JP2719168B2 - Aqueous dispersion type pressure sensitive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous dispersion type pressure-sensitive adhesive having excellent adhesive strength, particularly excellent curved surface adhesiveness and low-temperature adhesiveness, to a film or molded article of a non-polar polymer such as polyolefin. Agent.

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

Conventionally, natural rubber, synthetic rubber, 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 based on an aqueous dispersion of an acid-type acrylic copolymer do not contain an organic solvent and do not cause fires or pollution, so they are gradually being widely used. It has become

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. In JP-A-58-79068,
100 parts by weight of an acrylic emulsion for a pressure-sensitive adhesive, 5 to 30% by weight of ethylene, 20 to 90% by weight of vinyl acetate and 5 to 50% by weight of an alkyl (meth) acrylate having 1 to 12 alkyl groups. An aqueous dispersion-type acrylic pressure-sensitive adhesive containing 5 to 35 parts by weight of an ethylene / vinyl acetate / acrylic copolymer emulsion obtained by polymerization is disclosed. This pressure-sensitive adhesive can improve the adhesive strength of a nonpolar polymer such as polyolefin to an adherend by adding a specific amount of the above-mentioned ethylene / vinyl acetate / acrylic copolymer to a conventional acrylic emulsion. It is to be improved.

The pressure-sensitive adhesive disclosed in JP-A-58-79068 can certainly improve the adhesive strength of a non-polar polymer to an object to be bonded, but as the practical application progresses, a curved surface of a non-polar polymer molded article such as polyolefin is obtained. It has become increasingly apparent that it has disadvantages inferior in adhesion and low-temperature adhesion.

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.

According to the present invention, (A) an acrylic copolymer having a gel content of 40% by weight or more, preferably 50 to 80% by weight, and most preferably 55 to 80% by weight, and a glass transition point of -40 ° C or less. (B) ethylene 5 to 40% by weight, preferably 10 to 38% by weight, most preferably 15 to 35% by weight, and (b) vinyl acetate 5 to 100 parts by weight of the polymer and (B) the acrylic copolymer. 60 wt%, preferably from 10 to 50% by weight, most preferably 15 to 45 wt%, and (c) C ₄ -C ₁₈ alkyl acrylate or C ₄ -C ₁₈ alkyl methacrylate 15-70% by weight, preferably 20 ~ 70% by weight, most preferably 25 ~ 65% by weight (however (a) ~
(The total of (c) is assumed to be 100% by weight) as a copolymer component, and the glass transition point is -30.
° C or less, preferably -35 ° C or less, most preferably -40 ° C
The following ethylene / vinyl acetate / acrylic copolymer is contained as an active ingredient in an amount of from 0.1 part by weight to less than 5 parts by weight, preferably from 0.5 part by weight to less than 5 parts by weight, and most preferably from 1 to 4.5 parts by weight. An aqueous dispersion-type acrylic pressure-sensitive adhesive composition is provided.

The details of the invention, including the above and further objects and advantages of the invention, will be more apparent from the following description.

The acrylic copolymer which is the component (A) of the present invention is not particularly limited, but i.CH ₂ = CH-COOR ₁ [provided that the resulting pressure-sensitive adhesive has excellent physical properties. Wherein R ₁ represents a C _{2 to} C ₁₂ , preferably a C _{4 to} C ₁₀ , most preferably a C ₈ linear or branched alkyl group], and the glass transition point of the homopolymer thereof. Acrylic ester 50 to 99.9 is -20 ° C or less
% By weight, preferably 60-99% by weight, most preferably 65-99% by weight.
98 wt%, II.C ₃ -C _5, preferably C ₃ -C ₄ of alpha, beta-unsaturated mono- or di - 0.1 to 1.5 wt% carboxylic acid, preferably 0.2
１1% by weight, most preferably 0.3-0.8% by weight, and iii. 0-50% by weight, preferably 1-45% by weight of a comonomer copolymerizable with the monomers i and ii above. % By weight, most preferably 1 to 35% 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 or more, preferably 50 to 80% by weight. %, Most preferably 55 to
It is preferably 80% by weight and an acrylic copolymer having a glass transition point of -40 ° C or lower.

