JP3123779B2 - Method for producing pressure-sensitive emulsion having heat resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat-sensitive pressure-sensitive emulsion used for adhesive tapes, adhesive labels, adhesives for automobile interior materials and the like. More specifically, in the aqueous emulsion of the solution of the tackifier resin, instead of the usual emulsification with water,
By using colloidal silica having a solid content and an aqueous emulsion and utilizing water in these, a stable emulsion is produced without causing a decrease in the solid content of the emulsion, and
By internally adding colloidal silica in the emulsion,
The present invention relates to a method for producing a pressure-sensitive emulsion, which is intended to impart heat resistance and improve the separation phenomenon during storage.

[0002]

2. Description of the Related Art Tackifying resins are used in the fields of pressure-sensitive adhesive tapes, pressure-sensitive labels, adhesives for automobile interior materials, etc., for the purpose of improving adhesive strength and adhesion to adherends, etc. It is well known that the compound is used in an aqueous emulsion such as an emulsion or a synthetic rubber latex. When the tackifying resin is added to the aqueous emulsion, an aqueous emulsion or a dispersion is usually used as the tackifying resin.

[0003]

The aqueous emulsion or dispersion of these tackifier resins is once dissolved in an organic solvent, a surfactant is blended, and water is gradually added with stirring to change from an oily to an aqueous solution. In general, a phase conversion method is adopted, and in some cases, complete aqueous conversion is carried out in a desolvation step. These solids are 40-55
% Concentrations are common and relatively expensive. As such a water-soluble emulsion, the present applicant has previously proposed Japanese Patent Application Laid-Open No. H2-255782, and even when a water-soluble emulsion or dispersion according to such a method is used for an adhesive tape, an adhesive label, or an automobile interior material, Although the adhesive performance is satisfactory, the need for high solid differentiation is high due to the recent problem of energy saving, and the emulsification method using water directly has a limitation in the high solid differentiation of the final emulsion. In addition, it cannot meet the needs for increasing the heat resistance of adhesives for the automobile field, which have been increasing in recent years.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that when producing a pressure-sensitive adhesive comprising a tackifying resin and an aqueous emulsion, a high solidification is required. For the purpose of imparting heat resistance and improving storage stability, instead of simply using water for emulsification of the tackifying resin, the emulsification method using colloidal silica and water in an aqueous emulsion is employed to achieve high solid differentiation. And by continuously administering colloidal silica and an aqueous emulsion in this order, the heat resistance and the stability during storage were measured, and the present invention was completed. That is,
The present invention, i. A homogeneous solution containing 100 parts by weight of a tackifying resin, 2 to 10 parts by weight of a surfactant, and 10 to 100 parts by weight of an organic solvent is heated and kept at a temperature in the range of 30 to 80 ° C. , and under stirring conditions,
5 to 100 parts by weight of colloidal silica as solid content continuously , ethylene vinyl acetate copolymer, acrylic
A method for producing a heat-resistant pressure-sensitive emulsion, comprising administering 100 to 500 parts by weight of a water-based emulsion selected from a liquid emulsion and a synthetic rubber latex as a solid content. B. The method for producing a heat-sensitive pressure-sensitive emulsion according to the above (a) , wherein the colloidal silica is an aqueous dispersion and the particle size is in the range of 5 to 50 μm. C. The method for producing a heat-resistant pressure-sensitive emulsion according to the above (a) , wherein colloidal silica and an aqueous emulsion are continuously administered to a homogeneous solution containing a tackifier resin, a surfactant, and an organic solvent in the order of (a). is there.

