JPH07173445A - Water-swellable pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide a composition which shows high adhesiveness at ordinary temperature and low temperatures and can be swollen with water to be easily released by using a copolymer comprising methoxyethyl acrylate and/or caprolactone acrylate, a carboxylic monomer and other monomers. CONSTITUTION:This composition is formed by mixing a copolymer comprising 15-100 wt. % methoxyethyl acrylate and/or caprolactone acrylate (the amount of the caprolactone acrylate used is 50 wt. % or below) with 10-0 wt. % carboxylic monomer other than caprolactone acrylate and 85-0 wt. % other comonomers with a crosslinking agent and optionally other additives so that the gel fraction after crosslinking may be 20-70%, and the degree of swelling after crosslinking may be 20 or above. It is desirable that the crosslinking agent is polyethylene glycol diglycidyl ether.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-swellable pressure-sensitive adhesive composition, that is, an adhesive composition which has a constant pressure-sensitive adhesive property and is swollen by water and easily peeled off.

[0002]

2. Description of the Related Art Pressure-sensitive adhesives which can be peeled off with water include water-soluble adhesives, water-dispersible adhesives and water-swellable adhesives.
However, in the former two, it takes time to completely dissolve or disperse, and although it usually peels off in the middle, a part of the adhesive remains on the adherend due to cohesive failure, so the adherend is Contamination and washing with water after peeling are indispensable. Moreover, especially with water-dispersible substances, there is concern about the adhesive properties themselves.

On the other hand, a water-swelling material loses its adhesive force at the interface by absorbing water and can be peeled off relatively quickly, and the adhesive layer is not destroyed at that time,
There is no need to worry about contaminating the adherend. Therefore, it can be said that the water-swellable pressure-sensitive adhesive is most preferable as the pressure-sensitive adhesive that can be peeled off with water.

A conventional water-swellable pressure-sensitive adhesive is disclosed in US Pat. No. 2,838,421, JP-B-50-84578.
JP-B, JP-B-52-22768, JP-B-49-
As disclosed in Japanese Patent No. 23813, a polymer containing a carboxyl group in the molecule such as polyacrylic acid is used as a base polymer, and a polyfunctional cross-linking agent is added to the polymer to make it water-swellable. It was used as a pressure sensitive adhesive.

However, a polymer obtained by polymerizing a monomer containing a carboxyl group which is a highly polar functional group in the molecule has a high glass transition temperature, and this polymer alone has a sufficient pressure-sensitive property at room temperature. Since it is difficult to obtain adhesiveness and the hardness is increased by crosslinking with a polyfunctional crosslinking agent, the pressure-sensitive adhesiveness is apt to deteriorate. Therefore, in order to improve the pressure-sensitive adhesiveness, a large amount of a plasticizer is blended with the polymer.

[0006]

However, the above conventional water-swellable pressure-sensitive adhesives tend to have low adhesive strength at low temperatures due to the use of a large amount of plasticizer, and the plasticizer is usually water-soluble. Therefore, a large amount of the compound makes the entire adhesive almost water-soluble and contaminates the adherend. Further, since the polyfunctional cross-linking agent is used for the cross-linking, the distance between the polymer molecules is shortened, the space where water molecules enter is small, and the water swelling property is poor.

In view of the above conventional circumstances, the present invention has a pressure-sensitive adhesive property at all times, exhibits a large adhesive force at room temperature as well as at a low temperature, and is excellent in water swelling property.
It is an object of the present invention to provide a pressure-sensitive adhesive composition that can be easily and relatively quickly peeled off with water and does not contaminate an adherend at that time.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, found that a copolymerized polymer having a low glass transition temperature obtained by polymerizing a specific monomer is Shows good pressure-sensitive adhesiveness alone, and when a crosslinking agent is added to this and the gel fraction and the degree of swelling after crosslinking are set to specific values, excellent water swellability is also exhibited, It was found that a pressure-sensitive adhesive having excellent adhesive properties at room temperature and low temperature, which can be easily and relatively quickly peeled off with water, and which does not contaminate an adherend at that time, is obtained, It was completed.

That is, the present invention comprises: a) 15 to 100% by weight of methoxyethyl acrylate and / or caprolactone acrylate (however, caprolactone acrylate is 50% by weight or less); and b) caprolactone acrylate. Carboxyl group-containing monomer other than rate 10-0
% By weight, c) another monomer 85 copolymerizable with them
To 0% by weight of a copolymerized polymer with a crosslinking agent and, if necessary, a plasticizer and other compounding agents, the gel fraction after crosslinking is 20 to 70%, and the swelling degree is 20 or more. The present invention relates to a characteristic water-swellable pressure-sensitive adhesive composition.

