JPH04320476A - Adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an adhesive composition which is watersoluble, has suitable humidity resistance and is improved in adhesiveness by using a polymer having a specified amount of iminosulfonate groups as a base polymer. CONSTITUTION:A compound having a double bond and an iminosulfonate group of the formula [wherein R1 and R2 are each (un)substituted alkyl, cycloalkyl, phenyl or a condensed aromatic group, and they together with the adjoining carbon atom may be combined with each other to form a cyclic group] is copolymerized with another monomer having a polymerizable double bond to obtain a base polymer having 1.0X10<-4> to 3.0X10<-3> equivalents/g of iminosulfonate groups of the formula as the side chains. This polymer is optionally mixed with a plasticizer, a surfactant, a tackifying agent, a stabilizer, etc., to obtain the title composition.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides pressure-sensitive adhesives such as
Alternatively, the present invention relates to an adhesive composition that can be used as a hot melt adhesive. More specifically, when a base material such as a label or tape to which an adhesive has been applied is no longer needed, the adhesive remaining on the adherend after peeling off the base material can be removed using water or water without using an organic solvent or the like. The present invention relates to an adhesive composition that can be easily removed with an alkaline aqueous solution.

0002

[Prior Art] Pressure-sensitive adhesives are applied to base materials such as labels, tapes, posters, etc. to attach these base materials to predetermined surfaces to protect the surface of objects, temporarily fix articles, etc. widely used. Among adhesives, those whose base polymer has a high melting point and exhibit tackiness above room temperature are used as hot melt adhesives. Hot melt adhesives can bond various base materials such as paper, wood, plastic, metal, and glass, so they are used in packaging, bookbinding, architecture,
It is used in a wide range of industrial fields such as the manufacture of electrical parts and automobile parts, and by using it, it is possible to work with high efficiency without using solvents.

[0003] When the base material to which the pressure-sensitive adhesive or hot-melt adhesive is applied is peeled off from a predetermined location, it often becomes a problem that the adhesive remains on the adherend. Many of the above adhesives that have been used in the past have water-insoluble polymers such as natural rubber, synthetic rubber, polyacrylic ester, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer as their main components. , an organic solvent was required to remove the remaining adhesive. For this reason, there is a problem that adherends such as plastics may dissolve when removed, and may have an adverse effect on the human body and the environment. Therefore, a water-soluble adhesive that can be removed with water is desired.

As water-soluble adhesives, adhesives whose base polymers are copolymers of polar monomers such as acrylic acid and methacrylic acid and vinyl acetate and acrylic acid ester type monomers are well known. However, base polymers containing many hydrophilic groups generally have too high cohesive force and poor adhesive strength. In order to impart adhesive strength, it is necessary to add a large amount of plasticizer. Adhesives containing large amounts of plasticizers have poor heat resistance and moisture resistance. Furthermore, since the base polymer is essentially water-soluble, it necessarily has poor water resistance, making it impossible to use it in locations with high humidity or exposure to water. As a means to solve this problem, for example,
4-15680 proposes a label with a barrier layer, but such a label has the disadvantage that it has a complicated structure and is not sufficiently effective against moisture penetration from the edges. be.

[0005]

[Problems to be Solved by the Invention] The present invention solves the above-mentioned conventional drawbacks, and its purpose is to provide a water-soluble adhesive that has excellent adhesiveness and appropriate moisture resistance. The object of the present invention is to provide an adhesive composition capable of forming a pressure adhesive or a hot melt adhesive. Another object of the present invention is to provide an adhesive composition that does not contain excessive polar components in the base polymer, does not require a plasticizer, and therefore has the above-mentioned excellent properties.

[0006]

[Means for solving the problem] The iminosulfonate group represented by the following formula (I) is 1.0×10−4 to 3.0×
Adhesive composition containing as a base polymer a polymer introduced into the side chain at a ratio of 10-3 equivalents/g:

0
007]

[Case 2]

In the formula, R1 and R2 are each independently,
Substituted or unsubstituted alkyl group, cycloalkyl group,
Represents a phenyl group or a fused aromatic group, R1 and R2
may be bonded to each other to form a cyclic group together with adjacent carbon atoms.

