JPH11140407A - Water macerating adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition excellent in adhesion properties with little time-dependent change in adhesive properties and redispersion properties even under wet and hot environments and useful for paper labels, etc., by allowing a specific acrylic copolymer containing carboxylic groups to include a neutralized alkali, a basic phosphate and a specific surfactant. SOLUTION: This water macerating adhesive composition is obtained by blending (A) a water dispersion obtained by neutralizing with an alkali a part or all of carboxyl groups in a copolymer prepared by polymerizing in an emulsion 50-90 wt.% of (i) a (meth)acrylic acid alkyl ester having a 4-12C alkyl group, 5-45 wt.% of (ii) an alkoxyalkyl (meth)acrylate such as methoxyethyl acrylate, or the like, 5-20 wt.% of (iii) a carboxylic acid group-containing acid such as acrylic acid, or the like, and 0-30 wt.% of (iv) a copolymerizable monomer such as vinyl acetate with 1-10 pts.wt. of (B) a basic phosphate and 5-40 pts.wt. of (C) a nonionic surfactant having 9-18 HLB based on 100 pts.wt. of the above copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive for tack paper used for paper labels, kraft tapes and the like.
The present invention relates to a water-disintegratable pressure-sensitive adhesive composition that can be easily disintegrated in water to recover waste paper when repulp is performed for the purpose of protecting resources, and that does not adversely affect recycled paper.

[0002]

2. Description of the Related Art In recent years, the importance of recycling paper has increased, and various efforts have been made to develop a pressure-sensitive adhesive that can satisfy those requirements. As an example of such an attempt, Japanese Patent Application Laid-Open No. 5-156222 discloses, for example, an alkali resin obtained by adding a surfactant capable of imparting plasticity to a copolymer mainly containing a carboxyl group-containing vinyl monomer such as (meth) acrylic acid. A melt-type adhesive composition is described.
This application is a pressure-sensitive adhesive that is soluble in alkaline water, and is accompanied by contamination of wastewater discharged in a repulping process from waste paper, and thus has a problem in terms of protection of the water environment. On the other hand, JP-A-5-70755 discloses that as base polymers, 20 to 99% by weight of alkoxyethyl acrylate, 30 to 1% by weight of styrene sulfonate and 50 to 0% by weight of other copolymerizable monomers. It is described that the pressure-sensitive adhesive comprising a copolymer of the above is redispersible in water.

[0003] The redispersion type is characterized in that the pressure-sensitive adhesive film can be recovered as a solid by being ruptured or dispersed to an appropriate size in the repulp process, thereby preventing wastewater contamination. At present, however, there are problems such as deterioration of performance and deterioration of repulpability over time in a moist heat environment, and deterioration of paper quality due to an adhesive component mixed into recycled paper.

In general, a pressure-sensitive adhesive which emphasizes repulpability is designed to increase the hydrophilicity of a polymer, so that a relatively large amount of a polar group such as a carboxyl group or a hydroxyl group is introduced. In the case of a carboxyl group, hydrophilicity is enhanced by neutralization with an alkali. Caustic alkali, ammonia, and amines are generally used as the neutralizing agent. For example, Japanese Patent Publication No. 22-22768 discloses a water-dispersible pressure-sensitive adhesive composition in which a copolymer comprising an acrylic ester and a vinyl carboxylic acid is neutralized with a secondary or tertiary alkanolamine. I have. However, this method also has a problem that the balance between the adhesive force and the cohesive force changes with time. As a cause of such a change with time, it is known that fillers such as calcium carbonate and clay used in a process of manufacturing a base paper react with carboxyl groups in a polymer to change physical properties.

[0005]

Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive which has excellent pressure-sensitive adhesive properties, and has little change with time in pressure-sensitive adhesive properties and redispersibility even under a moist heat environment.
An object of the present invention is to provide a pressure-sensitive adhesive in which the pressure-sensitive adhesive phase is redispersed in water at an appropriate size, does not contaminate water quality, and does not adversely affect the performance of recycled paper.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of a water-soluble or water-redispersible pressure-sensitive adhesive, and comprises a carboxyl group-containing monomer and a specific acrylic monomer as main components. An aqueous dispersion containing a neutralized alkali, a basic phosphate, and a specific surfactant in a copolymer obtained by emulsion copolymerization, and an adhesive that provides excellent adhesive properties and water redispersibility. The present invention relates to an agent composition.

Specifically, (a) 50 to 90% by weight of an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms and (b) 5 to 45% by weight of an alkoxyalkyl (meth) acrylate And (c) 5 to 20% by weight of a carboxyl group-containing monomer and (d) 0 to 30% by weight of another copolymerizable monomer, and part of the carboxyl group in the copolymer obtained by emulsion copolymerization. Or 1 to 10 parts by weight of a basic phosphate per 100 parts by weight of the copolymer with respect to an aqueous dispersion which is entirely neutralized with an alkali;
And HLB 9-18 nonionic surfactants in 5-4
It is a water disintegratable pressure-sensitive adhesive composition containing 0 parts by weight.

Further, the present invention provides the above-mentioned pressure-sensitive adhesive composition containing 0.1% of a fatty acid soap per 100 parts by weight of a copolymer of the composition.
It is a pressure-sensitive adhesive composition to which 2 to 3 parts by weight are added.

The alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms of the component (a) used in the copolymer of the present invention includes butyl (meth) acrylate and (meth) acrylic acid. Examples thereof include octyl acid, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, and dodecyl (meth) acrylate. This component (a) is a component that gives an adhesive force and an internal cohesive force, and requires at least 50% by weight. (B) Component alkoxyalkyl (meth)
As acrylates, methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, (meth) acrylate
Ethoxyethyl acrylate, ethoxypropyl (meth) acrylate and the like are used in an amount of 5 to 45% by weight, and particularly, methoxyethyl acrylate or methoxypropyl acrylate is copolymerized in an amount of 10 to 30% by weight. It is preferable in improving both the adhesive properties and the water redispersibility of the product.

As the carboxyl group-containing monomer of the component (c), acrylic acid, methacrylic acid, acrylic acid dimer, caprolactan adduct of (meth) acrylic acid, ethylene oxide-added succinic monoacrylate and itaconic acid, fumaric acid, maleic acid One or two or more selected from acids or monoalkyl esters thereof are used. These carboxyl group-containing monomers have a function of imparting water redispersibility to the pressure-sensitive adhesive by neutralizing with an alkali, and at least 5% by weight is required. On the other hand, if the copolymerization ratio is too high, the water solubility of the pressure-sensitive adhesive increases, leading to wastewater contamination during repulping, and the pressure-sensitive adhesive properties of the pressure-sensitive adhesive composition of the present invention are reduced.
Use no more than% by weight.

Other copolymerizable monomers of component (d) include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, vinyl acetate, styrene, α-methylstyrene, and itaconic acid. , Fumaric acid, dialkyl ester of maleic acid, 2-hydroxyethyl (meth) acrylate, ethylene oxide adduct of (meth) acrylic acid, propylene oxide adduct of (meth) acrylic acid, (meth) acrylonitrile,
(Meth) acrylamide, N-methylol (meth) acrylamide, glycidyl (meth) acrylate and the like can be mentioned. One or more monomers selected from these can be used in an amount of 0 to 30% by weight. When a vinyl monomer having a functional group such as an amide group, a hydroxyl group or an epoxy group is used among these copolymerizable monomers, a preferable amount of the vinyl monomer unit in the copolymer is 5% by weight or less, and more than 5% by weight. As the number increases, the adhesive performance decreases.

The above monomer mixture is copolymerized by a usual emulsion polymerization method in the presence of at least a polymerization initiator and an emulsifier. At that time, a chain transfer agent, a pH buffer, an alkali and the like may be added as necessary. In the obtained copolymer, a part or all of the carboxyl groups in the copolymer are neutralized with an alkali. The neutralization reaction may be performed before or after the polymerization reaction. As the alkali used for neutralization, ammonia, caustic alkalis, and amines can be used. However, when ammonia or highly volatile amines are used, the adhesive properties and redispersibility are reduced due to volatilization, and the aging of the tack paper is reduced. It is preferable to use an alkali selected from caustic alkalis and amines having low volatility, since they cause changes.

Particularly preferred alkalis in the present invention are:
Tertiary amino alcohols having a boiling point (760 mmHg) of about 220 ° C. or higher. Tertiary amino alcohols include triethanolamine, tripropanolamine,
It is a tertiary amine having 1 to 3 hydroxyl groups such as triisopropanolamine, N-methyldiethanolamine and N, N-dibutylethanolamine. One or more compounds selected from these tertiary amino alcohols are added to an aqueous dispersion of the copolymer of the present invention in an amount corresponding to 50 to 120 mol% of the carboxyl groups in the copolymer. I do. If the amount is less than 50 mol%, the adhesiveness and water redispersibility of the pressure-sensitive adhesive film are insufficient, and if the amount is more than 120 mol%, bleeding to the base paper may occur, which may cause the aging of the tack paper. A more preferred addition amount of the tertiary amino alcohol is 60 to 100 mol%. When a tertiary amino alcohol having a boiling point of about 220 ° C. or higher is used as a neutralizing agent in the aqueous dispersion of the copolymer of the present invention, the tertiary amino alcohol functions as a plasticizer for the copolymer and volatilizes over time. Little change in adhesive performance due to Also, not only has the effect of preventing a change over time in water redispersibility at the time of repulping,
This is advantageous for balancing the adhesive performance, particularly the adhesive strength and the cohesive strength.

Further, the pressure-sensitive adhesive composition of the present invention contains a basic phosphate in an amount of 1 to 10 per 100 parts by weight of the copolymer.
Use parts by weight. Part or all of the basic phosphate may be used in the emulsion polymerization of the monomer mixture. The use of a basic phosphate has the effect of suppressing the reaction between calcium carbonate used as a filler in a paper base and the carboxyl group in the adhesive, thereby preventing the adhesive performance from changing over time. As the basic phosphate used in the present invention, sodium tripolyphosphate, sodium hexametaphosphate,
Potassium pyrophosphate, sodium pyrophosphate, sodium dibasic phosphate, sodium tertiary phosphate, sodium pyrophosphate and the like can be mentioned. By using these phosphates, the tack paper produced from the pressure-sensitive adhesive composition of the present invention has significantly reduced changes in pressure-sensitive adhesive properties and redispersibility with time even under a moist heat environment. When the content of the basic phosphate is 1% by weight or less, the effect of improving the change with time is low, and when the content is 10% by weight or more, the adhesive performance is unfavorably reduced.

Further, the pressure-sensitive adhesive composition of the present invention contains H
LB9-18 nonionic surfactant was prepared by using the above copolymer 1
Use 5 to 40 parts by weight per 00 parts by weight. Use of such a surfactant has an effect of facilitating redispersion of the pressure-sensitive adhesive film in the repulping step and reducing the size of dispersed particles. As the nonionic surfactant, a water-soluble surfactant having an ethylene oxide chain at room temperature can be used.For example, polyoxyethylene lauryl ether, ether type such as polyoxyethylene stearyl ether, polyoxyethylene nonyl Alkylphenol types such as phenyl ether and polyoxyethylene octyl phenyl ether; ester types such as polyoxyethylene monolaurate and polyoxyethylene monooleate; and sorbitan esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monooleate One or two or more selected from nonionic surfactants such as ether type surfactants are used. These nonionic surfactants can be used as part or all of the emulsifier during emulsion polymerization, or may be added to the aqueous dispersion of the copolymer of the present invention. When the amount of the nonionic surfactant used is 5 parts by weight or less, the effect of improving the redispersibility is small, and when the amount is 40 parts by weight or more, the adhesive properties are reduced, and bleeding may occur on the base paper.

Still more preferably, the pressure-sensitive adhesive composition of the present invention contains 0.2 to 3 parts by weight of a fatty acid soap per 100 parts by weight of the above copolymer. The incorporation of the fatty acid soap is effective in removing the slight tackiness caused by the adhesion of the fine film of the pressure-sensitive adhesive redispersed in the repulping process to the recycled paper, and the production of the recycled paper. It is effective in preventing the paper surface from fluffing due to the adhesive in a process or the like. Examples of the fatty acid soap used include sodium or potassium salts such as palmitic acid, stearic acid, and oleic acid.

The pressure-sensitive adhesive composition of the present invention contains known adhesives, tackifiers, coloring agents, thickeners, defoamers, leveling agents, etc. for the purpose of enhancing its performance and adjusting its properties. It can be added as appropriate. In particular, by blending an aqueous dispersion of ethylene-vinyl acetate-acrylic copolymer,
This has the effect of further improving the adhesive properties, particularly the physical properties such as adhesion and cohesion to an adherend such as polyolefin. As the ethylene-vinyl acetate-acrylic copolymer, known commercial products can be used. For example, 5 to 30% by weight of ethylene and vinyl acetate 20 as described in Japanese Patent Publication No. 1-48953. A copolymer obtained by copolymerizing an alkyl (meth) acrylate having from 90 to 90% by weight and an alkyl group having from 1 to 12 carbon atoms with 5 to 50% by weight, or JP-A-2-212542. 5 to 40% by weight of ethylene, 5 to 60% by weight of vinyl acetate and an alkyl group having a carbon number of 4 to 4 as described.
18 (meth) acrylic acid alkyl esters 15
There is a copolymer obtained by copolymerizing ７０70% by weight, and those having a glass transition temperature of −30 ° C. or less are preferred.

As described above, the water-disintegratable pressure-sensitive adhesive composition of the present invention has excellent adhesive properties and can be easily disintegrated in water when repulpted after being used as a tack paper or kraft tape. Moreover, it is a pressure-sensitive adhesive that has little change with time in pressure-sensitive adhesive properties and redispersibility under a moist heat environment.
In addition, the adhesive is redispersed and retained in the pulp instead of flowing out into the wastewater as in the prior art, so that a high-quality recycled paper can be manufactured without deteriorating the quality of the wastewater.

[0019]

The present invention will be specifically described below with reference to examples. All parts and percentages in the text are based on weight. The following abbreviations were used: 2-EHA 2-ethylhexyl acrylate PL-AA Caprolactone adduct of acrylic acid (Aronix M-5300, trade name of Toagosei Chemical Industry Co., Ltd.)
AAc Acrylic acid Me-EA Methoxyethyl acrylate VAc Vinyl acetate Nonionic surfactant A: NS-210 (HLB13.3) manufactured by NOF Corporation

Example 1 65 parts of 2-ethylhexyl acrylate, 10 parts of acrylic acid
Part, caprolactone adduct of acrylic acid (trade name ARONIX M-5300, manufactured by Toagosei Chemical Industry Co., Ltd.) 5
Parts, 20 parts of methoxyethyl acrylate, 140 parts of water,
Sodium tripolyphosphate 2 parts, ammonium persulfate 0.4
Part, anionic surfactant (trade name Newcol 560)
2 parts of SF, manufactured by Nippon Emulsifier Co., Ltd.) were reacted by a conventional emulsion polymerization method to obtain an aqueous dispersion of a copolymer having a viscosity of 300 centipoise, an evaporation residue of 42.3%, a pH of 3.1, and a particle diameter of 0.65 μm. A liquid was obtained. Next, 17.4 parts of triethanolamine corresponding to 0.75 equivalent to 1 equivalent of carboxyl group in the aqueous dispersion of the copolymer was weighed, and this was added to the aqueous dispersion of the copolymer. And neutralized, 20 parts of a 15% aqueous solution of sodium tripolyphosphate and HLB1
3.3 Nonionic surfactant (trade name: Nonion NS-
210, manufactured by NOF Corporation). Thereafter, 5 parts of a thickening agent (trade name Boncoat 3750, manufactured by Dainippon Ink and Chemicals, Inc.) were added, and the mixture was adjusted to pH 7 with 25% aqueous ammonia.
The composition was adjusted to 5 to obtain a pressure-sensitive adhesive composition of the present invention.

Examples 2 to 5 A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the monomer composition, the neutralizing agent and the components were changed as shown in Table 1. Here, sodium stearate was mixed in a predetermined amount as a 3% aqueous solution.

Comparative Examples 1-4 A pressure-sensitive adhesive composition was obtained according to the method of Example 1, except that the monomer composition, the neutralizing agent and the components were changed as shown in Table 1.

The pressure-sensitive adhesive compositions obtained in Examples and Comparative Examples were tested by the following methods, and the results are shown in Table 1. Here, high-quality paper 55K was used as the base material of the tack paper to be used, and applied to a release paper at an application amount of 25 g-dry / m ² ,
After drying at ℃ for 1 minute, it was transferred to the substrate. This sample is 25
The result measured after standing at a temperature of 65 ° C. and a humidity of 65% for one day was defined as an initial value, while the result measured after aged at a temperature of 40 ° C. and a humidity of 80% for 7 days was defined as a wet heat aging.

