JPH04323289A - Aqueous dispersion type tacky agent composition - Google Patents

Abstract

PURPOSE:To obtain a composition having excellent initial bond strength, bond strength to.rough face, bond strength to a low polar material to be bonded and excellent high-temperature cohesive force, comprising a mixture of specific two kinds of aqueous dispersions, polymers consisting essentially of an acrylic alkyl ester monomer. CONSTITUTION:The objective composition comprising a mixture of (A) 5-95wt.% (calculated as solid content) aqueous dispersion of a copolymer having 0.01-1mum) average particle diameter and <35-wt.% gel content and (B) 95-5wt.% aqueous dispersion of a copolymer having an average particle diameter twice that of the component A and 0.1-3mum and >=35wt.% gel content, obtained by subjecting a monomer mixture consisting essentially of an acrylic acid alkyl ester monomer containing preferably 2-8C alkyl group to emulsion polymerization in an aqueous medium.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous dispersion adhesive composition having a high level of well-balanced adhesive performance.

0002

[Prior Art] In recent years, in the field of adhesives, there has been a strong demand for solvent-free adhesives from the perspectives of pollution control, health and safety, and resource conservation. Adhesives are being replaced.

0003

[Problems to be Solved by the Invention] However, water-based dispersion adhesives have not yet reached the level of solvent-based adhesives in terms of adhesive performance. type adhesives have been used, and further improvements in aqueous dispersion type adhesives are desired. One of the major drawbacks of aqueous dispersion type adhesives is that it is extremely difficult to balance the adhesive properties. In other words, initial adhesion (tack), adhesion to rough surfaces, adhesion and cohesive force to low polarity adherends such as polyolefin (
In order to improve the former adhesive performance, methods such as lowering the molecular weight or adding a tackifying resin are generally known. In such cases, the cohesive force, especially the holding power at high temperatures, is significantly impaired, and it is difficult to maintain a high level of well-balanced adhesive performance. Conventionally, in response to the above problems,
Improvement studies have been carried out mainly on water-based dispersion type acrylic pressure-sensitive adhesives, but no effective means have been found so far. In particular, there are only a few studies on improving adhesive performance that focus on particle size, which is an important factor for aqueous dispersions. Among them, for example, JP-A No. 63-234076 discloses a composition in which particles having a specific average particle size are mixed in a specific ratio in an aqueous dispersion type acrylic adhesive. However, according to the research of the present inventors, as proposed above, it is not possible to balance the adhesive properties at a high level by simply mixing particles whose particle diameters have two peaks in a copolymer with the same composition. That is not enough. An object of the present invention is to provide an aqueous dispersion adhesive composition that overcomes the drawbacks of conventional aqueous dispersion adhesives and has a high level of well-balanced adhesive performance.

0004

[Means for Solving the Problems] In order to solve these problems, the present inventors have conducted intensive research focusing on the fact that the particle size of an aqueous dispersion has an extremely large effect on adhesive performance. , in an aqueous dispersion of a copolymer containing an acrylic acid alkyl ester as a main component, a mixture of dispersions having a specific average particle diameter is determined, the average particle diameter ratio of each dispersion is specified, and each dispersion is It has been discovered that by using a specific copolymer composition with a different composition, a pressure-sensitive adhesive composition having a high level and well-balanced adhesive performance can be obtained, and the present invention has been achieved.

That is, the present invention contains the following two types of aqueous dispersions A and B obtained by emulsion polymerization of a monomer mixture containing an acrylic acid alkyl ester monomer as a main component in an aqueous medium, The mixing ratio of A is 5 to 95% by weight (in terms of solid content),
An aqueous dispersion type adhesive composition characterized in that it is a mixture containing 95 to 5% by weight of B. (1) A is an aqueous dispersion with an average particle size in the range of 0.01 to 1 μ and a copolymer gel content of less than 35% by weight. (2) B is an aqueous dispersion with an average particle size smaller than that of A. An aqueous dispersion in which the gel content of the copolymer is 35% by weight or more, which is 2 times or more and is in the range of 0.1 to 3μ.

