(Meth)acrylic copolymer, adhesive composition containing same, and adhesive sheet

Abstract

A (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000, in which the (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture including a macromonomer (a) that has a number average molecular weight of 500 or more and less than 6000 and a vinyl monomer (b), and preferably includes 7 to 40% by mass of a repeat unit derived from the macromonomer (a), has sufficient coating workability, adhesive holding power and adhesive property as an adhesive composition.

Claims

1. An adhesive composition comprising a (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000, wherein the (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture comprising a macromonomer (a) having a number average molecular weight of 500 or more and 4,500 or less and a vinyl monomer (b), wherein the monomer (a) is represented by Formula (1): ##STR00003## where in Formula (1), n is 4 to 5,999; each of R and R1 to Rn is independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, in which the alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group optionally have a substituent; each of X1 to Xn is independently a hydrogen atom or a methyl group; and Z is a terminal group of the macromonomer (a), wherein the adhesive composition is in a solution state in the presence of at least one of a solvent and a liquid vinyl monomer, or is a hot melt-based adhesive composition without solvent.

2. The adhesive composition according to claim 1, wherein the (meth)acrylic copolymer (A) has a mass average molecular weight of 120,000 to 700,000.

3. The adhesive composition according to claim 1, wherein the glass transition temperature (Tga) of the macromonomer (a) is 30 to 120° C.

4. The adhesive composition according to claim 1, wherein the (meth)acrylic copolymer (A) has a melt viscosity at 130° C. of 20 to 800 Pa's.

5. The adhesive composition according to claim 1, wherein the vinyl monomer (b) is any of 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, and ethyl acrylate.

6. The adhesive composition according to claim 1, wherein a glass transition temperature (Tgb) of the vinyl monomer (b) is −100 to 10° C.

7. The adhesive composition according to claim 1, wherein the macromonomer (a) is obtained from methyl (meth)acrylate and isobornyl (meth)acrylate.

8. An adhesive sheet using the adhesive composition according to claim 1.

9. An adhesive composition comprising a (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000, wherein the (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture comprising a macromonomer (a) having a number average molecular weight of 500 or more and 4,500 or less and a vinyl monomer (b), wherein the adhesive composition is in a solution state in the presence of at least one of a solvent and a liquid vinyl monomer, or is a hot melt-based adhesive composition without solvent.

10. The adhesive composition according to claim 9, wherein the (meth)acrylic copolymer (A) has a mass average molecular weight of 120,000 to 700,000.

11. The adhesive composition according to claim 9, wherein the glass transition temperature (Tga) of the macromonomer (a) is 30 to 120° C.

12. The adhesive composition according to claim 9, wherein the (meth)acrylic copolymer (A) has a melt viscosity at 130° C. of 20 to 800 Pa.Math.s.

13. The adhesive composition according to claim 9, wherein the vinyl monomer (b) is any of 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, and ethyl acrylate.

14. The adhesive composition according to claim 9, wherein a glass transition temperature (Tgb) of the vinyl monomer (b) is −100 to 10° C.

15. The adhesive composition according to claim 9, wherein the macromonomer (a) is obtained from methyl (meth)acrylate and isobornyl (meth)acrylate.

16. An adhesive sheet using the adhesive composition according to claim 9.

Description

EXAMPLES

(1) Examples and Comparative Examples are shown below, and the adhesive resin composition of the invention is described further in detail. However, the invention is not limited thereto. Meanwhile, “part” in present Examples means “mass part”.

Synthesis of Macromonomer (a-1)

Preparation of Dispersion 1

(2) 900 Parts of deionized water, 60 parts of sodium 2-sulfoethyl methacrylate, 10 parts of potassium methacrylate and 12 parts of methyl methacrylate (MMA) were put into a polymerization apparatus provided with a stirrer, a cooling tube and a thermometer, and stirred, and heated to 50° C. while substituting the inside of the polymerization apparatus with nitrogen. 0.08 Parts of 2,2′-azobis(2-methyl propioneamidine) dihydrochloride as a polymerization initiator were added into the polymerization apparatus, and further heated to 60° C. After the heating, MMA was continuously dropped for 75 minutes at a speed of 0.24 parts/minute using a dropping pump. The reaction solution was kept at 60° C. for 6 hours and then cooled to room temperature, to give Dispersion 1 having 10% by mass of the solid content, which is a transparent aqueous solution.

(3) 145 Parts of deionized water, 0.1 part of sodium sulfate and 0.25 parts of Dispersion 1 (10% by mass of the solid content) were put into a polymerization apparatus provided with a stirrer, a cooling tube and a thermometer, and stirred to give a uniform aqueous solution. Next, 100 parts of MMA, 0.008 parts of bis[(difluoroboryl)diphenyl glyoximate] cobalt (II) as a chain transfer agent and 0.8 parts of “PEROCTA” (trade name) O (1,1,3,3-tetramethyl butyl peroxy2-ethyl hexanoate, manufactured by NOF CORPORATION) as a polymerization initiator were added, to give an aqueous suspension.

(4) Next, the inside of the polymerization apparatus was substituted with nitrogen, heated to 80° C. and reacted for one hour, and heated to 90° C. and kept for one hour in order to further increase the polymerization ratio. Then, the reaction solution was cooled to 40° C., to give an aqueous suspension including the macromonomer. This aqueous suspension was filtered, and the residue was washed with deionized water, dehydrated, and dried at 40° C. for 16 hours, to give the macromonomer (a-1). The number average molecular weight of this macromonomer (a-1) was 1400, and the glass transition temperature by DSC measurement was 55° C.

Preparation of Macromonomers (a-2) to (a-9)

(5) Macromonomers (a-2) to (a-9) were prepared with a similar method to that of the macromonomer (a-1) except that the charge-in quantities (parts) of the monomer, the polymerization initiator and the chain transfer agent added to Dispersion 1 were changed to those shown in Table 1. The number average molecular weight (Mn) of the obtained macromonomer (a) and the glass transition temperature (Tga) are shown in Table 1 together.

(6) TABLE-US-00001 TABLE 1 Monomer (a) a-1 a-2 a-3 a-4 a-5 a-6 a-7 a-8 a-9 MMA 100 100 100 100 100 100 100 100 50 IBXMA — — — — — — — — 50 Polymerization 0.8 0.45 0.43 0.4 0.35 0.2 0.15 1.3 0.5 initiator (parts) Chain transfer agent 0.008 0.0045 0.0043 0.004 0.0035 0.002 0.0015 0.013 0.005 (parts) Physical Mn 1400 1900 2100 2500 3000 5100 7000 1000 2600 property Tga (° C.) 55 73 77 80 90 95 105 44 92 MMA: Methyl methacrylate IBXMA: Isobornyl methacrylate

Evaluation Method

(7) Glass transition temperature (Tga) of macromonomer (a) Glass transition temperature (Tga) of the macromonomer (a) was measured at a heating speed of 5° C./minute under nitrogen atmosphere using a differential scanning calorimeter (DSC SmartRoader manufactured by Rigaku). Meanwhile, aluminum oxide was used as a standard substance.

Molecular Weights of Macromonomer (a) and Acrylic Copolymer (A)

Macromonomer (a)

(8) The molecular weight of the macromonomer (a) was measured using gel permeation chromatography (GPC) (HLC-8320 manufactured by TOSOH CORPORATION). A tetrahydrofuran solution of the macromonomer (a) was adjusted to 0.2% by mass and then 10 μl of the solution was injected to an apparatus equipped with a column manufactured by TOSOH CORPORATION (TSKgel SuperHZM-M×HZM-M×HZ2000, TSKguardcolumn SuperHZ-L), and the molecular weight was measured at conditions of flow rate: 0.35 ml/minute, eluting solvent: tetrahydrofuran (stabilizer BHT) and column temperature: 40° C., and the number average molecular weight (Mn) was calculated as conversion to standard polystyrene.

Acrylic Copolymer (A)

(9) The molecular weight of the acrylic copolymer (A) was measured using gel permeation chromatography (GPC) (HLC-8120 manufactured by TOSOH CORPORATION). A tetrahydrofuran solution of the acrylic copolymer (A) was adjusted to 0.3% by mass and then 20 μl of the solution was injected into an apparatus equipped with a column manufactured by TOSOH CORPORATION (TSKgel SuperHM-H*4, TSKguardcolumn SuperH-H), and the molecular weight was measured at conditions of flow rate: 0.6 ml/minute, eluting solvent: tetrahydrofuran (stabilizer BHT) and column temperature: 40° C., and the weight average molecular weight (Mw) was calculated as conversion to standard polystyrene.

Transparency

(10) The resin solution after polymerization was solvent-dehydrated with drying under reduced pressure, and the resultant is picked in a 200 mL transparent wide-mouth screwed bottle, and observed by the naked eyes under scattering daylight. A case where the resultant is transparent and no contaminant or isolation is admitted, was indicated as “◯”, and a case where any of cloudiness, contaminant, isolation and the like is observed, is indicated as “x”.

Evaluation for Coating Property (Melt Viscosity at 130° C.)

(11) The coating property was measured using a viscoelasticity measurement apparatus Rheosol-G5000 manufactured by UNIVERSAL BUILDING MATERIALS MERCHANTS CO. LTD., and the value of the viscosity (η*) measured at 130° C., 0.7% distortion and 0.02 Hz using a 25 mm ϕ cone plate was assumed as the value of the melt viscosity at 130° C., and the coating property was rated according to the following criteria.

(12) No more than 500 Pa.Math.s: ◯

(13) More than 500 Pa.Math.s and no more than 800 Pa.Math.s: Δ

(14) More than 800 Pa.Math.s: x

Test and Evaluation for Holding Power

(15) In accordance with JIS Z0237, double sides of the acrylic copolymer (A) were sandwiched between peeling films and made to a sheet, and one of the peeling films was peeled off, and a polyethylene terephthalate film (hereinafter, referred to as the PET film) was crimped instead with a 2 kg hand roller. This was cut to a strip form of 20 mm×100 mm. The other peeling film was peeled off, and the acrylic copolymer (A) was horizontally stuck on a 30 mm×100 mm SUS plate using a 2 kg hand roller so that the sticking face was 20×20 mm. The acrylic copolymer (A) was cured for 30 minutes at 40° C. and then the PET film was loaded with a weight of 0.5 kg on the tip, and the holding time was measured in 40° C. constant temperature zone. The holding power was rated according to the following criteria.

(16) Holding time is

(17) 30 minutes or more: ⊙

(18) 5 minutes or more and less than 30 minutes: ◯

(19) Less than 5 minutes: x

(20) In addition, with changing the temperature to 90° C. (50% relative humidity), the holding time was measured similarly. Overall holding power was evaluated by the following Formula.

(21) (Holding time at 40° C.)/(holding time at 90° C.)=X

(22) Rating is as follows.

(23) X≥230: ⊙

(24) 230>X≥200: ◯

(25) 200>X≥100: Δ

(26) 100>X: x

Adhesive Property Test

(27) The peeling strength Y for a glass base material was measured at 180° peeling angle and 60 mm/min tension speed in accordance with JIS Z0237. In addition, the peeled face of the glass base material was visually observed, and the presence or absence of the adhesive residue was checked. The adhesive force was rated according to the following criteria.

(28) Y≥3N/25 mm, and absence of adhesive residue: ◯

(29) Y≥3N/25 mm, and presence of adhesive residue: Δ

(30) Y<3N/25 mm: x

Preparation Example 1

Preparation of (Meth)Acrylic Copolymer (A-1)

(31) Into a four-neck flask provided with a stirring device, a thermometer, a cooling tube and an opening for nitrogen gas introduction, 40 parts of ethyl acetate as a charge solvent and 10 parts of the macromonomer (a-1) were charged, and heated to 85° C. under nitrogen gas aeration. After the temperature reached 85° C., a mixture including 20 parts of ethyl acetate, 90 parts of n-butyl acrylate and 0.04 parts of benzoyl peroxide was dropped over 4.5 hours. The reaction solution was kept for one hour after completion of the dropping, and then a mixture including 0.5 parts of “PEROCTAO” and 10 parts of ethyl acetate was added over one hour. Then, the reaction solution was kept for 2 hours, and then added with 0.5 parts of “IRGANOX 1010” (trade name, manufactured by BASF) as an antioxidant and 20.5 parts of ethyl acetate, and then cooled to room temperature to give a (meth)acrylic copolymer (A-1).

Preparation Examples 2 to 21

Preparation of (Meth)Acrylic Copolymers (A-2) to (A-21)

(32) (Meth)acrylic copolymers (A-2) to (A-21) were obtained in a similar manner to Preparation Example 1 except that the composition of the monomer mixture (the macromonomer (a) and the vinyl monomer (b)) and the initial charge solvent used were changed to Table 2.

(33) Meanwhile, (A-12) is an example where the macromonomer (a) was not used.

(34) TABLE-US-00002 TABLE 2 Preparation Example 1 2 3 4 5 6 7 8 9 10 11 (Meth)acrylic copolymer (A) A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10 A-11 Monomer Macromonomer a-1 10 — — — — — — — — — — mixture (a) (parts) a-2 — 15 — — — — — — — — — a-3 — — 15 — — — — — — — — a-4 — — — 10 10 15  7 — 11 — — a-5 — — — — — — — 15 — — — a-6 — — — — — — — — — 10 — a-7 — — — — — — — — — — — a-8 — — — — — — — — — — — a-9 — — — — — — — — — — — AA-6 — — — — — — — — — — 10 Vinyl monomer MMA — — — — — — — — — — — (b) (parts) n-BA 90 81 81 90 86 81 93 81 — 90 90 2-EHA — — — — — — — — 86 — — CHMA AA —  4  4 —  4  4 —  4  3 — — 2-HEMA — — — — — — — — — — — TgB (° C.) −49  −45  −45  −49  −45  −45  −49  −45  −50  −49  −49  Initial charge solvent EtOAc 40 40 40 40 40 40 40 40 40 40 40 (parts) IPA —   1.7   2.5  4  4   4.5  3   4.5  7 12 — Weight average molecular 40 30 27 25 23 23 31 24  8   9.4   12.6 weight (ten thousand) Preparation Example 12 13 14 15 16 17 18 19 20 21 (Meth)acrylic copolymer (A) A-12 A-13 A-14 A-15 A-16 A-17 A-18 A-19 A-20 A-21 Monomer Macromonomer a-1 — — — — 20 — — — — — mixture (a) (parts) a-2 — — — — — — — — — — a-3 — — — — — — — — — — a-4 — — 11 10 — — 20 20 20 — a-5 — — — — — — — — — — a-6 — — — — — — — — — — a-7 — 10 — — — — — — — — a-8 — — — — — 20 — — — — a-9 — — — — — — — — — 10 AA-6 — — — — — — — — — — Vinyl monomer MMA 10 — — — — — — — — — (b) (parts) n-BA 90 90 79   85.9 80 80 80 80 80 80 2-EHA — — — — — — — — — — CHMA 10 — — — — — — — AA — — —  4 — — — — — — 2-HEMA — — —   0.1 — — — — — — TgB (° C.) −39  −49  −39  −45  −49  −49  −49  −49  −49  −49  Initial charge solvent EtOAc 40 40 40 70 40 20 40 40 40 40 (parts) IPA  7 18  7 — — —  5  7 15  4 Weight average molecular 23   8.5  8 34 30 29 18 14  8 24 weight (ten thousand) AA-6: Macromonomer manufactured by TOAGOSEI CO., LTD., product name, Mn = 6000 MMA: Methyl methacrylate n-BA: n-butyl acrylate 2-EHA: -2-ethylhexyl acrylate CHMA: Cyclohexyl methacrylate AA: Acrylic acid 2-HEMA: -2-hydroxyethyl methacrylate EtOAc: Ethyl acetate IPA: Isopropyl alcohol

Examples 1 to 19 and Comparative Examples 1 to 3

(35) The melt viscosity at 130° C., the transparency, the holding power and the adhesive force of the (meth)acrylic copolymer (A-1) prepared in Preparation Example 1 were measured, and the results are shown in Table 3. Similarly, similar measurements were performed for the (meth)acrylic copolymers (A-2 to A-21) of Preparation Examples 2 to 21 similarly (Tables 3 and 4). Meanwhile, Example 11 represents an example where a (meth)acrylic copolymer (A-4) was used, and the coating method was changed to a hot melt method.

(36) TABLE-US-00003 TABLE 3 Example Example Example Example Example Example 1 2 3 4 5 6 (Meth)acrylic copolymer A-1 A-2 A-3 A-4 A-5 A-6 Coating Melt viscosity at 200 260  230  230  230 280  property 130° C. (Pa .Math. s) Rating ◯ ◯ ◯ ◯ ◯ ◯ Coating method Solution Solution Solution Solution Solution Solution coating coating coating coating coating coating Transparency ◯ ◯ ◯ ◯ ◯ ◯ Holding power Time 10 min 18 h >24 h >24 h >24 h >24 h of 0.5 Kg at Rating ◯ ⊙ ⊙ ⊙ ⊙ ⊙ 40° C. Holding power Time (s)  2 15 18 10  14 22 of 0.5 Kg at 90° C. X 40° C./ 300 4320  4800  8640  6171  3927  90° C. Ratio Overall evaluation for holding power ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ Adhesive force Y (N/25 mm)  20 15 14 10  8 14 Adhesive residue Presence Absence Absence Absence Absence Absence Rating ◯ ⊙ ⊙ ⊙ ⊙ ⊙ Example Example Example Example Example 7 8 9 10 11 (Meth)acrylic copolymer A-7 A-8 A-9 A-10 A-4 Coating Melt viscosity at 400  500 490 270 230  property 130° C. (Pa .Math. s) Rating ◯ ◯ ◯ ◯ ◯ Coating method Solution Solution Solution Solution Hot coating coating coating coating melt Transparency ◯ ◯ ◯ ◯ ◯ Holding power Time 20 h >24 h 10 h 77 min >24 h of 0.5 Kg at Rating ⊙ ⊙ ⊙ ⊙ ⊙ 40° C. Holding power Time (s) 6 330  20  10 12 of 0.5 Kg at 90° C. X 40° C./ 12000   262 1900  462 7200  90° C. Ratio Overall evaluation for holding power ⊙ ⊙ ⊙ ⊙ ⊙ Adhesive force Y (N/25 mm) 7  11  4  5 11 Adhesive residue Absence Absence Absence Presence Absence Rating ◯ ◯ ◯ Δ ◯

(37) TABLE-US-00004 TABLE 4 Example Example Example Example Example Example 12 13 14 15 16 17 (Meth)acrylic copolymer A-14 A-15 A-16 A-17 A-18 A-19 Coating Melt viscosity at 500 500 90 80 270 150 property 130° C. (Pa .Math. s) Rating ◯ ◯ ◯ ◯ ◯ ◯ Coating method Solution Solution Solution Solution Solution Solution coating coating coating coating coating coating Transparency ◯ ◯ ◯ ◯ ◯ ◯ Holding power Time 4 h >24 h 1 h 7 min >24 h 12 h of 0.5 Kg at Rating ⊙ ⊙ ⊙ ◯ ⊙ ⊙ 40° C. Holding power Time (s)  16  18  4  2 144  10 of 0.5 Kg at 90° C. X 40° C./ 900 4800  900  210  600 4320  90° C. Ratio Overall evaluation for holding power ⊙ ⊙ ⊙ ◯ ⊙ ⊙ Adhesive Y (N/25 mm)  3  8 35 47  8  8 force Adhesive residue Absence Absence Presence Presence Absence Absence Rating ◯ ◯ Δ Δ ⊙ ⊙ Example Example Comparative Comparative Comparative 18 19 Example 1 Example 2 Example 3 (Meth)acrylic copolymer A-20 A-21 A-11 A-12 A-13 Coating Melt viscosity at 60  280 580  250 250 property 130° C. (Pa .Math. s) Rating ◯ ◯ Δ ◯ ◯ Coating method Solution Solution Solution Solution Solution coating coating coating coating coating Transparency ◯ ◯ X ◯ ◯ Holding power Time 5 h >24 h 20 min 1 min 38 min of 0.5 Kg at Rating ⊙ ⊙ ◯ X ◯ 40° C. Holding power Time (s) 9  15 1  1  13 of 0.5 Kg at 90° C. X 40° C./ 2000   5760  1200    60 175 90° C. Ratio Overall evaluation for holding power ⊙ ⊙ ⊙ X Δ Adhesive Y (N/25 mm) 8  8 2 4  2 force Adhesive residue Absence Absence Presence Presence Presence Rating ⊙ ⊙ X Δ X

(38) In [Example 1] to [Example 19], the (meth)acrylic copolymers exhibited good coating property and holding power as an adhesive. On the other hand, in [Comparative Example 1], the (meth)acrylic copolymer (A-11) using a commercial one having a number average molecular weight of 6000 of the macromonomer (a) had high melt viscosity at 130° C., and poor coating property. In addition, the transparency was also bad, and the adhesive force was poor. In [Comparative Example 2], the (meth)acrylic copolymer (A-12) not using the macromonomer (a) was used. In [Comparative Example 3], the number average molecular weight of the macromonomer (a) was large as 7000, and the total evaluation of the holding powers of the (meth)acrylic copolymer (A-13) using this was slightly reduced, and further the adhesive force was deteriorated.

Examples 20 to 23

(39) The adhesive compositions of the compositions shown in Table 5 were cured or cross-linked by ultraviolet irradiation or the like. This case also had good holding power and adhesive force.

Curing Condition

(40) Apparatus: 2P curing apparatus, light source: metal halide lump, irradiation intensity: 100 mW/cm.sup.2, irradiation amount: 3000 mJ/cm.sup.2

(41) TABLE-US-00005 TABLE 5 Example 20 Example 21 Example 22 Example 23 Adhesive A-4 30 composition A-6 100 100 A-15 100 2-EHA 50 ACMO 20 NK-A-600 0.1 IRG184 0.3 Pentaerythritol 10 triacrylate Benzophenone 0.5 0.5 TPA-100 0.6 Holding power of Time >24 h >24 h >24 h >24 h 0.5 Kg at 40° C. Rating ⊙ ⊙ ⊙ ⊙ Adhesive force Y(N/25 mm) 27.5 11 8 9 Adhesive residue Absence Absence Absence Absence Rating ⊙ ⊙ ⊙ ⊙ ACMO: Acryloyl morpholine NK-A-600: “NKester 600” trade name, manufactured by Shin-Nakamura Chemical Co., Ltd (polyethylene glycol#600 diacrylate) IRG184: “IRGACURE184” trade name, manufactured by BASF (1-hydroxy-cyclohexyl- phenyl-ketone) TPA-100: “DURANATE TPA-100” trade name, manufactured by Asahi Kasei Corporation (polyisocyanurate)