JPH0257111B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel adhesive composition with excellent curability. More specifically, it can be suitably used for pressure-sensitive adhesives such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, and pressure-sensitive adhesive sheets, and has excellent cohesive force development after drying (cohesive force rise) and adhesive strength. The present invention also relates to an excellent new adhesive composition. [Prior Art] Pressure-sensitive adhesives include natural rubber, synthetic rubber, and acrylic adhesives, and are used for many purposes in the form of tapes, sheets, labels, and the like.
Among these, acrylic pressure-sensitive adhesives have become widely popular in recent years due to their excellent adhesiveness and durability. Resins for acrylic pressure-sensitive adhesives include:
The main component is alkyl acrylate, and a monomer that gives a relatively hard polymer such as vinyl acetate, styrene, acrylonitrile, alkyl methacrylate, etc., and a crosslinkable monomer having functional groups such as carboxyl group, hydroxyl group, and amide group. A copolymerized product is used. The acrylic copolymer obtained in this way is put into practical use as a pressure-sensitive adhesive by a process that usually includes a crosslinking agent.
Many formulations have been put into practical use in which acrylic copolymers such as hydroxyethyl acrylate and hydroxyethyl methacrylate are combined with crosslinking agents capable of crosslinking with hydroxyl groups such as polyisocyanate compounds, melamine resins, and epoxy resins. It is provided. [Problems to be solved by the invention] However, conventional resins for acrylic pressure-sensitive adhesives that are copolymerized with hydroxyethyl acrylate, hydroxyethyl methacrylate, etc.
When used as a pressure-sensitive adhesive by crosslinking with polyisocyanate compounds, melamine resins, epoxy resins, etc., there was a problem with curing properties in that the crosslinking rate was slow and sufficient cohesive force could not be obtained in a short time. In addition, if a large amount of crosslinking agent is used to obtain sufficient cohesive strength, the adhesive strength may decrease, and unreacted components may remain, causing the crosslinking reaction to progress gradually over time, making it impossible to stably obtain the desired adhesive strength. There was a problem. In view of the current situation, the present inventors aimed to obtain a pressure-sensitive adhesive that can obtain sufficient cohesive force in a short time, does not change in adhesive force over time, and has an excellent balance between cohesive force and adhesive force. As a result of research aimed at this purpose, we have completed the present invention. [Means and effects for solving the problems] The present invention is based on the general formula (However, in the formula, R is a hydrogen atom or a methyl group, which may be the same or different, and Z is a divalent organic group having 2 to 20 carbon atoms, which may be the same or different. by polymerizing a polymerizable monomer (I) containing a hydroxyl group-containing (meth)acrylate oligomer (A) as an essential component, n being an integer of 1 to 100. The present invention relates to an adhesive composition comprising the obtained polymer. In particular, the present invention uses a hydroxyl group-containing (meth)acrylate oligomer (A) represented by the above general formula as a hydroxyl group-containing monomer when preparing a resin for pressure-sensitive adhesives, thereby producing polyisocyanate compounds, melamine A pressure-sensitive adhesive that has a high crosslinking speed when crosslinked with resin, epoxy resin, etc., and can provide sufficient cohesive force in a short period of time.It also does not lose adhesive strength over time, and has an excellent balance between cohesive strength and adhesive strength. The present invention provides a composition for use. The polymer constituting the adhesive composition of the present invention is
It is obtained by polymerizing a polymerizable monomer (I) containing a hydroxyl group-containing (meth)acrylate oligomer (A) represented by the above general formula as an essential component. As the polymerization method, conventionally known methods such as solution polymerization, bulk polymerization, and emulsion polymerization can be employed.
For example, when a solution polymerization method is adopted, a radical polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, or di-tertiary butyl peroxide can be used as a polymerization initiator, and a polymerization solvent can be used as a polymerization initiator. ,toluene,
Xylene and other high boiling point aromatic solvents; Ester solvents such as ethyl acetate, butyl acetate and cellosolve acetate; Ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; Alcohol solvents such as methyl alcohol, ethyl alcohol and butyl alcohol. can be used alone or in combination. The hydroxyl group-containing (meth)acrylate oligomer (A) used in the present invention has the general formula (In the formula, R is a hydrogen atom or a methyl group, Z
is a divalent organic group having 2 to 20 carbon atoms. ) is obtained by addition polymerizing hydroxy (meth)acrylate (a) to oligomerize it. Hydroxy (meth)acrylate (a)
Specific examples include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate,
Hydroxybutyl methacrylate, hydroxyhexyl acrylate, hydroxyhexyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate,
Examples include dipropylene glycol monoacrylate, dipropylene glycol monomethacrylate, hydroxycyclohexyl acrylate, hydroxycyclohexyl methacrylate, and the like. These may be used alone or as a mixture. In order to add-polymerize hydroxy (meth)acrylate (a) to oligomerize it, for example,
As described in No. 59-256558, hydroxy (meth)acrylate (a) is mixed with a protonic acid such as sulfuric acid or para-toluenesulfonic acid; a Lewis acid such as boron trifluoride or tin tetrachloride; or an oxysulfate such as titanium oxysulfate. ; The temperature may be maintained at 10 to 150°C in the presence of a catalyst such as a heteropolyacid such as tungstophosphoric acid, tungstosilicic acid, molybdophosphoric acid, and molybdosilicic acid. Monomers other than the hydroxyl group-containing (meth)acrylate oligomer (A) constituting the polymerizable monomer (I) include alkyl carbon, which is commonly used as a monomer component of pressure-sensitive adhesive resins. Alkyl (meth)acrylates (B) and other monomers (C) having a number of 4 to 18 can be used. Alkyl (meth)acrylate whose alkyl group has 4 to 18 carbon atoms that can be used in the present invention
(B) includes butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, Acrylate, cyclohexyl (meth)acrylate,
Heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)
Acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)
acrylate, dodecyl (meth)acrylate,
Examples include stearyl (meth)acrylate. Other monomers (C) include monomers having a carboxyl group in the molecule such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic acid monoalkyl ester; acrylamide, methylol acrylamide, butoxymethyl acrylamide, etc. acrylamide derivatives; monomers having a glycidyl group in the molecule such as glycidyl methacrylate and allyl glycidyl ether; Aromatic vinyls such as styrene, vinyltoluene, etc. ; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers;
Fumaric acid diester, ethylene, propylene, etc. can be used, and divinylbenzene,
Polymerization into one molecule of diallyl phthalate, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, triallyl isocyanurate, N,N'-methylenebis(meth)acrylamide, etc. A crosslinkable monomer having two or more double bonds can also be used. There is no particular restriction on the amount of each monomer component used in the polymerizable monomer (I), but considering its use as a pressure-sensitive adhesive, the hydroxyl group-containing (meth)acrylate oligomer (A) is It is preferably used in an amount of 0.05 to 20% by weight in the monomer (I). If the amount is less than 0.05% by weight, it may be difficult to obtain sufficient cohesive force even in the crosslinking reaction, and if the amount is more than 20% by weight, sufficient adhesive strength may not be obtained. In addition, alkyl (meth)acrylate (B) whose alkyl group has 4 to 18 carbon atoms is a polymerizable monomer (I)
It is preferable to use it in the range of 30 to 99.95% by weight,
If it is less than 30% by weight, sufficient adhesive strength may not be obtained. Further, it is preferable to use the other monomer (C) in a range of 0 to 50% by weight, and if the amount exceeds 50% by weight, sufficient adhesive strength may not be obtained. The adhesive composition of the present invention contains a polymer obtained by polymerizing the polymerizable monomer (I). It contains a compound having two or more functional groups that acts as a crosslinking agent, a known tackifier, an anti-aging agent, a solvent, a diluent, etc. Examples of the crosslinking agent include tolylene diisocyanate, isophorone diisocyanate, Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Sumidyur N.
(manufactured by Sumitomo Bayer Urethane Co., Ltd.), melamine resins, epoxy resins, etc. Tackifiers include rosin, rosin derivatives, terpene resins, terpene phenol resins, phenolic resins, xylene resins, etc. , coumaron resin, coumaron indene resin, aliphatic petroleum resin, aromatic petroleum resin, etc. When the adhesive composition of the present invention is applied to paper, plastic film, etc. and dried, the crosslinking reaction progresses and cohesive force and adhesive force are developed in a well-balanced manner, resulting in performance as a pressure-sensitive adhesive. Obtainable. It can also be used as a two-component adhesive in which a crosslinking agent is mixed at the time of use. [Effects of the Invention] The adhesive composition of the present invention has excellent curability, and when used in particular for pressure-sensitive adhesive applications, it develops sufficient cohesive force in a short period of time due to crosslinking reaction, and also exhibits no tackiness over time. There is no change in force, and an adhesive with an excellent balance between cohesive force and adhesive force can be obtained.
Furthermore, by utilizing its excellent curability, it is also effective as a two-component adhesive consisting of a main ingredient and a curing agent. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Reference Examples, but the present invention is not limited to these Examples. In addition, all parts and % in each example shall mean parts by weight and % by weight unless otherwise specified. Reference Example 1 A reaction vessel equipped with a thermometer and a stirrer was charged with 232 parts of 2-hydroxyethyl acrylate, 0.07 parts of hydroquinone monomethyl ether as a polymerization inhibitor, and 2.3 parts of 12-tungstophosphoric acid as a catalyst, and then heated to 80°C for 7.5 parts. Holds time. After the reaction is complete, add 12 parts of powdered magnesium silicate as an adsorbent and
After stirring at °C for 30 minutes, the mixture was purified by pressure filtration to obtain 228 parts (yield: 98.3%) of a colorless transparent liquid reaction product with a color number of 10 (APHA). As a result of NMR analysis, the abundance of acryloyl groups and hydroxyl groups is the same equivalent, and the average molecular weight by GPC is 401
It was hot. Furthermore, the results of IR, NMR, and GPC analyzes revealed that the reaction product (hereinafter referred to as hydroxyl group-containing acrylate oligomer (1)) was a hydroxyl group-containing acrylate oligomer having the following structure. Reference Example 2 After charging 260 parts of 2-hydroxypropyl acrylate, 0.08 parts of hydroquinone monomethyl ether as a polymerization inhibitor, and 2.6 parts of 12-tungstophosphoric acid as a catalyst into a reaction vessel similar to Reference Example 1,
It was kept at 100℃ for 4 hours. After the reaction was completed, 13 parts of powdered magnesium silicate as an adsorbent was added and the mixture was heated at 40℃ for 30 minutes.
After stirring for a minute, the reaction product was purified by pressure filtration and the reaction product was a colorless transparent liquid with a color number (APHA) of 10.
(yield 97.3%). As a result of NMR analysis,
The amounts of acryloyl groups and hydroxyl groups present were the same equivalent, and the average molecular weight by GPC was 378. Furthermore, the results of IR, NMR, and GPC analysis revealed that the reaction product (hereinafter referred to as hydroxyl group-containing acrylate oligomer (2)) was a hydroxyl group-containing acrylate oligomer having the following structure. Reference Example 3 Into a reaction vessel similar to Reference Example 1, 260 parts of 2-hydroxyethyl methacrylate, 0.13 parts of hydroquinone monomethyl ether as a polymerization inhibitor, and 2.6 parts of tungstophosphoric acid as a catalyst were charged.
It was kept at ℃ for 4 hours. After the reaction was complete, 260 parts of water was added, stirred at room temperature, left to stand, and the aqueous layer (upper layer) was removed. As a result of removing a portion of the raw material, 102 parts (yield: 39.2%) of the reaction product was obtained as a colorless transparent liquid with a color number (APHA) of 10.
The reaction product (hereinafter referred to as hydroxyl group-containing methacrylate oligomer (3)) was analyzed by IR, NMR,
As a result of analysis by GPC, it was found that the amounts of methacryloyl groups and hydroxyl groups present were the same equivalent, and that it was a hydroxyl group-containing methacrylate oligomer with an average molecular weight of 297 and the following structure. Example 1 Hydroxyl group-containing acrylate oligomer (1) 2 obtained in Reference Example 1 was placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen gas introduction tube, and a reflux condenser.
1 part, 3 parts of acrylic acid, 65 parts of 2-ethylhexyl acrylate, 30 parts of vinyl acetate, 120 parts of ethyl acetate, and 0.4 parts of benzoyl peroxide.
After maintaining the mixture at 80°C for 4 hours under a nitrogen atmosphere, 66 parts of ethyl acetate and 0.4 parts of benzoyl peroxide were added, and the mixture was further maintained at 80°C for 4 hours to complete the polymerization. The obtained ethyl acetate solution of the polymer was cooled to obtain an adhesive composition (1) of the present invention having a nonvolatile content of 34.1% and a viscosity of 2200 cps. Example 2 The hydroxyl group-containing acrylate oligomer obtained in Reference Example 2 was placed in the same reaction vessel as in Example 1.
(2) 2 parts, 2 parts of acrylic acid, 80 parts of butyl acrylate
parts, methyl methacrylate 16 parts, ethyl acetate 150 parts
and 1 part of benzoyl peroxide were charged and held at 80° C. for 8 hours under a nitrogen atmosphere to complete the polymerization. The obtained ethyl acetate solution of the polymer was cooled to obtain an adhesive composition (2) of the present invention having a nonvolatile content of 40.0% and a viscosity of 3000 cps. Example 3 In a reaction vessel similar to Example 1, 2 parts of the hydroxyl group-containing methacrylate oligomer (3) obtained in Reference Example 3, 1 part of methacrylic acid, 50 parts of 2-ethylhexyl acrylate, 47 parts of butyl acrylate,
120 parts of ethyl acetate, 30 parts of toluene and 1 part of benzoyl peroxide were charged, and the mixture was heated under a nitrogen atmosphere.
The polymerization was completed by holding at 85°C for 7 hours. The resulting solution of the polymer in an ethyl acetate-toluene mixed solvent was cooled to obtain an adhesive composition (3) of the present invention having a nonvolatile content of 40.0% and a viscosity of 2500 cps. Comparative Example 1 A comparative composition for an adhesive having a nonvolatile content of 34.0% and a viscosity of 2000 cps was prepared in the same manner as in Example 1, except that 2 parts of hydroxyethyl acrylate was used instead of the hydroxyl group-containing acrylate oligomer (1) in Example 1. I got item (1). Example 4 Coronate L (Japanese After adding 0.5 part of Polyurethane Kogyo Co., Ltd.), the thickness
It was coated on a 25μ polyester film to a dry film thickness of 30μ and dried at 80°C for 2 minutes to prepare a pressure-sensitive adhesive sheet for performance testing. The resulting pressure-sensitive adhesive sheets were left at room temperature for 1 hour and 7 days, respectively, and then their holding power, tack, and adhesive strength were measured by the following performance test methods, and the results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the adhesive composition of the present invention quickly builds up cohesive force after drying, has excellent curability, and has almost no change in tack or adhesive strength over time. , which provides excellent and stable adhesive strength.

Claims (1)

[Claims] 1. General formula (However, in the formula, R is a hydrogen atom or a methyl group, which may be the same or different, and Z is a divalent organic group having 2 to 20 carbon atoms, which may be the same or different. by polymerizing a polymerizable monomer (I) containing a hydroxyl group-containing (meth)acrylate oligomer (A) as an essential component, n being an integer of 1 to 100. An adhesive composition comprising the obtained polymer. 2 The polymerizable monomer (I) is hydroxyl group-containing (meth)acrylate oligomer (A) 0.05 to 20% by weight,
Alkyl (meth)acrylate (B) whose alkyl group has 4 to 18 carbon atoms 30 to 99.95% by weight and other monomers (C) 0 to 50% by weight (however, (A), (B) and
The total amount of component (C) is 100% by weight. ) The adhesive composition according to claim 1.