In this specification, the gel fraction and the swelling degree are values measured and calculated by the following methods.
First, about 0.5 g of the adhesive composition is weighed and its weight is set to A. Next, this is immersed in 500 ml of water for 48 hours and then filtered through a nylon mesh to measure the weight (B) of the adhesive composition containing water. After that, 130 ℃
After drying for 5 hours, the weight (C) of the non-volatile matter is measured. From these measured values A to C, the gel fraction and the degree of swelling can be determined as gel fraction (%) = [C / A] × 100 and degree of swelling = B / C, respectively.

[0011]

One of the monomers of the component a used in the present invention has the following formula: This monomer is a methoxyethyl acrylate represented by and the homopolymer has a glass transition temperature of -20.
It has a temperature of not higher than 0 ° C and effectively functions as a monomer that imparts pressure-sensitive adhesiveness.

Another one of the a-component monomers used in the present invention has the following formula: A caprolactone acrylate represented by the formula wherein the number of m is in the range of 1 to 10 and the average value of m is 1 to
It is a monomer mixture in the range of 5. In this type of monomer, the distance between the polymerizable carbon-carbon double bond and the carboxyl group is large, and when this is subjected to addition polymerization, the carboxyl group bonded as a side chain to the polymerization main chain is the above-mentioned. Since it has a molecular structure such that it exists at a position away from the main chain, it gives a polymer with a low glass transition temperature,
Moreover, it also gives favorable results in improving the water swelling property after crosslinking.

The monomer of component b used in the present invention is a carboxyl group-containing monomer other than the above-mentioned caprolactone acrylate, and specifically, acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-carboxyethyl acrylate etc. can be mentioned.
These carboxyl group-containing monomers are mainly used as needed for adjusting the adhesive strength, and particularly a
When methoxyethyl acrylate is used alone as the component monomer, it is desirable to use the component b monomer.

The monomer of the component c used in the present invention is a copolymer which can be copolymerized with the monomer of the components a and b, and this monomer is also used for adjusting the adhesive properties such as the adhesive force and the cohesive force. Is used as necessary. Specifically, a hydroxyl group-containing monomer such as an alkyl ester of (meth) acrylic acid having an alkyl group having 1 to 12 carbon atoms, 2-hydroxyethyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate, Examples thereof include vinyl acetate, vinyl propionate, styrene or a derivative thereof (eg sodium styrenesulfonate), acrylonitrile, methacrylonitrile and the like.

In the present invention, the proportions of the monomers of the a, b, and c components used are such that the monomer of the a component is 15 to 100% by weight (preferably 40 to 95% by weight), and the b component is all monomers. 10 to 0% by weight (preferably 5 to 0% by weight), and the component c monomer is 85 to 0% by weight.
(Preferably 55 to 5% by weight) is appropriately determined according to the individual purpose of use of the adhesive composition. Also,
The monomer of component a may be either methoxyethyl acrylate alone, caprolactone acrylate alone, or a combination of both, but in the case of a combination, the total amount thereof should be the above ratio. Also, caprolactone acrylate
When used alone or in the combination system described above, the amount of caprolactone acrylate used should be 50% by weight or less (preferably 40% by weight or less) based on the total monomers.

The component a monomer is less than 15% by weight, the caprolactone acrylate is more than 50% by weight, and the component b monomer is more than 10% by weight.
Further, when the amount of the component c monomer exceeds 85% by weight, favorable results cannot be obtained in properties such as pressure-sensitive adhesiveness, particularly low temperature adhesiveness and water swelling property. When the monomer of the component a is methoxyethyl acrylate alone, the monomer of the component b is 1 to 10% by weight, preferably 3 to 10% by weight based on the total amount of the monomers.
It is desirable to use 5% by weight to improve the adhesive strength, but the caprolactone acrylate is added to the monomer of the component a.
When the component b is included, the component b monomer may not be used.

In the present invention, in order to form a copolymerized polymer from these monomers, the above-mentioned monomers are prepared by a suitable radical polymerization technique such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization. May be copolymerized. Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile and azobisvaleronitrile, peroxides such as benzoyl peroxide and lauroyl peroxide, persulfates such as ammonium persulfate and potassium persulfate, and hydrogen sulfite. Redox catalysts with sodium, sodium ascorbate, metal salts and the like are used.

The copolymerized polymer thus obtained
Has a glass transition temperature of usually 0 ° C. or lower, preferably −10.
C. to -70.degree. C., and even by itself, it exhibits good pressure-sensitive adhesiveness. In order to adjust the adhesive properties, this copolymer is added with polyether polyol, polyhydric alcohol,
A water-soluble plasticizer such as an alkanolamine salt of rosin oxide may be added, but the amount thereof should be 100 parts by weight based on 100 parts by weight of the copolymerized polymer so as not to impair the low temperature adhesive strength and the non-staining property. Parts by weight or less, preferably 50 parts by weight or less,
More preferably, the amount is 20 parts by weight or less.

