JPH0449866B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aqueous suspensions of sticky microspheres. More specifically, the present invention relates to an aqueous sticky microsphere suspension having the characteristics that the particle size distribution of the microspheres in the suspension is narrow and that it is difficult to swell with a solvent. In recent years, researchers have discovered that microspheres of adhesive resin are lined up and adhered to the surface of paper, the side of the paper where the microspheres are lined up is pasted to another surface, then peeled off, reattached, and then peeled off again. There are office supplies on the market that can be repeatedly attached and detached. This utilizes the characteristics of sticky resin microspheres with particle diameters ranging from several microns to several hundred microns. That is, since the spherical adhesive resin is lined up on the surface of the paper like the suction cups of an octopus, when another surface comes into contact with that surface, adhesion occurs at countless points and both surfaces are bonded. Then, when both sides are peeled off, the adhesive resin microspheres are exposed as they are because they are peeled off from the point-adhesive area, and can be reattached to the adherend. Such repeatedly removable paper is obtained by applying a suspension of adhesive resin microspheres to the paper. However, when a solvent solution or water-based emulsion of an adhesive resin is applied to paper, an adhesive film is formed on the surface of the paper, and when the paper is attached to an adherend, surface adhesion occurs, so when the paper is peeled off, It does not peel off at the interface, causing delamination between the paper layers and making it impossible to stick it again. Furthermore, even when applied using a suspension, when the particle size reaches 1000 microns (1 mm), the number of contact points per unit area decreases, resulting in weak adhesive strength, and the adhesive area becomes thick, making it practical. Not on point. Therefore, it is preferable that microspheres with an average particle diameter of several microns to several hundred microns are closely arranged on the surface of the paper. Further, it is preferable that the shape of the fine spheres be as true as possible. If the paper is crushed like a rugby ball, it becomes close to surface adhesion, and the adhesive strength becomes strong, causing paper layer separation (paper tearing). Further, it is preferable that the particle size distribution is as narrow as possible. This is because only large particles selectively participate in adhesion, resulting in weak adhesion and impractical use. By the way, this type of sticky resin microspheres that have been known in the past are manufactured by suspension polymerizing acrylic monomers in water using an oil-soluble polymerization initiator. There is no problem when applying an aqueous suspension of microspheres to a non-water-absorbing substrate, but when applied directly to paper, the paper curls due to moisture and its commercial value is significantly reduced. , water, which is the solvent of the aqueous suspension, is replaced with a solvent such as toluene, ethyl acetate, or 1,1,1-trichloroethane, and the resulting suspension is applied to paper as a solvent-based suspension. Moreover, by using a solvent-based material, it has the advantage that it has a faster drying rate than a water-based material and has extremely good mechanical stability. However, even if a poor solvent with low affinity is selected, conventionally used resins tend to swell to varying degrees and adherent microspheres fuse together to form fibroids. Therefore, surface adhesion occurs with other adhered surfaces, and when peeled off, the paper layer peels, resulting in poor re-adhesion. The present inventor has made it difficult to swell in solvents, and
We investigated internal crosslinking of the adhesive resin in order to provide appropriate adhesive performance. That is, when carrying out the polymerization reaction, an attempt was made to add an appropriate amount of a monomer having two polymerizable functional groups to carry out the polymerization. Polymerization was performed using divinylbenzene, butanediol diacrylate, ethylene dimethacrylate, and diacetone acrylamide as crosslinking monomers, but all of them had poor reactivity and did not crosslink uniformly, so they were replaced with a solvent. When it was applied to paper, it swelled and dissolved in some areas, and when it was applied to paper, it flowed and formed a film, which was adhered everywhere. If the amount of crosslinkable monomer used is increased in order to minimize solvent swelling, the tackiness will decrease and the tackiness will become insufficient. The present inventor conducted further studies and polymerized with different types of internal crosslinking monomers, and found that tetraallyloxyethane, triallyl cyanurate, and triallyl isocyanurate had extremely high reactivity. We discovered that because of uniform internal crosslinking, even if the water in the suspension medium is replaced with a solvent, it is possible to obtain an aqueous suspension of perfectly spherical microspheres with uniform particles that do not swell or dissolve. completed. That is, the present invention comprises: (a) acrylate of alcohol having 1 carbon number and/or methacrylate of alcohol having 1 to 5 carbon atoms and/or 2 to 10% by weight of styrene; (b) acrylate of alcohol having 2 to 12 carbon atoms and/or styrene; or methacrylate of alcohol having 6 to 12 carbon atoms 98 to 90% by weight (c) maleic anhydride 0.1 to 2.0% by weight (d) one or two selected from tetraallyloxyethane, triallyl cyanurate, triallyl isocyanurate A sticky microsphere aqueous suspension consisting of microspheres with a particle diameter of 5 to 200 microns made of an internally crosslinked copolymer obtained by copolymerizing 0.05 to 1.0% by weight, water, and a suspension stabilizer. be. The acrylate of alcohol having 1 carbon number shown in item (a) used in the present invention is methyl acrylate, and the homopolymer of this acrylate has a glass transition temperature (Tg) of 8°C. In addition, methacrylates of alcohols having 1 to 5 carbon atoms include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and pentyl methacrylate.