The tackifying resin used in the present invention includes natural or polymerized rosin, modified rosin and hydrogenated rosin, polyterpene resin, terpene modified product, aliphatic hydrocarbon resin, cyclopentadiene resin, aromatic petroleum resin, phenol Resins such as resins, alkylphenol acetylene-based resins, styrene-based resins, xylene-based resins, and coumarone-indene resins having a softening point of 60 to 130 ° C. may be used alone or in combination of two or more. The softening point is preferably around 100 ° C. from the viewpoint of emulsion stability, pressure sensitivity, heat resistance and the like. Surfactants used in the present invention, anionic, nonionic alone or in combination thereof, examples thereof include aliphatic salts, alkyl sulfates, alkylbenzene sulfonates,
Dialkyl sulfosuccinates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl sulfates, and the like. Among them, the emulsifying power of the tackifying resin and the foaming properties of the final product indicate emulsifying power. A dialkyl sulfosuccinate salt having a high surface tension and a high effect of lowering the surface tension is preferred. HLB (Hydrophile-Lipophile Balance) is one of the nonionics.
0 to 15 polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester,
Examples thereof include polyoxyethylene sorbitan fatty acid esters and glycerin fatty acid esters, and specifically, polyethylene glycol alkyl allyl ether is preferable from the viewpoint of the inner foamability. The usage ratio of the present surfactant is in the range of 2 to 10 parts by weight based on 100 parts by weight of the tackifying resin. More preferably, it is in the range of 4 to 7 parts by weight. When the use ratio is less than 2 parts by weight, stability at the time of emulsification is lacking, and in some cases, coarse aggregates are generated. Also, 10
When the amount is more than parts by weight, the viscosity of the final emulsion is high, and the foaming, water resistance and moisture resistance are not practical.

The organic solvent used in the present invention can be basically used as long as it can dissolve the tackifier resin. Typically, toluene, xylene, mineral spirit, benzene, petroleum benzine, n-hexane are used. , N-heptane,
As methyl ethyl ketone, acetone, alcohols, and plasticizers, dibutyl phthalate, dioctyl phthalate, and the like may be used alone or in combination of two or more. In particular, when the final emulsion is used as an adhesive, a combination of two or more kinds having different boiling points from the viewpoint of drying properties is preferable. The proportion of the present organic solvent is based on 100 parts by weight of the tackifier resin.
The range is from 10 to 100 parts by weight, preferably from 20 to 50 parts by weight. If the amount is less than 10 parts by weight, the uniform dissolution of the tackifier resin is hindered, and at the same time, the viscosity of the melt is too high to obtain a stable emulsion. On the other hand, if the amount is more than 100 parts by weight, not only the desired high solid content emulsion cannot be obtained, but also problems such as odor of the final emulsion, adverse effects on the human body, and danger of fire occur. Chip. The colloidal silica used in the present invention is a colloidal solution in which ultrafine particles of silicic acid anhydride are dispersed in water.
H9-11, viscosity 2-50 cps, specific gravity 1.11-1.50, transparent or translucent aqueous solution. Of these, the product having a particle size of 20 to 30 micron and a silicic acid content of 30 to 50% by weight is used to obtain the emulsification stability and stability during storage of the tackifying resin, and further to obtain an emulsion having a high solid content. Is preferred. The use ratio of the present colloidal silica is in the range of 5 to 100 parts by weight, preferably 10 to 50 parts by weight, as a solid content with respect to 100 parts by weight of the tackifying resin. If the amount is less than 5 parts by weight, the intended improvement in heat resistance is insignificant. If the amount is more than 100 parts by weight, the viscosity of the final emulsion is unusually increased, and at the same time, the pressure sensitivity is extremely lowered and lacks practicality.

The order of administration of the colloidal silica and the aqueous emulsion to the homogeneous solution containing the tackifier resin, surfactant and organic solvent of the present invention is as follows: first, colloidal silica is continuously administered, and then aqueous emulsion is continuously administered. This is a method for producing a pressure-sensitive emulsion by emulsifying a solution of a resin solution. This administration method results in the heat resistance and stability during storage of the pressure-sensitive emulsion. When the order of administration is reversed, no improvement in heat resistance is observed, the intended pressure sensitivity is reduced, and a separation phenomenon occurs during storage, which is not practical. Inferring the heat resistance and the effect of imparting stability during storage, it is presumed that the emulsion has a hetero-phase structure. That is, the tackifier resin becomes the core of the particles, the intermediate layer forms a colloidal silica layer, and the particle surface layer forms particles covered with the aqueous emulsion layer, so that heat resistance is imparted while maintaining pressure sensitivity. It is presumed that the stability during storage was also measured. Examples of the aqueous emulsion used in the present invention include an ethylene-vinyl acetate copolymer emulsion, an acrylic emulsion, and a synthetic rubber latex. These aqueous emulsions have a solid content of 45 to 65% and a viscosity of 1%.
Those having a particle size of 0 to 200 cps and a particle size of 0.1 to 5 microns are preferable. The use ratio of the aqueous emulsion of the present invention is 100 to 5 parts by weight based on 100 parts by weight of the tackifying resin.
It is in the range of 00 parts by weight, preferably in the range of 200 to 400 parts by weight. If the amount is less than 100 parts by weight, it is difficult to completely change the phase from oily to aqueous because the absolute water content is small, and the emulsion becomes extremely unstable. If the amount is more than 500 parts by weight, the desired high solid differentiation is hindered, the tackiness is also reduced, and the function as a pressure-sensitive emulsion-based adhesive is not exhibited.