In the present invention, the above copolymerized polymer
Examples of the cross-linking agent to be blended in include epoxy cross-linking agents, metal salts, water-soluble phenols and the like. Among these, a particularly preferable crosslinking agent has the following formula; A diglycidyl ether having a polyethylene glycol (polymerization degree n of 9 or more, usually up to about 22) represented by the formula (1), which has a bifunctional and long polyethylene glycol chain, It has a function of increasing the intermolecular weight to give the adhesive composition after crosslinking excellent water swellability.

Such a cross-linking agent is a copolymerized polymer-10.
It is usually 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, and more preferably 0.1 to 1 part by weight, relative to 0 parts by weight. If the amount is less than 0.01 part by weight, sufficient water swellability cannot be obtained. Further, even if it is used in an amount of more than 5 parts by weight, there is no further effect, which is economically disadvantageous and tends to cause a decrease in adhesive strength and the like.

The water-swellable pressure-sensitive adhesive composition of the present invention comprises the above-mentioned copolymerized polymer and the above-mentioned crosslinking agent and, if necessary, the above-mentioned plasticizer, and if necessary, a coloring agent and a filler. Various known compounding agents such as antiaging agents can be added, but the gel fraction after crosslinking is 20 to 7
0%, the degree of swelling should be 20 or more, preferably the gel fraction after crosslinking is 35 to 60%, and the degree of swelling is 5
It is preferable to set it to 0 or more and about 200. If the gel fraction after cross-linking is less than 20%, the water-soluble property may be strengthened to contaminate the adherend, and if the gel fraction exceeds 70% or the swelling degree is less than 20, When the absorption of swelling is slow, and it takes time before swelling and peeling off or the peeling does not occur, some problems occur.

The water-swellable pressure-sensitive adhesive composition of the present invention, when used, is coated on one or both sides of various substrates such as non-woven fabric, polyvinyl chloride, polyethylene, polypropylene, polyethylene laminated paper, Adhesive sheets in the form of sheets, tapes, etc. may be obtained by appropriately performing crosslinking treatment at the same time as or after the drying step. This adhesive sheet
When it is peeled off after being adhered to an adherend, if water is applied to cause it to swell, the adhesive strength is greatly reduced, and peeling can be performed easily and in a short time, which is effective for recycling the adherend. Can be contributed.

[0023]

EXAMPLES Next, examples of the present invention will be described to explain more specifically. In the following, “parts” means “parts by weight” and “viscosity” means the viscosity at 30 ° C. measured by a B-type viscometer.

Example 1 A 1-liter three-necked flask was charged with caprolactone acrylate [trade name "Aronix M-5 manufactured by Toagosei Co., Ltd.].
300 "; m = 1-5 in the above formula (mean value = about 1.
8)] 45 parts, butyl acrylate 50 parts, sodium styrenesulfonate 5 parts, potassium hydroxide 8.8
Parts, 96 parts of water, 144 parts of methanol, and 0.175 parts of azobisisobutyronitrile were added and mixed, and the contents of the flask were replaced with nitrogen, and polymerization was carried out at 60 ° C. for 5 hours.

The glass transition temperature of the copolymer thus obtained was -36 ° C., and the viscosity of the solution containing this polymer was 30 poises. In this polymer solution, with respect to 100 parts of the copolymer polymer, 20 parts of a water-soluble plasticizer (trade name "Sannix SP750" manufactured by Sanyo Kasei Co., Ltd. and a crosslinking agent [trade name "EX-830 manufactured by Nagase Chemical Co., Ltd." 0.2 parts of polyethylene glycol diglycidyl ether having a degree of polymerization (n) ≈9] was mixed and uniformly mixed to obtain a water-swellable pressure-sensitive adhesive composition.

Example 2 The cross-linking agent was trade name "EX-512" manufactured by Nagase Chemical Co., Ltd.
(Linear, tetrafunctional epoxy compound) A water-swellable pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the content was changed to 0.1 part.

Example 3 Polymerization raw materials were mixed with 55 parts of methoxyethyl acrylate and 40 parts of caprolactone acrylate (the same as in Example 1).
Parts, sodium styrenesulfonate 5 parts, potassium hydroxide 8.8 parts, water 96 parts, methanol 144 parts, and azobisisobutyronitrile 0.175 parts except that the polymerization was carried out in the same manner as in Example 1. As a result, a polymer solution having a glass transition temperature of the copolymerized polymer of -33 ° C and a solution viscosity of 70 poise was obtained. The same water-soluble plasticizer 2 as in Example 1 was added to this solution.
0 parts and chromium acetate monohydrate [Cr (C
H ₃ COO) ₃ · H ₂ O] 1 part was blended to give a water-swellable pressure-sensitive adhesive composition.

