JPH10330722A - Acrylic adhesive composition - Google Patents

Abstract

(57) [Problem] To provide an acrylic pressure-sensitive adhesive composition which is excellent in adhesive properties from normal temperature to high temperature and excellent in peeling force to a low-polarity adherend. An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer, a tackifying resin and a crosslinking agent, wherein the acrylic copolymer has an alkyl group having 2 to 14 carbon atoms.
Of the alkyl (meth) acrylate and a carboxyl group-containing vinyl monomer. The tackifier resin has a softening point of 120 to 160 ° C. and a hydroxyl value of 15 to 80 mg. KOH
/ G of a polymerized rosin esterified product, wherein the crosslinking agent is
An acrylic pressure-sensitive adhesive composition comprising an isocyanate compound and an aziridine compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition, and more particularly, to an acrylic pressure-sensitive adhesive composition having excellent adhesive properties from room temperature to high temperature, and in particular, excellent peeling resistance to low-polarity adherends. Agent composition.

[0002]

2. Description of the Related Art In recent years, acrylic pressure-sensitive adhesives have been widely used in place of natural rubber-based pressure-sensitive adhesives and synthetic rubber-based pressure-sensitive adhesives due to their excellent balance of physical properties and durability. Acrylic adhesives are widely used because they are excellent in various performances such as heat resistance, durability and water resistance, and can control required physical properties such as adhesive strength by changing the combination of various acrylic monomers. ing.

[0003] Acrylic copolymers themselves have tackiness properties and can be pressure-sensitive adhesives without the addition of tackifying resins, but for low-polarity adherends such as polyethylene and polypropylene, Low peel force. For this reason, as in the case of other pressure-sensitive adhesives, an attempt has been made to add a tackifying resin to improve the peeling force on a low-polarity adherend.

[0004] Japanese Patent Publication No. 3-281587 discloses an acrylic pressure-sensitive adhesive composition using a resin ester having a high hydroxyl value as a tackifying resin. However, even when such a tackifier resin is added, no significant improvement in the peeling force at a speed lower than the peeling speed based on the JIS peeling test (hereinafter referred to as “slow peeling speed”) is not observed. That is, there has been a problem that when a constant load is applied for a long time, it is easily peeled off.

[0005]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an acrylic pressure-sensitive adhesive composition which has excellent adhesive properties from normal temperature to high temperature and excellent peeling power to a low-polarity adherend. And

[0006]

The present invention relates to an acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer, a tackifier resin and a crosslinking agent, wherein the acrylic copolymer has a carbon number of an alkyl group. Consists of an alkyl (meth) acrylate of 2 to 14 and a carboxyl group-containing vinyl monomer,
The tackifying resin has a softening point of 120 to 160 ° C and a hydroxyl value of 15 to 80 mg. It is a polymerized rosin esterified product of KOH / g, and the crosslinking agent is an acrylic pressure-sensitive adhesive composition obtained by blending an isocyanate compound and an aziridine compound. Hereinafter, the present invention will be described in detail.

The acrylic copolymer comprises an alkyl (meth) acrylate having 2 to 14 carbon atoms in the alkyl group and a carboxyl group-containing vinyl monomer. When the number of carbon atoms in the alkyl group is 1 or exceeds 14, the properties of the acrylic pressure-sensitive adhesive composition as a pressure-sensitive adhesive are impaired, and thus the range is limited to the above range. Preferably, it has 4 to 9 carbon atoms. The alkyl group has 2 to 2 carbon atoms.
The alkyl (meth) acrylate of No. 14 is not particularly limited, and for example, ethyl acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, ter -Butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate,
Lauryl (meth) acrylate and the like. These may be used alone or in combination of two or more.

The carboxyl group-containing vinyl monomer is not particularly restricted but includes, for example, (meth) acrylic acid,
Itaconic acid, maleic acid, maleic anhydride, fumaric acid,
Fumaric anhydride and the like.

In the acrylic copolymer, the compounding amount of the carboxyl group-containing vinyl monomer is from 1 to 7
% By weight is preferred. When the amount is less than 1% by weight, the degree of crosslinking of the acrylic pressure-sensitive adhesive composition does not increase, and not only sufficient creep properties cannot be obtained, but also the peeling strength at a low peeling rate with respect to a low-polarity adherend is improved. If it exceeds 7% by weight,
It is not preferable because the initial adhesive strength is reduced.

[0010] The acrylic copolymer may be used in combination with other monomers copolymerizable with the alkyl (meth) acrylate. The other monomer copolymerizable with the alkyl (meth) acrylate is not particularly limited as long as it hardly reacts with a crosslinking agent to be added. For example, n-vinylpyrrolidone, n-vinylcaprolactam, acryloylmorpholine and the like can be used. And vinyl monomers having a highly polar group; and copolymerizable vinyl monomers such as methyl (meth) acrylate, styrene, and vinyl acetate. The amount of the other monomer is 0.5 to 3 with respect to the total amount of the monomers constituting the acrylic copolymer.
0% by weight is preferred.

The weight average molecular weight of the acrylic copolymer is preferably 200,000 to 1.5 million. Weight average molecular weight 2
If it is less than 0,000, the required cohesive force cannot be obtained, and if it exceeds 1,500,000, the viscosity becomes high, and the productivity in the mixing and application step of the tackifying resin is unfavorably deteriorated. More preferably, it is 300,000 to 1,200,000.

In order to adjust the molecular weight, a chain transfer agent may be added. The chain transfer agent is not particularly limited, and examples thereof include those having high chain transfer properties such as thiol compounds and halogen compounds.

The thiol compound is not particularly restricted but includes, for example, n-dodecyl mercaptan, 2-mercaptoethanol, β-mercaptopropionic acid, octyl β-mercaptopropionate, methoxybutyl β-mercaptopropionate and trimethylolpropanetris. (Β-thiopropionate), butyl thioglycolate; propanethiols; butanethiols; thiophosphites.

The halogen compound is not particularly restricted but includes, for example, carbon tetrachloride.

The method for producing the acrylic copolymer is not particularly limited, and examples thereof include known polymerization methods such as bulk polymerization, solution polymerization, dispersion polymerization, and emulsion polymerization. The method of initiating the polymerization in the above polymerization method is not particularly limited, for example, benzoyl peroxide, lauroyl peroxide,
Methods using a thermal polymerization initiator such as azoisobutyroylnitrile; methods using a photopolymerization initiator such as benzoin, benzoin methyl ether, and benzophenone; and methods using these methods in combination with ultraviolet irradiation or electron beam irradiation. Can be

The tackifier resin used in the present invention has a softening point of 120 to 160 ° C. and a hydroxyl value of 15 to 80 mg. KOH
/ G of polymerized rosin ester. The softening point is 1
When the temperature is less than 20 ° C., the improvement of the peeling force at a low peeling rate for the low-polarity adherend is small, and when the softening point exceeds 160 ° C., the compatibility with the acrylic copolymer becomes poor,
Since the initial adhesive strength as well as the peeling strength to the low-polarity adherend is reduced, it is limited to the above range. Preferably, 1
20-140 ° C. The hydroxyl value is 15 mg. KO
If it is less than H / g, the peeling strength at a low peeling rate for a low-polarity adherend is not improved, and the hydroxyl value is 80 mg. K
If it exceeds OH / g, the initial adhesive strength is remarkably reduced, so that it is limited to the above range. Preferably, 25 to 60 m
g. KOH / g.

The polymerized rosin ester is an ester of a polymerized rosin compound and a polyhydric alcohol. Examples of the polymerized rosin-based compound include polymerized rosin, rosin monomer, disproportionated rosin, hydrogenated rosin, partially disproportionated rosin, and a mixture thereof. The polyhydric alcohol is not particularly limited, and includes, for example, diethylene glycol, glycerin, pentaerythritol and the like. Above all,
Pentaerythritol ester of polymerized rosin is preferably used because of its excellent cross-linking property and very large effect of improving physical properties.

The crosslinking agent used in the present invention is a mixture of an isocyanate compound and an aziridine compound. The isocyanate compound is capable of reacting with a hydroxyl group and is used for crosslinking between tackifying resins. The aziridine compound is capable of reacting with a carboxyl group, and for crosslinking between acrylic copolymers, for grafting the crosslinked tackifying resins to the acrylic copolymer, and by the carboxyl group of the tackifying resin. It is used for further crosslinking between tackifying resins.

The above isocyanate compound is not particularly limited. For example, tolylene diisocyanate (TD
I), aromatic diisocyanate compounds such as tolidine diisocyanate (TODI), xylylene diisocyanate, diphenylmethane diisocyanate (MDI); aliphatic or alicyclic diisocyanate compounds such as hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IDI); trimethylol Triisocyanate compounds such as tolylene diisocyanate trimer adduct of propane, triphenylmethane triisocyanate, and methylenebis (4-phenylmethane) triisocyanate; and alkoxysilane compounds such as trimethoxysilane, triethoxysilane, and tributoxysilane. No.

The difference in the glass transition point (Tg) between the value of the tackifier resin alone and the value of the compound obtained by blending the isocyanate compound with the tackifier resin to complete the crosslinking is as follows. The amount is preferably 4 ° C. or more, and more preferably the amount at which the Tg difference is maximized, that is, the amount at which all crosslinking between tackifying resins is considered to be completed. The Tg can be measured by differential scanning calorimetry (DSC). T above
When the g difference is less than 4 ° C., a sufficient improvement in the peeling force at a low peeling rate with respect to the low-polarity adherend cannot be seen. In the present invention, the point at which the above Tg difference becomes the maximum has the highest low-speed peeling force. Further, if the isocyanate compound is added too much, the pressure-sensitive adhesive becomes too hard, and JIS for the low-polarity adherend
The peeling strength and the initial adhesive strength of the peeling rate based on the peeling test (hereinafter referred to as “high-speed peeling rate”) decrease.

The aziridine compound is not particularly restricted but includes, for example, N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate. ,
N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β- (2-methylaziridine) propionate and the like can be mentioned.

The amount of the above aziridine compound is such that the gel fraction of the acrylic copolymer composition after crosslinking is from 20 to 50.
% By weight. If the gel fraction is less than 20% by weight, the creep properties are not improved, and if it is more than 50% by weight, the peeling performance at a high peeling rate and the initial adhesive properties are undesirably reduced. The gel fraction is obtained by immersing the crosslinked acrylic pressure-sensitive adhesive composition in tetrahydrofuran, and by weight ratio of the dried insoluble content remaining after standing for 24 hours to the acrylic pressure-sensitive adhesive composition before immersion. is there.

In the above-mentioned pressure-sensitive adhesive composition, in addition to the above-mentioned acrylic copolymer, other tackifying resins and crosslinking agents may be used in addition to the above-mentioned acrylic copolymer as long as the peeling resistance to a low-polar adherend is not impaired. Good. As the other tackifying resin, for example,
Petroleum resins such as C5 (aliphatic) and C9 (aromatic); terpenes such as α-pinene, β-pinene polymer, diterpene polymer, α-pinene-phenol copolymer and derivatives thereof, xylene Examples of the resin include a resin or a modified product thereof, and an esterified product of rosin.

The esterified rosin is an esterified product of a rosin compound and a polyhydric alcohol. Examples of the rosin-based compound include a rosin monomer, a disproportionated rosin, a hydrogenated rosin, a partially disproportionated rosin, and a mixture thereof. The polyhydric alcohol is not particularly limited, and includes, for example, diethylene glycol, glycerin, pentaerythritol and the like. These tackifying resins may be used alone or in combination of two or more kinds. However, if the amount is too large, the peeling resistance decreases, so that 20 parts by weight to 100 parts by weight of the acrylic copolymer is used. Parts or less.

The acrylic pressure-sensitive adhesive composition of the present invention can be prepared by blending the above-mentioned various materials in predetermined amounts and dissolving them in a suitable organic solvent such as ethyl acetate or toluene as in the prior art. Incidentally, the acrylic pressure-sensitive adhesive composition of the present invention,
If necessary, known additives used in the acrylic pressure-sensitive adhesive composition such as a filler, a pigment, and a dye may be blended.

The application of the acrylic pressure-sensitive adhesive composition of the present invention is not particularly limited, and examples thereof include paints, adhesives, pressure-sensitive adhesives, sealing materials and the like. When the acrylic pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive, its use includes, for example, pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, labels, double-sided pressure-sensitive adhesive tapes, and the like.

When the acrylic pressure-sensitive adhesive composition is used for the production of a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet, the acrylic pressure-sensitive adhesive composition is converted into a solution, for example, applied to one or both sides of a substrate, and dried. I do. As the substrate, for example,
Paper; non-woven fabric; synthetic resin films of polyester, polyolefin and the like; synthetic resin foam sheets of polyurethane, polychloroprene, acrylic resin and the like. In addition, the acrylic pressure-sensitive adhesive composition can be a double-sided pressure-sensitive adhesive tape without a substrate in which the acrylic pressure-sensitive adhesive itself is formed into a release sheet.

In the acrylic pressure-sensitive adhesive composition of the present invention, it is necessary that the resins are cross-linked after being applied to a base material. For this reason, after the production of a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet,
Heat curing may be performed.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Preparation of acrylic copolymer) 97 parts by weight of n-butyl acrylate and 3 parts by weight of acrylic acid are blended, and lauryl mercaptan 0.1 part as a chain transfer agent.
06 parts by weight together with 80 parts by weight of ethyl acetate were charged into a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, stirred and dissolved to form a uniform mixture. For about 30 minutes to remove oxygen present in the monomer solution. Thereafter, the air in the flask was replaced with nitrogen gas, and the temperature was increased while stirring, and the temperature was maintained at 70 ° C. and the benzoyl peroxide 0.0
A solution prepared by dissolving 3 parts by weight of 1 part by weight of ethyl acetate is
After dropping with a dropping funnel, polymerization reaction was performed at the same temperature for 10 hours to obtain an acrylic copolymer solution. When the molecular weight of this copolymer was measured by GPC, the weight average molecular weight (Mw) was 470,000 and the molecular weight distribution (Mw / Mn) was 3.5.

Example 1 A tackifier resin (pentaerythritol esterified polymer rosin; softening point 125 ° C., hydroxyl value 31 mg.KOH /) was added to 100 parts by weight of the acrylic copolymer obtained above.
g, manufactured by Arakawa Chemical Co., Ltd., trade name "Pencel D125")
25 parts by weight, 2.8 parts by weight of an isocyanate compound (ethyl acetate solution of tolylene diisocyanate adduct of trimethylolpropane; trade name “Coronate L55E”, manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 55% by weight), and
Aziridine compound (N, N'-hexamethylene-1,6
0.125 parts by weight of -bis (1-aziridine carboxide; manufactured by Nippon Shokubai Co., Ltd.) was uniformly mixed while being diluted with toluene to obtain a 45% by weight acrylic pressure-sensitive adhesive composition. .

The obtained acrylic pressure-sensitive adhesive composition was applied to a 38 μm-thick polyethylene terephthalate (PET) substrate having a corona-treated surface, and dried at 110 ° C. for 5 minutes in a gear oven to obtain a 50 μm-thick adhesive. An adhesive tape having an agent layer formed thereon was obtained. Then, the above sample was
Cured for 3 days at 0 ° C. Here, the gel fraction of the acrylic pressure-sensitive adhesive composition was 36% by weight. Further, the above isocyanate compound was added to the tackifying resin alone and the tackifying resin in the same amount as the above compounding amount, and Tg measurement by DSC (manufactured by PerkinElmer) was performed on each of the crosslinked products. Was determined.
However, the sample used in this measurement was prepared by dissolving the tackifier resin in ethyl acetate at a solid content concentration of 70% by weight, adding a crosslinking agent to 100 parts by weight of the tackifier resin, stirring well, and then drying under vacuum. It was produced by drying at 80 ° C. for 24 hours using a machine. As a result, the Tg difference was 9.8 ° C. The adhesive tape was evaluated by the following method, and the results are shown in Table 1.

(Evaluation method of pressure-sensitive adhesive tape) Evaluation of pressure-sensitive adhesive strength to polypropylene adherend The obtained pressure-sensitive adhesive tape was adhered to a polypropylene plate with a width of 20 mm and a 2-kg rubber roller with a reciprocating load of 23 ° C.
After leaving for 20 minutes at 23 ° C, 40 ° C, 60 ° C, 80 ° C
After a lapse of 30 minutes at 90 ° C., the peeling force was measured by a peel test in a 90 ° direction. The peeling rate at this time is 0.01 to 5
6 points were measured in the range of mm / sec, and based on the speed dependency of the peeling force at each temperature obtained here, a master curve based on 60 ° C. was obtained according to the temperature-speed conversion rule. The peeling speed is 10 mm / sec and 0.00
A peeling force of 01 mm / sec was read.

Evaluation of the holding power against SUS The obtained adhesive tape was compliant with JIS Z 0237,
Cut to 20mm width and 100mm length, 1.5m thickness
m, width 25 mm, length 100 mm, SUS304 plate with an adhesion length of 20 mm, 2 kg of rubber roll, and reciprocating load, left at 23 ° C., 60% RH atmosphere for 20 minutes, and placed 1 kg on the lower end of the adhesive tape. The specimen was left standing vertically with a load, and the displacement distance (mm) after one hour was measured.

EXAMPLE 2 Pentaerythritol esterified polymerized rosin (softening point 135 ° C., hydroxyl value 45.3 mg.K) was added to the tackifier resin.
OH / g, manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Pencel D13
5 ") and the amount of the isocyanate compound was changed to 4.2 parts by weight. The gel fraction of the acrylic pressure-sensitive adhesive composition was 37% by weight. In addition,
The Tg difference between the tackifier resin alone and the one obtained by blending the isocyanate compound with the tackifier resin and crosslinking is 12.1 ° C.
Met. The adhesive tape was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that the isocyanate compound was not used and the amount of the aziridine compound was 0.085 parts by weight. The adhesive tape was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the amount of the isocyanate compound was changed to 1.0 part by weight and the amount of the aziridine compound was changed to 0.095 part by weight. The gel fraction of the acrylic pressure-sensitive adhesive composition was 34% by weight. In addition, the Tg difference between the tackifier resin alone and the crosslinkable resin after mixing the isocyanate compound with the isocyanate compound was 2.3 ° C. The adhesive tape was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 A pentaerythritol ester of disproportionated rosin (softening point 125 ° C., hydroxyl value 18.1 mg.
KOH / g, manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Superester A125"), the amount of the isocyanate compound was set to 1.0 part by weight, and the amount of the aziridine compound was set to 0.0
The procedure was the same as in Example 1 except that the amount was 95 parts by weight. The gel fraction of the acrylic pressure-sensitive adhesive composition was 34% by weight. The Tg difference between the tackifier resin alone and the crosslinkable resin after the isocyanate compound was blended with the isocyanate compound was 3.5 ° C. The adhesive tape was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0039]

[Table 1]

[0040]

Since the present invention has the above-mentioned structure, the polymerized rosin esterified products as tackifying resins are positively crosslinked with the isocyanate compound, and the crosslink between the acrylic copolymers and the tackifier are imparted with the aziridine compound. Grafting of an acrylic copolymer of crosslinked resins,
And further crosslinking between the tackifying resins is performed by the carboxyl group of the tackifying resin. This suppresses the displacement due to the viscous flow during creep, so that a higher low-speed peeling force can be obtained. As a result, an acrylic pressure-sensitive adhesive composition having excellent adhesive properties from room temperature to high temperature, and particularly having a high peeling power to a low-polarity adherend such as polyolefin, is obtained, and is widely used for applications such as bonding and fixing of plastic parts. It can be suitably used for an adhesive tape, an adhesive sheet and the like.

Claims (2)

[Claims] 1. An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer, a tackifier resin and a crosslinking agent, wherein the acrylic copolymer has an alkyl group having 2 to 14 carbon atoms.
Of the alkyl (meth) acrylate and a carboxyl group-containing vinyl monomer, and the tackifier resin has a softening point of 120 to 160 ° C and a hydroxyl value of 15 to 80 mg. KOH
/ G of a polymerized rosin esterified product, wherein the crosslinking agent is
An acrylic pressure-sensitive adhesive composition comprising an isocyanate compound and an aziridine compound. 2. The compounding amount of the isocyanate compound is such that the glass transition point (Tg) is the value of the tackifier resin alone,
The difference between the value obtained by blending the isocyanate compound in the tackifier resin and completing the crosslinking is an amount of 4 ° C. or more, and the blending amount of the aziridine compound is determined after the crosslinking of the acrylic pressure-sensitive adhesive composition. Gel fraction is 20-50% by weight
2. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the amount is