[0008] The heating and keeping conditions of the homogeneous solution of the tackifier resin, surfactant and organic solvent of the present invention are in the range of 30 to 80 ° C. Considering the case where a low boiling point organic solvent is used in combination, the temperature is preferably in the range of 40 to 60 ° C. When emulsification is carried out at a temperature lower than 30 ° C., the viscosity of the tackifier resin at the time of dissolution is high, so that uniform emulsification becomes difficult and the stability is remarkably reduced. When the temperature is higher than 80 ° C., the low-boiling solvent causes reflux, and the final emulsion causes separation of the organic solvent, which is not practical because of stability. To describe the emulsification method of the present invention more specifically, first, a tackifier resin, a surfactant, and an organic solvent are charged into a flask equipped with a condenser, and the temperature is increased while stirring at a low speed to uniformly dissolve the tackifier resin. Next, the rotation of the stirring is increased, and a predetermined amount of colloidal silica is continuously and gradually administered. Subsequently, the aqueous emulsion is continuously administered in the same manner as the administration of colloidal silica. The viscosity gradually increases until the phase is changed from oily to aqueous, and the viscosity rapidly decreases at the next point after the phase is changed to aqueous, whereby a stable and washable emulsion can be obtained. The emulsion thus obtained is cooled to room temperature and then adjusted to pH with aqueous ammonia to form a pressure-sensitive emulsion having stable heat resistance.

At the time of production or use of the present emulsion, if necessary, an antifoaming agent, an antioxidant, a leveling agent,
You may use a coloring agent, a thickener, a filler, etc. As described above, the method for producing a heat-resistant pressure-sensitive emulsion of the present invention comprises emulsifying a tackifying resin, colloidal silica, and
It is an emulsification method that uses water in an aqueous emulsion, and because of the problems of conventional pressure-sensitive emulsions, high solid differentiation and heat resistance can be provided in a consistent manufacturing process, it is economical. It is extremely significant, and has a very high practical value as a pressure-sensitive adhesive especially in the field of bonding automotive interior materials requiring high heat resistance.

[0010]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following Examples.
The present invention will be described with reference to Examples, Reference Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, parts and percentages are by weight unless otherwise specified. Example 1 As a tackifying resin, 100 parts of ester gum S-100 [manufactured by Arakawa Chemical Industry Co., Ltd., glycerin ester of modified rosin, softening point 100 ° C], 100 parts of Neocol P [Daiichi Kogyo Seiyaku Co., Ltd. as a surfactant Co., Ltd., dialkyl sulfosuccinate, active ingredient 75%] 5 parts, and as an organic solvent, 10 parts of toluene, 10 parts of n-hexane, 3 parts of dioctyl phthalate, and 7 parts of ethyl alcohol in 1 L equipped with a condenser and a stirrer The mixture was charged into a flask and heated and dissolved at 80 ° C. while stirring at a low speed. After confirming uniform dissolution, the temperature was lowered to 50 ° C., and the rotation speed of a stirrer [Three One Motor, manufactured by Shinto Kagaku Co., Ltd.] was set to 300 rpm. In this solution, Snowtex 5 was used as colloidal silica.
0 [manufactured by Nissan Chemical Industries, Ltd., silicic acid content 50%, particle size 10-20 micron micron, specific gravity 1.375, viscosity 16c
ps] was continuously dropped at a speed of 100 g / min at a speed of 100 g / min, and subsequently as an aqueous emulsion, Structbond 1351 [SBR latex manufactured by Mitsui Toatsu Chemicals, Inc.
Solid content 48%, viscosity 150cps, glass transition temperature -3
[0 ° C] 600 parts was continuously dropped by the same operation as colloidal silica. The resulting emulsion was adjusted to a pH of 8 using aqueous ammonia diluted to 14%, and then filtered through a 100-mesh wire net to obtain a heat-sensitive pressure-sensitive emulsion of the present invention. The physical properties of the emulsion were evaluated by the following methods,
The results are shown in Table 3.