Examples of the acrylic acid alkyl ester monomer used in the present invention include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, and acrylic acid. Examples include octyl, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, etc., but particularly desirable ones include those having 2 carbon atoms.
It is an acrylic acid alkyl ester having ~8 alkyl groups. In addition to these main monomers, other monomers copolymerizable therewith can also be used. Examples of such copolymerizable monomers include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, acrylamide, and methacrylate. Functional group-containing monomers such as amide and N-methylolacrylamide, methacrylic acid alkyl ester monomers such as methyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, and other vinyl monomers such as vinyl acetate, styrene, acrylonitrile, and vinyl chloride. Examples include crosslinkable monomers such as butadiene, divinylbenzene, (poly)ethylene glycol diacrylate, (poly)ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.

[0007] In order to obtain an aqueous dispersion of these monomer mixtures, conventional emulsion polymerization methods known in the art are applied. That is, in an aqueous dispersion system basically consisting of water, a monomer mixture, a surfactant, a chain transfer agent (polymerization degree regulator), and a radical polymerization initiator, the monomer mixture is mixed into an aqueous dispersion of copolymer particles. It can be synthesized using the same manufacturing method. The copolymer particle concentration at this time is generally appropriate in the range of 30 to 70% by weight. Examples of the surfactant include fatty acid soap,
Anionic surfactants such as rosin acid soaps, alkyl sulfonates, alkylbenzene sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylaryl sulfates, polyoxyethylene Examples include nonionic surfactants such as alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitan fatty acid esters, and oxyethylene oxypropylene block copolymers. It is usually used as an anionic surfactant alone or in a mixed system of an anionic surfactant and a nonionic surfactant, and the proportion used in the monomer mixture is generally in the range of 0.01 to 5% by weight. . Examples of the chain transfer agent include mercaptans such as n-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan, and mercaptoethanol, and halogenated hydrocarbons such as carbon tetrachloride. Examples of the radical polymerization initiator include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, peroxides such as hydrogen peroxide, benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. , 2,2-azobisisobutyronitrile and other azobis compounds, among which persulfates are most preferred. In addition, the polymerization temperature is usually 60 to 90°C.
However, low-temperature redox polymerization in which a reducing agent such as sodium bisulfite, ascorbic acid (salt), Rongalit, etc. is combined with a radical polymerization initiator can also be used. If desired, P such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, etc.
Polymerization regulators such as H regulators can also be added. The particle size of the aqueous dispersion particles varies depending on various polymerization factors such as monomer mixture composition and polymerization temperature, but the particle size is generally controlled by the proportion of surfactant used, and It will be simpler if a seed polymerization method is used.

The average particle diameter of the aqueous dispersion in the present invention is measured using a submicron particle analyzer model N4SD (manufactured by Coulter Electronic Co., Ltd.). In addition, the gel content of the copolymer obtained by emulsion polymerization varies depending on various polymerization factors as well as the particle size, but the gel content is generally controlled by using chain transfer agents and crosslinking monomers. It's simple. The gel content in the present invention is 3
1 g of the copolymer dried under reduced pressure at 0°C was immersed in 200 cc of tetrahydrofuran at 30°C for 24 hours, filtered through a glass filter (No. 3), and the original weight of the filtered copolymer was is the ratio to the copolymer weight.

