JP2824775B2 - Acrylic water-based pressure-sensitive adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a film or molded article of a non-polar polymer such as polyolefin, which has excellent adhesive strength, particularly excellent curved surface adhesion and low-temperature adhesion, The present invention relates to an aqueous dispersion type pressure-sensitive adhesive having:

[Conventional technology]

Applications for pressure-sensitive adhesives include tapes, labels, stickers,
The materials to be adhered to cover a wide range of fields such as wallpaper, plastics, metals, glass, pottery, paper, cloth, building materials, fruits and the like.

Conventionally, natural rubbers, synthetic rubbers, solution-type acrylic copolymers, aqueous dispersion-type acrylic copolymers, and the like have been used as main raw materials for pressure-sensitive adhesives. Among these, pressure-sensitive adhesives mainly composed of an aqueous dispersion type acrylic copolymer are:
Since they do not contain organic solvents and have no fire or pollution problems, they have become increasingly widely used.

However, pressure-sensitive adhesives based on aqueous dispersion-type acrylic copolymers are more water-resistant and have higher adhesive strength, especially polyolefins, than pressure-sensitive adhesives based on solution-type acrylic copolymers. However, there is a drawback that the adhesive strength to non-polar polymer films and molded products is poor.

As a typical attempt to improve the above-mentioned disadvantages of the aqueous dispersion type acrylic pressure-sensitive adhesive, JP-A-58-79068 can be mentioned.

The above proposals include: (A) 100 parts by weight of an acrylic pressure-sensitive adhesive emulsion (solid basis), (B) 5 to 30% by weight of ethylene, (b) 20 to 90% by weight of vinyl acetate and (C) obtained by copolymerizing 5 to 50% by weight of at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates, wherein the alkyl group has 1 to 12 carbon atoms. Ethylene-vinyl acetate-alkyl acrylate and / or alkyl methacrylate-based multi-component copolymer emulsion 5
An emulsion-type pressure-sensitive adhesive characterized in that the active ingredient is from 35 to 35 parts by weight (based on solid content). And (A) 100 parts by weight of an acrylic pressure-sensitive adhesive emulsion (solids basis), (B) 5 to 30% by weight of ethylene, (b) 20 to 90% by weight of vinyl acetate, (c) 5 to 50% by weight of at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 12 carbon atoms, and (d) 5 to 35 parts by weight of an ethylene-vinyl acetate-alkyl acrylate and / or alkyl methacrylate-based multicomponent copolymer emulsion obtained by copolymerizing 0.1 to 5% by weight of a monomer having a polymerizable functional group (solid content And a base) as an active ingredient. "

This pressure-sensitive adhesive increases the adhesive strength of a non-polar polymer such as polyolefin to an adherend by blending it with a specific amount of the above-mentioned ethylene / vinyl acetate / acrylic copolymer with a conventional acrylic emulsion. It is to be improved.

However, although the proposed pressure-sensitive adhesive can certainly improve the adhesive strength of a nonpolar polymer to an adherend at room temperature, for example, in the pressure-sensitive adhesive described in the examples of the proposal, For example, low-temperature adhesiveness required in the application of various labels and the like to packaged foods and the like in a freezer, for example, a small rod having a diameter of about 10 to 20 mmφ,
There is a problem that the curved surface adhesion to a non-polar polymer molded product such as a molded product having an edge portion is not sufficient.

[Problems to be solved by the invention]

The present inventors have developed a good balance of the inherent properties of a pressure-sensitive adhesive, that is, tack, normal adhesive strength, cohesive strength and storage stability, as well as curved surface adhesiveness and low-temperature adhesiveness to non-polar polymer molded products. As a result of repeated studies to obtain an excellent aqueous dispersion type acrylic pressure-sensitive adhesive, the present invention has been completed.

[Means for solving the problem]

The present invention provides the following (A) and (B): (A) an acrylic copolymer having a gel content of 40% by weight or more and a glass transition point of -40 ° C or less; system copolymer, per 100 parts by weight of (a) ethylene 5 to 40 wt%, (ii) vinyl acetate 5-60% by weight, and, (iii) CH ₂ = CR'-COOR "[However, R 'is H Or CH ₃ , R ″
15-70% by weight of acrylic acid or methacrylic acid ester represented by a linear or branched alkyl group of C ₄ -C _18] (provided that (the sum of a) to (c) is 100 wt%), Is contained as a copolymer component, and has a glass transition point of -30.
Ethylene / vinyl acetate / acrylic copolymer 5 ° C. or lower
An acrylic water-based pressure-sensitive adhesive composition comprising 20 parts by weight of as an active ingredient.

 Hereinafter, the present invention will be described in detail.

The acrylic copolymer as the component (A) in the present invention is not particularly limited. However, due to the excellent physical properties of the obtained pressure-sensitive adhesive composition, the acrylic copolymer (A) may have i CH ₂ CHCH—COOR ₁ [wherein, R ₁ represents a C ₂ -C ₁₂ linear or branched alkyl group], and the homopolymer has a glass transition point of −20. 50 to 99.9% by weight of acrylic acid acrylate which is not more than ℃, ii α of C _{3 to} C ₅ . 0.1 to 1.5% by weight of a β-unsaturated mono- or di-carboxylic acid and iii a comonomer 0 copolymerizable with the monomers of i and ii above.
-50% by weight (provided that the sum of i to iii is 100% by weight) as a copolymer component and a gel content of 40% by weight.
It is preferably an acrylic copolymer having a glass transition point of -40 ° C or less by weight or more.