Reference Example-Method for Evaluating Physical Properties (1) Stability of emulsification 100 g of the emulsion immediately after pH adjustment was collected, and 1
The solution was filtered through a 00 mesh wire mesh, and the residue was dried in a dryer at 100 ° C. for 1 hour. The difference in weight from the original wire mesh was indicated in mg.
(If the value is large, it means that large particles are frequently generated and lack stability.) (2) Stability during storage 100 g of the emulsion is collected in a 100 cc glass measuring cylinder, and a 40 ° C constant temperature bath is used. After standing for one week, the separation was visually observed, and when the graduated cylinder was tilted and the emulsion was transferred to another container, the presence or absence of abnormal deposits on the lower portion of the cylinder was observed and indicated as follows. 〇 → Separation, no abnormal deposit on lower part of cylinder △ → Slight separation, abnormal adhesion on lower part of cylinder × → Separation, large extraneous deposit on lower part of cylinder (3) Measurement of pressure-sensitive adhesiveness 150g / on stainless steel plate m ² of this emulsion was uniformly applied, dried for 2 minutes in a drier at 100 ° C., left at room temperature for 5 minutes, immediately pressed with a 40 mm cotton cloth having a width of 25 mm, and peeled 180 ° after 30 minutes using a Tensilon tensile tester. The strength was measured and expressed as peel strength per kg / 25 mm. (4) Heat resistance A sample was prepared by the same operation as in the pressure-sensitive adhesion test, and
A 350 g weight is hung in the shearing direction in a 0 ° C. constant temperature bath, and is indicated by the time until the weight falls. (A larger value indicates better heat resistance.)

[0012]

[Table 1] Table-1

Examples 2 to 12 Heat-resistant pressure-sensitive emulsions of the present invention were produced according to the method of Example 1 under the composition conditions shown in Table 1, and subjected to the same evaluation as in Example 1. Table 3 shows the results. Comparative Examples 1 to 7 According to the method of Example 1, under the composition conditions shown in Table 2,
A pressure-sensitive emulsion was manufactured and subjected to the same test as in Example 1, and the results are shown in Table-3.

[0014]

[Table 2]

[0015]

[Table 3] Table-3

[0016]

[Table 4]

[0017]

As is evident from Table 3, the method of the present invention is capable of emulsifying a tackifying resin without using water in a homogeneous solution of a tackifying resin, a surfactant and an organic solvent. This is a method of directly emulsifying with colloidal silica and an aqueous emulsion, that is, a method of emulsifying using water in these, and an emulsion having a high solid content can be easily obtained, and colloidal silica is present in the emulsion particles. The stability during storage is remarkably improved, high heat resistance not found in conventional pressure-sensitive emulsions is also obtained, and furthermore, the combination of tackifying resin, colloidal silica and aqueous emulsion is performed in an integrated process. Practical value as a pressure-sensitive adhesive in the bonding of automotive interior materials is extremely high, especially for heat-resistant adhesive tapes and adhesive labels.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-68868 (JP, A) JP-A-62-68870 (JP, A) JP-A-4-342502 (JP, A) JP-A 60-68850 51769 (JP, A) JP-A-58-40377 (JP, A) JP-A-4-342728 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 1 / 00-201 / 10 C08L 1/00-101/16

Claims (3)

(57) [Claims] 1. A homogeneous solution containing 100 parts by weight of a tackifier resin, 2 to 10 parts by weight of a surfactant, and 10 to 100 parts by weight of an organic solvent is heated and kept at 30 to 80 ° C. under stirring conditions. , Continuously using colloidal silica as solid
To 100 parts by weight and an ethylene-vinyl acetate copolymer,
Selected from Krill emulsion and synthetic rubber latex
A method for producing a heat-sensitive pressure-sensitive emulsion, comprising administering 100 to 500 parts by weight of an aqueous emulsion as a solid content. Wherein the colloidal silica is an aqueous dispersion, and wherein the particle size is in the range of 5-50 micro microns
Item 6. A method for producing a heat-sensitive pressure-sensitive emulsion according to item 1 . 3. The heat resistance according to claim 1 , wherein colloidal silica and an aqueous emulsion are continuously administered to a homogeneous solution containing a tackifier resin, a surfactant and an organic solvent in the order of: A method for producing a pressure-sensitive emulsion having: