JPH09217040A - Vinyl chloride resin based pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinyl chloride resin-based pressure-sensitive adhesive tape having reduced change of adhesion with time and causing no loosening and peeling for a long period of time in the case that it is applied to a curved face board, in other word, having good peel-resistance under 90 deg. constant load. SOLUTION: An acrylic pressure-sensitive adhesive is prepared by copolymerizing 100 pts.wt. of n-butyl acrylate, 3-10 pts.wt. of acrylic acid and 0.03-0.2 pt.wt. of 2-hydroxyethyl (meth)acrylate, crosslinking the resultant acrylate copolymer with a weight-average molecular weight of 700,000-950,000 with a crosslinking agent to prepare an acrylic pressure-sensitive adhesive with a gel fraction of 35-50%. This pressure-sensitive adhesive is laminated on one surface of a vinyl chloride resin sheet containing a plasticizer with a molecular weight of 180-500 and an epoxidized soybean oil. The tensile shear displacement of this acrylic adhesive is 30-50μm/40μm in the cohesive force test.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vinyl chloride resin adhesive sheet.

[0002]

2. Description of the Related Art Conventionally, nails are made of metal, painted wood, or other plastic to display product advertisements, company names, building names, etc. on outdoor advertising towers or inside and outside wall surfaces of buildings, or for other decorations. A method of fixing to various adherends with an adhesive or the like and a method of expressing characters and figures on the surface of various adherends by using paint or the like have been adopted. In recent years, instead of the above construction method, a vinyl chloride resin adhesive sheet in which an adhesive has been laminated on a vinyl chloride resin sheet of many colors has been cut out with a cutting machine, etc. The construction method used for the above-mentioned decoration and the like in a form that can be efficiently carried out has been adopted.

Usually, a vinyl chloride resin sheet is added with a plasticizer such as dioctyl phthalate or a polyester-based high molecular weight plasticizer to lower the melting temperature of the resin to facilitate the molding process and to improve the flexibility. In general, the amount of addition is 30 parts by weight or more based on 100 parts by weight of the resin when used as a base material for an adhesive sheet. Further, stabilizers such as epoxidized soybean oil and metal soap are added in order to reduce decomposition degradation due to heat, light, oxygen, etc. during production, processing, use, etc. of the vinyl chloride resin sheet.

An acrylic adhesive having good weather resistance is usually used as the adhesive for the vinyl chloride resin adhesive sheet.
Various studies have been continued on various factors such as monomer composition, molecular weight distribution, gel fraction, etc. of acrylic copolymers used in acrylic pressure-sensitive adhesives to obtain quality suitable for vinyl chloride resin pressure-sensitive adhesive sheet applications. There is. However, the plasticizer compounded in the vinyl chloride resin sheet migrates to the adhesive layer and the adhesive layer softens, or the epoxidized soybean oil compounded in the vinyl chloride resin sheet migrates to the adhesive layer and promotes cross-linking. However, there is a problem that the adhesive strength of the vinyl chloride resin pressure-sensitive adhesive sheet changes with time, and the vinyl chloride resin pressure-sensitive adhesive sheet peels off after construction.

As a method of suppressing the migration of the plasticizer compounded in the vinyl chloride resin sheet to the pressure-sensitive adhesive layer, there is a method of forming a barrier layer such as a primer layer between the vinyl chloride resin sheet and the pressure-sensitive adhesive layer. . However, since the vinyl chloride resin pressure-sensitive adhesive sheet itself becomes rigid due to the barrier layer, there is a problem that the sticking work is difficult and the workability is poor when used for decoration.

[0006] As means for solving the above problem, Japanese Patent Laid-Open No. Hei 2
No. 18486 discloses a method of using an acrylic pressure-sensitive adhesive prepared by previously mixing a specific amount of a plasticizer with a copolymer. According to this method, the change with time of the adhesive force due to the transfer of the plasticizer compounded in the vinyl chloride resin sheet to the adhesive layer is reduced, but when it is attached to a curved plate such as a corrugated plate, it is likely to remain in the valley for a long time. There was a problem that a constant load was applied across the surface, causing floating and peeling.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is that the adhesive strength is little changed with time, and when it is attached to a curved plate or the like, it does not float or peel for a long period of time, that is, 90 ° constant load peeling and holding. It is to provide a vinyl chloride resin adhesive sheet having good strength.

