JPH0768499B2 - Aqueous dispersion type pressure sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aqueous dispersion-type pressure-sensitive adhesive composition. More specifically, an aqueous dispersion-type pressure-sensitive adhesive composition containing two kinds of polymers having a specific composition and capable of forming a pressure-sensitive adhesive layer excellent in tack, adhesive strength, cohesive strength, water resistance and weather resistance. It is about things.

(Problems to be Solved by Prior Art and Invention) Conventionally, pressure-sensitive adhesive compositions containing an aqueous dispersion type resin as a main component have been used for pressure-sensitive adhesive tapes, sheets, labels and the like. However, the conventional pressure-sensitive adhesive composition containing an aqueous dispersion type resin as a main component is economically advantageous as compared with the pressure-sensitive adhesive composition containing an organic solvent solution type resin as a main component, Since it is difficult to develop sufficient cohesive strength and water resistance,
The actual use of the pressure-sensitive adhesive tape, sheet, label, etc. is extremely limited.

(Technical Means for Solving Problems) As a result of intensive studies conducted by the present inventors in view of such circumstances, an aqueous dispersion-type pressure-sensitive adhesive containing two kinds of polymers having a specific composition is obtained. A pressure-sensitive adhesive having a composition that is economically dispersed due to the fact that it is an aqueous dispersion type, yet has dramatically improved cohesive strength and water resistance and is excellent in tack, adhesive strength and weather resistance. It was found that the above problems were solved all at once by forming a layer. Then, they have found that the composition can be widely used for various purposes such as pressure-sensitive adhesive tapes, sheets, labels, etc., and completed the present invention.

That is, the present invention comprises 1 to 20% by weight of an unsaturated monomer having a carboxyl group (a), 50 to 99% by weight of an alkyl (meth) acrylate (b) having an alkyl group having 4 to 18 carbon atoms, and other Unsaturated monomer component (0 to 49% by weight of the copolymerizable unsaturated monomer (c) (however, the total of (a), (b) and (c) is 100% by weight)) Copolymer (I) obtained by emulsion polymerization of A) and having a weight average molecular weight of 200,000 to 800,000, and general formula (1) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen, halogen, alkyl, aralkyl, phenyl or a substituted phenyl group, and R ₅ is an acyclic organic compound having an addition polymerizable unsaturated bond. An unsaturated monomer component (B) consisting of an addition-polymerizable oxazoline (d) represented by a group and optionally one or more other copolymerizable unsaturated monomers (e). The (co) polymer (II) obtained by emulsion polymerization and having a weight average molecular weight of 200,000 to 800,000 is (co) polymer (II) based on 1 equivalent of the carboxyl group in the copolymer (I). The present invention relates to an aqueous dispersion-type pressure-sensitive adhesive composition, characterized in that the oxazoline group in (1) is contained in a ratio of 0.05 to 200 equivalents.

The unsaturated monomer (a) having a carboxyl group used for producing the copolymer (I) may be one having at least one carboxyl group and at least one polymerizable unsaturated group in the molecule. There is no particular limitation, and examples thereof include unsaturated monocarboxylic acids such as (meth) acrylic acid, cinnamic acid and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid and citraconic acid; and these unsaturated dicarboxylic acids. And the like, and one or more of these can be used. The amount of the unsaturated monomer (a) used is 1 in the unsaturated monomer component (A).
~ 20% by weight. If the proportion is less than 1% by weight, sufficient cohesive strength and water resistance will not be exhibited, and if it exceeds 20% by weight, tack and adhesive strength will be reduced, such being undesirable.

Examples of the alkyl (meth) acrylate (b) having 4 to 18 carbon atoms in the alkyl group used for producing the copolymer (I) include butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl ( (Meth) acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate and the like. , These one or two
More than one species can be used. The alkyl (meth) acrylate (b) is an essential component for imparting tack and adhesive force to the pressure-sensitive adhesive composition, and its amount is 50 to 99% by weight in the unsaturated monomer component (A). is there. When the ratio is less than 50% by weight, sufficient tack and adhesive strength are not exhibited, and when it exceeds 99% by weight, the amount of the unsaturated monomer (a) used is less than the specified amount, and the cohesive strength and water resistance are reduced. It is not preferable because it decreases.

As the other copolymerizable unsaturated monomer (c) used in the production of the copolymer (I), the unsaturated monomer (a) and / or the alkyl (meth) acrylate (b) are used.
There is no particular limitation as long as it is copolymerizable with, for example, an alkyl (meth) acrylate other than the above-mentioned alkyl (meth) acrylate (b); having an OH group, amino group, amide group, epoxy group, ether group, (Meth) acrylates; Aliphatic unsaturated hydrocarbons such as ethylene and butadiene, halogen-substituted aliphatic unsaturated hydrocarbons such as vinyl chloride; Aromatic unsaturated hydrocarbons such as styrene and α-methylstyrene Vinyl esters such as vinyl acetate;
Vinyl ethers; esters of allyl alcohol and various organic acids, ethers of various alcohols, unsaturated cyanide compounds such as acrylonitrile, and the like, and one or more of these can be used. .

The unsaturated monomer (c) is used as necessary for imparting properties other than the above to the pressure-sensitive adhesive composition, and the amount thereof is 0 to 0 in the unsaturated monomer component (A). 49% by weight. When it exceeds 49% by weight, the amount of the unsaturated monomer (a) and the alkyl (meth) acrylate (b) used is less than the specified amount, and the characteristics of the present invention are not exhibited.

The addition-polymerizable oxazoline (d) used for producing the (co) polymer (II) is represented by the general formula (1) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen, halogen, alkyl, aralkyl, phenyl or substituted phenyl, and R ₅ is an acyclic organic group having an addition polymerizable unsaturated bond. It is represented by.

Specific examples include 2-vinyl-2-oxazoline, 2-
Vinyl-4-methyl-2-oxazoline, 2-vinyl-
5-methyl-2-oxazoline, 2-isopropenyl-
2-oxazoline, 2-isopropenyl-4-methyl-
2-oxazoline, 2-isopropenyl-5-ethyl-
2-oxazoline and the like can be mentioned, and one kind or a mixture of two or more kinds selected from these groups can be used. Among them, 2-isopropenyl-2-oxazoline is industrially easily available and suitable.

The addition-polymerizable oxazoline (d) is a component for imparting excellent cohesive force to the pressure-sensitive adhesive composition, and the amount used is not particularly limited, but the unsaturated monomer component (B) is used.
It is suitable that the content is 1% by weight or more, and more preferably 5 to 100% by weight. If the amount is less than 1% by weight, it may not be a substantially effective amount in order to obtain a pressure-sensitive adhesive layer having excellent cohesive strength.

The unsaturated monomer component (B) for obtaining the (co) polymer (II) optionally contains at least one other copolymerizable unsaturated monomer (e). May be. As the other copolymerizable unsaturated monomer (e), the alkyl (meth) acrylate (b) used in the preparation of the aqueous dispersion of the above copolymer (I) and other copolymerizable unsaturated monomers are used. Those exemplified as the monomer (c) can be mentioned as they are, and one kind or two or more kinds thereof can be appropriately selected and used. However, the unsaturated monomer (e) is preferably selected in consideration of the compatibility between the copolymer (I) and the (co) polymer (II), in order to sufficiently exert the effect of the present invention. . Both the copolymer (I) and the (co) polymer (II) need to have a weight average molecular weight in the range of 200,000 to 800,000,
It is preferably in the range of 400,000 to 600,000. If the weight average molecular weight of the copolymer (I) and (co) polymer (II) is less than 200,000, the cohesive force of the pressure-sensitive adhesive composition obtained will be inferior, and if it exceeds 800,000. The homogenization of the copolymer (I) and the (co) polymer (II) in the pressure-sensitive adhesive layer after drying becomes insufficient, and it is difficult to maximize the effects of the present invention.

The aqueous dispersion of the copolymer (I) and (co) polymer (II), which is an essential component of the pressure-sensitive adhesive composition of the present invention, comprises the unsaturated monomer component (A) or the unsaturated monomer. The body component (B) may be emulsion polymerized by a conventionally known method in the presence or absence of an emulsifier.

At this time, as the emulsifier used as necessary, one or more kinds of conventionally known emulsifiers such as various anionic emulsifiers, various cationic emulsifiers and various nonionic emulsifiers can be used. The amount used is preferably 10% by weight or less based on the unsaturated monomer component (A) or (B). If necessary, protective colloids may be used alone or together with an emulsifier.

Examples of the polymerization catalyst for emulsion-polymerizing the unsaturated monomer component (A) or (B) include inorganic peroxides such as ammonium persulfate and hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide. Oxide; other radical-forming polymerization initiator can be used, and the amount thereof is usually 100 parts by weight of the unsaturated monomer component (A) or (B).
It is in the range of 0.01 to 3 parts by weight, preferably 0.1 to 1 part by weight. When using a peroxide, if it is necessary to increase the polymerization rate or lower the reaction temperature, a reducing agent such as soluble sulfite or ascorbic acid, or a metal that generates heavy metal ions in water such as ferrous sulfate. The compounds can be combined with peroxides to make redox systems.

The temperature of the emulsion polymerization is appropriately selected depending on the molecular weight of the copolymer (I) and the (co) polymer (II), the composition of the unsaturated monomer component (A) or (B), the type of the polymerization catalyst, and the like. However, it is usually in the range of 0 to 100 ° C. The amount of water during emulsion polymerization is usually in the range of 300 to 40 parts by weight with respect to 100 parts by weight of each of the monomer components (A) and (B).

Specific polymerization methods include, for example, a monomer dropping polymerization method, a pre-emulsion dropping polymerization method, a seed polymerization method and a multistage polymerization method. In particular, the multistage polymerization method may be able to bring out the characteristics of the present invention to a large extent.

In addition, in the emulsion polymerization of the unsaturated monomer component (B) of the present invention, in order to keep the oxazoline group of the addition-polymerizable oxazoline (d) stable, a pH adjusting agent such as ammonia is appropriately added to adjust the pH. It is preferable to carry out emulsion polymerization while maintaining the value of 7 to 10.

The weight average molecular weights of the copolymer (I) and the (co) polymer (II) are controlled within the above range by, for example, using a molecular weight regulator represented by mercaptans such as dodecyl mercaptan and the amount of the polymerization catalyst. Can be achieved by a method such as appropriately selecting emulsion polymerization conditions such as the amount of emulsifier and the polymerization temperature,
The method using a molecular weight regulator is convenient.

The aqueous dispersion-type pressure-sensitive adhesive composition of the present invention comprises the copolymer (I) and the (co) polymer (II). The copolymer (I) and the (co) The polymer (II) is usually obtained in the form of an aqueous dispersion by the above-mentioned procedure, and an aqueous dispersion of the copolymer (I) and (co)
The mixture of the aqueous dispersion of the polymer (II) can be directly used as the aqueous dispersion-type pressure-sensitive adhesive composition of the present invention. The use ratio of the copolymer (I) and the (co) polymer (II) is not particularly limited, but in order to sufficiently exert the effects of the present invention, the carboxyl group in the copolymer (I) is used. The oxazoline group in the (co) polymer (II) is usually 0.05 to 200 equivalents to 1 equivalent of the group. When the amount of the oxazoline group is less than 0.05 equivalent, the cohesive force is not expressed, and when it is added in excess of 200 equivalent, the cohesive force may be rather reduced economically. It is preferably 0.05 to 0.5 equivalent or 2 to 100 equivalent. When it is more than 0.5 equivalent and less than 2 equivalent, good pressure-sensitive adhesive properties are provided, but the crosslink density becomes high and the adhesive strength may be slightly deteriorated. More preferably, it is used in a ratio of 0.05 to 0.3 equivalent.

The aqueous dispersion-type adhesive composition of the present invention can be sufficiently used as it is, but in terms of storage stability of the composition,
For example, add a basic substance such as ammonia to adjust the pH of the solution to 7
It is preferable to adjust to ~ 10. The basic substance can be added before or after mixing the aqueous dispersion of the copolymer (I) and the aqueous dispersion of the (co) polymer (II). Further, if necessary, various additives shown below can be added.

First, when it is necessary to further increase the adhesive strength of the pressure-sensitive adhesive composition of the present invention, a tackifying resin having a softening point of about 60 ° C. or higher, such as rosin resin, petroleum resin resin, coumarone indene. A resin or a phenol resin may be added in an amount of 200 parts by weight or less, preferably 5 to 60 parts by weight, based on 100 parts by weight of the total amount of the copolymer (I) and the (co) polymer (II). it can. When it is necessary to increase tack, a liquid tackifying resin, a low molecular weight polymer having an average molecular weight of 8,000 to 20,000, a plasticizer and the like can be added.

When it is necessary to further increase the cohesive force of the pressure-sensitive adhesive composition of the present invention, 0.005 to 2 is added to 100 parts by weight of the total of the copolymer (I) and the (co) polymer (II). Within the range of parts by weight, an epoxy compound which can act as an external crosslinking agent,
The melamine compound, the isocyanate compound and the like can be added in the form of an aqueous solution, an aqueous dispersion or an organic solvent solution.

The pressure-sensitive adhesive composition of the present invention further, if necessary,
It is also possible to add known additives such as antifoaming agents, thickeners, viscosity modifiers, coloring agents, fillers and antiaging agents.

(Effects of the Invention) The aqueous dispersion-type pressure-sensitive adhesive composition of the present invention thus obtained is excellent in tack and adhesive strength, and also in cohesive strength, and is also excellent in weather resistance and water resistance. Therefore, the above-mentioned conventional problems are solved all at once,
It can be widely used as a pressure-sensitive adhesive tape, sheet, label, etc. for various purposes.

(Examples) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. Unless otherwise noted, all parts are parts by weight and all% are% by weight.
Shall be represented.

Reference Example 1 Unsaturated monomer component consisting of 360 parts of butyl acrylate, 20 parts of vinyl acetate, and 20 parts of methacrylic acid, 0.7 part of t-dodecyl mercaptan as a molecular weight regulator, and "Hitenol N-08" (No. 8 parts of an emulsifier manufactured by Ichigo Seiyaku Co., Ltd. and 120 parts of deionized water were mixed with stirring to obtain 528 parts of a pre-emulsion of an unsaturated monomer mixture.

268.8 parts of deionized water was charged into a glass flask No. 2 equipped with a reflux condenser, a thermometer, a nitrogen gas inlet, a dropping funnel and a stirrer, and the temperature was raised to 70 ° C., and thereafter this temperature was maintained. 16 parts of a 10% aqueous solution of ammonium persulfate was added with stirring in a nitrogen stream, and then 8 parts of a 10% aqueous solution of pre-emulsion and sodium bisulfite were added dropwise in parallel over 90 minutes. 80 after dropping
The temperature was raised to ℃ and kept for 60 minutes to complete the polymerization, and then cooled to obtain an aqueous dispersion of the copolymer (I-1) having a nonvolatile content of 50%.

The weight average molecular weight of the copolymer (I-1) was 550,000.

Reference Example 2 and Comparative Reference Examples 1 to 3 The same operation as in Reference Example 1 was performed except that the type and amount of unsaturated monomer and the amount of t-dodecyl mercaptan in Reference Example 1 were as shown in Table 1. Repeatedly, an aqueous dispersion of the copolymer (I-2) and comparative copolymers (I'-1) to (I'-3) each having a nonvolatile content of 50% were obtained.

Reference Example 3 In a flask equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, a thermometer and a dropping funnel, 782.4 parts of deionized water and Hitenol N-08 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., an emulsifier) 15
% Aqueous solution 128 parts was added, and an appropriate amount of ammonia water (28%)
Adjust to pH 9.0 with 70 and slowly flowing nitrogen gas.
Heated to ° C. 64 parts of a 5% aqueous solution of potassium persulfate was injected into it, and then butyl acrylate was previously prepared.
576 parts and 2-isopropenyl-2-oxazoline 64
A solution of 1 part of t-dodecyl mercaptan dissolved in 1 part of the unsaturated monomer component was added dropwise over 3 hours. During the reaction, nitrogen gas was continuously blown in to keep the internal temperature at 70 ± 1 ° C. After the dropping was completed, the same temperature was maintained for 2 hours, then the internal temperature was raised to 80 ° C., and stirring was continued for 1 hour to complete the reaction. Then, it was cooled to obtain an aqueous dispersion of a copolymer (II-1) having a nonvolatile content of 40%.

The weight average molecular weight of the copolymer (II-1) was 520,000.

Reference Example 4 and Comparative Reference Examples 4 to 5 The same operation as in Reference Example 3 was performed except that the type and amount of unsaturated monomer and the amount of t-dodecyl mercaptan in Reference Example 3 were as shown in Table 2. Repeatedly, an aqueous dispersion of copolymer (II-2) and an aqueous dispersion of comparative copolymers (II'-1) to (II'-2) each having a nonvolatile content of 40% were obtained.

Examples 1 to 7 and Comparative Examples 1 to 3 With the composition shown in Table 3, the aqueous dispersion of the copolymer (I) and the (co) polymer (II) obtained in the above Reference Examples and Comparative Reference Examples were used. 2) was mixed with the aqueous dispersion to prepare an aqueous dispersion-type pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition thus obtained was applied onto one side of a polyester film having a thickness of 25 μm so that the thickness after drying would be 20 μm, and dried at 80 ° C. for 2 minutes to prepare a pressure-sensitive adhesive tape. With respect to the obtained pressure-sensitive adhesive tape, tack, adhesive strength, holding power as a measure of cohesive strength, and water resistance were measured by the following methods. The results are shown in Table 3.

<Tack> The tack was measured by the ball rolling method specified in JIS Z 0237.

<Adhesive strength> The 180 ° peeling adhesive strength (adherend: stainless steel plate, g / 25 mm) specified in JIS Z 0237 was measured.
Also, the adhesive force when a polyethylene plate was used as an adherend was measured by the same method.

<Holding power> According to the method defined in JIS Z 0237, a stuck time of 20 mm x 20 mm and a load of 1 kg at 70 ° C were applied to measure the holding time or the deviation width after a certain time.

<Water resistance> When measuring the above-mentioned adhesive force to a stainless steel plate, the above-mentioned adhesive is used except that the entire sample attached to the stainless steel plate is previously immersed in water at 23 ° C for 24 hours to measure the adhesive force immediately after the immersion. The same measurement as the force measurement method was performed. It can be considered that the water resistance of the pressure-sensitive adhesive is better as the measured value is closer to the measured value measured by the above-mentioned adhesive force without immersion in water.

Claims (1)

[Claims] 1. An unsaturated monomer having a carboxyl group (a) in an amount of 1 to 20% by weight, an alkyl (meth) acrylate (b) in which an alkyl group has 4 to 18 carbon atoms in an amount of 50 to 99% by weight, and other Unsaturated monomer component (0 to 49% by weight of the copolymerizable unsaturated monomer (c) (however, the total of (a), (b) and (c) is 100% by weight)) Copolymer (I) obtained by emulsion polymerization of A) and having a weight average molecular weight of 200,000 to 800,000, and general formula (1) (In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are each independently hydrogen, halogen, alkyl, aralkyl, phenyl, or a substituted phenyl group, and R ₅ is an acyclic organic group having an addition polymerizable unsaturated bond. Emulsifying an unsaturated monomer component (B) consisting of an addition-polymerizable oxazoline (d) represented by the formula (1) and optionally one or more other copolymerizable unsaturated monomer (e). The (co) polymer (II) obtained by polymerization and having a weight average molecular weight of 200,000 to 800,000 is (co) polymer (II) based on 1 equivalent of the carboxyl group in the copolymer (I). An aqueous dispersion-type pressure-sensitive adhesive composition, characterized in that the oxazoline group therein is contained in a ratio of 0.05 to 200 equivalents.