Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

A polyester-based pressure-sensitive adhesive composition which can be produced even from plant-derived raw materials with no need of using a costly silicone-based pressure-sensitive adhesive or the like and which is usable for producing a pressure-sensitive adhesive sheet excellent in wettability to an adherend, light peelability (removability), anti-staining property (little adhesive residues), and workability, and to provide a pressure-sensitive adhesive sheet using the composition. A polyester-based pressure-sensitive adhesive composition comprising a polyester obtained by condensation polymerization of at least a carboxylic acid component and a diol component, and a crosslinking agent, wherein the carboxylic acid component contains a dicarboxylic acid having a side chain in an amount of 50 to 90% by weight and a tricarboxylic acid having a side chain in an amount of 10 to 50% by weight, and wherein the polyester has a weight average molecular weight of 5000 to 150000.

Claims

1. A polyester-based pressure-sensitive adhesive composition comprising a polyester and a crosslinking agent, wherein the polyester is obtained by condensation polymerization of only a carboxylic acid component and a diol component, the carboxylic acid component contains only a dicarboxylic acid having a side chain and a tricarboxylic acid having a side chain, the carboxylic acid component contains a dicarboxylic acid having a side chain in an amount of 60 to 85% by weight and a tricarboxylic acid having a side chain in an amount of 15 to 40% by weight, and the polyester has a weight average molecular weight of 10000 to 150000.

2. The polyester-based pressure-sensitive adhesive composition according to claim 1, wherein the diol component contains an aliphatic diol having 3 to 10 carbon atoms.

3. The polyester-based pressure-sensitive adhesive composition according to claim 1, further comprising a polyether polyol.

4. A pressure-sensitive adhesive sheet comprising a support and a pressure-sensitive adhesive layer obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to claim 1 and formed on at least one surface of the support, wherein the pressure-sensitive adhesive layer has a gel fraction of 70 to 98% by weight.

5. The pressure-sensitive adhesive sheet according to claim 4, which has an adhesive strength to glass of 0.5 N/25 mm or less.

6. The pressure-sensitive adhesive sheet according to claim 4, which is used for surface protection.

Description

EXAMPLES

(1) The present invention will be described more in detail with reference to Examples of the present invention; however, the present invention is not limited by Examples. In Examples, part(s) means part(s) by weight. The physical properties of polyesters are shown in Table 1, and the blending contents and evaluation results of the pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) are shown in Table 2. The physical properties of polyether polyols used in Examples are shown in Table 3.

(2) <Preparation of Polyester A>

(3) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1025, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 80% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 20% by weight) and 30.3 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:1.9, and 0.1 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(4) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 2 hours to obtain a polyester A. The polyester A had a weight average molecular weight (Mw) of 10000.

(5) <Preparation of Polyester B>

(6) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1025, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 80% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 20% by weight) and 25.5 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:1.6, and 0.1 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(7) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 4 hours to obtain a polyester B. The polyester B had a weight average molecular weight (Mw) of 120000.

(8) <Preparation of Polyester C>

(9) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1006, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 96% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 4% by weight) and 23.9 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:1.5, and 0.1 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(10) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 10 hours to obtain a polyester C. The polyester C had a weight average molecular weight (Mw) of 30000.

(11) <Preparation of Polyester D>

(12) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1009, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 99% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 1% by weight) and 23.9 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:1.5, and 0.1 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(13) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 10 hours to obtain a polyester D. The polyester D had a weight average molecular weight (Mw) of 20000.

(14) <Preparation of Polyester E>

(15) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1025, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 80% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 20% by weight) and 35 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:2.2, and 0.1 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(16) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 1.5 hours to obtain a polyester E. The polyester E had a weight average molecular weight (Mw) of 4000.

