KR20010019893A - Heat activatable, pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE: Provided is a heat active adhesive composition, which is excellent in cohesive force at room temperature as well as fluidity when temperature is raised, and is applicable for in a seat, a film, a label and a tape. CONSTITUTION: The heat active adhesive composition contains i) 100pts.wt. of an acrylic copolymer having 200,000-2,000,000 of molecular weight obtained by copolymerizing a) 55-99.3pts.wt. of methacrylic acid ester monomer, b) 0.5-20pts.wt. of alpha, beta-unsaturated carboxylic acid monomer, c) 0.1-20pts.wt. of tert-amine compound having vinyl group, and d) 0.1-5pts.wt. of a vinyl monomer containing hydroxyl group; ii) 0.01-5pts.wt. of a crosslinking agent; and iii) 1-100pts.wt. of an adhesion-providing resin.

Description

Heat-active adhesive composition {HEAT ACTIVATABLE, PRESSURE-SENSITIVE ADHESIVE COMPOSITION}

[Industrial use]

The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a high functional pressure sensitive agent composition used to prepare a pressure-sensitive adhesive product excellent in heat activatable effect. Specifically, the present invention relates to a heat-activated pressure-sensitive adhesive composition having excellent flow characteristics when heated and activated by heat, while having high cohesive strength at room temperature.

[Prior art]

The pressure-sensitive adhesive is used for a wide variety of applications such as sheets, films, labels, and tapes because of its ease of use, and recently, the field of application of the pressure-sensitive adhesive for optical films, which requires various high functionalities and durability, has been expanded.

Generally, there are rubber-based, acrylic-based, and silicone-based adhesives, of which acrylic adhesives are most widely used for various application characteristics.

A general acrylic pressure-sensitive adhesive mainly exhibits excellent adhesive properties when light pressure is applied at room temperature. This is because the polymer molecules constituting the pressure-sensitive adhesive have flow characteristics, and thus are sensitive to pressure and adhere to the adherend.

In general, heat-active adhesives have a wide variety of uses, such as reflective sheets, durable labels, and fixing electronic components, and require excellent adhesion and cohesion to various adherends, and at the same time, long-term durability reliability is also required. In addition, some adhesive properties at room temperature before heating are also required in order to facilitate convenience such as positioning before attachment in use.

In general, the pressure-sensitive adhesive usually exhibits an adhesive force of 100 to 2000 gm / in, while the heat-activated pressure-sensitive adhesive is heated and attached to give more stable adhesive properties, and has a high adhesive strength of about 2000 to 5000 gm / in at room temperature after the adhesion. . However, in order to heat and attach, the flow characteristics should be excellent at elevated temperatures. In general, the heat-active adhesive has a disadvantage in that the flow characteristics are improved only by reducing the cohesive force at room temperature. That is, if the crosslinking density is improved for the cohesion at room temperature, the fluidity is lowered at elevated temperature, and if the fluidity at the elevated temperature is enhanced, the coagulation force is often lowered.

On the other hand, U.S. Patent No. 3,635,754 discloses a temperature-active adhesive composition, which has no tack characteristic at room temperature by using a phase change phenomenon of a crystalline material, and is characterized by expressing strong adhesive properties in a heated state. However, only temporary adhesive strength is given.

U. S. Patent No. 4,199, 646 discloses a heat-activated pressure-sensitive adhesive that causes strong adhesion by heat, which is a blend of a reactive hotmelt adhesive to an acrylic polymer and commercialized using a reactive functional group. And to improve the pressure-sensitive adhesive flow characteristics of the general elastomer type was tried to improve the composition of the thermosetting adhesive, the pressure-sensitive adhesive manufacturing process is complicated, the adhesive strength is too strong disadvantages.

U.S. Patent No. 4,427,744 discloses a heat-activated pressure-sensitive adhesive using an interaction of additives with temperature, and the selection of additives is limited, which makes it difficult to control adhesive properties.

U. S. Patent No. 4,248, 748 discloses a heat-activated pressure-sensitive adhesive in which an excess pressure-sensitive resin is added to an acrylic pressure-sensitive adhesive.

In addition, the prior art has a disadvantage of low heat activity efficiency of the resin used to propose a heat activated pressure-sensitive adhesive through the compounding process of the additive, a complicated manufacturing process.

The present invention takes into account the problems of the prior art, it is excellent in flow characteristics during heating to activate the initial contact (wetting) with the adherend, and after the attachment at room temperature, the use temperature is crosslinked and excellent cohesive force, such as adhesive, work characteristics And it is an object to provide a heat-active pressure-sensitive adhesive composition with significantly improved physical properties.

Another object of the present invention is to improve the efficiency by changing the heat-active properties of the acrylic copolymer resin as a main component of the pressure-sensitive adhesive, and to provide a simple heat-active pressure-sensitive adhesive composition.

Still another object of the present invention is to provide a heat-activated pressure-sensitive adhesive composition using an acrylic copolymer composition having excellent cohesive force at room temperature and imparting flow characteristics by using an acidic group interaction in which the intermolecular binding force is lowered at elevated temperatures.

[Means for solving the problem]

The present invention to achieve the above object,

a) iii) a (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms

55 to 99.3 parts by weight;

Ii) 0.5 to 20 parts by weight of an α, β unsaturated carboxylic acid monomer;

Iii) 0.1 to 20 parts by weight of a tertiary amine compound having a vinyl group; And

Iii) 0.1 to 5 parts by weight of a vinyl monomer containing a hydroxyl group

100 parts by weight of an acrylic copolymer obtained by copolymerizing;

b) 0.01 to 5 parts by weight of a crosslinking agent; And

c) 1 to 100 parts by weight of tackifying resin

It provides a heat-active adhesive composition comprising a.

[Action]

The present invention provides an excellent cohesive force and fluidity by incorporating an acrylic copolymer composition having excellent cohesive force at room temperature and giving flow characteristics by using an acid-base interaction in which the intermolecular binding force is lowered at an elevated temperature. It is intended to exhibit the characteristics.

To this end, the acrylic copolymer imparting the tackiness of a) is prepared using a general solution polymerization method, a photopolymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like. . Particularly, it is preferable to polymerize in a temperature rising process for the heat-active adhesive, which is to reduce the heterogeneity of the polymerization reaction by the interaction of the monomers during the polymerization. As for polymerization temperature, 50-140 degreeC is preferable, and it is preferable to add an initiator in the state in which monomer was mixed uniformly. Viscoelastic properties of the pressure-sensitive adhesive mainly depends on the molecular weight of the polymer chain, molecular weight distribution, and the amount of branched structure, which is mainly determined by the molecular weight, and the preferred molecular weight is 100,000 to 2 million. Can be.

In the raw materials used to prepare the acrylic copolymer of a), the (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms of (i) has a high cohesive force of the pressure-sensitive adhesive when the alkyl group is in a long chain form under high temperature. It is more preferable to select the carbon number of an alkyl group in the range of 4-8 in order to maintain cohesion force.

The usage-amount is preferably 55 to 99.3 parts by weight within 100 parts by weight of the acrylic copolymer of a), and more preferably 60 to 97 parts by weight to copolymerize. When the amount used is 55 parts by weight or less, the initial adhesive properties of the pressure-sensitive adhesive is lowered and the cost increases. In addition, when used excessively, cohesion becomes low.

Examples of the (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms of iii) include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, and methyl (meth) acryl. Rate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylic Rate and the like. In addition, copolymerization monomers such as acrylonitrile, styrene, glycidyl (meth) acrylate, and vinyl acetate may be used to control the glass transition temperature of the pressure-sensitive adhesive and to impart other functional properties. It can also mix and use above.

In the raw materials used to prepare the acrylic copolymer of a), the α, β unsaturated carboxylic acid monomer of ii) is copolymerized by including 0.5 to 20 parts by weight within 100 parts by weight of the acrylic copolymer of a). It is preferable. Use of less than 0.5 parts by weight lowers the adhesive force, when used in excess of 20 parts by weight will lower the elevated temperature flow characteristics due to the increase in cohesive force. Examples of such α, β unsaturated carboxylic monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, and the like, and these may be used alone or in combination.

In the raw materials used to prepare the acryl-based copolymer of a), the tertiary amine compound having a vinyl group of iii) interacts with a carboxylic acid functional group to impart a heat-activating function according to temperature. It is preferable to copolymerize 0.1-20 weight part in 100 weight part of acrylic copolymers of this. The use of less than 0.1 parts by weight has a low heat-activating effect, and the use of 20 parts by weight or more reduces the temperature rising flow characteristics. Examples of tertiary amine compounds having such a vinyl group include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, and the like. In addition, any other tertiary amine compound including a vinyl group may be used as long as it is suitable for the purpose of the present invention.

In the raw materials used to prepare the acrylic copolymer of a), the vinyl monomer including the hydroxyl group of iii) is used alone or by reacting with a crosslinking agent to increase the cohesive force by chemical bonding so that the pressure-sensitive adhesive is not destroyed when the temperature is elevated. In particular, it is possible to react with the crosslinking agent of b) to form a partially crosslinked structure. It is preferable to copolymerize this monomer by including 0.1-5 weight part in 100 weight part of acryl-type copolymers of a). Use of less than 0.1 parts by weight tends to cause cohesive failure at elevated temperatures, and use of more than 5 parts by weight will reduce the elevated flow characteristics. Examples of vinyl monomers containing such hydroxyl groups include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, and 2-hydroxypropylene. Glycol (meth) acrylates and the like, and these may be used alone or in combination if necessary. In addition, other vinyl monomers including a hydroxyl group may be used as long as they meet the object of the present invention.

The crosslinking agent of b) may be an isocyanate-based, epoxy-based, aziridine-based, blocked isocyanate-based, etc. Among them, isocyanate-based is easy to use. The crosslinking agent is used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer of a). These crosslinking agents enhance the holding strength of the pressure-sensitive adhesive at elevated temperatures through the crosslinking structure, thereby improving adhesion reliability. Examples of such a crosslinking agent include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, adduct of tolylene diisocyanate of trimethylolpropane, and the epoxy type is ethylene glycol diglycidyl ether and triglycis. Diethyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'-tetraglycidylethylenediamine, and the like.

The tackifying resin of c) is used in an amount of 1 to 100 parts by weight based on 100 parts by weight of the acrylic copolymer of a) to improve the initial adhesive properties of the pressure-sensitive adhesive. Excessive use reduces the cohesion of the adhesive and should be added as appropriate. Examples of such tackifying resins include (hydrogenated) hydrocarbon resins, (hydrogenated) rosin resins, (hydrogenated) rosin ester resins, (hydrogenated) terpene resins, (hydrogenated) terpene phenol resins, polymerized rosin resins, and polymerized rosin esters. Resins and the like, and these may be used alone or in combination of two or more thereof.

The heat-activated pressure-sensitive adhesive composition of the present invention can be used by mixing an epoxy resin, a curing agent, and the like for a specific purpose in addition to the above components, and can also be used by appropriately adding ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers and the like. It may also be prepared by the photopolymerization curing method with the addition of suitable photoinitiators, which are generally well known.

It is preferable that the heat-active adhesive composition of this invention shows the crosslinking density of 10-90.

The heat-activated pressure-sensitive adhesive composition of the present invention can be used in the adhesive products requiring heat activity without limitation, in particular, industrial sheets, such as reflective sheets, structural adhesive sheets, photographic adhesive sheets, lane marking adhesive sheets, optical adhesive products, Or an adhesive for an electronic component.

The present invention will be described in detail through the following examples and comparative examples. However, the examples are only for illustrating the present invention and are not limited thereto.

EXAMPLE

Example 1

(Acrylic copolymer production)

52 parts by weight of n-butylacrylate (BA; n-butylacrylate), methylacrylate (MA; methylacrylate) as shown in Table 1 in a 1000 ml reactor equipped with a refrigeration system to facilitate nitrogen temperature reflux and temperature control. ) 35 parts by weight, acrylic acid (AA) 7 parts by weight, diethylaminoethyl methacrylate (DEAMA; diethylaminoethylmethacrylate) 5 parts by weight, 2-hydroxyethyl (meth) acrylate (2-HEMA; 2-hydroxyethyl 100 parts by weight of ethylacetate (EAc) was added as a monomer mixture and 1 part by weight of (metha) acrylate.

In order to remove oxygen, nitrogen gas was supplied for 20 minutes, maintained at 70 ° C., uniformed, and then diluted with ethyl acetate to 0.035 parts by weight of benzoylperoxide (BPO) as a reaction initiator at 50 concentration. After the reaction for 10 hours to prepare a final acrylic copolymer.

The molecular weight of the prepared acrylic copolymer was measured using a polystyrene standard sample, and the results are shown in Table 1.

(Preparation of a heat-active adhesive composition)

As shown in Table 2, 2 parts by weight of the tolylene diisocyanate adduct of trimethylolpropane with a crosslinking agent in 100 parts by weight of the acryl-based copolymer obtained above was diluted to 50 concentrations in an ethyl acetate solution and a rosin ester resin (A Hercules Co., Ltd.). 30 parts by weight of foam 85) was uniformly mixed to prepare a heat-active adhesive composition.

(Heat active adhesive layer production)

The heat-active adhesive prepared above was diluted to an appropriate concentration in consideration of coating property, uniformly mixed, coated on a release paper, and dried to obtain a uniform heat-active adhesive layer having a thickness of 50 μm.

(Manufacture of adhesive sheet by plywood processing)

The pressure-sensitive adhesive layer was prepared by heat-laminating a pressure-sensitive adhesive layer prepared above to a surface treated polyester film having a thickness of 80 μm using a laminator.

Initial adhesive property evaluation

The pressure-sensitive adhesive sheet prepared above was cut to a size of 2.54 cm x 12.7 cm, and the initial adhesive properties (positioning properties) were measured and evaluated. This measurement depends on the specific angle and peel rate, but was evaluated relative to the peel strength of 180 °.

The adherend to be adhered was a stainless steel plate washed with ethyl acetate, which was left in a constant temperature and humidity bath at 25 ° C. and 50 ° C. for 24 hours before use for measurement.

The adhesive sheet was removed from the backside film, placed on a stainless steel plate and pressed with a rubber squeeze roll weighing 2 kg. After 20 minutes, the adhesive sheet was measured at a peeling speed of 300 mm / min. The adhesive strength was evaluated as follows. 2 is described.

The case where the initial adhesive force is 100 gm / in or less is represented by ○, the case of 100 to 200 gm / in is represented by Δ, and the case where 200 gm / in or more is represented by X.

(180。 Adhesion)

The pressure-sensitive adhesive sheet prepared above was cut to a size of 2.54 cm x 12.7 cm to evaluate the adhesive strength at 180 ° peel strength.

The adherend to be adhered was a stainless steel plate washed with ethyl acetate, which was left in a constant temperature and humidity bath at 25 ° C. and 50 ° C. for 24 hours before use for measurement.

The adhesive sheet was removed from the backside release film, placed on a stainless steel plate, and adhered using a vacuum compression method at a temperature of 80 ° C for 3 minutes. After cooling to room temperature after 20 minutes was measured at a peeling rate of 300 mm / min and the adhesive strength is shown in Table 2.

(retention)

The durability of the sample was evaluated by cutting the sample coated with the pressure-sensitive adhesive composition on the polyester film prepared above to a size of 25 mm x 50 mm to measure the holding force.

The adherend to be adhered was a stainless steel plate washed with ethyl acetate, which was left in a constant temperature and humidity bath at 25 ° C. and 50 ° C. for 24 hours before use for measurement.

After leaving the sample for 1 hour by applying a weight of 1 kg using a thermostat maintained at a temperature of 50 ℃ and measured the distance (mm) the sample slips and the results are shown in Table 2.

The adhesive sheet was removed from the backside release film, placed on a stainless steel plate, and adhered using a vacuum compression method at a temperature of 80 ° C for 3 minutes.

(Contamination at the time of desorption)

In the evaluation of the adhesive strength with 180 ° peel strength, the adhesive transfer phenomenon to the stainless steel plate was observed as it was peeled off immediately before the temperature was lowered to room temperature after adhesion.

The case where few residues remain is indicated by (circle), the case where some contamination is indicated by (triangle | delta), and the case where serious contamination is indicated by X.

Example 2, 3

An acrylic copolymer, a heat-active adhesive composition, a heat-active adhesive layer, and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except for changing the composition for preparing the acrylic copolymer shown in Table 1. The evaluation was performed in the same manner as in Example 1 to measure the initial adhesive properties, 180 ° adhesion, holding force, and contamination during desorption and are listed in Table 2.

Comparative Examples 1 to 4

Acrylic acid (AA), diethylaminoethyl methacrylate (DEAMA; diethylaminoethylmethacrylate), or 2-hydroxyethyl (meth) in the composition of Example 1 for preparing an acrylic copolymer as shown in Table 1 Copolymerization by adding or not adding acrylate (2-HEMA; 2-hydroxyethyl (metha) acrylate), and changing the amount of crosslinking agent or tackifying resin in the composition of the heat-active adhesive composition as shown in the composition ratios of Table 2. Except for the acrylic copolymer, a heat-active pressure-sensitive adhesive composition, a heat-active pressure-sensitive adhesive layer and an adhesive sheet were prepared in the same manner as in Example 1.

The evaluation was performed in the same manner as in Example 1 to measure the initial adhesive properties, 180 ° adhesion, holding force, and contamination during desorption and are listed in Table 2.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Acrylic copolymer blend composition (parts by weight) BA 52.0 52.0 40.0 59.0 59.0 59.0 52.5 MA 35.0 25.0 47.0 40.0 33.0 35.0 35.5 AA 7.0 13.0 7.0 0 7.0 0 7.0 DEAMA 5.0 9.0 5.0 0 0 5.0 5.0 2-HEMA 1.0 1.0 1.0 1.0 1.0 1.0 0 BPO 0.035 0.035 0.035 0.035 0.035 0.035 0.035 Solvent (EAc) 100 100 100 100 100 100 100 Manufactured Acrylic Copolymer Molecular Weight 370,000 280,000 350,000 420,000 290,000 310,000 320,000

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Heated adhesive composition composition (parts by weight) Acrylic Copolymer 100 100 100 100 100 100 100 Crosslinking agent 2.0 2.0 2.0 2.0 2.0 2.0 0 Tackifying resin 30 30 30 0 30 0 30 Property evaluation Initial adhesion ○ ○ ○ X ○ △ ○ 180。 Adhesive force (gm / in) 2300 2500 3500 1500 1200 800 2000 Holding force (mm) 0.5 or less 0.5 or less 0.5 or less 3.3 5.8 2.8 1.5 Contamination at Desorption ○ ○ ○ △ X △ X

The heat-activated pressure-sensitive adhesive composition of the present invention is a composition having a high adhesive strength at room temperature because of excellent flow characteristics at room temperature and excellent cohesive force at room temperature, and the composition is adhesive which requires heat activity such as sheet, film, label, or tape. The product can be used without any limitation, and in particular, it can be suitably used for industrial sheets such as reflective sheets, structural adhesive sheets, photographic adhesive sheets, lane marking adhesive sheets, optical adhesive products, or adhesives for electronic parts.

Claims (11)

a) iii) a (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms 55 to 99.3 parts by weight; Ii) 0.5 to 20 parts by weight of an α, β unsaturated carboxylic acid monomer; Iii) 0.1 to 20 parts by weight of a tertiary amine compound having a vinyl group; And Iii) 0.1 to 5 parts by weight of a vinyl monomer containing a hydroxyl group 100 parts by weight of an acrylic copolymer prepared by copolymerizing; b) 0.01 to 5 parts by weight of a crosslinking agent; And c) 1 to 100 parts by weight of tackifying resin Heating active pressure-sensitive adhesive composition comprising a. The method of claim 1, Heating active pressure-sensitive adhesive composition wherein the molecular weight of the acrylic copolymer of a) is 200,000 to 2 million. The method of claim 1, The acrylic copolymer of a) is a heat-activated pressure-sensitive adhesive composition prepared by a polymerization method selected from the group consisting of a solution polymerization method, a photopolymerization method, a suspension polymerization method, and an emulsion polymerization method. The method of claim 1, (Meth) acrylic acid ester monomer which has a C1-C12 alkyl group of said a) iii) is butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acryl Latex, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, n-octyl (meth) acrylate, and isononyl (meth) Heat-active adhesive composition selected from the group consisting of acrylates. The method of claim 1, The α, β unsaturated carboxylic acid monomer of a) ii) is at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and maleic anhydride. The method of claim 1, Tertiary amine compounds having a vinyl group of a) iii) include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylaminopropyl (meth). Heat-active adhesive composition selected from the group consisting of acrylates. The method of claim 1, The vinyl monomer containing the hydroxyl group of said a) iii) is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, and 2 -Heat-active adhesive composition selected from the group consisting of hydroxypropylene glycol (meth) acrylates. The method of claim 1, The crosslinking agent of b) is selected from an isocyanate group consisting of an adduct of tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and tolylene diisocyanate of trimethylolpropane, or ethylene glycol diglycidyl ether, triglycis A heat-activated pressure-sensitive adhesive composition selected from the group consisting of dil ether, trimethylolpropanetriglycidyl ether, and N, N, N ', N'-tetraglycidyldiamine. The method of claim 1, The tackifying resin of c) is (hydrogenated) hydrocarbon resin, (hydrogenated) rosin resin, (hydrogenated) rosin ester resin, (hydrogenated) terpene resin, (hydrogenated) terpene phenol resin, polymerized rosin resin, and polymerization furnace Heat-active adhesive composition selected from the group consisting of gin ester resins. The method of claim 1, A heat-activated pressure-sensitive adhesive composition wherein the vinyl monomer containing a hydroxyl group of a) i) and the crosslinking agent of b) react to form a partially crosslinked structure. The method of claim 1, Heat-active adhesive composition whose crosslinking density of the said heat-active adhesive composition is 10-90.