[0008]

The vinyl chloride resin pressure-sensitive adhesive sheet of the present invention comprises 100 parts by weight of n-butyl acrylate,
An acrylic copolymer having a weight average molecular weight of 700,000 to 950,000 obtained by copolymerizing 3 to 10 parts by weight of acrylic acid and 0.03 to 0.2 parts by weight of 2-hydroxyethyl (meth) acrylate is used as a crosslinking agent. Crosslinked gel fraction is 35-
50% acrylic adhesive has a molecular weight of 180-5
00 plasticizer and epoxidized soybean oil are laminated on one surface of a vinyl chloride resin sheet.

The acrylic copolymer used in the present invention is obtained by uniformly mixing and copolymerizing n-butyl acrylate, acrylic acid and 2-hydroxyethyl (meth) acrylate.

When the amount of the acrylic acid compounded is small, the cohesive force of the obtained acrylic pressure-sensitive adhesive is low and the 90 ° constant load peeling retention force is low, and when it is high, the adhesive force of the obtained acrylic pressure-sensitive adhesive is aged. Therefore, it is 3 to 10 parts by weight, preferably 4 to 9 parts by weight, and more preferably 5 to 7 parts by weight with respect to 100 parts by weight of n-butyl acrylate.

The above-mentioned 2-hydroxyethyl (meth) acrylate is copolymerized for the purpose of forming a crosslinking base point,
The smaller the amount of the compound, the lower the 90 ° constant load peeling retention force of the resulting acrylic adhesive, and the higher the gel fraction, the higher the gel fraction over time and the 90 ° constant load peeling. Since the holding power decreases, it is 0.03 to 0.2 part by weight, preferably 0.1 to 0.15 part by weight, relative to 100 parts by weight of n-butyl acrylate.

As the above-mentioned copolymerization method, any conventionally known polymerization method can be adopted, and examples thereof include solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization and the like. Polymerization is preferred.

A thermal polymerization initiator is generally used for the solution polymerization. Examples of the thermal polymerization initiator include ketone peroxides such as methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, and cyclohexanone peroxide, isobutyryl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, P-chlorobenzoyl. Diacyl peroxides such as peroxides, diisopropylbenzene hydroperoxide, hydroperoxides such as t-butyl hydroperoxide, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane,
1,3-bis- (t-butylperoxyisopropyl)
Benzene, dialkyl peroxides such as di-t-butyl peroxide, 1,1-di- (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,
Peroxyketals such as 1-di- (t-butylperoxy) cyclohexane, t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate and the like In addition to organic peroxides such as alkyl peresters, di-2-ethylhexyl peroxydicarbonate and bis- (4-t-butylcyclohexyl) peroxydicarbonate, 2,2′-azobis -Isobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis-1-cyclohexanecarbonitrile, dimethyl- 2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis- Examples thereof include azobis compounds such as (2-aminopropane) dihydrochloride.

When the weight average molecular weight of the above-mentioned acrylic copolymer is small, the 90% constant load peeling retention force is lowered even if the gel fraction is increased, and when it is large, the gel fraction is increased with the passage of time. The adhesive strength of the pressure-sensitive adhesive and the 90 ° constant load peeling / holding power are lowered, so that it is 700,000 to 950,000, preferably 800,000 to 900,000.

The weight average molecular weight is measured as a standard polystyrene-equivalent molecular weight by gel permeation chromatography (GPC) method. Specifically, the acrylic copolymer is dissolved in tetrahydrofuran to give 0.5-1.
It can be obtained from the relationship between the elution time and the refractive index of the elution solution, which is a 0% by weight solution and tetrahydrofuran is used as a dispersion medium for separation with a gel-filled column.

The acrylic pressure-sensitive adhesive used in the present invention is obtained by crosslinking the above acrylic copolymer with a crosslinking agent.

As the cross-linking agent, a polyfunctional isocyanate compound containing two or more isocyanate groups in the molecule is used. For example, tolylene diisocyanate, hydrogenated tolylene diisocyanate, naphthylene-1,5-diisocyanate, diphenylmethane diisocyanate. ,
Hexamethylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate and the like can be mentioned. The crosslinking agent may be used alone or in combination of two or more kinds.
When the addition amount of the cross-linking agent is small, the gel fraction of the acrylic adhesive obtained is low and the heat resistance is low, and when it is large, the gel fraction of the acrylic adhesive obtained is high and the adhesive strength and 90 ° Since the load peeling retention force decreases, it is preferably 0.001 to 5 parts by weight, and more preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer.

The smaller the gel fraction of the acrylic pressure-sensitive adhesive used in the present invention, the lower the 90 ° constant load peel holding force, and the larger the gel fraction, the lower the adhesive strength over time and the 90 ° constant load peel holding force. Therefore, it is 35 to 50%.

The above gel fraction is a value measured by the following method. First, about 0.2 g of an acrylic pressure-sensitive adhesive was weighed and immersed in 50 g of tetrahydrofuran for 24 hours. This was filtered through a 200-mesh stainless steel wire net, the residue on the wire net was dried in an oven at 110 ° C. for 3 hours, and then the weight was weighed. The ratio of the weight of the residue to the weight of the acrylic adhesive weighed out was calculated as a gel fraction in percentage.

When the amount of tensile shear displacement in the cohesive strength test of the above acrylic pressure-sensitive adhesive becomes smaller, the pressure-sensitive adhesive force decreases with time, and when it becomes larger, the 90 ° constant load peel holding force of the obtained vinyl chloride resin pressure-sensitive adhesive sheet decreases. 30-50 μm
/ 40 μm is preferable, more preferably 35 to 45 μm
m / 40 μm.

The method of measuring the amount of tensile shear displacement in the cohesive strength test referred to in the present invention is as follows: As shown in FIG. × Stainless steel plate with a length of 5 mm (SUS #
304) 1 is fixed, and this is arranged in the center of a vinyl chloride resin pressure-sensitive adhesive sheet 20 having a width of 25 mm and a length of 200 mm so that the entire surface is in contact with the width direction being parallel, and the contact portion is placed on the vinyl chloride resin adhesive sheet Stick it back and forth twice with a 2 kg roller. Incidentally, 21 is a vinyl chloride resin sheet, and 22 is an acrylic adhesive layer. At this time, the vinyl chloride resin adhesive sheet passes through the pulleys 3 and 3 and has a 50 g weight 4 at both ends.
0 and 40 are hung with a thread and balanced. Polyethylene terephthalate films 5 and 5 are provided between the vinyl chloride resin adhesive sheet and the pulley so as not to stick to each other. Next, 300 g of weight 41 is added to one weight 40 and left for 3 minutes. After that, the weight 41 is removed, and the amount of displacement after standing for 3 minutes in a balanced state is measured by a detection means (not shown). Since this deviation depends on the thickness of the acrylic pressure-sensitive adhesive, it is converted per 40 μm of the thickness of the acrylic pressure-sensitive adhesive layer. Also, the displacement of the vinyl chloride resin sheet shall be negligible.

For the measurement, a commercially available measuring machine, for example, a Yamamoto type flat plate type cohesive force measuring machine manufactured by Asahi Seiko Co., Ltd. can be used to obtain a measured value in the unit of μm.

The vinyl chloride resin sheet used in the present invention is obtained by molding a composition comprising a vinyl chloride resin, a plasticizer having a molecular weight of 180 to 500, and epoxidized soybean oil into a sheet by a calendar method or the like.

The above-mentioned plasticizer is particularly preferably used when a vinyl chloride resin sheet is produced by a calendar method or the like. For example, dioctyl phthalate (molecular weight 39
1), dimethyl phthalate (molecular weight 194), diethyl phthalate (molecular weight 222), dibutyl phthalate (molecular weight 278), diheptyl phthalate (molecular weight 36)
3), dibutyl adipate (molecular weight 258), dihexyl adipate (molecular weight 314), diethylene glycol dibenzoate (molecular weight 314) and the like. The plasticizers may be used alone or in combination of two or more.

If necessary, a heat stabilizer other than epoxidized soybean oil, a colorant, etc. may be added to the vinyl chloride resin sheet.

Examples of the heat stabilizer include metal soap heat stabilizers, organotin heat stabilizers, lead heat stabilizers, non-metal heat stabilizers and the like. Examples of the metal soap-based heat stabilizer include Pb, Cd, Ba, Zn, Ca and the like and stearic acid, lauric acid, ricinoleic acid, naphthenic acid, 2-
Examples thereof include metal soaps such as ethylhexoic acid, and specifically, Cd—Ba heat stabilizers, Ba—Zn heat stabilizers, Ca—Zn heat stabilizers, Ba—Pb heat stabilizers, C.
Examples thereof include d-Ba-Zn heat stabilizers and Cd-Mg-Zn heat stabilizers.

Examples of the above organic tin-based heat stabilizer include dibutyltin dilaurate, dibutyltin maleate,
Dibutyltin mercaptide and the like can be mentioned. Examples of the lead-based heat stabilizer include lead white, basic lead sulfite, tribasic lead sulfate, dibasic lead phosphite, dibasic lead phthalate,
Examples thereof include tribasic lead maleate, silica gel co-precipitated lead silicate, dibasic lead stearate and lead stearate.

Examples of the non-metal heat stabilizer include (i) epoxidized vegetable oil, epoxidized fatty acid ester,
Epoxidized alicyclic compounds, bisphenol A diglycidyl ether, epoxy compounds such as epoxidized polybutadiene, (ii) trialkyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trialkyl phosphite such as trilauryl phosphite ,
(Iii) Alkylaryl phosphites such as monoisooctyldiphenylphosphite, monoisodecyldiphenylphosphite, diisooctylmonophenylphosphite, (iv) triphenylphosphite, tris (p
-Phenylphenyl) phosphite, phosphite such as tris (o-cyclohexylphenyl) phosphite,
(V) β-diketones such as acetylacetone, benzoylacetone, benzoylpropionylmethane and the like.

Examples of the colorant include azo-based, phthalocyanine-based, benzophenone-based, benzotriazole-based organic pigments, carbon black, oxides, chromate molybdic acid-based, sulfide / selenide-based, ferrocyanide Inorganic pigments and the like are listed.

The vinyl chloride resin pressure-sensitive adhesive sheet of the present invention is obtained by applying the acrylic pressure-sensitive adhesive to one surface of the vinyl chloride resin sheet and drying it. As a coating method, any conventionally known method can be adopted, and examples thereof include a knife coater, a comma roll coater, and other roll coaters. In addition to the method of directly applying and drying the acrylic adhesive on the vinyl chloride resin sheet, once the acrylic adhesive is once applied and dried on the release treated surface of the release-processed process paper, one surface of the vinyl chloride resin sheet The transfer method of transferring to

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0032]

【Example】

(Examples 1 to 4, Comparative Examples 1 to 5) Production of Vinyl Chloride Resin Sheet Vinyl Chloride Resin (Kanefuchi Chemical Co., Ltd., trade name "PSH1"
0 ") 100 parts by weight, dioctyl phthalate (molecular weight =
390) 50 parts by weight, epoxidized soybean oil (manufactured by Tokyo Fine Chemical Co., trade name "NF-3000") 3 parts by weight,
Ba-Zn stabilizer (manufactured by Sakai Chemical Co., Ltd., trade name "LBZ-9
00 ") 2 parts by weight, carbon black (manufactured by Dainichiseika Co., Ltd.,
3 parts by weight of the product name "Dynic Color SZ7740B") were uniformly mixed and then molded into a sheet having a thickness of 120 μm by a calender method to obtain a vinyl chloride resin sheet.

Preparation of Acrylic Adhesive In a separable flask equipped with a reflux condenser, a thermometer and a stirrer, the predetermined amounts of n-butyl acrylate, acrylic acid and 2-hydroxyethyl methacrylate shown in Table 1 were added to ethyl acetate. It was added together with 100 parts by weight, and the temperature was raised and maintained until it was refluxed while purging with nitrogen gas. Next, a 5 wt% ethyl acetate solution of 2,2′-azobis-isobutyronitrile was first added in 0.1 parts by weight, 0.1 part by weight after 30 minutes, and 0.2 parts by weight after 1 hour and 30 minutes. After 3 hours, 0.8 parts by weight of each was added over 30 minutes, and after addition of the total amount, polymerization was continued for 5 hours to obtain a solution of an acrylic copolymer. The weight average molecular weight of the obtained acrylic copolymer was as shown in Table 1.

Next, 1.8 parts by weight of a crosslinking agent (trade name "Coronate L-55" manufactured by Nippon Polyurethane Industry Co., Ltd.) was uniformly mixed with 100 parts by weight of the solid content of the acrylic copolymer solution. Cross-linking was performed to obtain an acrylic adhesive solution. The obtained acrylic pressure-sensitive adhesive solution was applied to the release-treated surface of the release-processed process paper and dried to obtain a 40-μm-thick acrylic pressure-sensitive adhesive sheet on the process paper. The gel fraction of the obtained acrylic pressure-sensitive adhesive sheet and the amount of tensile shear displacement in the cohesive strength test are as shown in Table 1.

Preparation of Vinyl Chloride Resin Adhesive Sheet A vinyl chloride resin adhesive sheet was obtained by laminating the above acrylic adhesive layer at 40 ° C. on one surface of the above vinyl chloride resin sheet by a transfer method.

In order to evaluate the performance of the vinyl chloride resin pressure-sensitive adhesive sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 5, the gel fraction, the pressure-sensitive adhesive force and the 90 ° constant load peeling retention force were tested by the following methods. The test results are shown in Tables 1 and 2.

Gel Fraction Immediately after preparation, 70 ° C. × 5 days, 70 ° C. × 10 days, 70 ° C. × 1
The gel fraction of the vinyl chloride resin adhesive sheet after 5 days was calculated.

Adhesive strength Immediately after production, 70 ° C. × 5 days, 70 ° C. × 10 days, 70 ° C. × 1
With respect to the vinyl chloride resin pressure-sensitive adhesive sheet having a width of 25 mm after 5 days, 180 ° peeling adhesion was measured according to JIS Z 0237.

90 ° constant load peeling retention force Immediately after production, 70 ° C. × 5 days, 70 ° C. × 10 days, 70 ° C. × 1
After the lapse of 5 days, the vinyl chloride resin adhesive sheet was cut into a strip of 25 mm width, and the attachment area was 25 x 80 at the center of a 50 x 120 x 2 mm stainless steel plate (SUS # 304).
After being reciprocated with a 2 kg pressure roller to make the pressure of 2 mm and pressure-bonded, the vinyl chloride resin pressure-sensitive adhesive sheet is placed face down in a thermostatic chamber at 60 ° C. and left for 20 minutes. The peeling length was measured 2 hours after a load of 100 g was applied to one end of the stainless steel plate in the direction of 90 °.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

EFFECTS OF THE INVENTION The vinyl chloride resin pressure-sensitive adhesive sheet of the present invention has the above-mentioned constitution so that its adhesive strength is little changed with time, and when it is attached to a curved plate or the like, it does not float or peel off for a long period of time. Has become.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cohesive strength test of the present invention.

[Explanation of reference symbols] 1 stainless steel plate 20 vinyl chloride resin adhesive sheet 21 vinyl chloride resin sheet 22 acrylic adhesive layer 3 pulley 40 weight of 50 g 41 weight of 300 g 5 polyethylene terephthalate film

Claims (2)

[Claims] 1. 100 parts by weight of n-butyl acrylate,
An acrylic copolymer having a weight average molecular weight of 700,000 to 950,000 formed by copolymerizing 3 to 10 parts by weight of acrylic acid and 0.03 to 0.2 parts by weight of 2-hydroxyethyl (meth) acrylate is used as a crosslinking agent. Crosslinked gel fraction is 35-
50% acrylic adhesive has a molecular weight of 180-5
A vinyl chloride resin pressure-sensitive adhesive sheet, which is laminated on one surface of a vinyl chloride resin sheet containing 00 plasticizer and epoxidized soybean oil. 2. The vinyl chloride resin pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic pressure-sensitive adhesive has a tensile shear displacement amount of 30 to 50 μm / 40 μm in a cohesive strength test.