JPH08269431A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE: To obtain an emulsion-type pressure-sensitive adhesive composition high-level both in adhesiveness and in a holding force. CONSTITUTION: This composition comprises a solution (A) containing a resin of a glass transition temperature of 20 deg.C or above, which is prepared by copolymerizing 3-60wt.% unsaturated carboxylic monomer with 40-97wt.% hydrophobic monomer and 0-50wt.% other monomers and at least 5wt.% of which is solubilized and an water-based acrylic resin emulsion (B) comprising a resin of a glass transition temperature of -30 deg.C or below in an A/B ratio of 1/99 to 20/80 (wherein A is the weight of the nonvolatiles of component A, and B is that of component B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion-type pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition having a high level of adhesiveness and especially retention.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Acrylic emulsion pressure-sensitive adhesives have excellent transparency, heat resistance and weather resistance, and have been widely used with rubber-based pressure-sensitive adhesives. Compared with rubber-based adhesives, acrylic-based emulsion adhesives have superior holding power, which is one of the adhesive properties, and also have excellent transparency, heat resistance, and weather resistance, but the adhesive strength is not sufficient and the adhesive strength is low. To reduce the molecular weight of the acrylic resin constituting the pressure-sensitive adhesive using a chain transfer agent, or to use a resin having a low glass transition temperature, or to further add a tackifier is proposed to improve the According to these methods, the adhesive force is improved, but on the contrary, the holding force as the pressure-sensitive adhesive is lowered. Also,
In order to improve the holding power, there are methods of using an unsaturated monomer having a large cohesive force as a component of the acrylic resin, or a resin having a high glass transition temperature. According to these methods, the holding power of the adhesive is However, there was a problem that the adhesive strength was decreased. Adhesive strength and holding power, which are the basic physical properties of an adhesive, are contradictory physical properties, but the development of a pressure-sensitive adhesive excellent in both adhesive strength and holding power is an issue.

[0003]

The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and as a result, by adopting the following constitution, the object of the present invention, that is, both the adhesive force and the holding force are It has been found that an excellent pressure-sensitive adhesive can be provided, and the present invention has been completed.

That is, the pressure-sensitive adhesive composition of the present invention is
(A) Unsaturated monomer having a carboxyl group (a) 3 to
A resin having a glass transition temperature of 20 ° C. or higher obtained by copolymerizing 60% by weight, 40 to 97% by weight of a hydrophobic monomer (b) and 0 to 50% by weight of another monomer (c), ,
And a resin-containing solution containing a resin in which 5% by weight or more is solubilized, and (B) a glass transition temperature of -30.
Acrylic resin aqueous emulsion consisting of resin below ℃, non-volatile weight ratio of each component (A) /
(B) is in the pressure-sensitive adhesive composition having a ratio of 1/99 to 20/80.

The resin that constitutes the resin-containing solution (A) that constitutes the pressure-sensitive adhesive composition of the present invention comprises 3 to 60% by weight of an unsaturated monomer (a) having a carboxyl group and a hydrophobic monomer (b). ) 40-97% by weight and other monomer (c) 0
It is a resin obtained by copolymerizing 50% by weight to 50% by weight.

Examples of the unsaturated monomer (a) having a carboxyl group include acrylic acid (105 ° C.), methacrylic acid (130 ° C.) and itaconic acid (160 ° C.) (the values in parentheses are The glass transition temperature of the homopolymer, and the same shall apply hereinafter). The component (a) is used so as to account for 3 to 60% by weight, preferably 5 to 50% by weight of the resin constituting the resin-containing solution (A) in the present invention. When it is less than 3% by weight, it is difficult to sufficiently solubilize the obtained resin in water, and as a result, there is a problem that the miscibility with the acrylic resin aqueous emulsion of the component (B) described later is lowered, On the other hand, if it exceeds 60% by weight, there arises a problem that the viscosity of the resin-containing solution increases with time.

Examples of the hydrophobic monomer (b) include methyl methacrylate (105 ° C), ethyl acrylate (-22 ° C), butyl acrylate (-54 ° C), 2
-Vinyl aromatic compounds such as ethylhexyl acrylate (-85 ° C) and styrene (100 ° C), vinyl chloride (8
Vinyl halides such as vinylidene chloride (-20 ° C), vinyl acetate (30 ° C), vinyl propionate (1
0 ° C) vinyl ester, ethylene (-125 ° C),
Examples thereof include olefinic monomers such as butadiene (-109 ° C) and acrylonitrile (130 ° C).

The component (b) is used so as to occupy 40 to 97% by weight, preferably 50 to 95% by weight, of the resin constituting the resin-containing solution (A) in the present invention. Four
When the content is less than 0% by weight, the affinity between the resin of the resin-containing solution (A) and the resin of the acrylic resin aqueous emulsion (B) cannot be secured, and the viscosity is easily increased during storage, and the adhesive composition If the storage stability is deteriorated and conversely exceeds 97% by weight, the proportion of the component (a) is relatively decreased, which causes aggregation and precipitation of the resin in the resin-containing solution (A). Become.

The term "hydrophobic" as used herein means that the solubility in water at 20 ° C. is 8 g / 100 ml or less. Specific examples of the other monomer (c) include acrylamide (153 ° C.), 2-hydroxyethyl acrylate (-15 ° C.), diacetone acrylamide (65 ° C.) and the like.

The component (c) is used in an amount of 0 to 50% by weight, preferably 0 to 50% by weight, of the resin constituting the resin-containing solution (A) in the present invention in order to secure the water solubility of the resin or to adjust the glass transition temperature described later. Is used so as to occupy 0 to 40% by weight. When it exceeds 50% by weight, the proportion of the component (a) and / or the component (b) is relatively decreased, and the miscibility with the aqueous emulsion of the component (B) described later is decreased and the viscosity is increased with time. Raises the problem.

The resin-containing solution (A) is a component for improving the holding power of the pressure-sensitive adhesive composition. Therefore, the glass transition temperature of the resin is 20 ° C. or higher, preferably 30 ° C.-1.
It needs to be 30 ° C. When the glass transition temperature is less than 20 ° C, it is not possible to expect a sufficient improvement in holding power. Further, if the glass transition temperature is too high, the heating temperature for expressing the tackiness becomes high, leading to high energy consumption.

The component (A) of the present invention is 5% by weight.
As described above, it is necessary to use a resin-containing solution containing a resin in which 10% by weight is preferably solubilized. In the present invention, the solubilization rate means that the resin-containing solution obtained by polymerization by the polymerization method described below is diluted with water so that the nonvolatile content becomes 15% by weight, and then the diluted solution is subjected to centrifugal acceleration of 1.8 ×.
Centrifuging at 10 ⁵ g for 60 minutes, the non-volatile content in the obtained supernatant was measured to be w parts by weight, and the non-volatile content in the diluent used for centrifugation was measured to be W parts by weight. Is the solubilization rate represented by the following formula.

Solubilization rate = w / W × 100 (% by weight)

Therefore, for example, in the case where an alkali and / or an organic solvent is added to a polymerization system before or during the polymerization for producing a resin-containing solution to carry out the copolymerization, When the solubilization rate of the obtained polymerization product containing the produced copolymer resin is already 5% by weight or more, the alkali and / or organic solvent for the solubilization treatment is added again. You don't have to.

The alkali used for the solubilization treatment is an inorganic water-soluble alkali such as sodium hydroxide or potassium hydroxide; or an inorganic salt which shows alkalinity when dissolved in water, such as sodium hydrogen carbonate or pyrophosphate. Sodium and the like; other examples include aqueous ammonia and organic amines. Addition of alkali is as described above.
It is not always necessary to carry out after the polymerization of the resin-containing solution, and in some cases, copolymerization may be carried out after neutralizing the monomer before the polymerization by adding an alkali. The amount of the alkali used may be an amount that completely neutralizes the carboxyl group in the copolymer resin, or may be an amount that partially neutralizes the carboxyl group.

The organic solvent used for the solubilization treatment may be supplementarily added when it cannot be sufficiently solubilized in water only by adding an alkali, or may be solubilized by adding only an organic solvent. The organic solvent to be used is not particularly limited, but texanol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether and their acetates, benzyl alcohol, butyl carbitol acetate, 2,2,4-trimethyl-1,3,3
-Pentanediol and the like.

Furthermore, the weight average molecular weight (Mw) of the resin constituting the resin-containing solution of the component (A) is 3000.
It is desirable that it is ˜30,000 because it is excellent in miscibility with the acrylic resin aqueous emulsion (B) component and the holding power is remarkably improved. If the Mw is 3000 or less, the holding power of the adhesive tends not to be sufficiently improved, and the Mw
When it is 30,000 or more, the stability when mixed with the resin aqueous emulsion of the component (B) tends to decrease.

As a method for producing the resin-containing solution which is the above-mentioned component (A), for example, in a organic solvent, each constituent monomer mixture is prepared by a conventional method using a polymerization initiator such as benzoyl peroxide or t-butyl hydroperoxide. Examples of the method include solution polymerization using an organic peroxide such as oxide or an azo initiator such as azobisisobutyronitrile. At this time, it is also possible to use a chain transfer agent such as an organic halide or an alkyl mercaptan as a molecular weight regulator. After distilling off the solvent from the resin solution thus obtained under reduced pressure, water is added and, if necessary, an alkali and / or a solvent is further added to obtain a resin-containing solution (A) of the resin having the above-mentioned solubilization rate. To do.

As another method for producing the resin-containing solution which is the component (A), emulsion polymerization of a conventional method is carried out, that is, the monomer mixture constituting the copolymerization is emulsified and copolymerized by using an emulsifier. There is also a method of adding an alkali to solubilize water, but in this method, it is essential to use a chain transfer agent for controlling the molecular weight. The alkali used herein may be ammonia, an organic amine such as triethylamine or ethanolamine, or an inorganic alkali such as sodium hydroxide, but it is most preferable to use ammonia.

The emulsifiers used are sodium dialkylsulfosuccinate, alkali salts of alkyl sulfonic acids, alkali metal salts of oxyalkylated alcohols or alkylphenols, alkali salts of fatty acids, anionic surfactants, nonionic surfactants, etc. Various kinds of surfactants can be used alone or in combination. The amount used is usually 0.1 to 10% by weight with respect to the resin content. In addition, depending on the purpose, a cationic surfactant may be used alone or in combination with a nonionic surfactant.

The polymerization initiator used in the emulsion polymerization is preferably an inorganic peroxide such as potassium persulfate, sodium persulfate, ammonium persulfate or hydrogen peroxide, but other than azobisisobutyronitrile or azobisvaleronitrile. Azo initiators; organic peroxide initiators such as benzoyl peroxide, lauroyl peroxide and t-butyl peroxide can also be used. Further, a reducing agent such as Rongalit, L-ascorbic acid, an organic amine, or a metal salt may be used in combination with these initiators and used as a redox initiator.

Further, the resin constituting the acrylic resin aqueous emulsion (B) constituting the pressure-sensitive adhesive composition of the present invention has a glass transition temperature of -30 ° C or lower, preferably -40.
It must be below ℃. This component (B) is for developing tackiness.

The acrylic resin aqueous emulsion comprising a resin having a glass transition temperature of -30 ° C or lower is, for example, butyl acrylate (-54 ° C), 2-ethylhexyl acrylate (-85 ° C), lauryl acrylate (-65).
(.Degree. C.) and the like, which are mainly composed of monomers having a low glass transition temperature of a homopolymer. Further, in order to adjust the glass transition temperature, ethylene (-125 ° C) or butadiene (-10
It is also possible to copolymerize (9 ° C.).

As the method for producing the resin aqueous emulsion (B), a method of emulsion copolymerizing a monomer mixture constituting a copolymer by an ordinary method of emulsion polymerization, that is, (A) is used. The same as the emulsion polymerization method at the time of production). In the present invention, instead of using an ordinary emulsifier, a so-called protective colloid in which a monomer mixture constituting a resin is copolymerized or polymerized by using various protective colloid agents in the resin-containing solution (A) component of the present invention. A polymerization method can also be adopted.

Examples of the protective colloid agent include hydroxyethyl cellulose, polyethylene oxide propylene oxide block polymer, and alkali soluble products of unsaturated carboxylic acid copolymers. The weight ratio (A) / (B) of the non-volatile components of each component is 1/99 to 20/80, preferably 1/99 to 15/85. When the ratio of the component (A) is less than 1, the holding force of the pressure-sensitive adhesive becomes insufficient, and when the ratio of the component (A) exceeds 99, the holding force of the pressure-sensitive adhesive is improved, but the adhesive force is low. It will be extremely reduced.

When the glass transition temperature of the resin constituting the component (A) is 20 to 50 ° C., the weight ratio (A) / (B) of the nonvolatile components is 10/90 to 20.
/ 80 is preferable, and when the glass transition temperature of the resin constituting the component (A) is 50 to 80 ° C, the weight ratio (A) / (B) of the nonvolatile components of the components is 5 /. 95
Further, when the glass transition temperature of the resin constituting the component (A) is higher than 80 ° C., the weight ratio (A) / (B) of the non-volatile components of the components is 1 to 15/85. / 99
It is preferably from 10/90.

The present pressure-sensitive adhesive composition contains a tackifying resin, for example, a rosin derivative, for the purpose of improving the adhesive strength.
It is also possible to add terpene resins, petroleum resins, etc., or waxes such as paraffin, long-chain fatty acids and their amides, and inorganic fillers such as titanium oxide and talc, to the extent that they do not impair the thickness-sensitive adhesiveness. It is possible. Further, the drying temperature after applying the pressure-sensitive adhesive composition to the substrate strongly depends on the glass transition temperature of the resin constituting the resin-containing solution of the component (A) of the present invention, that is, the drying temperature is (A The glass transition temperature of the resin in component () is preferably + 50 ° C. or lower, and if it exceeds that temperature, sufficient improvement in holding power cannot be expected.

[0028]

EXAMPLES Next, the present invention will be described in detail with reference to Examples and Comparative Examples. Parts and% in the examples are parts by weight and% by weight, unless otherwise specified. Production Example 1 150 parts of methyl cellosolve was charged into a reactor equipped with a temperature controller, a stirrer, a reflux condenser, a supply container and a nitrogen introducing tube, and the atmosphere was replaced with nitrogen. After heating the reactor to 80 ° C., a mixture of 100 parts of the monomer mixed solution shown in Table 1 and 0.1 part of t-dodecyl mercaptan was supplied from a supply container I, and 2 parts of azobisisobutyronitrile was added to 50 parts of methyl cellosolve. What was melt | dissolved in was added uniformly over 4 hours each from the supply container II.

After the addition was completed, the reactor was kept at 80 ° C. and aged for 2 hours to obtain a uniform polymer solution. Then, by using a rotary evaporator under reduced pressure, methyl cellosolve was almost completely distilled off, and then deionized water was added,
Ammonia is further added to neutralize the solution, and the pH is 8 and the nonvolatile content is 25.
% Resin containing solution was obtained.

The solubilization rate of the resin in the resin-containing solution was 100%, and the weight average molecular weight was about 5 when measured by gel permeation chromatography (GPC).
It was 000.

[0031]

[Table 1]

Production Examples 2 to 7 Using the same equipment as in Production Example 1, the monomer composition, solvent, initiator, etc. were changed as shown in Table 1 to obtain a uniform polymer solution, and then the solvent was added. A resin-containing solution as shown in Table 1 was obtained by distillative water replacement and neutralization.

Production Example 8 Using the same apparatus as in Production Example 1, 40 parts of water and 0.06 part of sodium persulfate were charged into the reactor. Separately, the following was prepared as the feed I.

Feed I 2 Ethylhexyl acrylate 85 parts Methyl methacrylate 9 parts Vinyl acetate 4 parts Acrylic acid 2 parts t-Dodecyl mercaptan 0.02 parts Water 40 parts Nonylphenol ethylene oxide 20 mol Sulfate ester sodium salt 30% Aqueous solution 6.6 parts

Separately, as a feed II, an initiator solution prepared by dissolving 0.7 part of sodium persulfate in 10 parts of water was prepared. After the inside of the reactor charged with the above-mentioned initiator solution was replaced with nitrogen gas, 10% of the above-mentioned feed I was added into the same reactor, and the mixture was heated to 90 ° C. Then, 10% of the feed II was charged into the reactor, and the rest of the feed I and the feed II were uniformly fed to the reactor over 3 to 3.5 hours. After the end of the supply, the mixture was kept at 90 ° C. for 1.5 hours for emulsion polymerization to obtain a resin aqueous emulsion.
The nonvolatile content of this resin aqueous emulsion was about 52%.

Table 2 shows the composition of the monomer, the non-volatile content of the produced emulsion and the glass transition temperature (calculated value) of the resin.

[0037]

[Table 2]

Production Examples 9 and 10 Using the same equipment as in Production Example 8, except that the monomer composition was changed as shown in Table 2, a resin aqueous emulsion was obtained according to Production Example 8. The results are shown in Table 2.

Examples 1 to 7 and Comparative Examples 1 to 6 The resin-containing solutions prepared in the above Production Examples and the resin aqueous emulsion were mixed in the proportions shown in Tables 3 and 4 and stirred to prepare pressure-sensitive adhesive compositions. did. The obtained composition was applied to the surface of a polyester film using an applicator so that the dry coating film would be 25 ± 1 g / m ^2, and dried at the drying temperatures shown in Tables 3 and 4 to give test pieces. It was created. Each of the above test pieces was evaluated by the following test methods and evaluation criteria, and the results are shown in Tables 3 and 4.

Adhesion test: the above test piece (2.5 × 10
cm) is adhered to a stainless steel plate (SUS) whose surface has been polished, and a tensile tester (manufactured by Instron) is used for 18
The 0 ° tensile strength (tensile speed: 300 mm / min) was measured and evaluated according to the following criteria.

∘: more than 1000 g / 25 mm ∘: 750 to 1000 g / 25 mm Δ: 500 to 750 g / 25 mm x: less than 500 g / 25 mm

Holding power test: The above test piece (2.0 × 2.
(0 cm) is adhered to a stainless steel plate (SUS) whose surface has been polished, and is reciprocated once with a 2 kg roller, and after 30 minutes, 1 kg
Was applied, the holding power (time until peeling) was measured under the conditions of 40 ° C. and a humidity of 65%, and the following criteria were evaluated.

◎ ・ ・ ・ more than 120 minutes ○ ・ ・ ・ 80-120 minutes △ ・ ・ ・ 50-80 minutes × ... less than 50 minutes

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

EFFECTS OF THE INVENTION The pressure-sensitive adhesive composition of the present invention can provide tackiness with a high level of both adhesive strength and especially holding power.圍 ■

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Noriyoshi Kato 1000 Kawajiri-cho, Yokkaichi-shi, Mie Mitsubishi Chemical BSF Corporation

Claims (6)

[Claims] 1. An unsaturated monomer (a) having 3 to 60% by weight of a carboxyl group (A) and a hydrophobic monomer (b) 40 to 40% by weight.
97% by weight and other monomer (c) 0 to 50% by weight
A resin-containing solution containing a resin having a glass transition temperature of 20 ° C. or higher obtained by copolymerization of 5% by weight or more and having 5% by weight or more thereof solubilized, and (B) a glass transition temperature of − A pressure-sensitive adhesive composition comprising an acrylic resin aqueous emulsion comprising a resin at 30 ° C. or lower, and having a nonvolatile content of each component (A) / (B) of 1/99 to 20/80. 2. The weight ratio (A) / nonvolatile content of each component
The pressure-sensitive adhesive composition according to claim 1, wherein (B) is 1/99 to 15/85. 3. The resin constituting the component (A) has a glass transition temperature of 20 to 50 ° C., and the weight ratio (A) / (B) of the nonvolatile components of each component is 10/90 to. 20 /
The pressure-sensitive adhesive composition according to claim 1, which is 80. 4. The glass transition temperature of the resin constituting the component (A) is 50 to 80 ° C., and the weight ratio (A) / (B) of the nonvolatile components of the components is 5/95 to. 15/8
The pressure-sensitive adhesive composition according to claim 1, which is 5. 5. The glass transition temperature of the resin constituting the component (A) is higher than 80 ° C., and the weight ratio (A) / (B) of the nonvolatile components of the respective components is 1/99 to 10/90. The pressure-sensitive adhesive composition according to claim 1, which is 6. The pressure-sensitive adhesive composition according to claim 1, wherein the resin constituting the component (A) has a weight average molecular weight (Mw) of 3,000 to 30,000.