The Tg of each homopolymer is 105, respectively.
℃, 66℃, 35℃, 21℃, 10℃. Furthermore, the Tg of styrene homopolymer is 100°C. That is, all of the monomers shown in item (a) have a homopolymer Tg of 0°C or more and around 100°C. Furthermore, the acrylates of alcohols having 2 to 12 carbon atoms and/or the methacrylates of alcohols having 6 to 12 carbon atoms shown in item (b) include ethyl acrylate (Tg=-22°C), butyl acrylate (Tg=
-52℃), 2-ethylhexyl acrylate (Tg
= -70℃), hexyl methacrylate (Tg = -5
℃), the monomers shown in item (b) all exhibit a homopolymer Tg of less than 0℃ minus several 10℃. 2 to 10% by weight of the monomer in section (a) and 98 to 10% by weight of the monomer in section (b)
The reason for using 90% by weight is to essentially impart adhesive properties to the resulting resin. Adhesive resin cannot be obtained outside this range. The maleic anhydride in item (c) is used in an amount of 0.1 to 2.0% by weight in order to carry out the polymerization reaction smoothly and obtain a stable suspension. Tetraallyloxyethane in paragraph (d) is It is shown by the structural formula, and triallyl cyanurate is It is shown by the structural formula, and triallylisocyanurate is It is shown by the structural formula: Compared to ordinary internal crosslinking agents, it has 3 polymerizable functional groups.
It is thought that the reactivity is extremely high, and that the internal crosslinking occurs uniformly. These may be used alone or in combination. The amount used is suitably 0.05 to 1.0% by weight. If it is less than 0.05% by weight, the internal crosslinking effect will be small, resulting in insufficient solvent resistance, and if it is more than 1.0% by weight, crosslinking will proceed too much and adhesive performance will deteriorate, which is not preferable. In the present invention, other monomers may be used in amounts that do not impair adhesive performance, such as N-methylolacrylamide, acrylonitrile, ethylene, vinyl chloride,
Vinyl acetate, Beoba (trade name of vinyl ester manufactured by Ciel Chemical), etc. can be used in combination within a range of 10% by weight or less. As a method for producing the aqueous suspension of sticky microspheres of the present invention, a known suspension polymerization method is used. For example, polymerization method by bulk charging, monomer dropwise polymerization method,
Examples include emulsifying monomer drop polymerization method. As a polymerization initiator, benzoyl peroxide, azobisisobutyronitrile, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl ) Peroxydicarbonate, tert-
Oil-soluble starters such as butyl peroxy neodecanoate, tert-butyl peroxy pivalate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, dipropionyl peroxide, diacetyl peroxide, etc. agent is used. Suspension stabilizers include polyvinyl alcohol,
Water-soluble polymers such as hydroxyethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose, and carboxy-modified polyacrylamide are used. Moreover, an anionic surfactant and a nonionic surfactant can be used in combination. In particular, in order to stably produce a suspension, it is preferable to use a large amount of anionic surfactant. The particle diameter of the microspheres is suitably within the range of 5 microns to 200 microns. Therefore, the width of the particle size distribution containing 80% of the microspheres is preferably about 10 microns when the average particle diameter is around 5 microns, and about 30 microns when the average particle diameter is around 200 microns. The aqueous suspension of adhesive microspheres of the present invention has extremely good retention of the spherical shape because the microspheres are internally crosslinked, and when used as an adhesive,
Since contact with the object to be adhered is maintained by point adhesion of the sphere, re-adhesion is extremely good. This effect is effectively achieved both when water is replaced with an organic solvent and when the aqueous dispersion is used as it is. Of course, as mentioned above, the problem of swelling, which could not be solved in the past when replacing water with an organic solvent, has been completely solved. Next, the present invention will be explained with reference to Examples and Comparative Examples. Example 1 Methyl methacrylate 20 parts by weight (4.7%) 2-ethylhexyl acrylate
400 〃 (94.1%) Tetraallyloxyethane
1.0〃 (0.24%) maleic anhydride 4.0〃 (0.94%) consisting of an internally crosslinked copolymer, 80% of which has a particle size of 80 to 100 microns,
A viscous microsphere aqueous suspension consisting of water and a suspension stabilizer. This product was manufactured as follows. (Ingredients) (Parts by weight) Methyl methacrylate 20 2-ethylhexyl acrylate 400 Tetraallyloxyethane 1.0 Maleic anhydride 4.0 Sodium polyacrylate (degree of polymerization 3000-7000) 16 Water 600 Benzoyl peroxide 2.0 Sodium dodecylbenzenesulfonate 20 or more A polymerization reaction was carried out using the following components to obtain an aqueous suspension of sticky microspheres, 80% of which had a particle size of 80 to 100 microns. Example 2 Styrene 12 parts by weight (2.9%) Butyl acrylate 390〃 (95.6%) Triallylisocyanurate
1.0〃 (0.25%) maleic anhydride 5〃 (1.2%) consisting of an internally crosslinked copolymer, 80% of which has a particle size of 15 to 50 microns, suspended in water and Aqueous suspension of sticky microspheres consisting of stabilizers. This product was manufactured as follows. (Ingredients) (Parts by weight) Styrene 12 Butyl acrylate 390 Triallylisocyanurate 1.0 Maleic anhydride 5 Hydroxyethyl cellulose 20 Water 600 Benzoyl peroxide 2.0 Sodium dodecylbenzenesulfonate 20 A polymerization reaction is carried out using the above components to achieve a yield of 80% obtained an aqueous suspension of sticky microspheres with a particle size of 15-50 microns. Example 3 Methyl methacrylate 32 parts by weight (7.3%) Isononyl acrylate
400 〃 (91.5%) Triallyl cyanurate
3.7〃 (0.85%) maleic anhydride 1.5〃 (0.34%) consisting of an internally crosslinked copolymer, 80% of which has a particle size of 45-70 microns, suspended in water. Aqueous suspension of sticky microspheres consisting of stabilizers. This product was manufactured as follows. (Ingredients) (Parts by weight) Methyl methacrylate 32 Isononyl acrylate 400 Triallyl cyanurate 3.7 Maleic anhydride 1.5 Polyvinyl alcohol 15 Water 600 Benzoyl peroxide 2.0 Sodium dodecylbenzenesulfonate 20 A polymerization reaction is carried out using the above components, An aqueous suspension of 80% sticky microspheres with a particle size of 45-70 microns was obtained. Example 4 Methyl methacrylate 32 parts by weight (7.3%) Isononyl acrylate
400 〃 (91.8%) Tetraallyloxyethane
2 (0.46%) maleic anhydride 1.5 (0.34%) consisting of an internally crosslinked copolymer, 80% of which has a particle size of 35 to 60 microns, suspended in water. Aqueous suspension of sticky microspheres consisting of stabilizers. This product was manufactured as follows. (Components) (Parts by weight) Methyl methacrylate 32 Isononyl acrylate 400 Tetraallyloxyethane 2 Maleic anhydride 1.5 Polyvinyl alcohol 15 Water 600 Benzoyl peroxide 2.0 Sodium dodecylbenzenesulfonate 20 A polymerization reaction is carried out using the above components, An aqueous suspension of 80% sticky microspheres with a particle size of 35-60 microns was obtained. Comparative Example 1 Consisting of a copolymer obtained by copolymerizing in Example 1 without using tetraallyloxyethane,
Aqueous suspension of viscous microspheres with 80% particle size between 80 and 100 microns. The manufacturing method was based on Example 1. Comparative Example 2 In Example 1, 6.5 parts by weight of tetraallyloxyethane (1.5% by weight based on the total monomers) was copolymerized to form an internally crosslinked copolymer, and 80% of the particles were particles. Aqueous suspension of microspheres 80-100 microns in diameter. The manufacturing method was based on Example 1. Comparative Example 3 In Example 2, 2.0 parts by weight of divinylbenzene was used in place of 1.0 parts by weight of triallylisocyanurate to form an internally crosslinked copolymer, 80% of which had a particle size of 15 to 50. Aqueous suspension of micron microspheres. The manufacturing method was based on Example 2. Comparative Example 4 An internally crosslinked copolymer obtained by copolymerizing Example 3 except that triallyl cyanurate was changed to 6 parts by weight (1.4% by weight based on the total monomers), 80% of which was copolymerized. Aqueous suspension of microspheres with particle size 45-70 microns. The manufacturing method was the same as in Example 3. Comparative Example 5 In the production of Example 4, polymerization was carried out in the same manner as in Example 4 except that maleic anhydride was not used, but a large amount of aggregates were formed during the reaction and the target product could not be obtained. . Comparative Test 1 The aqueous suspensions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were added to methanol to coagulate, and after washing, the lumpy resin was taken out and reconstituted in various organic solvents shown in Table 1. A solvent-based suspension with a concentration of approximately 25% was prepared by dispersing the particles, and the degree of swelling of the particles was examined. The results were as shown in Table 1. (Test method) Particle swelling degree (rate of change) Approximately 30 g/m ² of the above solvent-based suspension was applied to a polyester film with a thickness of 38 microns, and the rate of change in particle diameter was determined immediately after application and after 30 minutes at room temperature. This was defined as the degree of swelling of the particles. Rate of change = Particle diameter immediately after application/Particle diameter after 30 minutes However, the particle diameter was measured using a microscopic photograph. Comparative test 2 Coponil 4081 (a 50% methanol solution of acrylic/vinyl acetate copolymer resin manufactured by Nippon Gosei Chemical Industry Co., Ltd.) was applied as an undercoat to high-quality paper (55K).
1.5 g/m ² was applied and dried, and then the solvent-based suspension prepared in Comparative Test 1 was applied with a solid content of approximately 7.5 g/m ² and dried with hot air at 40°C for 30 minutes to make it pressure sensitive. An adhesive sheet was prepared and the number of times of repeated adhesion/peeling was examined. The results were as shown in Table 1. (Test method) Number of repeated adhesion/peeling The adhesion/peeling was repeated on the printed newspaper surface, and the number of times until it stopped adhering was determined. We also checked for peeling of the print (paper tearing phenomenon). 【table】

Claims (1)

[Claims] 1(a) Acrylate of alcohol having 1 carbon number and/or methacrylate of alcohol having 1 to 5 carbon atoms and/or styrene 2 to 10% by weight Acrylate of alcohol having 2 to 12 carbon atoms and/or Methacrylate of alcohol having 6 to 12 carbon atoms 98 to 90% by weight (c) Maleic anhydride 0.1 to 2.0% by weight (d) One or two selected from tetraallyloxyethane, triallyl cyanurate, and triallyl isocyanurate A sticky microsphere aqueous suspension comprising microspheres with a particle size of 5 to 200 microns made of an internally crosslinked copolymer obtained by copolymerizing 0.05 to 1.0% by weight of the above, water, and a suspension stabilizer.