[0023]

[Table 1]

Test Method for Adhesive Properties Adhesive force: A test piece was cut into 25 × 150 mm, and the release paper was peeled off. Then, the test piece was pressure-bonded on a SUS304 plate and a polyethylene plate using a pressure-bonding device specified in JIS Z-0237. did. After a lapse of 20 minutes, 180 ° peel adhesion was measured using a Tensilon Universal Testing Machine Model LTM-4 manufactured by Orientec Co., Ltd. However, the pulling speed is 300
Performed at mm / min. Holding force (deviation distance): Based on JIS Z-0237,
One end of the SUS304 plate with the polished test piece
It was pressure-bonded with a sticking roller so that the area of 5 × 25 mm was in contact. After a lapse of 60 minutes, one end of the test piece is fixed with a clasp so that the test piece hangs vertically, and a 1 kg weight is attached to the tip. The displaced distance after 5 hours was measured in an atmosphere at 40 ° C. When it fell on the way, it was expressed in time.

Loop tack: The test was performed using the Tensilon universal testing machine described above. The test piece was cut into 25 × 140 mm, and the both ends were joined together at 20 mm to form a loop having a diameter of 31.85 mm, which was inserted into the chuck of the Tensilon universal testing machine. Next, the polished T-shaped SUS304 plate specified in JIS Z-0237 is raised at a speed of 300 mm / min to bring the plane into contact with the loop. The minor axis of the loop is 20mm
At this point, the SUS plate was lowered at the same speed. At this time, the peel strength between the SUS plate and the test piece was defined as a loop tack.

Repulpability: In order to measure the size of the redispersed pressure-sensitive adhesive particles, 0.01 parts of a coloring agent (methyl violet) was added to 100 parts of the pressure-sensitive adhesive composition, and colored tack paper was used. Produced. 32g of the tack paper is 10mm ×
It was cut into a size of 10 mm, taken into a container, added with 150 ml of water, and immersed for 60 minutes. Next, 1850 ml of water was added to dilute the mixture, and the mixture was diluted to 3000 using a standard disintegrator manufactured by Kumagai Riki Kogyo Co., Ltd.
Disintegration was performed by operating 50,000 rotations at a speed of rpm. A hand-made sheet was prepared using 500 ml of the disintegration liquid, and the size of the pressure-sensitive adhesive particles redispersed in recycled paper was measured. ○), and 50 to 100 μm (を), 100 μm
The repulpability was evaluated as a rejection (x) when exceeding.

Recycled paper blocking resistance: The hand-made sheet prepared under the above disintegration conditions was sandwiched between filter papers in a wet state, pressurized at a surface pressure of 3.5 kg / cm ² for 2 minutes, and air-dried.
The filter paper was peeled off, and the pulp state of the hand-made sheet adhered to the filter paper surface was observed. Those with no adhesion (の), those with slight fuzz (△), and those with much adhesion (×) were observed. Was evaluated.

[0028]

The pressure-sensitive adhesive composition of the present invention comprises a specific acrylic copolymer having a carboxyl group, a basic phosphate and a nonionic surfactant as main components, and a fatty acid soap. It can be easily disintegrated when re-pulping tack paper or kraft tape using this adhesive composition, and has excellent adhesive properties and disintegration properties even in a moist heat environment. Has the feature of maintaining the long term. In addition, the adhesive in the waste paper is finely redispersed during pulping and is made together with the pulp to obtain a recycled paper that does not adversely affect the mixing of the adhesive.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 220: 26 220: 06)

Claims (2)

[Claims] 1. An alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms (a) 50 to 90.
% By weight, (b) 5 to 45% by weight of an alkoxyalkyl (meth) acrylate, (c) 5 to 20% by weight of a carboxyl group-containing monomer and (d) 0 to 30% by weight of another copolymerizable monomer. Based on an aqueous dispersion obtained by neutralizing a part or all of the carboxyl groups in the copolymer obtained by copolymerization with an alkali, 1 to 10 parts by weight of a basic phosphate per 100 parts by weight of the copolymer. Part, and HLB9-
18. A water-disintegratable pressure-sensitive adhesive composition comprising 5 to 40 parts by weight of the nonionic surfactant of No. 18. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the fatty acid soap is added in an amount of from 0.2 to 100 parts by weight of the copolymer of the composition.
A water disintegratable pressure-sensitive adhesive composition containing 3 parts by weight.