As R ₁ of the above monomer i of CH ₂ CHCH—COOR ₁ , ethyl, n-propyl, n-butyl, isobutyl, n
-Hexyl group, 2-ethylhexyl group, n-octyl group, isooctyl group, isononyl group, n-decyl group, n
-Dodecyl group and the like. Further, as the monomer CH ₂ CHCH—COOR ₁ of i, ethyl acrylate, n
-Propyl acrylate, n-butyl acrylate isobutyl acrylate, n-hexyl acrylate, 2-
Examples thereof include alkyl acrylate monomers such as ethylhexyl acrylate, n-octyl acrylate, and isononyl acrylate.

If the above monomer i is used in an amount too small as less than the lower limit of 50% by weight, a good balance of adhesive strength, tack and cohesive strength tends to decrease, and the amount in excess of the above upper limit of 99.9% by weight is too large. When used, the mechanical stability (stability of the dispersion when shearing force is applied) and the cohesive strength of the obtained acrylic copolymer aqueous dispersion tend to decrease, and accordingly, it is appropriately selected and used within the above-mentioned usage amount range. By doing so, a better balance between better adhesion and better tack and better cohesion can be achieved.

On the other hand, alpha, beta-unsaturated mono C ₃ -C ₅ above ii - or di - Specific examples of the carboxylic acid, 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.

When the amount of the monomer (ii) is the lower limit (less than 0.1% by weight), the mechanical stability and cohesive strength of the aqueous copolymer dispersion become poor, and the upper limit amount is 1.5% by weight.
If used in excess of the above range, tack and water resistance will be reduced. Furthermore, if necessary, the suitable range can be selected experimentally in advance within the above range, if necessary, in consideration of the balance between tack and cohesive strength, the stability over time of adhesive strength, and the resistance to heat and humidity deterioration.

The copolymerizable with the monomer of i and the monomer of ii,
The comonomer iii, for example, an acrylic acid ester of the formula _{CH 2 = CH-COOR 2,} R 2 represents a linear or branched alkyl group of C ₁ -C _4, and, Acrylic esters having a glass transition point of the homopolymer exceeding −20 ° C. can be mentioned. Examples of R ₂ include a methyl group,
Examples thereof include an isopropyl group and a t-butyl group. Specific examples of the acrylate include methyl acrylate and t-butyl acrylate.

Further, as the comonomer of the above iii, for example, the formula CH ₂ CC
(CH ₃ ) —COOR ₃ , wherein R ₃ can be exemplified by a methacrylic acid ester having a C _{1 to} C ₄ linear or branched alkyl group. Examples of R ₃ include methyl group, ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group, and a t- butyl group and the like are. Specific examples of the methacrylate monomer include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate and isobutyl methacrylate.

Further, as the copolymer of the above iii, for example, the formula R ₄ OOC-
CH = CH-COOR ₅ is a maleic acid or fumarate represented by the formula: R ₄ and R ₅ are each independently
Copolymers having a linear or branched alkyl group of C _{1 to} C _10, preferably C _{1 to} C ₈ can be mentioned. Group R ₄ and
Examples of R ₅ include methyl group, ethyl group, n- butyl group,
Examples thereof include an n-hexyl group, a 2-ethylhexyl group, and an n-octyl group. Specific examples of such maleic acid or fumaric acid ester include dimethylmalate, di-n-butylmalate, di-2-ethylhexylmalate, di-n-octylmalate, dimethylfumarate, and di-n-butylfumarate. Rate, di-2-ethylhexyl fumarate, di-n-octyl fumarate and the like.

Further, as a comonomer of the above iii, for example, the formula CH ₂ CHCH
A saturated fatty acid vinyl ester represented by OCOR ₆ , wherein R ₆ is H or a linear or branched alkyl group of C _{1 to} C _18, preferably C _{1 to} C ₁₂ , and examples of the group R ₆ 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 include vinyl acetate, vinyl propionate, and vinyl versatate.

Further, as the comonomer of the above iii, for example, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene; and, for example, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile Selected copolymers can be used as well.

In addition, the comonomer of iii is not particularly limited, and various comonomers can be appropriately used as long as the excellent effects of the present invention are not impaired.