Example 4 Polymerization raw materials were mixed with 75 parts of methoxyethyl acrylate, 5 parts of acrylic acid, 20 parts of 2-ethylhexyl acrylate, 96 parts of water, 144 parts of methanol, 0.1 part of azobisisobutyronitrile. Polymerization was carried out in the same manner as in Example 1 except that the amount was 175 parts to obtain a polymer solution having a glass transition temperature of -30 ° C and a solution viscosity of 80 poise. To this solution, the same water-soluble plasticizer and crosslinking agent as in Example 1 were added,
The same amount as in Example 1 was blended to give a water-swellable pressure-sensitive adhesive composition.

Example 5 A water-swellable pressure-sensitive adhesive composition was prepared in the same manner as in Example 4 except that the amount of the crosslinking agent was changed to 1 part.

Comparative Example 1 Aqueous polyacrylic acid solution manufactured by Wako Pure Chemical Industries, Ltd. (concentration of solid content is 25% by weight, solution viscosity is about 100 poise) 10
400 parts of the same water-soluble plasticizer as in Example 1 and 0.2 part of the same cross-linking agent as in Example 1 were added to 0 parts and mixed to give a water-swellable pressure-sensitive adhesive composition.

Comparative Example 2 20 parts of the same water-soluble plasticizer as in Example 1 was added to the polymer solution obtained in Example 3 and a crosslinking agent [trade name "TEPIC" manufactured by Nissan Kagaku KK; triglycidyl isocyanate]. Nuret] 1
And a part thereof were added and mixed to obtain a water-swellable pressure-sensitive adhesive composition.

With respect to each of the pressure-sensitive adhesive compositions of Examples 1 to 5 and Comparative Examples 1 and 2 described above, the gel fraction and the degree of swelling after crosslinking were measured, and the peelability test and the room temperature were conducted as follows. An adhesion test and a low temperature adhesion test were performed. The results are shown in Table 1 below.

<Peelability Test> The pressure-sensitive adhesive composition was applied onto release paper so that the thickness after drying was 80 μm, and dried, and this was adhered to both sides of a substrate made of polyester nonwoven fabric, An adhesive sheet was prepared. A test piece having a width of 20 mm and a length of 100 mm was prepared from this sheet, adhered to a polystyrene plate as an adherend, and immersed in water with the adhesive surface exposed to confirm the releasability. The peelability was judged to be good, and the bad was judged to be bad.

<Normal temperature adhesive strength test> A test piece having a width of 20 mm and a length of 150 mm was prepared from a double-sided adhesive sheet prepared in the same manner as in the peelability test. This test piece was attached to the surface of an adherend made of a polystyrene plate with one reciprocation of a 2 kg rubber roller, left for about 30 minutes, and then pulled at a pulling speed of 300.
The peel adhesion strength was measured by a shocker type tensile tester at mm / min and a peel angle of 180 degrees. In addition, both the bonding and the measurement were performed in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%.

<Low Temperature Adhesion Test> A test piece prepared in the same manner as in the room temperature adhesion test and an adherend made of a polystyrene plate were both stored in an atmosphere of 10 ° C. for 30 minutes and then kept at the same temperature. Then, the above test piece was attached to the surface of the adherend by one round trip of a 2 kg rubber roller, and the same temperature was applied for 30 seconds.
After storing for 1 minute, take out and pull at the same temperature 300mm /
At a peeling angle of 180 degrees, the peeling adhesive force was measured by a shocker type tensile tester.

[0036]

[Table 1] (*) × Medium, Comparative Example 1 stains the adherend, Comparative Example 2 cannot be peeled off in a short time

[0037]

INDUSTRIAL APPLICABILITY As described above, the water-swellable pressure-sensitive adhesive composition of the present invention has a constant pressure-sensitive adhesive property and exhibits a large pressure-sensitive adhesive force at room temperature as well as at low temperature. Adhesive sheets that can be easily peeled off in various industrial fields because they have the property of swelling with water, can be easily peeled off with water in a short time, and there is no risk of contaminating the adherend at that time. It can be widely used as such.

Claims (2)

[Claims] 1. A) 15 to 100% by weight of methoxyethyl acrylate and / or caprolactone acrylate (provided that caprolactone acrylate is 50% by weight)
The following), b) 10 to 0% by weight of a carboxyl group-containing monomer other than caprolactone acrylate, and c) a copolymerized polymer of 85 to 0% by weight of another monomer copolymerizable therewith, A cross-linking agent and, if necessary, a plasticizer and other compounding agents are added, and the gel fraction after cross-linking is 20 to 70.
%, The degree of swelling is 20 or more, a water-swellable pressure-sensitive adhesive composition. 2. The water-swellable pressure-sensitive adhesive composition according to claim 1, wherein the cross-linking agent is polyethylene glycol (polymerization degree: 9 or more) diglycidyl ether.