The monomer (i) is an acrylate ester represented by the formula CH ₂ 2CH—COOR ¹ , wherein R ¹ represents a C _{2 to} C ₁₂ linear or branched alkyl group, and The glass transition point of the homopolymer is −20 ° C. or less, and examples of such a group R ¹ include an ethyl group, an n-propyl group, and an n-
Butyl group, n-hexyl group, 2-ethylhexyl group, n
-Octyl group, i-octyl group, n-nonyl group, i-
Examples include a nonyl group and an n-decyl group. Among these, n- butyl, n- hexyl, 2-ethylhexyl group, n- octyl group, i- octyl, n- nonyl group, i- nonyl group, C _4, such as n- decyl -C ₁₀ Is more preferable, and n-hexyl group, 2-ethylhexyl group, n-octyl group, i-
C ₆ -C ₉ such as octyl group, n-nonyl group, i-nonyl group
Is particularly preferred. Specific examples of such acrylates include ethyl acrylate, n-propyl acrylate, n-butyl acrylate, i-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-nonyl acrylate, and the like. Among these, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl acrylate and the like are more preferred. It is particularly preferable to use n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl acrylate, and the like.

The amount of the acrylic acid ester used as the monomer (i) is, for example, 50 to 9 in the total 100% by weight of (i) to (iii).
9.9% by weight, preferably 60-99% by weight, particularly preferred 6
5 to 98% by weight. By using the monomer (i) at or above the lower limit, excellent adhesion, low-temperature adhesion and a good balance of excellent tack and excellent holding power are achieved,
Further, by using the aqueous pressure-sensitive adhesive composition at or below the upper limit, the resulting aqueous pressure-sensitive adhesive composition has good mechanical stability (stability of the dispersion when shearing force is applied) and excellent holding power.
Therefore, one of the monomers (i) in the above usage amount range
By appropriately selecting and using the kind or two or more kinds, it is possible to achieve excellent adhesion, low-temperature adhesion, and a good balance between excellent tack and excellent holding power.

In addition, the monomer (ii) may be a C ₃ -C ₅ α. β-unsaturated mono- or di-carboxylic acids, specific examples of which include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid and the like. Among these, acrylic acid and methacrylic acid are more preferably used.

The amount of the monomer (ii) used is from the monomer (i) to the monomer (ii).
For example, 0.1 to 1.5% by weight, preferably 0.2 to 1% by weight of the total 100% by weight of (iii). When the amount of the monomer (ii) is equal to or more than the lower limit, the resulting water-based pressure-sensitive adhesive composition has excellent mechanical stability and holding power. Since low-temperature adhesiveness, tackiness and water resistance can be maintained well, it is preferable to select and use them appropriately in the above-mentioned usage range. Furthermore, considering the low-temperature adhesiveness, the balance between tack and holding power, the stability over time of the adhesive strength, and the like, if necessary, a suitable use amount range can be experimentally selected in advance within the above use amount range if necessary. .

Further, as the comonomer (iii), for example, CH ₂ =
An acrylate represented by CH-COOR ² , wherein R
Reference numeral ² denotes a C _{1 to} C ₄ linear or branched alkyl group, and examples thereof include acrylates whose homopolymer has a glass transition point exceeding −20 ° C. Examples of R ² include a methyl group, an isopropyl group, a t- butyl group and the like can be exemplified. Specific examples of the acrylate ester include methyl acrylate and t-butyl acrylate, and the use of methyl acrylate is preferred.

Further, as the comonomer (iii), for example, a compound represented by the formula CH ₂ ＣC
(CH ₃₎ represented by -COOR ^3, where R ³ may be exemplified methacrylic acid ester such as a linear or branched alkyl group of C ₁ -C _4. Examples of R ³ include a methyl group,
Examples include an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, and a t-butyl group. Specific examples of the methacrylate monomer include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate and the like, and the use of methyl methacrylate is preferred.

Further, as the comonomer (iii), for example, a compound represented by the formula CH ₂ =
A saturated fatty acid vinyl ester represented by CHOCOR ⁴ , wherein R ⁴ represents H or a C _{1 to} C _18, preferably a C _{1 to} C ₁₂ linear or branched alkyl group, and examples of the group R ⁴ include Methyl group, ethyl group, t-butyl group, t-octyl group, t
And monomers such as a nonyl group and a t-decyl group. Specific examples of such a saturated fatty acid vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl versatate, and the like,
The use of vinyl acetate is preferred.

Further, as the comonomer (iii), for example, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene (preferably styrene); and
Vinyl cyanide monomers such as acrylonitrile and methacrylonitrile (preferably acrylonitrile); comonomers selected more can be used as well.

In addition to these, as the comonomer (iii), for example, dimethyl malate, di-n-butyl malate, di-2-ethylhexyl malate, di-n-octyl malate, dimethyl fumarate, di-n- Butyl fumarate, di-2
Formulas such as -ethylhexyl fumarate, di-n-octyl fumarate and the like R ⁵ OOC-CH = CH-COOR ⁶ (where R ⁵ and R
⁶ each independently represents a C ₁ -C ₁₀ , preferably a C ₁ -C ₈ linear or branched alkyl group), maleic acid or fumaric acid ester represented by To the extent that the outstanding effects of the present invention are not impaired,
It can be appropriately used without any particular limitation.

The amount of the comonomer (iii) used is 0 to 50% by weight, preferably 1 to 45% by weight, particularly preferably 100% by weight of the total of the monomers (i) to (iii). It is 1 to 35% by weight. Since the use of the comonomer (iii) can vary depending on the type of the comonomer, the amount of the comonomer cannot be uniquely determined, but the balance between the adhesive force and the tack and the balance between these and the cohesive force. And the like can be adjusted as desired, so that the amount can be appropriately selected within the range so as to meet such purpose. When the amount of the comonomer (iii) is less than or equal to the upper limit of the above range, the tack does not become excessively small, and an appropriate balance of adhesive strength, low-temperature adhesiveness and tack can be easily maintained. When the monomer (iii) is used, it is preferable to select and use it appropriately in the above range.

The acrylic copolymer used in the present invention includes, for example, an acrylic copolymer obtained by aqueous emulsion copolymerization of a monomer mixture comprising the monomers (i) to (ii) as described in detail above. It is preferable that the acrylic copolymer has a glass transition point of −40 ° C. or lower, preferably −50 ° C. or lower, and a gel content in the copolymer of 40% by weight or higher, preferably It is necessary to be 50 to 80% by weight, particularly preferably 55 to 80% by weight.

When the glass transition point of the acrylic resin exceeds the above-mentioned temperature, tack tends to be insufficient, and adhesiveness at a low temperature such as 0 ° C. or less, particularly, adhesive strength to a nonpolar polymer such as polyethylene is insufficient. And the gel content is less than the above lower limit. It is not preferable because cohesive strength tends to be insufficient. It is particularly preferable to use a gel content of 80% by weight or less from the viewpoint of excellent adhesive strength and excellent anchoring property of the pressure-sensitive adhesive sheet to the sheet substrate (support).

In the present invention, the glass transition point of the acrylic copolymer is a value measured and determined as described below.

Glass transition point: About 10 mg of a sample of an aqueous dispersion of an acrylic copolymer is weighed into a cylindrical cell made of aluminum foil having a thickness of about 0.05 mm and having an inner diameter of about 5 mm and a depth of about 5 mm. The sample dried for 2 hours is used as a measurement sample. SSC-5 manufactured by Seiko Electronic Industry Co., Ltd.
Type 000 Differential Scanning Calorim
eter) at -150 ° C at a heating rate of 10 ° C / min.

In the present invention, the gel content in the acrylic copolymer is a value obtained by measuring the content of ethyl acetate-insoluble components in the acrylic copolymer by the following method.

Gel content: (a) Preparation of sample film The thickness of the obtained acrylic copolymer sample film is approximately
An aqueous dispersion of an acrylic copolymer is applied on a release material so as to have a thickness of 100 μm, and dried at room temperature for about 1 hour.
Dry at 0 ° C for 2 minutes to prepare a sample film.

(B) Hot water extraction The sample film of (a) was cut into a size of about 5 cm x about 15 cm, wound uniformly on a glass rod of about 1.5 cm in diameter, which was measured in advance, and weighed. W ₁₎ obtain. The sample film wound around the glass rod is placed in a cylindrical paper for Soxhlet extraction, and hot water extraction is performed for 4 hours at a reflux temperature (about 100 ° C.) using a Soxhlet extractor. The obtained hot water extract is heated to dryness to obtain a hot water extract weight (w ₁ ).

(C) Extraction with ethyl acetate In the same manner as in (b) above, the sample film (weight W ₂ ) wound around a glass rod is subjected to ethyl acetate extraction at a reflux temperature (about 77 ° C.) for 4 hours using a Soxhlet extractor. The obtained ethyl acetate extract is heated to dryness to obtain an ethyl acetate extract weight (w ₂ ).

(D) Calculation of gel content The gel content is calculated according to the following formula.

In addition, the aqueous pressure-sensitive adhesive composition, in addition to the acrylic copolymer and the surfactant, for example, a pigment, an inorganic filler,
When an additive such as a tackifying resin is contained, for example, the pressure-sensitive adhesive is appropriately diluted with ion-exchanged water or the like to reduce the viscosity (for example, about 50 cps or less), and then centrifuged. By separating these additives, it is possible to separate and collect an aqueous dispersion of the acrylic copolymer used for measuring the glass transition point and the gel content. The reason that such separation is possible is that the specific gravity of the acrylic resin used in the present invention is extremely close to 1, and is considerably lighter than other additives usually used for pressure-sensitive adhesives.

As a preferred method for producing the acrylic copolymer used in the present invention, for example, a monomer mixture of the above (i) to (iii) can be prepared by adding a suitable surfactant to a suitable surfactant in the presence of a water-soluble protective colloid. Can be used as an emulsifier for polymerization to carry out emulsion copolymerization in an aqueous medium.

In the present invention, the above-mentioned surfactants that can be used include, as nonionic surfactants, for example, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; Polyoxyethylene alkylphenol ethers such as ethylene octyl phenol ether and polyoxyethylene nonyl phenol ether; sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate and sorbitan trioleate; polyoxyethylene sorbitan monoester Polyoxyethylene sorbitan higher fatty acid esters such as laurate; for example, polyoxyethylene monolaurate, polyoxyethylene monostearate Polyoxyethylene higher fatty acid esters such as glycerin; glycerol higher fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride; and polyoxyethylene polyoxypropylene block copolymer. .

Examples of the anionic surfactants include higher fatty acid salts such as sodium oleate; alkylaryl sulfonates such as sodium dodecylbenzenesulfonate; alkyl sulfates such as sodium lauryl sulfate; Acid salts; for example, polyoxyethylene alkyl ether sulfates such as polyoxyethylene lauryl ether sodium sulfate; polyoxyethylene alkyl aryl ether sulfates such as polyoxyethylene nonylphenol ether sulfate; monooctyl sulfo succinate Alkyl sulfosuccinates such as sodium acid, sodium dioctylsulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate, and the like; and derivatives thereof.

When these surfactants are used as an emulsifier for polymerization, they may be used in appropriate combination, and the amount of the surfactant is generally 0.2 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer. , Preferably 0.5 to 5 parts by weight,
Particularly preferably, about 0.5 to 4 parts by weight can be exemplified. These surfactants are used not only as emulsifiers for polymerization, but also to improve the mechanical stability of the resulting water-based pressure-sensitive adhesive composition and to release materials (paper or plastic films release-treated with a silicone resin or the like). It is often added after the aqueous emulsion copolymerization for the purpose of improving coatability and the like. For example, a transfer method, that is, after applying the pressure-sensitive adhesive on a release material and drying to form a pressure-sensitive adhesive layer, the base material is overlaid on the pressure-sensitive adhesive layer and pressed, When the method of transferring the pressure-sensitive adhesive layer onto a substrate is employed, the sulfosuccinate ester-based anionic surfactants exemplified in the anionic surfactants are often used. This is used for the purpose of preventing repelling since repelling is likely to occur during coating on the release agent. The amount used is preferably 3.5 parts by weight or less based on 100 parts by weight in total of the acrylic copolymer and the ethylene / vinyl acetate / acrylic copolymer described below. When the amount is in the range of 3.5 parts by weight or less, a good level can be maintained without lowering the cohesive strength and water-resistant adhesiveness. The amount used is
It is particularly preferable to use 0.1 to 1.5 parts by weight from the viewpoints of the physical properties of the pressure-sensitive adhesive and the repellency.