(17) <Preparation of Polyester F>

(18) A four-neck separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser having a trap was charged with 100 parts of a carboxylic acid component (trade name: PRIPOL 1025, manufactured by Croda, which contains a dimer acid as a dicarboxylic acid (molecular weight: 565) in an amount of 80% by weight and a trimer acid as a tricarboxylic acid (molecular weight: 846) in an amount of 20% by weight) and 20.7 parts of 1,4-butanediol (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 90) as a diol component so that the mole ratio of the carboxylic acid component and the 1,4-butanediol was 1:1.3, and 0.2 parts of dibutyltin oxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and the contents were heated to 180 C. and kept at this temperature for 8 hours while being stirred in a nitrogen atmosphere.

(19) Thereafter, the nitrogen introduction tube and the condenser equipped with a trap were taken out and a vacuum pump was attached instead, and the contents were heated to 200 C. and kept at this temperature while being stirred in a reduced pressure atmosphere (0.002 MPa). The reaction was continued for about 4 hours to obtain a polyester F. The polyester F had a weight average molecular weight (Mw) of 160000, but gelation was significant, the viscosity was extremely high, and handling was difficult.

Example 1

(20) Twelve parts of polyhexamethylene diisocyanate (trade name: TPA-100, manufactured by Asahi Kasei Chemicals Corporation) as a crosslinking agent and 50 to 150 parts of toluene as a solvent were blended with 100 parts of the polyester A to adjust viscosity (e.g., about 10 Pa.Math.s) for easy application and processing, so that a polyester-based pressure-sensitive adhesive composition was obtained. This composition was applied to a polyethylene terephthalate (PET) film (trade name: Lumirror 38 S10, manufactured by PANAC Corporation) as the substrate with 38 m thickness in such a manner that the pressure-sensitive adhesive layer obtained by drying (after drying) had a thickness of 10 m, and dried at 100 C. for 3 minutes to obtain a pressure-sensitive adhesive layer. Thereafter, the pressure-sensitive adhesive layer was bonded to the peeling-treated surface of a polyethylene terephthalate (PET) film (thickness: 38 m, trade name: Diafoil MRE#38, manufactured by Mitsubishi Plastics Inc.) subjected to peeling treatment, and the resultant was left at 50 C. for 3 days to obtain a pressure-sensitive adhesive sheet (for surface protection) having a support and a pressure-sensitive adhesive layer formed on the support.

Example 2

(21) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 10 parts of the crosslinking agent was blended with 100 parts of the polyester B.

Example 3

(22) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 25 parts of polybutylene glycol containing hydroxyl groups at both terminals (trade name: Uniol PB-500, manufactured by Nippon Oil & Fats Co., Ltd., number average molecular weight (Mn): 500) and 20 parts of the crosslinking agent were blended with 100 parts of the polyester A.

Example 4

(23) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 50 parts of the crosslinking agent and 150 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 1000 (trade name: PTG-1000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A.

Example 5

(24) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 30 parts of the crosslinking agent and 150 parts of polytetramethylene ether glycol having a number average molecular weight (Mn) of 3000 (trade name: PTG-3000SN, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A.

Example 6

(25) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 50 parts of the crosslinking agent and 150 parts of polytrimethylene ether glycol having a number average molecular weight (Mn) of 1000 (trade name: Cerenol H1000, manufactured by DuPont) were blended with 100 parts of the polyester A.

Example 7

(26) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 50 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 1000 (trade name: PTG-L1000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A.

Example 8

(27) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 40 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 2000 (trade name: PTG-L2000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A.

Example 9

(28) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 30 parts of the crosslinking agent and 150 parts of copolyether polyol having a number average molecular weight (Mn) of 3000 (trade name: PTG-L3000, manufactured by Hodogaya Chemical Co., Ltd.) were blended with 100 parts of the polyester A.

Comparative Example 1

(29) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 10 parts of the crosslinking agent was blended with 100 parts of the polyester C.

Comparative Example 2

(30) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 10 parts of the crosslinking agent was blended with 100 parts of the polyester D.

Comparative Example 3

(31) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 20 parts of the crosslinking agent was blended with 100 parts of the polyester E.

Comparative Example 4

(32) Production of a pressure-sensitive adhesive sheet was attained by using the polyester F, but gelation of the polyester F was significant and the viscosity was extremely high, so that the polyester F could not be mixed with raw materials such as crosslinking agent, and a pressure-sensitive adhesive sheet was not obtained.

(33) (Weight Average Molecular Weight)

(34) The weight average molecular weight (Mw) was measured as follows: about 0.2 g of each polyester was collected on a petri dish, and the solvent was removed by drying at 120 C. for 2 hours. Then, 0.01 g of the polyester layer on the petri dish was weighed, which was added to 10 g of tetrahydrofuran (THF) and left for 24 hours for dissolution. The obtained solution was subjected to gel permeation chromatography (GPC), and the molecular weight of each polyester was measured based on the calibration curve produced using standard polystyrene.

(35) (Measurement Conditions)

(36) Apparatus name: HLC-8220GPC, manufactured by Tosoh Corporation

(37) Test piece concentration: 0.1% by weight (THF solution)

(38) Test piece injection amount: 20 l

(39) Fluent: THF

(40) Flow rate: 0.300 ml/min

(41) Measurement (column) temperature: 40 C.

(42) Column: Test piece column; TSKguardcolumn SuperHZ-L (1 column)+TSKgel SuperHZM-M (2 columns), reference column; TSKgel SuperH-RC (1 column), manufactured by Tosoh Corporation

(43) Detector: Differential refractometer (RI)

(44) (Gel Fraction of Pressure-sensitive Adhesive Layer)

(45) Each of the pressure-sensitive adhesive sheets having a thickness of 30 m obtained in Examples and Comparative Examples was cut in a size of 5 cm5 cm. The support was removed from the cut pressure-sensitive adhesive sheet to obtain a test piece, and this test piece was wrapped with a Teflon (registered trade name) sheet with a known weight, and the obtained test piece was weighed and then left at 23 C. for 7 days in toluene to extract the sol component from the test piece. Thereafter, the resulting test piece was dried at 120 C. for 2 hours and then weighed. The gel fraction was calculated according to the following equation.
Gel fraction (% by weight)=(weight after dryingweight of Teflon (registered trade name) sheet)/(weight before dryingweight of Teflon (registered trade name) sheet)100
(Adhesive Strength)

(46) Each of the pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer thickness of 10 m obtained in Examples and Comparative Examples was cut in 25 mm width, and the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet was bonded to a tin-untreated surface of alkali glass (manufactured by Matsunami Glass Ind., Ltd.) and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 30 m was bonded to a SUS 304 plate (manufactured by Toyo Seihaku Co., Ltd.) to obtain each test piece, and the adhesive strength to a blue plate glass (adhesive strength to glass) (N/25 mm) was measured. The pressure bonding at the time of bonding was carried out by reciprocating a 2 kg roller one time, and the measurement of adhering strength (adhesive strength) at 180 peeling was carried out using a tensile compression tester (apparatus name: TG-1 kN, manufactured by Minebea Co., Ltd.) in the following conditions.

(47) Tension (peeling) rate: 300 mm/min

(48) Measurement conditions: temperature: 232 C., humidity 655% RH

(49) The adhesive strength (peel strength) to glass is preferably 0.5 N/25 mm or less, more preferably 0.4 N/25 mm or less, and furthermore preferably 0.3 N/25 mm or less. If the adhesive strength exceeds 0.5 N/25 mm, the adhesive strength is too high so that light peelability (removability) cannot be attained, and for example, in the case of using the test piece as a pressure-sensitive adhesive sheet for surface protection, adhesive residues may remain on an adherend at the time of peeling thereafter, and the support (substrate) may be damaged, and therefore it is not preferable.

(50) (Anti-staining Property)

(51) Presence or absence of staining on an adherend was evaluated in accordance with presence or absence of traces of bleeding out or presence or absence of adhesive residues by visual observing, the surface of the adherend which had contact with pressure-sensitive adhesive layer after the measurement of the adhesive strength.

(52) (Wettability)

(53) Each of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was cut in 25 mm width and 70 mm length, and the pressure-sensitive adhesive surface was dropped calmly onto a glass plate, and the motion-pictures of widening of the surface area of the pressure-sensitive adhesive surface per one second were taken by a video camera. The color shades owing to wetting were then binarized for every 0.5 seconds so that the wet surface area was measured, and the wetting rate (cm.sup.2/s) was calculated for evaluation.

(54) The wetting rate of the pressure-sensitive adhesive sheet of the present invention is preferably 0.6 cm.sup.2/s or more, more preferably 1.0 cm.sup.2/s or more, and particularly preferably 3.0 cm.sup.2/s. If the wetting rate is less than 0.6 cm.sup.2/s, handleability may be inferior and air bubbles may be easily included, and the appearance of the adherend to which a surface protective sheet is bonded is worsened, and therefore it is not preferable.

(55) TABLE-US-00001 TABLE 1 Carboxylic acid component Diol Dicarboxylic Tricarboxylic component Molecular acid acid (carbon weight Polyester (% by weight) (% by weight) number) (Mw) A 80 20 1,4-butanediol 10,000 (4) B 80 20 1,4-butanediol 120,000 (4) C 96 4 1,4-butanediol 30,000 (4) D 99 1 1,4-butanediol 20,000 (4) E 80 20 1,4-butanediol 4,000 (4) F 80 20 1,4-butanediol 160,000 (4)

(56) TABLE-US-00002 TABLE 2 Blending and evaluation Example Comparative Example results Unit 1 2 3 4 5 6 7 8 9 1 2 3 4 Polyester A B A A A A A A A C D E F Parts by 100 100 100 100 100 100 100 100 100 100 100 100 100 weight Polyether G H I J K L polyol Parts by 150 150 150 150 150 150 weight Cross- Parts by 12 10 20 50 30 50 50 40 30 10 10 20 Non- linking weight mixable agent Gel % by 88 93 87 95 97 96 97 98 97 80 77 Non- Non- fraction weight measurable measurable Adhesive N/25 0.02 0.04 0.04 0.04 0.03 0.04 0.03 0.03 0.03 0.60 0.60 Non- Non- strength to mm evaluable evaluable glass Wetting cm.sup.2/sec 4.0 3.5 4.5 4.6 4.5 4.8 4.8 4.9 5.0 4.0 5.0 Non- Non- rate evaluable evaluable Presence Absence Absence Absence Absence Absence Absence Absence Absence Absence Absence Absence Presence Non- or absence evaluable of staining

(57) TABLE-US-00003 TABLE 3 Number average Polyether molecular weight polyol Kind (Mn) G Polytetramethylene 1,000 ether glycol H Polytetramethylene 3,000 ether glycol I Polytetramethylene 1,000 ether glycol J Copolyether polyol 1,000 K Copolyether polyol 2,000 L Copolyether polyol 3,000

(58) From the results of evaluation in Table 2, regarding Examples 1 to 9, since carboxylic acid components each containing a dicarboxylic acid and a tricarboxylic acid at a desired ratio were used and polyesters each with a desired weight average molecular weight were used, pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) were obtained which had desired gel fraction and adhesive strength (peel strength), had good wettability at the time of bonding to an adherend and excellent workability, had no adhesive residues even after being peeled off, and had excellent light peelability (removability), and anti-staining properties. It was confirmed that in the pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets), a wide range of pressure-sensitive adhesion design is possible.

(59) On the other hand, in Comparative Examples 1 and 2, it was confirmed that since a carboxylic acid component containing a dicarboxylic acid and a tricarboxylic acid at a desired ratio was not used, the adhesive strength was high and there was a problem on light peelability (removability). In Comparative Example 3, since a polyester having weight average molecular weight smaller than the desired weight average molecular weight was used, a pressure-sensitive adhesive sheet having a gelled pressure-sensitive adhesive layer could not be obtained, and staining such as adhesive residues on an adherend was observed. In Comparative Example 4, since a polyester having weight average molecular weight larger than the desired weight average molecular weight was used, gelation of the polyester was significant and the viscosity was extremely high, so that the polyester could not be mixed with other raw materials, and a pressure-sensitive adhesive sheet itself was not obtained.