The use of the comonomer of the above iii can vary depending on the type of the comonomer, so the amount of use is not uniquely determined, but the balance between adhesion and tack and the balance between these and cohesion, etc. To help adjust as desired,
The above range amount can be appropriately selected so as to meet such purpose. If the amount of the copolymer (iii) exceeds the upper limit of the above range of 50% by weight and is too large, the tack tends to be too small, and an appropriate balance between the adhesive strength and the tack tends to be difficult to maintain. When the comonomer of (iii) or (iii) is used, it is preferable to select and use it appropriately in the above range.

The aqueous dispersion of the acrylic copolymer of the component (A) suitably used in the present invention has a solid content of 30 to 70% by weight, preferably 45 to 65% by weight, and a viscosity of 50 to 3,000 cps (rotational viscometer). ), PH 2 to 8, and such an aqueous dispersion is, for example, an acrylic copolymer obtained by aqueous emulsion copolymerization of a monomer mixture of monomer compositions i to iii as described in detail above. A combined aqueous dispersion, wherein the glass transition point of the acrylic copolymer is -40 ° C or lower, and the gel content in the copolymer is 40% by weight or more, preferably 50 to 80% by weight, most preferably Is preferably 55 to 80% by weight.

In the emulsion copolymerization for the production of the aqueous dispersion of the acrylic copolymer used in the present invention, the monomer mixture of (i) to (iii) can be prepared by, for example, adding a water-soluble protective colloid, a nonionic surfactant and / or a nonionic surfactant. Alternatively, the reaction is performed in an aqueous medium in the presence of an anionic surfactant.

Examples of the above-mentioned water-soluble protective colloid include polyvinyl alcohols (hereinafter, sometimes abbreviated as PVA) such as partially saponified 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 PVAs from the viewpoints of ease of emulsion copolymerization and excellent cohesion of the resulting pressure-sensitive adhesive, and it is preferable to use partially saponified PVA and / or modified PVA. It is particularly preferable to use 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 copolymer. If the amount is less than 0.1 part by weight, the effect of improving the cohesive strength tends to be difficult to appear. If the amount is more than 2 parts by weight, abnormal thickening and coagulation of the reaction system during the emulsion copolymerization process. It is not preferable because it tends to cause trouble.

When the glass transition point of the acrylic copolymer thus obtained is higher than −40 ° C., it loses appropriate tackiness and, at the same time, adhesiveness at a low temperature such as 0 ° C. or lower, particularly to a nonpolar polymer. Adhesive strength may be insufficient,
On the other hand, if the gel content is less than 40% by weight, excellent cohesive strength cannot be obtained, which is not preferable. 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 addition, the glass transition point in this specification was measured as follows.

Glass transition point: Approximately 10 mg of an aqueous acrylic copolymer dispersion sample was 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 a period of time is used as the measurement sample. SSC-500 manufactured by Seiko Electronic Industry Co., Ltd.
Type 0 Differential Scanning Calorimeter
er) at -150 ° C at a heating rate of 10 ° C / min.

In addition, the gel content in the present specification is a value measured and determined 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 × about 15 cm, wound uniformly on a glass rod of about 1.5 cmφ measured in advance, weighed, and weighed. W ₁₎ obtain.

The sample film wound around the glass rod is placed in a cylindrical filter 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) Ethyl acetate extraction In the same manner as in (b) above, the sample film (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.

As described above, the ethylene-vinyl acetate-acrylic copolymer as the component (B) of the present invention comprises (a) 5 to 40% by weight of ethylene, preferably 10 to 38% by weight, and most preferably 15 to 38% by weight. 35 wt%, (ii) vinyl acetate 5-60% by weight, preferably 10 to 50 wt%, and most preferably 15 to 45 wt%, and (c) C ₄ -C ₁₈ alkyl acrylate or C ₄ -C ₁₈ Alkyl methacrylate 15 to 70% by weight, preferably 20 to 70% by weight, most preferably 25 to 65% by weight ((a) to
(C) is 100% by weight) as the copolymerization component, and has a glass transition point of -30 ° C or lower, preferably -35 ° C or lower, and most preferably -40 ° C or lower. It is a bi-acrylic copolymer.