As a method for using the above-mentioned sulfosuccinate ester-based anionic surfactant, generally, the surfactant is diluted with water, alcohols or the like as necessary, and then added to an aqueous dispersion of an acrylic copolymer. Usually, in producing the acrylic copolymer by aqueous emulsion copolymerization, a part or the front part of the surfactant may be used in combination as a polymerization emulsifier. In this case, the ratio of the sulfosuccinate ester-based anionic surfactant to the total amount of the emulsifier for polymerization is excellent in ease of production of the acrylic copolymer and in various physical properties of the obtained pressure-sensitive adhesive composition. It is preferably in the range of 0 to 40% by weight from the viewpoint of the size. In addition, among commercially available surfactants, there are those containing volatile solvents such as water and alcohols. In such a case, the amount of the surfactant in the present invention is determined in a hot air dryer. It refers to the amount obtained by drying at about 100 ° C. for 60 minutes to remove the volatile solvent.

Suitable methods for producing the aqueous acrylic copolymer aqueous dispersion suitably used in the present invention include, for example, the methods (i) to (i) above.
The monomer mixture of (iii) is preferably emulsion-copolymerized in an aqueous medium in the presence of a water-soluble protective colloid such as PVA using the above-mentioned surfactant as a polymerization emulsifier.

Examples of the above-mentioned water-soluble protective colloid include polyvinyl alcohols (hereinafter sometimes abbreviated as PVA) such as partially silicified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; hydroxyethyl cellulose, hydroxypropyl cellulose, Cellulose derivatives such as carboxymethylcellulose salts; natural polysaccharides such as guar gum; and the like, which can be used alone or in combination of two or more. Among these water-soluble protective colloids, it is preferable to use PVA from the viewpoint of easiness of emulsion copolymerization and excellent cohesive strength of the obtained pressure-sensitive adhesive composition. Alternatively, it is particularly preferable to use a modified PVA having an average degree of polymerization of 500 or less.

The water-soluble protective colloid is preferably used in an amount of 0.1 to 2 parts by weight per 100 parts by weight of the acrylic resin component. When the amount is 0.1 part by weight or more, a pressure-sensitive adhesive composition having excellent cohesive force is obtained, and when the amount is 2 parts by weight or less, abnormal thickening or coagulation of the reaction system during the emulsion copolymerization process is caused. 0.1 ~ 2
It is preferred to use in the range of parts by weight.

Further, in the emulsion copolymerization, for example, persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate; organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide and the like. Polymerization initiators such as oxides and hydrogen peroxide can be used. These can be used either in one kind or in a combination of plural kinds.

In the aqueous emulsion copolymerization, a reducing agent can be used, if desired. Examples thereof include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate metal salts; and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite. Can be illustrated.

Furthermore, in the aqueous emulsion copolymerization, a chain transfer agent can be used if desired. Examples of such a chain transfer agent include n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, and 2-ethylhexylthio. Glycolate, 2-mercaptoethanol,
Trichlorobromomethane and the like can be mentioned.

The copolymerization temperature suitably employed in the emulsion copolymerization of the acrylic copolymer used in the present invention is about 40 to 100 ° C, particularly about 60 to 90 ° C.

The average particle diameter of the copolymer particles in the aqueous acrylic copolymer dispersion obtained by the DLS method is generally 0.05%.
２2μ, preferably 0.05-1μ.

In addition, the DLS method referred to in the present invention is a “new experimental chemistry course”.
Basic Technology 3 Light (II) ”pp. 725-741 (edited by The Chemical Society of Japan)
(Showa 59 version) based on the principle described in
The average particle size of the acrylic copolymer in the aqueous dispersion is a value measured and determined as described below.

Average particle size: Aqueous dispersion of acrylic copolymer in distilled water of 50,000 to 15
After diluting by a factor of 10,000 and stirring and mixing sufficiently, about 10 ml of the sample was collected in a 21 mmφ glass cell using a Pasteur pipette, and the sample was collected using a dynamic light scattering photometer DLS-700 (manufactured by Otsuka Electronics Co., Ltd.). And measure it under the following measurement conditions.

Measurement conditions Measurement temperature 25 ± 1 ° C Clock rate 10 μsec Correlation channel (Core.Channel) 512 Total number of measurements 200 times Light scattering angle 90 ° The above measurement results are processed by computer to determine the average particle size.

The pH of the aqueous dispersion of the acrylic copolymer obtained as described above can be adjusted with ammonia water or the like, if necessary. Such a dispersion has a solid content concentration of 30 to
70% by weight, preferably 45-65% by weight of a B-type rotational viscometer
The viscosity at 20 ° C. and 20 RPM is preferably about 50 to 3000 cps. And the pH is about 2 to 8.

The acrylic water-based pressure-sensitive adhesive composition of the present invention comprises the acrylic copolymer (A) and the copolymer 100 as described above.
Per part by weight of the ethylene-vinyl acetate-acrylic copolymer (B), ie, the following (a) to (c) (a) ethylene 5 to 40% by weight (b) vinyl acetate 5 to 60% by weight and (c) CH ₂ = CR'-COOR "[However, R 'is H or CH _3,
R ″ represents a C ₄ -C ₁₈ linear or branched alkyl group.
Acrylic or methacrylic acid esters represented by 15 to
70% by weight (provided that the total of (a) to (c) is 100% by weight) as a copolymer component, and the glass transition point is -30.
Ethylene / vinyl acetate / acrylic copolymer 5 ° C. or lower
It contains 20 parts by weight as an active ingredient.

The copolymerization amount of the above monomer (a) ethylene is 5 to 40% by weight based on 100% by weight of the total of monomers (A) to (C).
And preferably 10 to 38% by weight, particularly preferably 15 to 35% by weight. If the copolymerization amount of ethylene is less than the lower limit and is too small, the resulting pressure-sensitive adhesive composition is not preferable because the adhesive strength to the non-polar polymer is insufficient.On the other hand, if the amount exceeds the upper limit, the amount is too large. In addition, the production of the above-mentioned ethylene / vinyl acetate / acrylic copolymer becomes difficult, and the tackiness of the obtained pressure-sensitive adhesive composition is undesirably reduced.

Further, the copolymerization amount of vinyl acetate of the monomer (b) needs to be 5 to 60% by weight based on 100% by weight of the total of the monomers (A) to (C), and is preferably It is 10 to 50% by weight, particularly preferably 15 to 45% by weight. If the copolymerization amount of vinyl acetate is too small and less than the lower limit, the resulting pressure-sensitive adhesive composition is not preferred because the adhesive strength and cohesive strength of the composition are reduced. The low-temperature adhesiveness and water resistance of the resulting pressure-sensitive adhesive composition are not preferred.

Further, the acrylic acid or methacrylic acid ester of the monomer (c) is represented by the general formula CH ₂ CRCR′—COOR ″, wherein R ′ represents hydrogen or CH ₃ , and R ″ represents C ₄ — C
₁₈ , preferably a C _{4 to} C ₁₂ linear or branched alkyl group, for example, n-butyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, i-
Examples include an octyl group, an n-nonyl group, an i-nonyl group, an n-decyl group, and an n-dodecyl group. Specific examples of such acrylic acid or methacrylic acid ester include, for example, n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl Acrylic esters such as acrylates; and methacrylic esters such as n-octyl methacrylate, 2-ethylhexyl methacrylate, n-nonyl methacrylate, i-nonyl methacrylate, n-decyl methacrylate and n-dodecyl methacrylate. One or more of the above monomers are appropriately selected and used. Among these, the use of an acrylate ester in which R ″ is C _{4 to} C ₁₂ is preferred, and the use of n-octyl acrylate, 2-ethylhexyl acrylate, i-octyl acrylate, n-nonyl acrylate and i-nonyl acrylate is particularly preferred. .

The copolymerization amount of the monomer (c) is from monomer (a) to
It is necessary to be 15 to 70% by weight based on the total 100% by weight of (c), preferably 20 to 70% by weight.
~ 65% by weight is particularly preferred. If the copolymerization amount of the monomer (c) is too small below the lower limit value, the compatibility with the acrylic copolymer to be compounded is insufficient, and the non-polar polymer of the obtained pressure-sensitive adhesive composition The adhesive strength and the curved surface adhesiveness tend to be insufficient, which is not preferable. On the other hand, if the upper limit is exceeded, the cohesive strength of the obtained pressure-sensitive adhesive composition is undesirably reduced.

The ethylene / vinyl acetate / acrylic copolymer of the component (B) is, in addition to the monomers (a) to (c), the (a) to (c).
Other copolymerizable comonomers of 10 parts by weight or less in total can be copolymerized with respect to 100 parts by weight in total of (c).

Such comonomers include methyl acrylate, ethyl acrylate, C ₁ -C acrylic acid or methacrylic acid esters of _3, such as methyl methacrylate;
For example, vinyl cyanide such as acrylonitrile and methacrylonitrile; for example, vinyl chloride, vinylidene chloride,
Vinyl halides of vinyl fluoride; for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, alpha of C ₃ -C ₅ such as fumaric acid, beta-mono- - or di - unsaturated carboxylic acid; for example, dibutyl Monoesters of di- or poly-unsaturated carboxylic acids such as malate; for example, acrylamide, methacrylamide, diacetoneacrylamide, N
-Unsaturated carboxylic amides such as methylol acrylamide and N-butoxymethyl acrylamide; for example, acrylic acid or methacrylic acid ester of an epoxy group-containing alcohol such as glycidyl acrylate and glycidyl methacrylate; for example, 2-hydroxyethyl acrylate, 2-hydroxy Acrylic acid or methacrylic acid ester of a hydroxyl group-containing alcohol such as propyl acrylate and 2-hydroxyethyl methacrylate; and the like.

The glass transition point of the ethylene / vinyl acetate / acrylic copolymer of the component (B) must be −30 ° C. or less, and −35 ° C.
C. or lower, particularly preferably -40.degree. C. or lower. If the glass transition point exceeds the above temperature, the low-temperature adhesion and the curved surface adhesion are undesirably reduced.

In the acrylic water-based pressure-sensitive adhesive composition of the present invention, the blending amount of the ethylene / vinyl acetate / acrylic copolymer of the component (B) is 5 to 20 per 100 parts by weight of the acrylic copolymer of the component (A). Parts by weight. When the amount of the component (B) is too small, less than 5 parts by weight, the low-temperature adhesiveness becomes insufficient. On the other hand, when the amount exceeds 20 parts by weight, the adhesive strength with time stability,
It is not preferable because the heat and humidity deterioration property, cohesive strength and water resistance are reduced.

As a preferable method for producing the ethylene / vinyl acetate / acrylic copolymer of the component (B) in the present invention, the above-mentioned monomers (a) to (c) and the comonomer used as necessary are used. The monomer mixture is appropriately pressurized, in the presence of the same emulsifier as used in the production of the acrylic copolymer, protective colloid, and the like, in the presence of a radical polymerization initiator, a pH regulator, a polymerization degree regulator, and the like. By emulsion copolymerization.

The obtained aqueous dispersion of ethylene / vinyl acetate / acrylic copolymer has a solid content of 30 to 70% by weight, preferably 45 to 70% by weight.
At 65% by weight, the viscosity is 50-3000 cps. (Rotational viscometer, 25 ° C,
20 rpm.) And pH 2 to 8.

The acrylic water-based pressure-sensitive adhesive composition of the present invention contains the acrylic copolymer (A) and the ethylene-vinyl acetate-acrylic copolymer (B). Preferably, (A) and (B) are each mixed in the form of an aqueous dispersion.

Using the acrylic water-based pressure-sensitive adhesive composition of the present invention,
As a method for forming the pressure-sensitive adhesive layer, a direct method in which the pressure-sensitive adhesive composition is directly applied to a substrate such as paper or plastic film and dried is employed. Further, the pressure-sensitive adhesive composition is applied onto a release material such as paper or a plastic film that has been release-treated with silicone or the like, and dried to form a pressure-sensitive adhesive layer. A method in which the substrate is overlaid on the pressure-sensitive adhesive layer and pressed to transfer the pressure-sensitive adhesive layer onto the substrate can also be used. In such a transfer method, repelling is likely to occur at the time of coating on the release material,
Sulfosuccinate-based anionic surfactants for the purpose of preventing cissing can be used. Examples of the sulfosuccinate anionic surfactant include alkyl sulfosuccinate salts such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, and sodium polyoxyethylene lauryl sulfosuccinate, and derivatives thereof, and the like. The amounts used are (A) the acrylic copolymer and (B) ethylene.
3.5 per 100 parts by weight of vinyl acetate / acrylic copolymer in total
Not more than parts by weight. If the amount exceeds 3.5 parts by weight, the cohesive strength, water-resistant adhesive strength and the like tend to decrease, which is not preferable. The amount is preferably in the range of 0.1 to 1.5 parts by weight from the viewpoints of the physical properties of the pressure-sensitive adhesive and the repellency.

As a method for using the above-mentioned sulfosuccinate-based anionic surfactant, generally, the surfactant is diluted with water, alcohols or the like as necessary, and then added to the acrylic aqueous pressure-sensitive adhesive composition by post-addition. In general, the surfactant is contained, but in the production of the acrylic copolymer (A) by aqueous emulsion copolymerization, a part or all of the surfactant may be used in combination as a polymerization emulsifier. In this case, the ratio of the sulfosuccinate-based anionic surfactant to the total amount of the emulsifier for polymerization is excellent in the ease of production of the acrylic copolymer and the excellent properties of various substances of the obtained pressure-sensitive adhesive composition. In light of the above, the content is preferably in the range of 0 to 40% by weight.

In the above-mentioned transfer method, the composition of the present invention is usually used after thickening using various thickeners. Examples of such a thickener include sodium polyacrylate, the PVAs, the cellulose derivative, and an aqueous dispersion-type poly (meth) acrylic acid-based copolymer thickener that thickens under alkaline conditions. . The amount of these thickeners can be appropriately determined depending on the desired viscosity, and is 0 to 10 parts by weight, preferably 0 to 10 parts by weight, as a solid based on 100 parts by weight of the acrylic copolymer.
-5 parts by weight.

Further, the pressure-sensitive adhesive composition of the present invention can be used by adding a plasticizer, a tackifier, a pH adjuster, a wetting agent, a fungicide and the like, if necessary. Further, the pressure-sensitive adhesive composition of the present invention can be used by adding a conventionally used synthetic rubber latex, natural rubber latex or other synthetic resin emulsion as long as the desired performance is not impaired.

The acrylic water-based pressure-sensitive adhesive composition of the present invention generally has a solid content of 30 to 70% by weight, a viscosity of 100 to 15,000 cps. (Rotational viscometer, 25 ° C., 20 rpm.), And a pH of about 3 to 8; When used in the transfer method, the solid content concentration is 30 to 70% by weight and the viscosity is 3000 to 15000 cps. (Rotational viscometer, 25 ° C, 20 rp.
m.), pH 4 to 8.5 are preferred.

Using the acrylic water-based pressure-sensitive adhesive composition of the present invention, using a plastic film, paper, metal foil or the like as a base material, an adhesive tape, label, sticker, wallpaper, or the like prepared by the direct method or the transfer method described above is used. It exhibits well-balanced and excellent performance in a wide range of applications using plastics, metals, glass, ceramics, paper, cloth, building materials, fruits and the like as adherends.

The acrylic water-based pressure-sensitive adhesive composition of the present invention has excellent adhesion to a molded article of a nonpolar polymer such as polyolefin. The acrylic water-based pressure-sensitive adhesive composition of the present invention is used in applications in which a non-polar polymer such as polyolefin is used as an adherend, in particular, curved surface adhesion, low-temperature adhesion, cohesive strength, stability over time of adhesion, Heat and humidity deterioration,
Excellent low temperature tackiness and water resistance.

Since the acrylic water-based pressure-sensitive adhesive composition of the present invention has excellent curved surface adhesiveness, for example, it is possible to extremely easily perform pressure-sensitive adhesion of an adhesive such as a label or a tape directly onto a polyolefin tubular molded product of about 10 mm. Because of its excellent low-temperature adhesion, pressure-sensitive adhesion to a nonpolar polymer molded article is extremely easy even in a large freezer at -10 ° C or lower or in a cold region at 0 ° C or lower. The acrylic water-based pressure-sensitive adhesive composition of the present invention is further excellent in cohesive strength, and when the adhesive tape is wrapped with an adhesive tape such as cellophane tape and stored for a long period of time, a drawback such that the adhesive comes out. Not even. Further, since the pressure-sensitive adhesive composition of the present invention is also excellent in heat and humidity deterioration,
Pressure-sensitive adhesive tapes based on art paper etc.
Alternatively, there is an advantage that the adhesive strength and tack are not reduced even when stored for a long time at a high temperature. Further, since the pressure-sensitive adhesive composition of the present invention is excellent in low-temperature tackiness, label adhesion by a labeler in a cold region is extremely easy. Further, since the pressure-sensitive adhesive composition of the present invention has good water resistance, the pressure-sensitive adhesive composition exhibits excellent adhesiveness even to the surface of the adherend taken out of the freezer and condensed on the surface. However, no decrease in adhesion occurs.

The acrylic water-based pressure-sensitive adhesive composition of the present invention is excellent in curved surface adhesiveness and low-temperature adhesiveness particularly in applications where a nonpolar polymer molded article is used as an adherend.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples along with Comparative Examples and Reference Examples.