[0009] In the aqueous dispersion (A) of the present invention, the average particle diameter is in the range of 0.01 to 1 μ, and the gel content of the copolymer is 35% by weight.
Preferably, the average particle diameter is in the range of 0.05 to 0.5μ, and the gel content of the copolymer is less than 25% by weight. In addition, the aqueous dispersion (B) has an average particle diameter in the range of 0.1 to 3μ and is at least twice as large as that of the aqueous dispersion (A), and furthermore, the copolymer contains gel. Preferably, the average particle diameter is in the range of 0.5 to 1.5μ, and the gel content of the copolymer is 45 to 85% by weight. be. If it falls within the above range, the effects of the present invention will be more than fully exhibited, but if it deviates from these ranges, the object of the present invention cannot be achieved. That is, when the average particle diameter of the aqueous dispersion (A) is less than 0.01μ, the viscosity of the aqueous dispersion increases significantly, making stable production difficult and making it difficult to increase the copolymer particle concentration. However, it is extremely difficult in practice. Moreover, if it exceeds 1μ, it becomes difficult to obtain a satisfactory cohesive force. In addition, the gel content of the copolymer is 3
If it exceeds 5% by weight, satisfactory adhesive performance such as initial tack cannot be obtained. If the average particle diameter of the aqueous dispersion (B) is less than twice that of the aqueous dispersion (A) or less than 0.1μ, it is extremely difficult to maintain the balance of adhesive performance at a high level, which is the objective of the present invention. It becomes difficult to use and aqueous dispersion (A
), the viscosity becomes relatively high, making it impossible to increase the copolymer particle concentration, which is inconvenient in practice. Also 3μ
Even if it exceeds 100%, there are problems in production, polymerization stability, storage stability, etc., and film forming properties during drying are also hindered, which is practically inconvenient. Furthermore, if the gel content of the copolymer is less than 35% by weight, it becomes difficult to obtain a satisfactory cohesive force. Furthermore, the present invention requires a mixture of the aqueous dispersion (A) and the aqueous dispersion (B), and the mixing ratio of the aqueous dispersion (A) is from 5 to 95% in terms of solid content weight. Must be within the range of % by weight. That is, if it is outside this range, the object of the present invention will not be achieved. Preferably, the mixing ratio of the aqueous dispersion (A) is 3% based on the solid content weight.
When the content is 0 to 80% by weight, the effects of the present invention are more than fully exhibited. The aqueous dispersion type adhesive of the present invention can be used with addition of a plasticizer, tackifier resin, thickener, PH adjuster, wetting agent, fungicide, etc., as necessary. Supports to which the aqueous dispersion type adhesive of the present invention is processed include, for example, papers such as high-quality paper, art paper, coated paper, and kraft paper, and films such as polyethylene, polypropylene, polyester, acetate, and polyvinyl chloride. Alternatively, a complex of these can be mentioned.

0010

[Examples] In order to explain the present invention more specifically, Examples and Comparative Examples will be given below, but the present invention is not limited to these Examples. In addition, parts indicate parts by weight.