Examples of the groups represented by R1 and R2 in the above formula (I) include methyl, ethyl, cyclohexyl, phenyl groups, and these groups having substituents. R1 and R2 bonded to each other together with adjacent carbon atoms
Examples of the cyclic group represented by include cyclohexylidene, 9
-Fluorenylidene group, etc. can be exemplified. Preferred combinations of groups represented by R1/R2 include methyl/ethyl, methyl/phenyl, p-phenyl/methyl, phenyl/phenyl groups and cyclohexylidene, 9-fluorenylidene groups bonded to each other together with adjacent carbon atoms. be.

The base polymer having iminosulfonate groups contained in the composition of the present invention can be obtained, for example, by the following method: (A) synthesizing a compound having both a polymerizable double bond and an iminosulfonate group; A method in which this compound is used as a monomer and copolymerized with another monomer having a polymerizable double bond, or (B) a compound having both a formyl group and an iminosulfonate group is synthesized, and this is reacted with a polymer having a hydroxyl group. A method of carrying out an acetalization reaction between a hydroxyl group and a formyl group contained in the polymer.

The method for synthesizing the compound having a polymerizable double bond and an iminosulfonate group used in the above method (A) is not particularly limited, but for example, as shown in the following formula, a sulfonic acid chloride (1) A practical method is to react the oxime (2) with the oxime (2).

0012

[Chemical formula 3]

In the formula, R1 and R2 have the same meanings as defined above, and R3 represents a group containing a polymerizable group.

[0014] As the sulfonic acid chloride, vinyl sulfonic acid chloride, styrene sulfonic acid chloride, etc. are preferably used. As the oxime (2), for example, methyl ethyl ketone oxime, cyclohexanone oxime, acetophenone oxime, p-nitroacetophenone oxime, benzophenone oxime, 9-fluorenone oxime, etc. are preferably used. Other copolymerizable monomers used in the above method (A) include acrylic acid, methacrylic acid, (meth)acrylic acid alkyl ester, hydroxyalkyl (meth)acrylate, aminoalkyl (meth)acrylate, (meth)acrylamide, etc. (meth)acrylic acid derivatives; and vinyl monomers other than acrylic monomers, such as vinyl acetate, styrene, and maleic anhydride, can be used alone or in combination.

The compound having a formyl group and an imisulfonate group used in the above method (B) can also be prepared by the method of the above formula, where R3 is a group containing a formyl group.

As such a sulfonic acid chloride, formylbenzenesulfonic acid chloride or the like is preferably used. Examples of the polymer having a hydroxyl group used in the above method (B) include polyvinyl alcohol, polyvinyl acetal, and the like.

The obtained base polymer has the above formula (I)
The base polymer is prepared so that the iminosulfonate group represented by the formula is contained in the side chain of the base polymer at a ratio of 1.0 x 10-4 to 3.0 x 10-3 equivalent/g. When the content of iminosulfonate groups is less than 1.0×10 −4 equivalent/g, the resulting adhesive containing the base polymer does not have water-soluble properties. 3.0×10-3 equivalent/
If it exceeds g, appropriate elasticity and viscosity for the base polymer of the adhesive cannot be obtained.

The iminosulfonate group contained in the base polymer thus obtained is
Chemie, Rapid
Communications vol. 5, 689
-693 (1984), it has the property of absorbing light and reducing and decomposing the O-N bond, thereby producing a sulfonic acid group. While the iminosulfonate group before photolysis exhibits only the same polarity as a normal ester bond, the sulfonic acid group generated after photolysis has strong polarity and greatly contributes to water solubility.

[0019] Therefore, this group is introduced into the side chain,
The base polymer has moderate adhesive strength, unlike polymers containing many hydrophilic groups, which have low adhesive strength. Therefore, there is no need to add other polar components such as plasticizers. When the adhesive remaining on the adherend after the substrate is peeled off is exposed to natural light such as sunlight or light from an artificial lamp, sulfonic acid is generated in the base polymer, and as a result, The adhesive can be easily removed by washing with water or an alkaline aqueous solution. Furthermore, photodecomposition of the adhesive during use can be suppressed by making the substrate to which the adhesive is attached light-shielding, or by appropriately adjusting the light sensitivity of the iminosulfonate group in the base polymer as described below. Alternatively, the sulfonic acid group may be generated only after the base material is peeled off after use. In this way, it is possible to obtain an adhesive that is water-resistant during use and can be removed by water after peeling.

Preferred combinations of groups represented by R1/R2 in the above formula (I) are methyl/ethyl, methyl/phenyl, p-phenyl/methyl, phenyl/phenyl groups and cyclohexyl groups bonded together with adjacent carbon atoms. silidene, 9-fluorenylidene group, etc. These R1
By selecting /R2, the photosensitive wavelength and sensitivity of the iminosulfonate group can be adjusted. For example, 9
- The iminosulfonate obtained from fluorenone oxime and benzenesulfonic acid chloride is sensitive to light of 350 nm or more, and when irradiated with 365 nm ultraviolet rays at 200 mJ/cm in a solution with an optical density of 1, the conversion rate is about 80%. Changes to sulfonic acid.

The obtained base polymer having an iminosulfonate group in its side chain can be further crosslinked with a conventional crosslinking agent for use.

Among the base polymers of the adhesive composition thus obtained, those having a melting point lower than room temperature are used as pressure-sensitive adhesives, and those having a melting point higher than room temperature, approximately 8.
Those with a temperature of 0 to 150°C are used for hot melt adhesives. Such base polymers may optionally contain plasticizers, surfactants, tackifiers, and
Stabilizers and the like are blended to obtain the desired pressure sensitive adhesive or hot melt adhesive.

[0023]

[Examples] In order to explain the present invention in more detail, Examples are given below. Note that "parts" in the examples mean "parts by weight."

(Example 1) Preparation of pressure-sensitive adhesive tape (A
) Synthesis of 9-fluorenylideneimino-p-styrene sulfonate 81 parts of 9-fluorenone oxime and 180 parts of pyridine were placed in a reaction vessel, and cooled in an ice bath with stirring to about 5°C.
I kept it. Into this solution, 93 parts of p-styrene sulfonic acid chloride was added dropwise over 30 minutes together with a small amount of pyridine. This solution was kept at about 10° C. and stirred for 10 hours, then slowly poured into 1800 parts of 5% hydrochloric acid cooled in an ice bath, extracted with chloroform, and the chloroform extract was washed with distilled water. Thereafter, the solvent was removed, recrystallized from benzene-petroleum ether, and 9-fluorenylideneimino-p-
110 parts of styrene sulfonate were obtained.

(B) Preparation of base polymer
-100 parts of butyl acrylate, 50 parts of 9-fluorenone oxime-p-styrene sulfonate, 5 parts of methacrylic acid, and 200 parts of methyl ethyl ketone were added and maintained at 70°C with stirring. One part of azobisisobutyronitrile was added to this solution and stirred for 10 hours while maintaining the temperature at 70°C to obtain a base polymer solution.

(C) Formulation and preparation of adhesive tape 3 parts of zinc acetate was added to the base polymer solution (solid content 100 parts),
An adhesive composition solution was obtained. This adhesive composition solution was applied onto a polyethylene terephthalate film (hereinafter referred to as PET film) to a dry film thickness of 40 μm and dried to produce an adhesive tape.

(D) Evaluation: The resulting tape was cut out into a size of 2 x 20 cm and attached to a stainless steel plate, and the 180° peel strength was measured and found to be 550 g/20 mm. The same sample, 10
When the peel strength was measured after being immersed in water for an hour, there was no substantial change in the peel strength, indicating good water resistance. Separately, when adhesive tape was applied to a stainless steel plate in the same manner and left for 10 days and then peeled off, a thin layer of adhesive remained on the entire surface of the stainless steel plate. When this adhered surface was exposed to sunlight for 5 hours, the adhered adhesive could be removed with a wet cloth without any problem.

(Comparative Example 1) (A) Polymerization of base polymer 150 parts of n-butyl acrylate, 5 parts of methacrylic acid, and 200 parts of methyl ethyl ketone were placed in a reaction vessel and maintained at 70° C. with stirring. Add 1 part of azobisisobutyronitrile to this solution, and add 1 part of azobisisobutyronitrile while keeping it at 70°C.
The mixture was stirred for 0 hours to obtain a base polymer solution.

(B) Formulation and preparation of adhesive tape 3 parts of zinc acetate was added to the base polymer solution (solid content 100 parts),
An adhesive composition solution was obtained. This adhesive composition was applied onto a PET film so that the film thickness after drying was 40 μm and dried to produce an adhesive tape.

(C) Evaluation The adhesive tape obtained was applied to a stainless steel plate, left for 10 days, and then peeled off. When the adhesive tape was peeled off, a thin layer of adhesive remained on the entire surface of the stainless steel plate. The adhered adhesive could not be removed simply by wiping it with a wet cloth even after 5 hours of exposure to sunlight, and it was necessary to wash it with an organic solvent such as methyl ethyl ketone to completely remove it.

(Example 2) Preparation of hot melt adhesive (
A) Synthesis of 9-fluorenylideneimino-p-styrenesulfonate 9-fluorenylideneimino-p-styrenesulfonate was synthesized in the same manner as in Example 1.

(B) Preparation of base polymer 40 parts of ethyl acrylate, 40 parts of vinyl acetate, 20 parts of 9-fluorenylideneimino-p-styrene sulfonate, and 150 parts of methyl ethyl ketone were placed in a reaction vessel, and heated to 70°C with stirring. I kept it. 0.5 part of azobisbutyronitrile was added to this solution and stirred for 10 hours while maintaining the temperature at 70°C to obtain a base polymer solution.

(C) Preparation of hot melt adhesive film
A hot melt adhesive film was obtained by coating and drying on the film so that the film thickness after drying was 40 μm.

(D) Evaluation The adhesive film peeled off from the PET film is sandwiched between two sheets of high-quality copying paper, and the laminate is passed through a laminator roll at 120°C, and the adhesive film is melted between the high-quality papers. Glued. The 180° peel strength of this adhesive was measured and found to be 600 g/cm. After peeling off the high-quality paper, the adhesive adhered to the high-quality paper was exposed to sunlight for 5 hours, and then the whole high-quality paper was immersed in a 3% NaOH aqueous solution, and the adhesive that had adhered to the paper was completely dissolved in 10 minutes. .

(Comparative Example 2) 40 parts of ethyl acrylate, 40 parts of vinyl acetate, 20 parts of methacrylic acid, and 150 parts of methyl ethyl ketone were placed in a reaction vessel and maintained at 70° C. with stirring. Add 0.5 part of azobisbutyronitrile to this solution and stir for 10 hours while keeping it at 70°C.
A base polymer solution was obtained.

Using the obtained base polymer, high-quality papers were bonded together in the same manner as in the example. When the 180° peel strength of this adhesive was measured, it was 10 g/cm, and no practical adhesive strength was obtained. After peeling off the high-quality paper, the adhered adhesive was immersed together with the high-quality paper in a 3% NaOH solution, but it took 5 to 50 minutes to completely dissolve the adhesive.
It took 10 hours.

[0037]

According to the present invention, a pressure-sensitive adhesive composition containing a base polymer having an iminosulfonate group introduced into its side chain can be obtained. Pressure-sensitive adhesives and hot melt adhesives using such compositions have sufficient adhesion, water resistance, and heat resistance, and can be made water-soluble by irradiation with light when no longer needed. Because it changes,
This can be removed by washing with water or an alkaline aqueous solution.

Claims (1)

[Claims] Claim 1: The iminosulfonate group represented by the following formula (I) is 1.0 x 10-4 to 3.0 x 10-3 equivalent/g
Adhesive composition containing the included polymer as a base polymer: [Formula 1] In the formula, R1 and R2 each independently represent a substituted or unsubstituted alkyl group, cycloalkyl group, phenyl group, or fused aromatic group. and R1 and R2 may be bonded to each other to form a cyclic group together with adjacent carbon atoms.