In addition, the preparation of the test piece, and various tests of normal adhesive strength, tack, cohesive strength, low-temperature adhesiveness, curved surface adhesiveness, water-resistant adhesiveness, adhesive force aging stability, and heat and humidity deterioration were performed according to the following methods. .

(1) Preparation of test piece A sample of the aqueous pressure-sensitive adhesive composition was applied onto the release material so that the dried pressure-sensitive adhesive layer was 25 ± 3 g / cm ² , and 100
After drying in a hot air circulating drier at 90 ° C. for 90 seconds, it is transferred to a 64 g / m ² cast coated paper to form a pressure-sensitive adhesive sheet.

(2) Normal adhesive strength test Brushed with # 280 water-resistant abrasive paper specified in JIS R-6253
SUS 304 stainless steel plate and polyethylene plate (JIS K
The test piece prepared in (1) was compression-bonded to γ ₀ = 43 dyn / cm according to the method specified in −6768 according to the method of JIS Z-238, and after 24 hours, 20 ° C., 65% RH, and peeling speed 300 mm / min. The peel strength (g / 25 mm) is measured under the conditions described in (1).

(3) Tack test According to the .J.DOW method, a test piece with a length of 100 mm is stuck on a slope with a slope angle of 30 °, and a steel ball with a diameter of x / 32 inches is rolled from a position 100 mm above the slope. , The size x of the largest diameter ball that stops on the sample.

(4) Cohesion test Scored with water-resistant abrasive paper of # 280 specified in JIS R-6253
Specimen stuck area of 25 × 2 on SUS 304 stainless steel plate
It was adhered so as to be 5 mm ² , and was pressure-bonded by reciprocating a 2 kg roller once.

A static load of 1 kg is applied to the sample in an atmosphere of 40 ° C. × 30% RH, and the time until the load drops is measured.

(5) Low-temperature adhesion test The test piece prepared in (1) and the same polyethylene plate used in (2) were left in a constant temperature room at 0 ° C or -10 ° C for 24 hours or more, and then 0 ° C or -10 ° C, respectively. Crimping according to the method of JIS Z-238, and left at 0 ° C or -10 ° C for 20 hours,
The peel strength (g / 25 mm) is measured under the conditions of 0 ° C. or −10 ° C. and a peel rate of 300 mm / min, respectively, and evaluated as follows.

；: Adhesive strength of 50 g or more △: Adhesive strength of 50 g or more but discontinuous peeling.

×: Adhesive strength of 50 g or less (6) Curved surface adhesion test A 10 mm × 20 mm test piece was made of a 10 mm φ polyethylene rod [same material as the polyethylene plate used in (2)]
After leaving it for 24 hours at 20 ° C and 65% RH,
Observe how the test piece floats from the rod.

○: No lifting △: Slight lifting ×: Complete lifting, (7) Water-resistant adhesion test JIS Z so that the adhesion area of the test piece on the same polyethylene plate as before (2) is 25 × 25 mm ² Crimping according to the method of -238, immersion in water at 25 ° C, and measuring the time until the test piece peels off and rises.

(8) Adhesive strength aging stability test After standing at 20 ° C. and 65% RH for 14 days, the adhesive strength to the stainless steel plate was measured according to (2) above, and the adhesive strength before leaving as 100% was calculated as the retention rate. I do.

(9) Heat / humidity deterioration test After leaving it in an atmosphere of 65 ° C. and 80% RH for 5 days, the adhesion retention rate is calculated in the same manner as (8).

Reference Example 1 70 parts by weight of ion-exchanged water was charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser.
Raise the temperature to ° C. On the other hand, in a separate container, 30 parts by weight of ion-exchanged water, 1.6 parts by weight of a polyoxyethylene alkyl phenol ether type nonionic surfactant (HLB about 11), and a polyoxyethylene alkyl phenol ether sulfate soda salt type anionic surfactant Material aqueous solution (non-volatile
27% by weight) and 1.5 parts by weight and partially saponified PVA (degree of polymerization 30)
0.2) by weight of 0) was charged and dissolved by stirring, and then 88 parts by weight of 2-ethylhexyl acrylate (hereinafter sometimes abbreviated as 2EHA) and vinyl acetate (hereinafter sometimes abbreviated as VAc) were added. A monomer mixture consisting of 11.5 parts by weight and 0.5 parts by weight of acrylic acid (hereinafter sometimes abbreviated as AA) is added and stirred to obtain a monomer premix.
The contents of the reactor were heated with stirring under a nitrogen stream, and when the contents reached 80 ° C., ammonium persulfate and sodium metabisulfite were used as a polymerization initiator and a reducing agent, respectively.
After the addition of 0.05 parts by weight, the monomer premix and the polymerization initiator are sequentially added to start polymerization, and the polymerization reaction is performed for about 3 hours. After the completion of the polymerization reaction, stirring was continued for about 1 hour at the same temperature, followed by cooling. The pH was adjusted by adding 0.3 parts by weight of aqueous ammonia to obtain an aqueous dispersion of an acrylic copolymer. This dispersion had a solid content of 50.2% by weight, a pH of 5.6 and a viscosity of 120.
cps. (25 ° C., 20 rpm).

Reference Examples 2 to 4 In Reference Example 1, instead of 11.5 parts by weight of VAc, 15 parts by weight of methyl acrylate (hereinafter sometimes abbreviated as MA) and 8.5 parts by weight of methyl methacrylate (hereinafter sometimes abbreviated as MMA) Or 35.5 parts by weight of MMA, and methacrylic acid instead of AA (hereinafter sometimes abbreviated as MAA)
And an aqueous dispersion of an acrylic copolymer was obtained in the same manner as in Reference Example 1 except that an aqueous dispersion of an acrylic copolymer was prepared by changing the amount of 2EHA used.

Table 1 shows the composition of the monomer and various physical properties of the dispersion and the copolymer.

Reference Example 5 Reference Example is the same as Reference Example 1 except that 2EHA 88 parts by weight / VAc 11.5 parts by weight is replaced by 2EHA 45 parts by weight / butyl acrylate (hereinafter sometimes abbreviated as BA) 51.5 parts by weight VAc 3 parts by weight. In the same manner as in 1, an aqueous dispersion of an acrylic copolymer was obtained. Table 1 shows the composition of the monomer and various physical properties of the dispersion and the copolymer.

Reference Example 6 In Reference Example 1, dodecyl mercaptan 0.2 was used in the monomer premix without using partially saponified PVA.
An aqueous dispersion of an acrylic copolymer was obtained in the same manner as in Reference Example 1 except that an aqueous dispersion of an acrylic copolymer was prepared by adding parts by weight. Table 1 shows the monomer composition and various physical properties of the dispersion and the copolymer.

Reference Example A In a pressure-resistant autoclave equipped with a stirrer, at room temperature, 73 parts by weight of ion-exchanged water, 4.5 parts by weight of a polyoxyethylene nonylphenol ether type nonionic surfactant, 1.2 parts by weight of hydroxyethyl cellulose, 0.06 parts by weight of acetic acid, 0.3 parts by weight of sodium acetate An aqueous solution consisting of 0.6 parts by weight of formaldehyde sulfoxylate soda salt was added thereto, and nitrogen and ethylene were replaced with stirring.

Next, the temperature in the system was heated to 50 ° C., and 20 parts by weight of VAc, 2EHA
A monomer mixture consisting of 60 parts by weight and 32 parts by weight of a 5% by weight aqueous solution of ammonium persulfate were simultaneously and uniformly dropped over 4 hours. During this time, the reaction temperature was adjusted to 50 ° C., and the ethylene pressure was constantly kept at 60 kg / cm ² during the polymerization. Then further
Aging was performed at 50 ° C. for 1 hour. The resulting ethylene / vinyl acetate / acrylic copolymer aqueous dispersion has a solid content of 50.1%,
pH 5.7, viscosity 100 cps. (25 ° C., 20 rpm), the monomer composition was ethylene 20% by weight, VAc 20% by weight, 2EHA 60% by weight, and the Tg of this copolymer was −60 ° C. .

Reference Examples B to C In Reference Example A, polymerization was carried out in substantially the same manner except that the amounts of VAc and 2EHA were changed, and / or the ethylene pressure was changed, to obtain an aqueous dispersion of an ethylene / vinyl acetate / acrylic copolymer. Obtained. Table 2 shows the monomer composition of these dispersions, the physical properties of the dispersions, and the Tg of the copolymer.

Reference Example D In Reference Example A, polymerization was carried out in substantially the same manner as in Reference Example A except that ethyl acrylate (EA) was used instead of 2EHA, and the amount of VAc and the ethylene pressure were changed, and an aqueous dispersion of an ethylene / vinyl acetate / acrylic copolymer was obtained. A liquid was obtained. Table 2 shows the monomer composition of the dispersion, the physical properties of the dispersion, and the Tg of the copolymer.

Example 1 204 parts by weight of the dispersion of Reference Example 1 (about 1 part of an acrylic copolymer)
8.5 parts by weight of the dispersion of Reference Example A (about 4 parts by weight of ethylene / vinyl acetate / acrylic copolymer), and the solid content concentration
0.6% by weight of a 40% by weight sodium dioctyl sulfosuccinate type anionic surfactant is added, and then an alkali thickener and aqueous ammonia are added to adjust the pH to 7.0 and about 11000 cps.
(25 ° C., 20 rpm) aqueous pressure-sensitive adhesive composition was obtained. Using this composition, a pressure-sensitive adhesive sheet of a test piece was prepared according to the method of preparation of a test piece (1), and the test method (2) to
Physical properties of the pressure-sensitive adhesive sheet were measured according to (9).
Table 3 shows the composition of the pressure-sensitive adhesive composition, its physical properties, and various physical properties of the pressure-sensitive adhesive sheet.

Examples 2 to 4 and Comparative Examples 1 to 2 In Example 1, almost the same as Example 1 except that the dispersion of Reference Example B was used instead of the dispersion of Reference Example A, and the amount used was changed variously. A pressure-sensitive adhesive composition was prepared in the same manner, and various tests were performed in the same manner. FIG. 3 shows the composition of the composition, its physical properties, and various physical properties of the pressure-sensitive adhesive sheet.

Comparative Examples 3 and 4 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the dispersion of Reference Example C or D was used instead of the dispersion of Reference Example A. Was performed.
Table 3 shows the composition of the composition, its physical properties, and various physical properties of the pressure-sensitive adhesive sheet.

Examples 5 to 7 and Comparative Examples 5 to 6 In Example 1, the dispersions of Reference Examples 2 to 6 were used instead of the dispersion of Reference Example 1, and Reference Example B was used instead of the dispersion of Reference Example A.
A pressure-sensitive adhesive composition was prepared in the same manner except that the above dispersions were used, and various tests were carried out in the same manner.
Table 3 shows the composition of the composition, its physical properties, and various physical properties of the pressure-sensitive adhesive sheet.

Continuation of front page (56) References JP-A-58-79068 (JP, A) JP-A-61-12775 (JP, A) JP-A-52-151326 (JP, A) JP-A-58-101174 (JP) , A) JP-A-58-113278 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 133/04-133/14 C08L 33/04-33/14

Claims (1)

(57) [Claims] 1. An acrylic copolymer having the following (A) and (B): (A) a gel content of 40% by weight or more and a glass transition point of -40 ° C. or less; system copolymer, per 100 parts by weight of (a) ethylene 5 to 40 wt%, (ii) vinyl acetate 5-60% by weight, and, (iii) CH ₂ = CR'-COOR "[However, R 'is H Or CH ₃ , R ″
15-70% by weight of acrylic acid or methacrylic acid ester represented by a linear or branched alkyl group of C ₄ -C _18] (provided that (the sum of a) to (c) is 100 wt%), Is contained as a copolymer component, and has a glass transition point of -30.
Ethylene / vinyl acetate / acrylic copolymer 5 ° C. or lower
An acrylic water-based pressure-sensitive adhesive composition comprising 20 parts by weight of as an active ingredient.