C in the monomer C ₄ -C ₁₈ alkyl acrylate or C ₄ -C ₁₈ acrylic methacrylate of (c) ₄ -C ₁₈
Examples of the alkyl group include an n-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, an isooctyl group, an isononyl group, an n-decyl group, and an n-dodecyl group. Furthermore, the monomer C ₄ of (c)
Examples of C ₁₈ alkyl acrylate or C ₄ -C ₈ alkyl methacrylate, n- butyl acrylate, n-
Acrylic esters such as hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and isononyl acrylate; n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate And methacrylates such as n-dodecyl methacrylate.

C ₄ -C ₁₈ alkyl acrylates are more preferred,
Particularly, 2-ethylhexyl acrylate is preferred.

The ethylene-vinyl acetate-acrylic copolymer of the component (B) is used in addition to the copolymer components of the above-mentioned (a) to (c), in addition to the desired performance of the aqueous dispersion type acrylic pressure-sensitive adhesive of the present invention. Within a range where (A) to (C) can be optionally copolymerized with the monomers (A) to (C), 0 to 5% by weight [(B) ethylene.
Per vinyl acetate / acrylic copolymer] as a copolymer component.

As such copolymerizable monomers, such as methyl acrylate, ethyl acrylate, n- propyl acrylate, C ₁ -C ₃ alkyl acrylate, such as i- propyl acrylate, such as methyl methacrylate,
C ₁ -C ₃ alkyl methacrylate such as ethyl methacrylate; for example, styrene, alpha-methyl styrene, aromatic vinyl such as vinyl toluene; for example, acrylonitrile, methacrylonitrile vinyl cyanides such as nitrile; for example,
Vinyl chloride, vinylidene chloride, vinyl halide of vinyl fluoride; for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, alpha of C ₃ -C ₅ such as fumaric acid, beta-unsaturated mono- - or di - Carboxylic acid; for example, amides of acrylic acid or methacrylic acid such as acrylamide, methacrylamide, diacetone acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide or derivatives thereof; epoxy groups such as glycidyl acrylate and glycidyl methacrylate Acrylic acid or methacrylic acid ester of an alcohol containing alcohol; for example, acrylic acid or methacrylic acid ester of a hydroxyl group-containing alcohol such as hydroxyethyl acrylate, hydroxypropyl acrylate or hydroxyethyl methacrylate ; And the like can be exemplified.

If the ethylene (a) in the ethylene-vinyl acetate-acrylic copolymer of the component (B) is less than 5% by weight, the adhesion to the non-polar polymer is insufficient, which is not preferable.
On the other hand, if it exceeds 40% by weight, the tack is undesirably reduced.

If the vinyl acetate content of (b) is less than 5% by weight, the adhesiveness and cohesive strength are undesirably reduced. On the other hand, if it exceeds 60% by weight, the low-temperature adhesiveness and the water resistance are insufficient.

Further, when the content of the C ₄ -C ₁₈ alkyl • (meth) acrylate in (c) is less than 15% by weight, the compatibility of the acrylic copolymer is insufficient, so that the adhesiveness to a nonpolar polymer and the adhesiveness to a curved surface are reduced. On the other hand, if it exceeds 70% by weight, the cohesive strength is reduced, which is not preferable.

The glass transition point of the ethylene / vinyl acetate / acrylic copolymer of the component (B) is −30 ° C. or lower, and the glass transition point is −30 ° C.
If the temperature is higher than ℃, the low-temperature adhesion and the curved surface adhesion are undesirably reduced.

In the aqueous dispersion type acrylic pressure-sensitive adhesive composition of the present invention, the blending amount of the ethylene / vinyl acetate / acrylic copolymer of the component (B) is 0.1 to 100 parts by weight of the acrylic copolymer of the component (A). One feature point is that the content is not less than 5 parts by weight to less than 5 parts by weight. If the amount of the component (B) is less than 0.1 part by weight, the adhesiveness to a non-polar polymer and the curved surface adhesive strength are undesirably reduced. , Cohesive strength and water resistance are undesirably reduced.

The aqueous dispersion of the ethylene / vinyl acetate / acrylic copolymer of the component (B) in the present invention has a solid content of 30 to 70% by weight, preferably 45 to 65% by weight, and a viscosity of 50 to 3,000 c.
ps (rotational viscometer), pH 2 to 8. Such an aqueous dispersion is prepared by subjecting the monomer mixture of the above (a) to (c) to an appropriate emulsifier and, if necessary, a protective colloid. , Etc. in the presence of a radical co-polymerization initiator, a pH regulator and a polymerization degree regulator.

The aqueous dispersion-type acrylic pressure-sensitive adhesive of the present invention effectively uses the aqueous dispersion of the acrylic copolymer (A) and the aqueous dispersion of the ethylene / vinyl acetate / acrylic copolymer (B). Although it is contained as a component, the pressure-sensitive adhesive of the present invention may be used by adding a plasticizer, a tackifier, a thickener, a pH adjuster, a wetting agent, and a fungicide as necessary. Can be. Further, the pressure-sensitive adhesive 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 aqueous dispersion type acrylic pressure-sensitive adhesive of the present invention can be applied to a base material such as a plastic film, paper, or metal foil as an aqueous dispersion and dried to obtain an adhesive tape, label, sticker, wallpaper, or the like. . The adhesive tape using the aqueous dispersion type acrylic pressure-sensitive adhesive of the present invention,
Labels and stickers are plastic, metal, glass,
It exhibits well-balanced and excellent performance in a wide range of applications using ceramics, paper, cloth, building materials, fruits, etc. as adherends.

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

Since the aqueous dispersion type acrylic pressure-sensitive adhesive of the present invention has excellent curved surface adhesiveness, for example, it is extremely easy to apply pressure-sensitive bonding of an adhesive such as a label and a tape to a polyolefin tubular molded product having a diameter of about 10 mm. Because of its excellent low-temperature adhesiveness, 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 aqueous dispersion-type acrylic pressure-sensitive adhesive of the present invention has further excellent cohesive strength, and has a disadvantage that the adhesive comes out when stored for a long time by wrapping an adhesive tape such as a cellophane tape. There is no. Further, since the pressure-sensitive adhesive of the present invention has excellent heat and humidity deterioration resistance, the pressure-sensitive adhesive tape based on art paper or the like can be stored under a high humidity and / or high temperature for a long period of time to have an adhesive strength. Also, there is an advantage that the tack does not decrease. Further, since the pressure-sensitive adhesive 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 of the present invention has good water resistance, it shows excellent adhesiveness even to the surface of the adherend taken out from the freezer and condensed on the surface. There is no decrease in adhesion.

The aqueous dispersion type acrylic pressure-sensitive adhesive of the present invention is, in particular,
In applications where non-polar polymer molded products are used as adherends,
Excellent in curved surface adhesion and low temperature adhesion.

Hereinafter, the present invention will be described in more detail with reference to 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 dispersion-type pressure-sensitive adhesive composition was applied on the release material so that the dried pressure-sensitive adhesive layer became 25 ± 3 g / cm ^2, and was heated at 100 ° C. for 90 seconds. After drying with a hot air circulation type dryer, 64 g / m
Transfer to cast-coated paper of No. ² to make a pressure-sensitive adhesive sheet.

(2) Adhesion test in normal condition Stained with water-resistant abrasive paper of # 280 specified in JIS R-6253
SUS304 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 was stuck on a slope with a slope angle of 30 °, and a steel ball with a diameter of x / 32 inches was rolled from a position 100 mm above the slope, and tested. It is indicated by the size x of the largest diameter ball that stops above.

(4) Cohesive force test Brushed with # 280 waterproof abrasive paper specified in JIS R-6253
Specimen stuck area of 25 × 25 on SUS304 stainless steel plate
adhered to as to be in mm ^2, and pressed by one reciprocation of a 2kg roller.

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

(5) Low-temperature adhesion test The test piece prepared in (1) and the same polyethylene plate as used in (2) were left in a constant temperature room at 0 ° C for 24 hours or more.
Pressure bonding according to the method of JIS Z-238 at 0 ° C, leaving at 0 ° C for 20 minutes, peeling strength (g at 0 ° C, peeling speed 300mm / min)
/ 25mm) and evaluate as follows.

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

×: 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 [of the 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 floating △; there float slightly ×; completely float rises (7) The same polyethylene plate and water-resistant adhesion test before (2), as bonded area of the test piece is 25~25mm ² JIS Z- 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) Temporal stability test of adhesive strength After the test piece prepared in (1) was left at 20 ° C. and 65% RH for 14 days, the adhesive strength to the stainless steel plate was measured according to the above (2), and the adhesive strength before leaving was measured. Assuming 100%, calculate the retention.

(9) Heat / humidity degradation test The test piece prepared in (1) was left in an atmosphere of 65 ° C. and 80% RH for 5 days, and the adhesion retention rate was 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 (about 11 HLB), and a polyoxyethylene alkyl phenol ether sulfate soda salt type anionic surfactant Aqueous solution (non-volatile
27% by weight) and 1.5 parts by weight and partially saponified PVA (degree of polymerization 30)
0) was dissolved in 0.2 parts by weight of the mixture, followed by stirring, and then 27.4 parts by weight of 2-ethylhexyl acrylate (hereinafter sometimes abbreviated as 2EHA) and vinyl acetate (hereinafter, VAc).
A monomer mixture consisting of 22.1 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 adding 0.05 parts by weight, the monomer premix and the polymerization initiator are sequentially added to start the 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 130.
cps. (25 ° C., 20 rpm).

Reference Examples 2 to 4 In Reference Example 1, instead of 22.1 parts by weight of VAc, 28 parts by weight of methyl acrylate (hereinafter sometimes abbreviated as MA) and 14.5 parts by weight of methyl methacrylate (hereinafter sometimes abbreviated as MMA) were used. Parts or 35 parts by weight of MMA, and methacrylic acid instead of AA (hereinafter may be 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 In Reference Example 1, 45 parts by weight of 2EHA / butyl acrylate (hereinafter referred to as “77.4 parts by weight of 2EHA / 22.1 parts by weight of VAc”)
An aqueous dispersion of an acrylic copolymer was obtained in the same manner as in Reference Example 1 except that 51.5 parts by weight / vAc3 parts by weight was used.

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

Reference Example 6 The same procedure as in Reference Example 1 was carried out except that the partially saponified PVA was not used, and the content of dodecyl mercaptan in the monomer premix was 0.1%.
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 2 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, sodium acetate An aqueous solution consisting of 0.3 part by weight and 0.6 part by weight of formaldehyde sulfoxylate soda salt was added, 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 and 2EHA6
0 parts by weight of the monomer mixture 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 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 compositions 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 obtain a pH 7.0, about 10,000 cps.
(25 ° C., 20 rpm) aqueous dispersion type 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 physical properties of the pressure-sensitive adhesive sheet were measured according to test methods (2) to (9). Was. 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 2-3 and Comparative Examples 1-2 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. Table 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 4 to 6 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.

Claims (3)

(57) [Claims] (1) The gel content of (A) is 40% by weight or more,
An acrylic copolymer having a glass transition point of −40 ° C. or lower; and (B) 100 to 100 parts by weight of the acrylic copolymer, (a) 5 to 40% by weight of ethylene, (b) 5 to 60% by weight of vinyl acetate, and (c) C ₄ -C ₁₈ alkyl acrylate or C ₄ -C ₁₈ alkyl methacrylate 15-70% by weight (provided that (a) to
(The total of (c) is assumed to be 100% by weight) as a copolymer component, and the glass transition point is -30.
Ethylene / vinyl acetate / acrylic copolymer 0.1 ° C or lower
An aqueous dispersion-type acrylic pressure-sensitive adhesive composition, characterized by comprising as an active ingredient at least 5 parts by weight of at least 5 parts by weight. 2. An acrylic copolymer (A) comprising: i.CH ₂ CHCH—COOR _{1 wherein} R ₁ represents a C _{2 to} C ₁₂ linear or branched alkyl group. 50 to 99.9% by weight of an acrylate ester whose glass transition point of the homopolymer is -20 ° C or lower. α of ii.C ₃ ~C _5, β- unsaturated mono- or di -. 0.1 to 1.5 wt% carboxylic acid and iii monomer of monomers and ii of the above 1 copolymerizable comonomer The pressure-sensitive adhesive composition according to claim 1, which is a copolymer containing 0 to 50% by weight (wherein the sum of i to iii is 100% by weight) as a copolymerization component. . 3. An acrylic copolymer obtained by aqueous emulsion copolymerization in the presence of 0.1 to 2 parts by weight of an aqueous protective colloid per 100 parts by weight of the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein