer becomes 99.7 or more, the oxygen concentration in this irradiation atmosphere must be 5000 ppm or less. It is preferably 300 ppm or less. Irradiation time of 1 minute to 10 minutes is usually sufficient.

(Function) When the pressure-sensitive adhesive tape or sheet of the present invention is applied to a soft vinyl chloride resin product, the mechanism of exhibiting sufficient adhesive strength is not always clear, but a specific amount in the acrylic copolymer is specified. It is considered that the copolymerization of the N-vinylacetamide described above improves the adhesive strength due to the interaction between the amide group grafted in the copolymer and the vinyl chloride resin.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) 2-ethylhexyl acrylate 750
g, n-butyl acrylate 675 g, N-vinylacetamide 75 g, 1,6-hexanediol diacrylate 15 g, 2,2-dimethoxy-2-phenylacetophenone 15 g, fumed silica (Nippon Aerosil Gil Co.
200) 45g was uniformly dispersed and mixed to prepare a composition.
Next, this composition was purged with nitrogen gas to remove dissolved oxygen, and then applied to a release-treated polyester film having a thickness of 38 μm so that the coating thickness would be 0.5 mm. Next, a double-sided pressure-sensitive adhesive sheet was prepared by irradiating ultraviolet rays having an irradiation intensity of 10 mW / cm ² with a chemical lamp at an atmospheric oxygen concentration of 500 ppm to polymerize the pressure-sensitive adhesive.
The gel fraction measured by tetrahydrofuran (THF) insoluble matter of the obtained adhesive was 95%. Further, this double-sided pressure-sensitive adhesive sheet was attached to a stainless plate in an atmosphere of −10 ° C. and a test was conducted, but there was no problem in adhesion workability.

Example 2 750 g of 2-ethylhexyl acrylate, 675 g of n-butyl acrylate, N-
Vinylacetamide 45g, acrylic acid 30g, 1,6
A double-sided pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that 15 g of hexanediol diacrylate, 15 g of 2,2-dimethoxy-2-phenylacetophenone, and 45 g of fumed silica (# 200 of Nippon Aerosil Gil Co., Ltd.) were uniformly dispersed and mixed. Manufactured. The gel fraction measured by tetrahydrofuran (THF) insoluble matter of the obtained adhesive was 96%. Further, this double-sided pressure-sensitive adhesive sheet was attached to a stainless plate in an atmosphere of −10 ° C. and a test was conducted, but there was no problem in adhesion workability.

Example 3 1350 g of 2-ethylhexyl acrylate, 150 g of N-vinylacetamide, 30 g of acrylic acid, 15 g of 1,6-hexanediol diacrylate, 15 g of 2,2-dimethoxy-2-phenylacetophenone, fumed silica (Japan Aerosil Gil Company #
A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that 45 g of 200) was uniformly dispersed and mixed. The gel fraction measured by tetrahydrofuran (THF) insoluble matter of the obtained adhesive was 96%. Further, this double-sided pressure-sensitive adhesive sheet was attached to a stainless plate in an atmosphere of −10 ° C. and a test was conducted, but there was no problem in adhesion workability.

Comparative Example 1 A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example except that acrylic acid was used instead of N-vinylacetamide used in Example 3.
The gel fraction of the obtained pressure-sensitive adhesive measured by tetrahydrofuran (THF) -insoluble matter was 98%. Further, this adhesive tape was attached to a stainless steel plate in an atmosphere of −10 ° C. and a test was conducted, but there was no problem in adhesion workability.

Evaluation Items (Shear Test) The pressure-sensitive adhesive tapes obtained in Examples 1, 2, 3 and Comparative Example 1 were allowed to stand overnight under standard conditions of a temperature of 23 ° C. and a humidity of 60%, and then a size of 20 mm × 20 mm. Cut into
This cut adhesive tape is manually attached to the end of a soft vinyl chloride resin sheet having a thickness of 2 mm, a width of 25 mm and a length of 100 mm (manufactured by Chunchu Plastic Co., Ltd .: trade name "DN sheet") (hereinafter referred to as DN sheet). Then, a DN sheet of the same size was projected to the opposite side of the previous DN sheet, laminated so that only the adhesive tape portion was overlapped, and stuck using a 2 kg roller to obtain a shear test piece. The shear test piece is heated to a temperature of 23
After standing for 100 hours under conditions of 60 ° C. and 60 ° C. and 60 ° C. respectively, the DN sheet protruding on both sides was held and a shear test was performed at a speed of 50 mm / min. Table 1 shows the results.

[0029]

[Table 1]

As can be seen from this table, the adhesive tapes obtained in Examples 1, 2 and 3 containing N-vinylacetamide show little change in the adhesive strength of the adhesive tapes left at low temperature and high temperature, but N-vinyl. The change is large in Comparative Example 1 in which acetamide is not used. It is considered that this is because the adhesive tapes obtained in Examples 1, 2, and 3 had little migration of the plasticizer from the soft vinyl chloride resin film and little decrease in adhesiveness.

[0031]

The pressure-sensitive adhesive tape or sheet of the present invention comprises:
Even when it is attached to a soft vinyl chloride resin product, it adheres well and does not deteriorate over time and is good. Further, the adhesive strength to the soft vinyl chloride resin product is sufficient even under low temperature conditions.

Claims (1)

[Claims] 1. A copolymer obtained by copolymerizing 50 to 98% by weight of an alkyl (meth) acrylate having an alkyl group with 4 to 12 carbon atoms and 2 to 50% by weight of a polar group-containing vinyl monomer. An adhesive tape or sheet, wherein a part or all of the polar group-containing vinyl monomer is N-vinylacetamide, and the amount of the N-vinylacetamide is 1 to 15% by weight. Sheet.