Production Example 1 [Aqueous Dispersion (A)] 96 parts of distilled water, 0.3 parts of sodium dodecylbenzenesulfonate, and 1 part of potassium persulfate were placed in a temperature-adjustable reactor equipped with a nitrogen inlet tube and a stirrer. After charging .0 parts and raising the temperature to 70°C under a nitrogen stream, 66 parts of 2-ethylhexyl acrylate, 116 parts of butyl acrylate, 12 parts of methyl acrylate, 4 parts of 2-hydroxyethyl methacrylate, 2 parts of acrylic acid, and t- A monomer mixture consisting of 0.6 parts of dodecyl mercaptan was mixed with 0.8 parts of sodium dodecylbenzenesulfonate and 68 parts of distilled water.
The monomer emulsion that was emulsified and dispersed in the copolymer was added continuously over 3 hours, and the reaction was further continued at 80°C for 3 hours to complete the polymerization, yielding an aqueous dispersion with a copolymer particle concentration of 55%. Ta. This aqueous dispersion had an average particle diameter of 0.14 μm and a gel content of 21%. Production Example 2 [Aqueous dispersion (B)] In the same apparatus as Production Example 1, 68 parts of distilled water and 0.005 parts of sodium dodecylbenzenesulfonate were added.
1 part, 2.0 parts of potassium persulfate, and 7 parts of potassium persulfate were added.
After raising the temperature to 0°C, a monomer mixture consisting of 66 parts of 2-ethylhexyl acrylate, 116 parts of butyl acrylate, 12 parts of methyl acrylate, 4 parts of 2-hydroxyethyl methacrylate, and 2 parts of acrylic acid was added to sodium dodecylbenzenesulfonate. A monomer emulsion emulsified and dispersed in 0.8 parts and 68 parts of distilled water was continuously added over 5 hours,
The reaction was further continued at 80° C. for 3 hours to complete polymerization, and an aqueous dispersion having a copolymer particle concentration of 60% was obtained. The average particle size of this aqueous dispersion was 0.64μ, and the gel content was 48%.
Met. Production Example 3 [Aqueous dispersion (B)] In the same apparatus as Production Example 1, 68 parts of distilled water and 0.001 parts of sodium dodecylbenzenesulfonate were added.
1.0 parts of potassium persulfate and 6 parts of potassium persulfate were added.
After raising the temperature to 5°C, 116 parts of 2-ethylhexyl acrylate, 56 parts of butyl acrylate, and 20 parts of vinyl acetate were added.
parts, 4 parts of 2-hydroxyethyl methacrylate, 2 parts of methacrylic acid, 2 parts of acrylamide, 2 parts of divinylbenzene
A monomer emulsion prepared by emulsifying and dispersing a monomer mixture consisting of 1.0 parts of sodium dodecylbenzenesulfonate in 1.0 parts of sodium dodecylbenzenesulfonate and 68 parts of distilled water was added continuously over 6 hours, and then at 80°C for 3 hours. The reaction was continued to complete the polymerization, and an aqueous dispersion having a copolymer particle concentration of 60% was obtained. The average particle diameter of this aqueous dispersion was 0.87μ, and the gel content was 75%. Production Example 4 [Aqueous Dispersion of Comparative Example] To the monomer mixture of Production Example 2, t
An aqueous dispersion having a copolymer particle concentration of 60% was obtained in the same manner as in Production Example 2 except that 0.6 parts of -dodecyl mercaptan was added. The average particle size of this aqueous dispersion is 0.66μ
, the gel content was 19%. Production Example 5 [Aqueous Dispersion of Comparative Example] Copolymer particles were prepared in the same manner as Production Example 1 except that t-dodecylmercaptan was omitted from the monomer mixture of Production Example 1 and 2 parts of divinylbenzene was added. An aqueous dispersion with a concentration of 55% was obtained. This aqueous dispersion had an average particle diameter of 0.16 μm and a gel content of 74%.

Example 1 After mixing 40% by weight of the solid content of the aqueous dispersion of Production Example 1 and 60% by weight of the solid content of the aqueous dispersion of Production Example 2, the pH was adjusted to 8.5 with aqueous ammonia. Next is Primal ASE
Add a small amount of -60 (thickener: manufactured by Nippon Acrylic Co., Ltd.) to approx.
The viscosity increased to 000 cps. This was coated on release paper to a dry weight of about 20 g/m2, dried at 100°C for 3 minutes, and then transferred to high-quality paper to prepare a sample for measuring adhesive properties. Physical properties were measured by the following method. 1) Initial adhesive strength: A looped test piece of 25 mm width and 250 mm length was attached to a weight (50 g increments) with a polyethylene adherend attached to the upper horizontal surface in an atmosphere of 20°C, with an adhesive area of 25 mm x 3 at 25mm and 10g load
After pressure bonding for seconds, the weight was immediately pulled upward, and the weight of the maximum weight that could maintain the bond for 20 seconds or more was defined as the initial bond strength. 2) Adhesive force A test piece with a width of 25 mm and a length of 150 mm was pressure-bonded to polyethylene and K liner at a speed of 300 mm/min using a 2 kg rubber roll in an atmosphere of 20°C. After 30 minutes of crimping, the peeling strength was measured using a Tensilon type tensile tester at a loading speed of 30 mm/min. 3) Holding force A test piece with a width of 25 mm and a length of 150 mm was bonded to a stainless steel plate (SUS304) with an area of 25 mm x 2 using a 2 kg rubber roll in an atmosphere of 20°C.
After 30 minutes of crimping, the bonded sample was crimped to a thickness of 5 mm, hung vertically in an atmosphere at 70°C, and a
A weight of 1 kg was hung on it, and the time required for the weight to fall was measured.

Example 2 After mixing 70% by weight of the solid content of the aqueous dispersion of Production Example 1 and 30% by weight of the solid content of the aqueous dispersion of Production Example 3,
The adhesive physical properties of this were measured in the same manner as in Example 1.

Comparative Example 1 The aqueous dispersion of Production Example 1 was used alone and its adhesive properties were measured in the same manner as in Example 1. Comparative Example 2 The aqueous dispersion of Production Example 3 was used alone, and its adhesive properties were measured in the same manner as in Example 1. Comparative Example 3 After mixing 40% by weight of the solid content of the aqueous dispersion of Production Example 1 and 60% by weight of the solid content of the aqueous dispersion of Production Example 4,
The adhesive physical properties of this were measured in the same manner as in Example 1. Comparative Example 4 After mixing 70% by weight of the solid content of the aqueous dispersion of Production Example 5 and 30% by weight of the solid content of the aqueous dispersion of Production Example 3,
The adhesive physical properties of this were measured in the same manner as in Example 1. Comparative Example 5 After mixing 70% by weight of the solid content of the aqueous dispersion of Production Example 1 and 30% by weight of the solid content of the aqueous dispersion of Production Example 5,
The adhesive physical properties of this were measured in the same manner as in Example 1. Comparative Example 6 After mixing 40% by weight of the solid content of the aqueous dispersion of Production Example 4 and 60% by weight of the solid content of the aqueous dispersion of Production Example 2,
The adhesive physical properties of this were measured in the same manner as in Example 1. The table below shows the measurement results of these adhesive properties.

[0015]

[Table 1]

[0016]

According to the present invention, a high level and well-balanced adhesive performance, which has not been achieved with the prior art, can be achieved in an aqueous dispersion adhesive. That is, Comparative Examples 1 and 3, which are outside the scope of the present invention, have significantly poor cohesive strength at high temperatures, while Comparative Examples 2 and 4 have good cohesive strength at high temperatures, but have poor initial tack, etc. Inferior. Moreover, the adhesive performance of Comparative Examples 5 and 6 is also not satisfactory. On the other hand, Examples 1 and 2, which are within the scope of the present invention, are excellent in all adhesive properties and are well balanced at a high level. Therefore, if the aqueous dispersion type adhesive of the present invention is used, it is possible to achieve a highly balanced initial adhesive strength, which is a reciprocal physical property, adhesive strength to rough surfaces, adhesive strength to low polarity adherends such as polyolefin, and cohesive strength at high temperatures. It makes it possible to produce adhesive labels and adhesive tapes that have a smooth texture, and can be used in fields where water-based dispersion adhesives could not be used in the past.

Claims (1)

[Claims] Claim 1: Contains the following two aqueous dispersions A and B obtained by emulsion polymerization of a monomer mixture containing an acrylic acid alkyl ester monomer as a main component in an aqueous medium, and a mixture of A. The proportion is 5 to 95% by weight (solid content equivalent), and B is 95 to 95% by weight.
An aqueous dispersion type adhesive composition characterized in that it is a mixture consisting of 5% by weight. (1) A is an aqueous dispersion with an average particle size in the range of 0.01 to 1μ and a copolymer gel content of less than 35% by weight. (2) B is an aqueous dispersion with an average particle size of at least twice that of A. , and 0.1
Aqueous dispersion with a copolymer gel content of 35% by weight or more, in the range of ~3μ